Adding upstream version 1:2.3.21+dfsg1.upstream/1%2.3.21+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

33 files changed, 6276 insertions, 0 deletions

diff --git a/src/stats/Makefile.am b/src/stats/Makefile.am
new file mode 100644
index 0000000..0d6f598
--- /dev/null
+++ b/src/stats/Makefile.am
@@ -0,0 +1,102 @@
+pkglibexecdir = $(libexecdir)/dovecot
+
+pkglibexec_PROGRAMS = stats
+
+noinst_LTLIBRARIES = libstats_local.la
+
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/lib \
+	-I$(top_srcdir)/src/lib-settings \
+	-I$(top_srcdir)/src/lib-master \
+	-I$(top_srcdir)/src/lib-http \
+	-I$(top_srcdir)/src/lib-ssl-iostream \
+	-I$(top_srcdir)/src/lib-test \
+	$(BINARY_CFLAGS)
+
+stats_LDADD = \
+	$(noinst_LTLIBRARIES) \
+	$(LIBDOVECOT) \
+	$(DOVECOT_SSL_LIBS) \
+	$(BINARY_LDFLAGS) \
+	-lm
+
+stats_DEPENDENCIES = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT_DEPS)
+
+stats_services = \
+	stats-service-openmetrics.c
+
+stats_SOURCES = \
+	main.c
+
+libstats_local_la_SOURCES = \
+	client-reader.c \
+	client-writer.c \
+	client-http.c \
+	event-exporter-fmt.c \
+	event-exporter-fmt-json.c \
+	event-exporter-fmt-none.c \
+	event-exporter-fmt-tab-text.c \
+	event-exporter-transport-drop.c \
+	event-exporter-transport-http-post.c \
+	event-exporter-transport-log.c \
+	$(stats_services) \
+	stats-service.c \
+	stats-event-category.c \
+	stats-metrics.c \
+	stats-settings.c
+
+noinst_HEADERS = \
+	stats-common.h \
+	client-reader.h \
+	client-writer.h \
+	client-http.h\
+	event-exporter.h \
+	stats-service.h \
+	stats-service-private.h \
+	stats-event-category.h \
+	stats-metrics.h \
+	stats-settings.h \
+	test-stats-common.h
+
+test_libs = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT) \
+	$(BINARY_LDFLAGS) \
+	-lm
+
+test_deps = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT_DEPS)
+
+test_stats_metrics_SOURCES = test-stats-metrics.c test-stats-common.c
+test_stats_metrics_LDADD = $(test_libs)
+test_stats_metrics_DEPENDENCIES = $(test_deps)
+
+test_client_writer_SOURCES = test-client-writer.c test-stats-common.c
+test_client_writer_LDADD = $(test_libs)
+test_client_writer_DEPENDENCIES = $(test_deps)
+
+test_client_reader_SOURCES = test-client-reader.c test-stats-common.c
+test_client_reader_LDADD = $(test_libs)
+test_client_reader_DEPENDENCIES = $(test_deps)
+
+test_programs = test-stats-metrics test-client-writer test-client-reader
+noinst_PROGRAMS = $(test_programs)
+
+check-local:
+	for bin in $(test_programs); do \
+	  if ! $(RUN_TEST) ./$$bin; then exit 1; fi; \
+	done
+
+LIBDOVECOT_TEST_DEPS = \
+	../lib-ssl-iostream/libssl_iostream.la \
+	../lib-test/libtest.la \
+	../lib/liblib.la
+LIBDOVECOT_TEST = \
+	$(LIBDOVECOT_TEST_DEPS) \
+	$(MODULE_LIBS)
diff --git a/src/stats/Makefile.in b/src/stats/Makefile.in
new file mode 100644
index 0000000..b3bdf4d
--- /dev/null
+++ b/src/stats/Makefile.in
@@ -0,0 +1,1024 @@
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+dict_drivers = @dict_drivers@
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+pdfdir = @pdfdir@
+prefix = @prefix@
+program_transform_name = @program_transform_name@
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+top_builddir = @top_builddir@
+top_srcdir = @top_srcdir@
+noinst_LTLIBRARIES = libstats_local.la
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/lib \
+	-I$(top_srcdir)/src/lib-settings \
+	-I$(top_srcdir)/src/lib-master \
+	-I$(top_srcdir)/src/lib-http \
+	-I$(top_srcdir)/src/lib-ssl-iostream \
+	-I$(top_srcdir)/src/lib-test \
+	$(BINARY_CFLAGS)
+
+stats_LDADD = \
+	$(noinst_LTLIBRARIES) \
+	$(LIBDOVECOT) \
+	$(DOVECOT_SSL_LIBS) \
+	$(BINARY_LDFLAGS) \
+	-lm
+
+stats_DEPENDENCIES = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT_DEPS)
+
+stats_services = \
+	stats-service-openmetrics.c
+
+stats_SOURCES = \
+	main.c
+
+libstats_local_la_SOURCES = \
+	client-reader.c \
+	client-writer.c \
+	client-http.c \
+	event-exporter-fmt.c \
+	event-exporter-fmt-json.c \
+	event-exporter-fmt-none.c \
+	event-exporter-fmt-tab-text.c \
+	event-exporter-transport-drop.c \
+	event-exporter-transport-http-post.c \
+	event-exporter-transport-log.c \
+	$(stats_services) \
+	stats-service.c \
+	stats-event-category.c \
+	stats-metrics.c \
+	stats-settings.c
+
+noinst_HEADERS = \
+	stats-common.h \
+	client-reader.h \
+	client-writer.h \
+	client-http.h\
+	event-exporter.h \
+	stats-service.h \
+	stats-service-private.h \
+	stats-event-category.h \
+	stats-metrics.h \
+	stats-settings.h \
+	test-stats-common.h
+
+test_libs = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT) \
+	$(BINARY_LDFLAGS) \
+	-lm
+
+test_deps = \
+	$(noinst_LTLIBRARIES) \
+	$(DOVECOT_SSL_LIBS) \
+	$(LIBDOVECOT_DEPS)
+
+test_stats_metrics_SOURCES = test-stats-metrics.c test-stats-common.c
+test_stats_metrics_LDADD = $(test_libs)
+test_stats_metrics_DEPENDENCIES = $(test_deps)
+test_client_writer_SOURCES = test-client-writer.c test-stats-common.c
+test_client_writer_LDADD = $(test_libs)
+test_client_writer_DEPENDENCIES = $(test_deps)
+test_client_reader_SOURCES = test-client-reader.c test-stats-common.c
+test_client_reader_LDADD = $(test_libs)
+test_client_reader_DEPENDENCIES = $(test_deps)
+test_programs = test-stats-metrics test-client-writer test-client-reader
+LIBDOVECOT_TEST_DEPS = \
+	../lib-ssl-iostream/libssl_iostream.la \
+	../lib-test/libtest.la \
+	../lib/liblib.la
+
+LIBDOVECOT_TEST = \
+	$(LIBDOVECOT_TEST_DEPS) \
+	$(MODULE_LIBS)
+
+all: all-am
+
+.SUFFIXES:
+.SUFFIXES: .c .lo .o .obj
+$(srcdir)/Makefile.in: @MAINTAINER_MODE_TRUE@ $(srcdir)/Makefile.am  $(am__configure_deps)
+	@for dep in $?; do \
+	  case '$(am__configure_deps)' in \
+	    *$$dep*) \
+	      ( cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh ) \
+	        && { if test -f $@; then exit 0; else break; fi; }; \
+	      exit 1;; \
+	  esac; \
+	done; \
+	echo ' cd $(top_srcdir) && $(AUTOMAKE) --foreign src/stats/Makefile'; \
+	$(am__cd) $(top_srcdir) && \
+	  $(AUTOMAKE) --foreign src/stats/Makefile
+Makefile: $(srcdir)/Makefile.in $(top_builddir)/config.status
+	@case '$?' in \
+	  *config.status*) \
+	    cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh;; \
+	  *) \
+	    echo ' cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@ $(am__maybe_remake_depfiles)'; \
+	    cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@ $(am__maybe_remake_depfiles);; \
+	esac;
+
+$(top_builddir)/config.status: $(top_srcdir)/configure $(CONFIG_STATUS_DEPENDENCIES)
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+$(top_srcdir)/configure: @MAINTAINER_MODE_TRUE@ $(am__configure_deps)
+	cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+$(ACLOCAL_M4): @MAINTAINER_MODE_TRUE@ $(am__aclocal_m4_deps)
+	cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+$(am__aclocal_m4_deps):
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+	rm -f $$list || exit $$?; \
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+	list=`for p in $$list; do echo "$$p"; done | sed 's/$(EXEEXT)$$//'`; \
+	echo " rm -f" $$list; \
+	rm -f $$list
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+	@$(NORMAL_INSTALL)
+	@list='$(pkglibexec_PROGRAMS)'; test -n "$(pkglibexecdir)" || list=; \
+	if test -n "$$list"; then \
+	  echo " $(MKDIR_P) '$(DESTDIR)$(pkglibexecdir)'"; \
+	  $(MKDIR_P) "$(DESTDIR)$(pkglibexecdir)" || exit 1; \
+	fi; \
+	for p in $$list; do echo "$$p $$p"; done | \
+	sed 's/$(EXEEXT)$$//' | \
+	while read p p1; do if test -f $$p \
+	 || test -f $$p1 \
+	  ; then echo "$$p"; echo "$$p"; else :; fi; \
+	done | \
+	sed -e 'p;s,.*/,,;n;h' \
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+	    -e 'p;x;s,.*/,,;s/$(EXEEXT)$$//;$(transform);s/$$/$(EXEEXT)/' | \
+	sed 'N;N;N;s,\n, ,g' | \
+	$(AWK) 'BEGIN { files["."] = ""; dirs["."] = 1 } \
+	  { d=$$3; if (dirs[d] != 1) { print "d", d; dirs[d] = 1 } \
+	    if ($$2 == $$4) files[d] = files[d] " " $$1; \
+	    else { print "f", $$3 "/" $$4, $$1; } } \
+	  END { for (d in files) print "f", d, files[d] }' | \
+	while read type dir files; do \
+	    if test "$$dir" = .; then dir=; else dir=/$$dir; fi; \
+	    test -z "$$files" || { \
+	    echo " $(INSTALL_PROGRAM_ENV) $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL_PROGRAM) $$files '$(DESTDIR)$(pkglibexecdir)$$dir'"; \
+	    $(INSTALL_PROGRAM_ENV) $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL_PROGRAM) $$files "$(DESTDIR)$(pkglibexecdir)$$dir" || exit $$?; \
+	    } \
+	; done
+
+uninstall-pkglibexecPROGRAMS:
+	@$(NORMAL_UNINSTALL)
+	@list='$(pkglibexec_PROGRAMS)'; test -n "$(pkglibexecdir)" || list=; \
+	files=`for p in $$list; do echo "$$p"; done | \
+	  sed -e 'h;s,^.*/,,;s/$(EXEEXT)$$//;$(transform)' \
+	      -e 's/$$/$(EXEEXT)/' \
+	`; \
+	test -n "$$list" || exit 0; \
+	echo " ( cd '$(DESTDIR)$(pkglibexecdir)' && rm -f" $$files ")"; \
+	cd "$(DESTDIR)$(pkglibexecdir)" && rm -f $$files
+
+clean-pkglibexecPROGRAMS:
+	@list='$(pkglibexec_PROGRAMS)'; test -n "$$list" || exit 0; \
+	echo " rm -f" $$list; \
+	rm -f $$list || exit $$?; \
+	test -n "$(EXEEXT)" || exit 0; \
+	list=`for p in $$list; do echo "$$p"; done | sed 's/$(EXEEXT)$$//'`; \
+	echo " rm -f" $$list; \
+	rm -f $$list
+
+clean-noinstLTLIBRARIES:
+	-test -z "$(noinst_LTLIBRARIES)" || rm -f $(noinst_LTLIBRARIES)
+	@list='$(noinst_LTLIBRARIES)'; \
+	locs=`for p in $$list; do echo $$p; done | \
+	      sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
+	      sort -u`; \
+	test -z "$$locs" || { \
+	  echo rm -f $${locs}; \
+	  rm -f $${locs}; \
+	}
+
+libstats_local.la: $(libstats_local_la_OBJECTS) $(libstats_local_la_DEPENDENCIES) $(EXTRA_libstats_local_la_DEPENDENCIES) 
+	$(AM_V_CCLD)$(LINK)  $(libstats_local_la_OBJECTS) $(libstats_local_la_LIBADD) $(LIBS)
+
+stats$(EXEEXT): $(stats_OBJECTS) $(stats_DEPENDENCIES) $(EXTRA_stats_DEPENDENCIES) 
+	@rm -f stats$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(stats_OBJECTS) $(stats_LDADD) $(LIBS)
+
+test-client-reader$(EXEEXT): $(test_client_reader_OBJECTS) $(test_client_reader_DEPENDENCIES) $(EXTRA_test_client_reader_DEPENDENCIES) 
+	@rm -f test-client-reader$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(test_client_reader_OBJECTS) $(test_client_reader_LDADD) $(LIBS)
+
+test-client-writer$(EXEEXT): $(test_client_writer_OBJECTS) $(test_client_writer_DEPENDENCIES) $(EXTRA_test_client_writer_DEPENDENCIES) 
+	@rm -f test-client-writer$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(test_client_writer_OBJECTS) $(test_client_writer_LDADD) $(LIBS)
+
+test-stats-metrics$(EXEEXT): $(test_stats_metrics_OBJECTS) $(test_stats_metrics_DEPENDENCIES) $(EXTRA_test_stats_metrics_DEPENDENCIES) 
+	@rm -f test-stats-metrics$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(test_stats_metrics_OBJECTS) $(test_stats_metrics_LDADD) $(LIBS)
+
+mostlyclean-compile:
+	-rm -f *.$(OBJEXT)
+
+distclean-compile:
+	-rm -f *.tab.c
+
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/client-http.Plo@am__quote@ # am--include-marker
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/client-reader.Plo@am__quote@ # am--include-marker
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+$(am__depfiles_remade):
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+	@echo '# dummy' >$@-t && $(am__mv) $@-t $@
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+	case $$dist_files in \
+	  */*) $(MKDIR_P) `echo "$$dist_files" | \
+			   sed '/\//!d;s|^|$(distdir)/|;s,/[^/]*$$,,' | \
+			   sort -u` ;; \
+	esac; \
+	for file in $$dist_files; do \
+	  if test -f $$file || test -d $$file; then d=.; else d=$(srcdir); fi; \
+	  if test -d $$d/$$file; then \
+	    dir=`echo "/$$file" | sed -e 's,/[^/]*$$,,'`; \
+	    if test -d "$(distdir)/$$file"; then \
+	      find "$(distdir)/$$file" -type d ! -perm -700 -exec chmod u+rwx {} \;; \
+	    fi; \
+	    if test -d $(srcdir)/$$file && test $$d != $(srcdir); then \
+	      cp -fpR $(srcdir)/$$file "$(distdir)$$dir" || exit 1; \
+	      find "$(distdir)/$$file" -type d ! -perm -700 -exec chmod u+rwx {} \;; \
+	    fi; \
+	    cp -fpR $$d/$$file "$(distdir)$$dir" || exit 1; \
+	  else \
+	    test -f "$(distdir)/$$file" \
+	    || cp -p $$d/$$file "$(distdir)/$$file" \
+	    || exit 1; \
+	  fi; \
+	done
+check-am: all-am
+	$(MAKE) $(AM_MAKEFLAGS) check-local
+check: check-am
+all-am: Makefile $(PROGRAMS) $(LTLIBRARIES) $(HEADERS)
+installdirs:
+	for dir in "$(DESTDIR)$(pkglibexecdir)"; do \
+	  test -z "$$dir" || $(MKDIR_P) "$$dir"; \
+	done
+install: install-am
+install-exec: install-exec-am
+install-data: install-data-am
+uninstall: uninstall-am
+
+install-am: all-am
+	@$(MAKE) $(AM_MAKEFLAGS) install-exec-am install-data-am
+
+installcheck: installcheck-am
+install-strip:
+	if test -z '$(STRIP)'; then \
+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+	    install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+	      install; \
+	else \
+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+	    install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+	    "INSTALL_PROGRAM_ENV=STRIPPROG='$(STRIP)'" install; \
+	fi
+mostlyclean-generic:
+
+clean-generic:
+
+distclean-generic:
+	-test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
+	-test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
+
+maintainer-clean-generic:
+	@echo "This command is intended for maintainers to use"
+	@echo "it deletes files that may require special tools to rebuild."
+clean: clean-am
+
+clean-am: clean-generic clean-libtool clean-noinstLTLIBRARIES \
+	clean-noinstPROGRAMS clean-pkglibexecPROGRAMS mostlyclean-am
+
+distclean: distclean-am
+		-rm -f ./$(DEPDIR)/client-http.Plo
+	-rm -f ./$(DEPDIR)/client-reader.Plo
+	-rm -f ./$(DEPDIR)/client-writer.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-json.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-none.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-tab-text.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-drop.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-http-post.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-log.Plo
+	-rm -f ./$(DEPDIR)/main.Po
+	-rm -f ./$(DEPDIR)/stats-event-category.Plo
+	-rm -f ./$(DEPDIR)/stats-metrics.Plo
+	-rm -f ./$(DEPDIR)/stats-service-openmetrics.Plo
+	-rm -f ./$(DEPDIR)/stats-service.Plo
+	-rm -f ./$(DEPDIR)/stats-settings.Plo
+	-rm -f ./$(DEPDIR)/test-client-reader.Po
+	-rm -f ./$(DEPDIR)/test-client-writer.Po
+	-rm -f ./$(DEPDIR)/test-stats-common.Po
+	-rm -f ./$(DEPDIR)/test-stats-metrics.Po
+	-rm -f Makefile
+distclean-am: clean-am distclean-compile distclean-generic \
+	distclean-tags
+
+dvi: dvi-am
+
+dvi-am:
+
+html: html-am
+
+html-am:
+
+info: info-am
+
+info-am:
+
+install-data-am:
+
+install-dvi: install-dvi-am
+
+install-dvi-am:
+
+install-exec-am: install-pkglibexecPROGRAMS
+
+install-html: install-html-am
+
+install-html-am:
+
+install-info: install-info-am
+
+install-info-am:
+
+install-man:
+
+install-pdf: install-pdf-am
+
+install-pdf-am:
+
+install-ps: install-ps-am
+
+install-ps-am:
+
+installcheck-am:
+
+maintainer-clean: maintainer-clean-am
+		-rm -f ./$(DEPDIR)/client-http.Plo
+	-rm -f ./$(DEPDIR)/client-reader.Plo
+	-rm -f ./$(DEPDIR)/client-writer.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-json.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-none.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt-tab-text.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-fmt.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-drop.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-http-post.Plo
+	-rm -f ./$(DEPDIR)/event-exporter-transport-log.Plo
+	-rm -f ./$(DEPDIR)/main.Po
+	-rm -f ./$(DEPDIR)/stats-event-category.Plo
+	-rm -f ./$(DEPDIR)/stats-metrics.Plo
+	-rm -f ./$(DEPDIR)/stats-service-openmetrics.Plo
+	-rm -f ./$(DEPDIR)/stats-service.Plo
+	-rm -f ./$(DEPDIR)/stats-settings.Plo
+	-rm -f ./$(DEPDIR)/test-client-reader.Po
+	-rm -f ./$(DEPDIR)/test-client-writer.Po
+	-rm -f ./$(DEPDIR)/test-stats-common.Po
+	-rm -f ./$(DEPDIR)/test-stats-metrics.Po
+	-rm -f Makefile
+maintainer-clean-am: distclean-am maintainer-clean-generic
+
+mostlyclean: mostlyclean-am
+
+mostlyclean-am: mostlyclean-compile mostlyclean-generic \
+	mostlyclean-libtool
+
+pdf: pdf-am
+
+pdf-am:
+
+ps: ps-am
+
+ps-am:
+
+uninstall-am: uninstall-pkglibexecPROGRAMS
+
+.MAKE: check-am install-am install-strip
+
+.PHONY: CTAGS GTAGS TAGS all all-am am--depfiles check check-am \
+	check-local clean clean-generic clean-libtool \
+	clean-noinstLTLIBRARIES clean-noinstPROGRAMS \
+	clean-pkglibexecPROGRAMS cscopelist-am ctags ctags-am \
+	distclean distclean-compile distclean-generic \
+	distclean-libtool distclean-tags distdir dvi dvi-am html \
+	html-am info info-am install install-am install-data \
+	install-data-am install-dvi install-dvi-am install-exec \
+	install-exec-am install-html install-html-am install-info \
+	install-info-am install-man install-pdf install-pdf-am \
+	install-pkglibexecPROGRAMS install-ps install-ps-am \
+	install-strip installcheck installcheck-am installdirs \
+	maintainer-clean maintainer-clean-generic mostlyclean \
+	mostlyclean-compile mostlyclean-generic mostlyclean-libtool \
+	pdf pdf-am ps ps-am tags tags-am uninstall uninstall-am \
+	uninstall-pkglibexecPROGRAMS
+
+.PRECIOUS: Makefile
+
+
+check-local:
+	for bin in $(test_programs); do \
+	  if ! $(RUN_TEST) ./$$bin; then exit 1; fi; \
+	done
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/src/stats/client-http.c b/src/stats/client-http.c
new file mode 100644
index 0000000..1811917
--- /dev/null
+++ b/src/stats/client-http.c
@@ -0,0 +1,233 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "str.h"
+#include "array.h"
+#include "strescape.h"
+#include "connection.h"
+#include "ostream.h"
+#include "master-service.h"
+#include "http-server.h"
+#include "http-url.h"
+#include "stats-metrics.h"
+#include "stats-service.h"
+#include "client-http.h"
+
+struct stats_http_client;
+
+struct stats_http_client {
+	struct http_server_connection *http_conn;
+};
+
+struct stats_http_resource {
+	pool_t pool;
+	const char *title;
+	struct http_server_resource *resource;
+
+	stats_http_resource_callback_t *callback;
+	void *context;
+};
+
+static struct http_server *stats_http_server;
+static ARRAY(struct stats_http_resource *) stats_http_resources;
+
+/*
+ * Request
+ */
+
+static void
+stats_http_server_handle_request(void *context ATTR_UNUSED,
+				 struct http_server_request *http_sreq)
+{
+	http_server_request_fail(http_sreq, 404, "Path Not Found");
+}
+
+/*
+ * Connection
+ */
+
+static void
+stats_http_server_connection_destroy(void *context, const char *reason);
+
+static const struct http_server_callbacks stats_http_callbacks = {
+        .connection_destroy = stats_http_server_connection_destroy,
+        .handle_request = stats_http_server_handle_request
+};
+
+void client_http_create(struct master_service_connection *conn)
+{
+	struct stats_http_client *client;
+
+	client = i_new(struct stats_http_client, 1);
+
+	client->http_conn = http_server_connection_create(
+		stats_http_server, conn->fd, conn->fd, conn->ssl,
+		&stats_http_callbacks, client);
+}
+
+static void stats_http_client_destroy(struct stats_http_client *client)
+{
+	i_free(client);
+
+	master_service_client_connection_destroyed(master_service);
+}
+
+static void
+stats_http_server_connection_destroy(void *context,
+				     const char *reason ATTR_UNUSED)
+{
+	struct stats_http_client *client = context;
+
+	if (client->http_conn == NULL) {
+		/* Already destroying client directly */
+		return;
+	}
+
+	/* HTTP connection is destroyed already now */
+	client->http_conn = NULL;
+
+	/* Destroy the connection itself */
+	stats_http_client_destroy(client);
+}
+
+/*
+ * Resources
+ */
+
+/* Registry */
+
+static void
+stats_http_resource_callback(struct stats_http_resource *res,
+			     struct http_server_request *req,
+			     const char *sub_path)
+{
+	res->callback(res->context, req, sub_path);
+}
+
+#undef stats_http_resource_add
+void stats_http_resource_add(const char *path, const char *title,
+			     stats_http_resource_callback_t *callback,
+			     void *context)
+{
+	struct stats_http_resource *res;
+	pool_t pool;
+
+	pool = pool_alloconly_create("stats http resource", 2048);
+	res = p_new(pool, struct stats_http_resource, 1);
+	res->pool = pool;
+	res->title = p_strdup(pool, title);
+	res->callback = callback;
+	res->context = context;
+
+	res->resource = http_server_resource_create(
+		stats_http_server, pool, stats_http_resource_callback, res);
+	http_server_resource_add_location(res->resource, path);
+
+	pool_unref(&pool);
+	array_append(&stats_http_resources, &res, 1);
+}
+
+/* Root */
+
+static void
+stats_http_resource_root_make_response(struct http_server_response *resp,
+				       const struct http_request *hreq)
+{
+	struct stats_http_resource *res;
+	struct http_url url;
+	string_t *msg;
+
+	http_url_init_authority_from(&url, hreq->target.url);
+
+	msg = t_str_new(1024);
+
+	str_append(msg, "<!DOCTYPE html>\n");
+	str_append(msg, "<html lang=\"en\">\n");
+	str_append(msg, "\n");
+	str_append(msg, "<head>\n");
+	str_append(msg, "<meta charset=\"utf-8\">\n");
+	str_append(msg, "<title>Dovecot Stats</title>\n");
+	str_append(msg, "</head>\n");
+	str_append(msg, "\n");
+	str_append(msg, "<body>\n");
+
+	str_append(msg, "<h1>Dovecot Stats:</h1>\n");
+	str_append(msg, "<p><ul>\n");
+
+	array_foreach_elem(&stats_http_resources, res) {
+		if (res->title == NULL)
+			continue;
+
+		/* List the resource at its primary location. */
+		url.path = http_server_resource_get_path(res->resource);
+
+		str_append(msg, "<li><a href=\"");
+		str_append(msg, http_url_create(&url));
+		str_append(msg, "\">");
+		str_append(msg, res->title);
+		str_append(msg, "</a></li>\n");
+	}
+
+	str_append(msg, "</ul></p>\n");
+	str_append(msg, "</body>\n");
+	str_append(msg, "\n");
+	str_append(msg, "</html>\n");
+
+	http_server_response_set_payload_data(
+		resp, str_data(msg), str_len(msg));
+}
+
+static void
+stats_http_resource_root_request(void *context ATTR_UNUSED,
+				 struct http_server_request *req,
+				 const char *sub_path)
+{
+	const struct http_request *hreq = http_server_request_get(req);
+	struct http_server_response *resp;
+
+	if (strcmp(hreq->method, "OPTIONS") == 0) {
+		resp = http_server_response_create(req, 200, "OK");
+		http_server_response_add_header(resp, "Allow", "GET");
+		http_server_response_submit(resp);
+		return;
+	}
+	if (strcmp(hreq->method, "GET") != 0) {
+		http_server_request_fail_bad_method(req, "GET");
+		return;
+	}
+	if (*sub_path != '\0') {
+		http_server_request_fail(req, 404, "Not Found");
+		return;
+	}
+
+	resp = http_server_response_create(req, 200, "OK");
+	http_server_response_add_header(resp, "Content-Type",
+					"text/html; charset=utf-8");
+
+	stats_http_resource_root_make_response(resp, hreq);
+
+	http_server_response_submit(resp);
+}
+
+/*
+ * Server
+ */
+
+void client_http_init(const struct stats_settings *set)
+{
+	struct http_server_settings http_set = {
+		.rawlog_dir = set->stats_http_rawlog_dir,
+	};
+
+	i_array_init(&stats_http_resources, 8);
+
+	stats_http_server = http_server_init(&http_set);
+	stats_http_resource_add("/", NULL,
+				stats_http_resource_root_request, NULL);
+}
+
+void client_http_deinit(void)
+{
+	http_server_deinit(&stats_http_server);
+	array_free(&stats_http_resources);
+}
diff --git a/src/stats/client-http.h b/src/stats/client-http.h
new file mode 100644
index 0000000..4251ce3
--- /dev/null
+++ b/src/stats/client-http.h
@@ -0,0 +1,28 @@
+#ifndef CLIENT_HTTP_H
+#define CLIENT_HTTP_H
+
+struct master_service_connection;
+struct http_server_request;
+
+typedef void
+(stats_http_resource_callback_t)(void *context,
+				 struct http_server_request *req,
+				 const char *sub_path);
+
+void client_http_create(struct master_service_connection *conn);
+
+void stats_http_resource_add(const char *path, const char *title,
+			     stats_http_resource_callback_t *callback,
+			     void *context);
+#define stats_http_resource_add(path, title, callback, context) \
+	stats_http_resource_add(path, title, \
+		(stats_http_resource_callback_t *)callback, \
+		(TRUE ? context : \
+		 CALLBACK_TYPECHECK(callback, void (*)( \
+			typeof(context), struct http_server_request *req, \
+			const char *sub_path))))
+
+void client_http_init(const struct stats_settings *set);
+void client_http_deinit(void);
+
+#endif
diff --git a/src/stats/client-reader.c b/src/stats/client-reader.c
new file mode 100644
index 0000000..e944001
--- /dev/null
+++ b/src/stats/client-reader.c
@@ -0,0 +1,253 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "array.h"
+#include "str.h"
+#include "stats-dist.h"
+#include "strescape.h"
+#include "connection.h"
+#include "ostream.h"
+#include "master-service.h"
+#include "stats-metrics.h"
+#include "stats-settings.h"
+#include "client-reader.h"
+#include "client-writer.h"
+
+struct reader_client {
+	struct connection conn;
+};
+
+static struct connection_list *reader_clients = NULL;
+
+void client_reader_create(int fd)
+{
+	struct reader_client *client;
+
+	client = i_new(struct reader_client, 1);
+	connection_init_server(reader_clients, &client->conn,
+			       "stats-reader", fd, fd);
+}
+
+static void reader_client_destroy(struct connection *conn)
+{
+	connection_deinit(conn);
+	i_free(conn);
+
+	master_service_client_connection_destroyed(master_service);
+}
+
+static void reader_client_dump_stats(string_t *str, struct stats_dist *stats,
+				     const char *const *fields)
+{
+	for (unsigned int i = 0; fields[i] != NULL; i++) {
+		const char *field = fields[i];
+
+		str_append_c(str, '\t');
+		if (strcmp(field, "count") == 0)
+			str_printfa(str, "%u", stats_dist_get_count(stats));
+		else if (strcmp(field, "sum") == 0)
+			str_printfa(str, "%"PRIu64, stats_dist_get_sum(stats));
+		else if (strcmp(field, "min") == 0)
+			str_printfa(str, "%"PRIu64, stats_dist_get_min(stats));
+		else if (strcmp(field, "max") == 0)
+			str_printfa(str, "%"PRIu64, stats_dist_get_max(stats));
+		else if (strcmp(field, "avg") == 0)
+			str_printfa(str, "%.02f", stats_dist_get_avg(stats));
+		else if (strcmp(field, "median") == 0)
+			str_printfa(str, "%"PRIu64, stats_dist_get_median(stats));
+		else if (strcmp(field, "variance") == 0)
+			str_printfa(str, "%.02f", stats_dist_get_variance(stats));
+		else if (field[0] == '%') {
+			str_printfa(str, "%"PRIu64,
+				    stats_dist_get_percentile(stats, strtod(field+1, NULL)/100.0));
+		} else {
+			/* return unknown fields as empty */
+		}
+	}
+}
+
+static void reader_client_dump_metric(string_t *str, const struct metric *metric,
+				      const char *const *fields)
+{
+	reader_client_dump_stats(str, metric->duration_stats, fields);
+	for (unsigned int i = 0; i < metric->fields_count; i++) {
+		str_append_c(str, '\t');
+		str_append_tabescaped(str, metric->fields[i].field_key);
+		reader_client_dump_stats(str, metric->fields[i].stats, fields);
+	}
+	str_append_c(str, '\n');
+}
+
+static void
+reader_client_append_sub_name(string_t *str, const char *sub_name)
+{
+	for (; *sub_name != '\0'; sub_name++) {
+		switch (*sub_name) {
+		case '\t':
+		case '\n':
+		case '\r':
+		case ' ':
+			str_append_c(str, '_');
+			break;
+		default:
+			str_append_c(str, *sub_name);
+		}
+	}
+}
+
+static void
+reader_client_dump_sub_metrics(struct ostream *output, const struct metric *metric,
+			       const char *sub_name, const char *const *fields)
+{
+	size_t root_pos, name_pos;
+	struct metric *const *sub_metrics;
+	if (!array_is_created(&metric->sub_metrics))
+		return;
+	string_t *str = t_str_new(128);
+	reader_client_append_sub_name(str, sub_name);
+	str_append_c(str, '_');
+	root_pos = str->used;
+
+	array_foreach(&metric->sub_metrics, sub_metrics) {
+		str_truncate(str, root_pos);
+		reader_client_append_sub_name(str, (*sub_metrics)->sub_name);
+		name_pos = str->used;
+		reader_client_dump_metric(str, *sub_metrics, fields);
+		o_stream_nsend(output, str_data(str), str_len(str));
+		str_truncate(str, name_pos);
+		reader_client_dump_sub_metrics(output, *sub_metrics,
+					       str_c(str), fields);
+	}
+}
+
+static int
+reader_client_input_dump(struct reader_client *client, const char *const *args)
+{
+	struct stats_metrics_iter *iter;
+	const struct metric *metric;
+
+	o_stream_cork(client->conn.output);
+	iter = stats_metrics_iterate_init(stats_metrics);
+	while ((metric = stats_metrics_iterate(iter)) != NULL) T_BEGIN {
+		string_t *str = t_str_new(128);
+		str_append_tabescaped(str, metric->name);
+		reader_client_dump_metric(str, metric, args);
+		o_stream_nsend(client->conn.output, str_data(str), str_len(str));
+		reader_client_dump_sub_metrics(client->conn.output, metric,
+					       metric->name, args);
+	} T_END;
+	o_stream_nsend(client->conn.output, "\n", 1);
+	stats_metrics_iterate_deinit(&iter);
+	o_stream_uncork(client->conn.output);
+	return 1;
+}
+
+static int
+reader_client_input_dump_reset(struct reader_client *client,
+			       const char *const *args)
+{
+	(void)reader_client_input_dump(client, args);
+	stats_metrics_reset(stats_metrics);
+	return 1;
+}
+
+static int
+reader_client_input_metrics_add(struct reader_client *client,
+				const char *const *args)
+{
+	const char *error;
+
+	if (str_array_length(args) < 7) {
+		e_error(client->conn.event, "METRICS-ADD: Not enough parameters");
+		return -1;
+	}
+
+	struct stats_metric_settings set = {
+		.metric_name = args[0],
+		.description = args[1],
+		.fields = args[2],
+		.group_by = args[3],
+		.filter = args[4],
+		.exporter = args[5],
+		.exporter_include = args[6],
+	};
+	o_stream_cork(client->conn.output);
+	if (stats_metrics_add_dynamic(stats_metrics, &set, &error)) {
+		client_writer_update_connections();
+		o_stream_nsend(client->conn.output, "+", 1);
+	} else {
+		o_stream_nsend(client->conn.output, "-", 1);
+		o_stream_nsend_str(client->conn.output, "METRICS-ADD: ");
+		o_stream_nsend_str(client->conn.output, error);
+	}
+	o_stream_nsend(client->conn.output, "\n", 1);
+	o_stream_uncork(client->conn.output);
+	return 1;
+}
+
+static int
+reader_client_input_metrics_remove(struct reader_client *client,
+				   const char *const *args)
+{
+	if (str_array_length(args) < 1) {
+		e_error(client->conn.event, "METRICS-REMOVE: Not enough parameters");
+		return -1;
+	}
+
+	if (stats_metrics_remove_dynamic(stats_metrics, args[0])) {
+		client_writer_update_connections();
+		o_stream_nsend(client->conn.output, "+\n", 2);
+	} else {
+		o_stream_nsend_str(client->conn.output,
+				   t_strdup_printf("-metrics '%s' not found\n", args[0]));
+	}
+	return 1;
+}
+
+static int
+reader_client_input_args(struct connection *conn, const char *const *args)
+{
+	struct reader_client *client = (struct reader_client *)conn;
+	const char *cmd = args[0];
+
+	if (cmd == NULL) {
+		i_error("Client sent empty line");
+		return 1;
+	}
+	args++;
+	if (strcmp(cmd, "DUMP") == 0)
+		return reader_client_input_dump(client, args);
+	else if (strcmp(cmd, "METRICS-ADD") == 0)
+		return reader_client_input_metrics_add(client, args);
+	else if (strcmp(cmd, "METRICS-REMOVE") == 0)
+		return reader_client_input_metrics_remove(client, args);
+	else if (strcmp(cmd, "DUMP-RESET") == 0)
+		return reader_client_input_dump_reset(client, args);
+	return 1;
+}
+
+static struct connection_settings client_set = {
+	.service_name_in = "stats-reader-client",
+	.service_name_out = "stats-reader-server",
+	.major_version = 2,
+	.minor_version = 0,
+
+	.input_max_size = 1024,
+	.output_max_size = SIZE_MAX,
+	.client = FALSE,
+};
+
+static const struct connection_vfuncs client_vfuncs = {
+	.destroy = reader_client_destroy,
+	.input_args = reader_client_input_args,
+};
+
+void client_readers_init(void)
+{
+	reader_clients = connection_list_init(&client_set, &client_vfuncs);
+}
+
+void client_readers_deinit(void)
+{
+	connection_list_deinit(&reader_clients);
+}
diff --git a/src/stats/client-reader.h b/src/stats/client-reader.h
new file mode 100644
index 0000000..2acab19
--- /dev/null
+++ b/src/stats/client-reader.h
@@ -0,0 +1,11 @@
+#ifndef CLIENT_READER_H
+#define CLIENT_READER_H
+
+struct stats_metrics;
+
+void client_reader_create(int fd);
+
+void client_readers_init(void);
+void client_readers_deinit(void);
+
+#endif
diff --git a/src/stats/client-writer.c b/src/stats/client-writer.c
new file mode 100644
index 0000000..40772cf
--- /dev/null
+++ b/src/stats/client-writer.c
@@ -0,0 +1,373 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "array.h"
+#include "llist.h"
+#include "hash.h"
+#include "str.h"
+#include "strescape.h"
+#include "lib-event-private.h"
+#include "event-filter.h"
+#include "ostream.h"
+#include "connection.h"
+#include "master-service.h"
+#include "stats-event-category.h"
+#include "stats-metrics.h"
+#include "stats-settings.h"
+#include "client-writer.h"
+
+#define STATS_UPDATE_CLIENTS_DELAY_MSECS 1000
+
+struct stats_event {
+	struct stats_event *prev, *next;
+
+	uint64_t id;
+	struct event *event;
+};
+
+struct writer_client {
+	struct connection conn;
+
+	struct stats_event *events;
+	HASH_TABLE(struct stats_event *, struct stats_event *) events_hash;
+};
+
+static struct timeout *to_update_clients;
+static struct connection_list *writer_clients = NULL;
+
+static void client_writer_send_handshake(struct writer_client *client)
+{
+	string_t *filter = t_str_new(128);
+	string_t *str = t_str_new(128);
+
+	event_filter_export(stats_metrics_get_event_filter(stats_metrics), filter);
+
+	str_append(str, "FILTER\t");
+	str_append_tabescaped(str, str_c(filter));
+	str_append_c(str, '\n');
+	o_stream_nsend(client->conn.output, str_data(str), str_len(str));
+}
+
+static unsigned int stats_event_hash(const struct stats_event *event)
+{
+	return (unsigned int)event->id;
+}
+
+static int stats_event_cmp(const struct stats_event *event1,
+			   const struct stats_event *event2)
+{
+	return event1->id == event2->id ? 0 : 1;
+}
+
+void client_writer_create(int fd)
+{
+	struct writer_client *client;
+
+	client = i_new(struct writer_client, 1);
+	hash_table_create(&client->events_hash, default_pool, 0,
+			  stats_event_hash, stats_event_cmp);
+
+	connection_init_server(writer_clients, &client->conn,
+			       "stats", fd, fd);
+	client_writer_send_handshake(client);
+}
+
+static void writer_client_destroy(struct connection *conn)
+{
+	struct writer_client *client = (struct writer_client *)conn;
+	struct stats_event *event, *next;
+
+	for (event = client->events; event != NULL; event = next) {
+		next = event->next;
+		event_unref(&event->event);
+		i_free(event);
+	}
+	hash_table_destroy(&client->events_hash);
+
+	connection_deinit(conn);
+	i_free(conn);
+
+	master_service_client_connection_destroyed(master_service);
+}
+
+static struct stats_event *
+writer_client_find_event(struct writer_client *client, uint64_t event_id)
+{
+	struct stats_event lookup_event = { .id = event_id };
+	return hash_table_lookup(client->events_hash, &lookup_event);
+}
+
+static bool
+writer_client_run_event(struct writer_client *client,
+			uint64_t parent_event_id, const char *const *args,
+			struct event **event_r, const char **error_r)
+{
+	struct event *parent_event;
+	unsigned int log_type;
+
+	if (parent_event_id == 0)
+		parent_event = NULL;
+	else {
+		struct stats_event *stats_parent_event =
+			writer_client_find_event(client, parent_event_id);
+		if (stats_parent_event == NULL) {
+			*error_r = "Unknown parent event ID";
+			return FALSE;
+		}
+		parent_event = stats_parent_event->event;
+	}
+	if (args[0] == NULL || str_to_uint(args[0], &log_type) < 0 ||
+	    log_type >= LOG_TYPE_COUNT) {
+		*error_r = "Invalid log type";
+		return FALSE;
+	}
+	const struct failure_context ctx = {
+		.type = (enum log_type)log_type
+	};
+	args++;
+
+	struct event *event = event_create(parent_event);
+	if (!event_import_unescaped(event, args, error_r)) {
+		event_unref(&event);
+		return FALSE;
+	}
+	stats_metrics_event(stats_metrics, event, &ctx);
+	*event_r = event;
+	return TRUE;
+}
+
+static bool
+writer_client_input_event(struct writer_client *client,
+			  const char *const *args, const char **error_r)
+{
+	struct event *event, *global_event = NULL;
+	uint64_t parent_event_id, global_event_id;
+	bool ret;
+
+	if (args[1] == NULL || str_to_uint64(args[0], &global_event_id) < 0) {
+		*error_r = "Invalid global event ID";
+		return FALSE;
+	}
+	if (args[1] == NULL || str_to_uint64(args[1], &parent_event_id) < 0) {
+		*error_r = "Invalid parent ID";
+		return FALSE;
+	}
+
+	if (global_event_id != 0) {
+		struct stats_event *stats_global_event =
+			writer_client_find_event(client, global_event_id);
+		if (stats_global_event == NULL) {
+			*error_r = "Unknown global event ID";
+			return FALSE;
+		}
+		global_event = stats_global_event->event;
+		event_push_global(global_event);
+	}
+
+	ret = writer_client_run_event(client, parent_event_id, args+2,
+				      &event, error_r);
+	if (global_event != NULL)
+		event_pop_global(global_event);
+	if (!ret)
+		return FALSE;
+	event_unref(&event);
+	return TRUE;
+}
+
+static bool
+writer_client_input_event_begin(struct writer_client *client,
+				const char *const *args, const char **error_r)
+{
+	struct event *event;
+	struct stats_event *stats_event;
+	uint64_t event_id, parent_event_id;
+
+	if (args[0] == NULL || args[1] == NULL ||
+	    str_to_uint64(args[0], &event_id) < 0 ||
+	    str_to_uint64(args[1], &parent_event_id) < 0) {
+		*error_r = "Invalid event IDs";
+		return FALSE;
+	}
+	if (writer_client_find_event(client, event_id) != NULL) {
+		*error_r = "Duplicate event ID";
+		return FALSE;
+	}
+	if (!writer_client_run_event(client, parent_event_id, args+2, &event, error_r))
+		return FALSE;
+
+	stats_event = i_new(struct stats_event, 1);
+	stats_event->id = event_id;
+	stats_event->event = event;
+	DLLIST_PREPEND(&client->events, stats_event);
+	hash_table_insert(client->events_hash, stats_event, stats_event);
+	return TRUE;
+}
+
+static bool
+writer_client_input_event_update(struct writer_client *client,
+				 const char *const *args, const char **error_r)
+{
+	struct stats_event *stats_event, *parent_stats_event;
+	struct event *parent_event;
+	uint64_t event_id, parent_event_id;
+
+	if (args[0] == NULL || args[1] == NULL ||
+	    str_to_uint64(args[0], &event_id) < 0 ||
+	    str_to_uint64(args[1], &parent_event_id) < 0) {
+		*error_r = "Invalid event IDs";
+		return FALSE;
+	}
+	stats_event = writer_client_find_event(client, event_id);
+	if (stats_event == NULL) {
+		*error_r = "Unknown event ID";
+		return FALSE;
+	}
+	parent_stats_event = parent_event_id == 0 ? NULL :
+		writer_client_find_event(client, parent_event_id);
+	parent_event = parent_stats_event == NULL ? NULL :
+		parent_stats_event->event;
+	if (stats_event->event->parent != parent_event) {
+		*error_r = "Event unexpectedly changed parent";
+		return FALSE;
+	}
+	return event_import_unescaped(stats_event->event, args+2, error_r);
+}
+
+static bool
+writer_client_input_event_end(struct writer_client *client,
+			      const char *const *args, const char **error_r)
+{
+	struct stats_event *stats_event;
+	uint64_t event_id;
+
+	if (args[0] == NULL || str_to_uint64(args[0], &event_id) < 0) {
+		*error_r = "Invalid event ID";
+		return FALSE;
+	}
+	stats_event = writer_client_find_event(client, event_id);
+	if (stats_event == NULL) {
+		*error_r = "Unknown event ID";
+		return FALSE;
+	}
+
+	DLLIST_REMOVE(&client->events, stats_event);
+	hash_table_remove(client->events_hash, stats_event);
+	event_unref(&stats_event->event);
+	i_free(stats_event);
+	return TRUE;
+}
+
+static bool
+writer_client_input_category(struct writer_client *client ATTR_UNUSED,
+			     const char *const *args, const char **error_r)
+{
+	struct event_category *category, *parent;
+
+	if (args[0] == NULL) {
+		*error_r = "Missing category name";
+		return FALSE;
+	}
+	if (args[1] == NULL)
+		parent = NULL;
+	else if ((parent = event_category_find_registered(args[1])) == NULL) {
+		*error_r = "Unknown parent category";
+		return FALSE;
+	}
+
+	category = event_category_find_registered(args[0]);
+	if (category == NULL) {
+		/* new category - create */
+		stats_event_category_register(args[0], parent);
+	} else if (category->parent != parent) {
+		*error_r = t_strdup_printf(
+			"Category parent '%s' changed to '%s'",
+			category->parent == NULL ? "" : category->parent->name,
+			parent == NULL ? "" : parent->name);
+		return FALSE;
+	} else {
+		/* duplicate - ignore */
+		return TRUE;
+	}
+	return TRUE;
+}
+
+static int
+writer_client_input_args(struct connection *conn, const char *const *args)
+{
+	struct writer_client *client = (struct writer_client *)conn;
+	const char *error, *cmd = args[0];
+	bool ret;
+
+	if (cmd == NULL) {
+		i_error("Client sent empty line");
+		return 1;
+	}
+	if (strcmp(cmd, "EVENT") == 0)
+		ret = writer_client_input_event(client, args+1, &error);
+	else if (strcmp(cmd, "BEGIN") == 0)
+		ret = writer_client_input_event_begin(client, args+1, &error);
+	else if (strcmp(cmd, "UPDATE") == 0)
+		ret = writer_client_input_event_update(client, args+1, &error);
+	else if (strcmp(cmd, "END") == 0)
+		ret = writer_client_input_event_end(client, args+1, &error);
+	else if (strcmp(cmd, "CATEGORY") == 0)
+		ret = writer_client_input_category(client, args+1, &error);
+	else {
+		error = "Unknown command";
+		ret = FALSE;
+	}
+	if (!ret) {
+		i_error("Client sent invalid input for %s: %s (input: %s)",
+			cmd, error, t_strarray_join(args, "\t"));
+		return -1;
+	}
+	return 1;
+}
+
+static struct connection_settings client_set = {
+	.service_name_in = "stats-client",
+	.service_name_out = "stats-server",
+	.major_version = 4,
+	.minor_version = 0,
+
+	.input_max_size = 1024*128, /* "big enough" */
+	.output_max_size = SIZE_MAX,
+	.client = FALSE,
+};
+
+static const struct connection_vfuncs client_vfuncs = {
+	.destroy = writer_client_destroy,
+	.input_args = writer_client_input_args,
+};
+
+static void
+client_writer_update_connections_internal(void *context ATTR_UNUSED)
+{
+	struct connection *conn;
+	for (conn = writer_clients->connections; conn != NULL; conn = conn->next) {
+		struct writer_client *client =
+			container_of(conn, struct writer_client, conn);
+		client_writer_send_handshake(client);
+	}
+	timeout_remove(&to_update_clients);
+}
+
+void client_writer_update_connections(void)
+{
+	if (to_update_clients != NULL)
+		return;
+	to_update_clients = timeout_add(STATS_UPDATE_CLIENTS_DELAY_MSECS,
+					client_writer_update_connections_internal,
+					NULL);
+}
+
+void client_writers_init(void)
+{
+	writer_clients = connection_list_init(&client_set, &client_vfuncs);
+}
+
+void client_writers_deinit(void)
+{
+	timeout_remove(&to_update_clients);
+	connection_list_deinit(&writer_clients);
+}
diff --git a/src/stats/client-writer.h b/src/stats/client-writer.h
new file mode 100644
index 0000000..a88de38
--- /dev/null
+++ b/src/stats/client-writer.h
@@ -0,0 +1,13 @@
+#ifndef CLIENT_WRITER_H
+#define CLIENT_WRITER_H
+
+struct stats_metrics;
+
+void client_writer_create(int fd);
+
+void client_writer_update_connections(void);
+
+void client_writers_init(void);
+void client_writers_deinit(void);
+
+#endif
diff --git a/src/stats/event-exporter-fmt-json.c b/src/stats/event-exporter-fmt-json.c
new file mode 100644
index 0000000..25c6116
--- /dev/null
+++ b/src/stats/event-exporter-fmt-json.c
@@ -0,0 +1,249 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "array.h"
+#include "lib-event-private.h"
+#include "event-exporter.h"
+#include "str.h"
+#include "json-parser.h"
+#include "hostpid.h"
+
+static void append_str(string_t *dest, const char *str)
+{
+	str_append_c(dest, '"');
+	json_append_escaped(dest, str);
+	str_append_c(dest, '"');
+}
+
+static void append_str_max_len(string_t *dest, const char *str,
+			       const struct metric_export_info *info)
+{
+	str_append_c(dest, '"');
+	if (info->exporter->format_max_field_len == 0)
+		json_append_escaped(dest, str);
+	else {
+		size_t len = strlen(str);
+		json_append_escaped_data(dest, (const unsigned char *)str,
+			I_MIN(len, info->exporter->format_max_field_len));
+		if (len > info->exporter->format_max_field_len)
+			str_append(dest, "...");
+	}
+	str_append_c(dest, '"');
+}
+
+static void
+append_strlist(string_t *dest, const ARRAY_TYPE(const_string) *strlist,
+	       const struct metric_export_info *info)
+{
+	const char *value;
+	bool first = TRUE;
+
+	str_append_c(dest, '[');
+	array_foreach_elem(strlist, value) {
+		if (first)
+			first = FALSE;
+		else
+			str_append_c(dest, ',');
+		append_str_max_len(dest, value, info);
+	}
+	str_append_c(dest, ']');
+}
+
+static void append_int(string_t *dest, intmax_t val)
+{
+	str_printfa(dest, "%jd", val);
+}
+
+static void append_time(string_t *dest, const struct timeval *time,
+			enum event_exporter_time_fmt fmt)
+{
+	switch (fmt) {
+	case EVENT_EXPORTER_TIME_FMT_NATIVE:
+		i_panic("JSON does not have a native date/time type");
+	case EVENT_EXPORTER_TIME_FMT_UNIX:
+		event_export_helper_fmt_unix_time(dest, time);
+		break;
+	case EVENT_EXPORTER_TIME_FMT_RFC3339:
+		str_append_c(dest, '"');
+		event_export_helper_fmt_rfc3339_time(dest, time);
+		str_append_c(dest, '"');
+		break;
+	}
+}
+
+static void append_field_value(string_t *dest, const struct event_field *field,
+			       const struct metric_export_info *info)
+{
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+		append_str_max_len(dest, field->value.str, info);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		append_int(dest, field->value.intmax);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+		append_time(dest, &field->value.timeval,
+			    info->exporter->time_format);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		append_strlist(dest, &field->value.strlist, info);
+		break;
+	}
+}
+
+static void json_export_name(string_t *dest, struct event *event,
+			     const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_NAME) == 0)
+		return;
+
+	append_str(dest, "event");
+	str_append_c(dest, ':');
+	append_str(dest, event->sending_name);
+	str_append_c(dest, ',');
+}
+
+static void json_export_hostname(string_t *dest,
+				 const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_HOSTNAME) == 0)
+		return;
+
+	append_str(dest, "hostname");
+	str_append_c(dest, ':');
+	append_str(dest, my_hostname);
+	str_append_c(dest, ',');
+}
+
+static void json_export_timestamps(string_t *dest, struct event *event,
+				   const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_TIMESTAMPS) == 0)
+		return;
+
+	append_str(dest, "start_time");
+	str_append_c(dest, ':');
+	append_time(dest, &event->tv_created, info->exporter->time_format);
+	str_append_c(dest, ',');
+
+	append_str(dest, "end_time");
+	str_append_c(dest, ':');
+	append_time(dest, &ioloop_timeval, info->exporter->time_format);
+	str_append_c(dest, ',');
+}
+
+static void json_export_categories(string_t *dest, struct event *event,
+				   const struct metric_export_info *info)
+{
+	struct event_category *const *cats;
+	unsigned int count;
+
+	if ((info->include & EVENT_EXPORTER_INCL_CATEGORIES) == 0)
+		return;
+
+	append_str(dest, "categories");
+	str_append(dest, ":[");
+
+	cats = event_get_categories(event, &count);
+	event_export_helper_fmt_categories(dest, cats, count,
+					   append_str, ",");
+
+	str_append(dest, "],");
+}
+
+static void json_export_fields(string_t *dest, struct event *event,
+			       const struct metric_export_info *info,
+			       const unsigned int fields_count,
+			       const struct metric_field *fields)
+{
+	bool appended = FALSE;
+
+	if ((info->include & EVENT_EXPORTER_INCL_FIELDS) == 0)
+		return;
+
+	append_str(dest, "fields");
+	str_append(dest, ":{");
+
+	if (fields_count == 0) {
+		/* include all fields */
+		const struct event_field *fields;
+		unsigned int count;
+
+		fields = event_get_fields(event, &count);
+
+		for (unsigned int i = 0; i < count; i++) {
+			const struct event_field *field = &fields[i];
+
+			append_str(dest, field->key);
+			str_append_c(dest, ':');
+			append_field_value(dest, field, info);
+			str_append_c(dest, ',');
+
+			appended = TRUE;
+		}
+	} else {
+		for (unsigned int i = 0; i < fields_count; i++) {
+			const char *name = fields[i].field_key;
+			const struct event_field *field;
+
+			field = event_find_field_recursive(event, name);
+			if (field == NULL)
+				continue; /* doesn't exist, skip it */
+
+			append_str(dest, name);
+			str_append_c(dest, ':');
+			append_field_value(dest, field, info);
+			str_append_c(dest, ',');
+
+			appended = TRUE;
+		}
+	}
+
+	/* remove trailing comma */
+	if (appended)
+		str_truncate(dest, str_len(dest) - 1);
+
+	str_append(dest, "},");
+}
+
+/*
+ * Serialize the event as:
+ *
+ * {
+ *	"name": <event name>,
+ *	"hostname": <hostname>,
+ *	"start_time": <event creation timestamp>,
+ *	"end_time": <event export timestamp>,
+ *	"categories": [ <categories>, ... ],
+ *	"fields": {
+ *		<name>: <value>,
+ *		...
+ *	}
+ * }
+ *
+ */
+void event_export_fmt_json(const struct metric *metric,
+			   struct event *event, buffer_t *dest)
+{
+	const struct metric_export_info *info = &metric->export_info;
+
+	if (info->include == EVENT_EXPORTER_INCL_NONE) {
+		str_append(dest, "{}");
+		return;
+	}
+
+	str_append_c(dest, '{');
+
+	json_export_name(dest, event, info);
+	json_export_hostname(dest, info);
+	json_export_timestamps(dest, event, info);
+	json_export_categories(dest, event, info);
+	json_export_fields(dest, event, info, metric->fields_count,
+			   metric->fields);
+
+	/* remove trailing comma */
+	str_truncate(dest, str_len(dest) - 1);
+
+	str_append_c(dest, '}');
+}
diff --git a/src/stats/event-exporter-fmt-none.c b/src/stats/event-exporter-fmt-none.c
new file mode 100644
index 0000000..cd052c2
--- /dev/null
+++ b/src/stats/event-exporter-fmt-none.c
@@ -0,0 +1,12 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "event-exporter.h"
+
+void event_export_fmt_none(const struct metric *metric ATTR_UNUSED,
+			   struct event *event ATTR_UNUSED,
+			   buffer_t *dest ATTR_UNUSED)
+{
+	/* nothing to do */
+}
diff --git a/src/stats/event-exporter-fmt-tab-text.c b/src/stats/event-exporter-fmt-tab-text.c
new file mode 100644
index 0000000..49a065b
--- /dev/null
+++ b/src/stats/event-exporter-fmt-tab-text.c
@@ -0,0 +1,212 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "array.h"
+#include "lib-event-private.h"
+#include "event-exporter.h"
+#include "str.h"
+#include "strescape.h"
+#include "hostpid.h"
+
+static void append_strlist(string_t *dest, const ARRAY_TYPE(const_string) *strlist)
+{
+	string_t *str = t_str_new(64);
+	const char *value;
+	bool first = TRUE;
+
+	/* append the strings first escaped into a temporary string */
+	array_foreach_elem(strlist, value) {
+		if (first)
+			first = FALSE;
+		else
+			str_append_c(str, '\t');
+		str_append_tabescaped(str, value);
+	}
+	/* append the temporary string (double-)escaped as the value */
+	str_append_tabescaped(dest, str_c(str));
+}
+
+static void append_int(string_t *dest, intmax_t val)
+{
+	str_printfa(dest, "%jd", val);
+}
+
+static void append_time(string_t *dest, const struct timeval *time,
+			enum event_exporter_time_fmt fmt)
+{
+	switch (fmt) {
+	case EVENT_EXPORTER_TIME_FMT_NATIVE:
+		i_panic("tab-text format does not have a native date/time type");
+	case EVENT_EXPORTER_TIME_FMT_UNIX:
+		event_export_helper_fmt_unix_time(dest, time);
+		break;
+	case EVENT_EXPORTER_TIME_FMT_RFC3339:
+		event_export_helper_fmt_rfc3339_time(dest, time);
+		break;
+	}
+}
+
+static void append_field_str(string_t *dest, const char *str,
+			     const struct metric_export_info *info)
+{
+	if (info->exporter->format_max_field_len == 0)
+		str_append_tabescaped(dest, str);
+	else {
+		size_t len = strlen(str);
+		str_append_tabescaped_n(dest, (const unsigned char *)str,
+			I_MIN(len, info->exporter->format_max_field_len));
+		if (len > info->exporter->format_max_field_len)
+			str_append(dest, "...");
+	}
+}
+
+static void append_field_value(string_t *dest, const struct event_field *field,
+			       const struct metric_export_info *info)
+{
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+		append_field_str(dest, field->value.str, info);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		append_int(dest, field->value.intmax);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+		append_time(dest, &field->value.timeval,
+			    info->exporter->time_format);
+		break;
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		append_strlist(dest, &field->value.strlist);
+		break;
+	}
+}
+
+static void tabtext_export_name(string_t *dest, struct event *event,
+				const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_NAME) == 0)
+		return;
+
+	str_append(dest, "event:");
+	str_append_tabescaped(dest, event->sending_name);
+	str_append_c(dest, '\t');
+}
+
+static void tabtext_export_hostname(string_t *dest,
+				    const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_HOSTNAME) == 0)
+		return;
+
+	str_append(dest, "hostname:");
+	str_append_tabescaped(dest, my_hostname);
+	str_append_c(dest, '\t');
+}
+
+static void tabtext_export_timestamps(string_t *dest, struct event *event,
+				      const struct metric_export_info *info)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_TIMESTAMPS) == 0)
+		return;
+
+	str_append(dest, "start_time:");
+	append_time(dest, &event->tv_created, info->exporter->time_format);
+	str_append(dest, "\tend_time:");
+	append_time(dest, &ioloop_timeval, info->exporter->time_format);
+	str_append_c(dest, '\t');
+}
+
+static void append_category(string_t *dest, const char *cat)
+{
+	str_append(dest, "category:");
+	str_append_tabescaped(dest, cat);
+}
+
+static void tabtext_export_categories(string_t *dest, struct event *event,
+				      const struct metric_export_info *info)
+{
+	struct event_category *const *cats;
+	unsigned int count;
+
+	if ((info->include & EVENT_EXPORTER_INCL_CATEGORIES) == 0)
+		return;
+
+	cats = event_get_categories(event, &count);
+	event_export_helper_fmt_categories(dest, cats, count,
+					   append_category, "\t");
+
+	str_append_c(dest, '\t'); /* extra \t to have something to remove later */
+}
+
+static void tabtext_export_fields(string_t *dest, struct event *event,
+				  const struct metric_export_info *info,
+				  const unsigned int fields_count,
+				  const struct metric_field *fields)
+{
+	if ((info->include & EVENT_EXPORTER_INCL_FIELDS) == 0)
+		return;
+
+	if (fields_count == 0) {
+		/* include all fields */
+		const struct event_field *fields;
+		unsigned int count;
+
+		fields = event_get_fields(event, &count);
+
+		for (unsigned int i = 0; i < count; i++) {
+			const struct event_field *field = &fields[i];
+
+			str_append(dest, "field:");
+			str_append_tabescaped(dest, field->key);
+			str_append_c(dest, '=');
+			append_field_value(dest, field, info);
+			str_append_c(dest, '\t');
+		}
+	} else {
+		for (unsigned int i = 0; i < fields_count; i++) {
+			const char *name = fields[i].field_key;
+			const struct event_field *field;
+
+			field = event_find_field_recursive(event, name);
+			if (field == NULL)
+				continue; /* doesn't exist, skip it */
+
+			str_append(dest, "field:");
+			str_append_tabescaped(dest, name);
+			str_append_c(dest, '=');
+			append_field_value(dest, field, info);
+			str_append_c(dest, '\t');
+		}
+	}
+}
+
+/*
+ * Serialize the event as tab delimited collection of the following:
+ *
+ *    event:<event name>
+ *    hostname:<tab escaped hostname>
+ *    start_time:<event creation timestamp>
+ *    end_time:<event export timestamp>
+ *    category:<category>
+ *    field:<name>=<tab escaped value>
+ *
+ * Note: cat and field can occur multiple times.
+ */
+void event_export_fmt_tabescaped_text(const struct metric *metric,
+				      struct event *event, buffer_t *dest)
+{
+	const struct metric_export_info *info = &metric->export_info;
+
+	if (info->include == EVENT_EXPORTER_INCL_NONE)
+		return;
+
+	tabtext_export_name(dest, event, info);
+	tabtext_export_hostname(dest, info);
+	tabtext_export_timestamps(dest, event, info);
+	tabtext_export_categories(dest, event, info);
+	tabtext_export_fields(dest, event, info, metric->fields_count,
+			      metric->fields);
+
+	/* remove trailing tab */
+	str_truncate(dest, str_len(dest) - 1);
+}
diff --git a/src/stats/event-exporter-fmt.c b/src/stats/event-exporter-fmt.c
new file mode 100644
index 0000000..a4ec5a8
--- /dev/null
+++ b/src/stats/event-exporter-fmt.c
@@ -0,0 +1,78 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "hash.h"
+#include "ioloop.h"
+#include "event-exporter.h"
+
+void event_export_helper_fmt_unix_time(string_t *dest,
+				       const struct timeval *time)
+{
+	str_printfa(dest, "%"PRIdTIME_T".%06u", time->tv_sec,
+		    (unsigned int) time->tv_usec);
+}
+
+void event_export_helper_fmt_rfc3339_time(string_t *dest,
+					  const struct timeval *time)
+{
+	const struct tm *tm;
+
+	tm = gmtime(&time->tv_sec);
+
+	str_printfa(dest, "%04d-%02d-%02dT%02d:%02d:%02d.%06luZ",
+		    tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
+		    tm->tm_hour, tm->tm_min, tm->tm_sec,
+		    time->tv_usec);
+}
+
+HASH_TABLE_DEFINE_TYPE(category_set, void *, const struct event_category *);
+
+static void insert_category(HASH_TABLE_TYPE(category_set) hash,
+			    const struct event_category * const cat)
+{
+	/* insert this category (key == the unique internal pointer) */
+	hash_table_update(hash, cat->internal, cat);
+
+	/* insert parent's categories */
+	if (cat->parent != NULL)
+		insert_category(hash, cat->parent);
+}
+
+void event_export_helper_fmt_categories(string_t *dest,
+					struct event_category * const *cats,
+					unsigned int count,
+					void (*append)(string_t *, const char *),
+					const char *separator)
+{
+	HASH_TABLE_TYPE(category_set) hash;
+	struct hash_iterate_context *iter;
+	const struct event_category *cat;
+	void *key ATTR_UNUSED;
+	unsigned int i;
+	bool first = TRUE;
+
+	if (count == 0)
+		return;
+
+	hash_table_create_direct(&hash, pool_datastack_create(),
+				 3 * count /* estimate */);
+
+	/* insert all the categories into the hash table */
+	for (i = 0; i < count; i++)
+		insert_category(hash, cats[i]);
+
+	/* output each category from hash table */
+	iter = hash_table_iterate_init(hash);
+	while (hash_table_iterate(iter, hash, &key, &cat)) {
+		if (!first)
+			str_append(dest, separator);
+
+		append(dest, cat->name);
+
+		first = FALSE;
+	}
+	hash_table_iterate_deinit(&iter);
+
+	hash_table_destroy(&hash);
+}
diff --git a/src/stats/event-exporter-transport-drop.c b/src/stats/event-exporter-transport-drop.c
new file mode 100644
index 0000000..943f305
--- /dev/null
+++ b/src/stats/event-exporter-transport-drop.c
@@ -0,0 +1,9 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "event-exporter.h"
+
+void event_export_transport_drop(const struct exporter *exporter ATTR_UNUSED,
+				 const buffer_t *buf ATTR_UNUSED)
+{
+}
diff --git a/src/stats/event-exporter-transport-http-post.c b/src/stats/event-exporter-transport-http-post.c
new file mode 100644
index 0000000..6d328cd
--- /dev/null
+++ b/src/stats/event-exporter-transport-http-post.c
@@ -0,0 +1,76 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "str.h"
+#include "event-exporter.h"
+#include "http-client.h"
+#include "iostream-ssl.h"
+#include "master-service.h"
+#include "master-service-ssl-settings.h"
+
+/* the http client used to export all events with exporter=http-post */
+static struct http_client *exporter_http_client;
+
+void event_export_transport_http_post_deinit(void)
+{
+	if (exporter_http_client != NULL)
+		http_client_deinit(&exporter_http_client);
+}
+
+static void response_fxn(const struct http_response *response,
+			 void *context ATTR_UNUSED)
+{
+	static time_t last_log;
+	static unsigned suppressed;
+
+	if (http_response_is_success(response))
+		return;
+
+	if (last_log == ioloop_time) {
+		suppressed++;
+		return; /* don't spam the log */
+	}
+
+	if (suppressed == 0)
+		i_error("Failed to export event via HTTP POST: %d %s",
+			response->status, response->reason);
+	else
+		i_error("Failed to export event via HTTP POST: %d %s (%u more errors suppressed)",
+			response->status, response->reason, suppressed);
+
+	last_log = ioloop_time;
+	suppressed = 0;
+}
+
+void event_export_transport_http_post(const struct exporter *exporter,
+				      const buffer_t *buf)
+{
+	struct http_client_request *req;
+
+	if (exporter_http_client == NULL) {
+		const struct master_service_ssl_settings *master_ssl_set =
+			master_service_ssl_settings_get(master_service);
+		struct ssl_iostream_settings ssl_set;
+
+		struct http_client_settings set = {
+			.dns_client_socket_path = "dns-client",
+		};
+		if (master_ssl_set != NULL) {
+			master_service_ssl_client_settings_to_iostream_set(
+				master_ssl_set, pool_datastack_create(),
+				&ssl_set);
+			set.ssl = &ssl_set;
+		}
+		exporter_http_client = http_client_init(&set);
+	}
+
+	req = http_client_request_url_str(exporter_http_client, "POST",
+					  exporter->transport_args,
+					  response_fxn, NULL);
+	http_client_request_add_header(req, "Content-Type", exporter->format_mime_type);
+	http_client_request_set_payload_data(req, buf->data, buf->used);
+
+	http_client_request_set_timeout_msecs(req, exporter->transport_timeout);
+	http_client_request_submit(req);
+}
diff --git a/src/stats/event-exporter-transport-log.c b/src/stats/event-exporter-transport-log.c
new file mode 100644
index 0000000..a0cf67f
--- /dev/null
+++ b/src/stats/event-exporter-transport-log.c
@@ -0,0 +1,12 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "str.h"
+#include "event-exporter.h"
+
+void event_export_transport_log(const struct exporter *exporter ATTR_UNUSED,
+				const buffer_t *buf)
+{
+	i_info("%.*s", (int)buf->used, (const char *)buf->data);
+}
diff --git a/src/stats/event-exporter.h b/src/stats/event-exporter.h
new file mode 100644
index 0000000..64bb708
--- /dev/null
+++ b/src/stats/event-exporter.h
@@ -0,0 +1,31 @@
+#ifndef EVENT_EXPORTER_H
+#define EVENT_EXPORTER_H
+
+#include "stats-metrics.h"
+
+/* fmt functions */
+void event_export_fmt_json(const struct metric *metric, struct event *event, buffer_t *dest);
+void event_export_fmt_none(const struct metric *metric, struct event *event, buffer_t *dest);
+void event_export_fmt_tabescaped_text(const struct metric *metric, struct event *event, buffer_t *dest);
+
+/* transport functions */
+void event_export_transport_drop(const struct exporter *exporter, const buffer_t *buf);
+void event_export_transport_http_post(const struct exporter *exporter, const buffer_t *buf);
+void event_export_transport_http_post_deinit(void);
+void event_export_transport_log(const struct exporter *exporter, const buffer_t *buf);
+
+/* append a microsecond resolution RFC3339 UTC timestamp */
+void event_export_helper_fmt_rfc3339_time(string_t *dest, const struct timeval *time);
+/* append a microsecond resolution unix timestamp in seconds (i.e., %u.%06u) */
+void event_export_helper_fmt_unix_time(string_t *dest, const struct timeval *time);
+/* append category names using 'append' function pointer, separated by 'separator' arg
+
+   The result has no duplicates regardless of if the array has any or if any
+   of the categories' ancestors are implictly or explicitly duplicated. */
+void event_export_helper_fmt_categories(string_t *dest,
+					struct event_category *const *cats,
+					unsigned int count,
+					void (*append)(string_t *, const char *),
+					const char *separator);
+
+#endif
diff --git a/src/stats/main.c b/src/stats/main.c
new file mode 100644
index 0000000..15e0733
--- /dev/null
+++ b/src/stats/main.c
@@ -0,0 +1,117 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "restrict-access.h"
+#include "ioloop.h"
+#include "master-service.h"
+#include "master-service-settings.h"
+#include "stats-settings.h"
+#include "stats-event-category.h"
+#include "stats-metrics.h"
+#include "stats-service.h"
+#include "client-writer.h"
+#include "client-reader.h"
+#include "client-http.h"
+
+struct stats_metrics *stats_metrics;
+time_t stats_startup_time;
+
+static const struct stats_settings *stats_settings;
+
+static bool client_is_writer(const char *path)
+{
+	const char *name, *suffix;
+
+	name = strrchr(path, '/');
+	if (name == NULL)
+		name = path;
+	else
+		name++;
+
+	suffix = strrchr(name, '-');
+	if (suffix == NULL)
+		suffix = name;
+	else
+		suffix++;
+
+	return strcmp(suffix, "writer") == 0;
+}
+
+static void client_connected(struct master_service_connection *conn)
+{
+	if (strcmp(conn->name, "http") == 0)
+		client_http_create(conn);
+	else if (client_is_writer(conn->name))
+		client_writer_create(conn->fd);
+	else
+		client_reader_create(conn->fd);
+	master_service_client_connection_accept(conn);
+}
+
+static void stats_die(void)
+{
+	/* just wait for existing stats clients to disconnect from us */
+}
+
+static void main_preinit(void)
+{
+	restrict_access_by_env(RESTRICT_ACCESS_FLAG_ALLOW_ROOT, NULL);
+	restrict_access_allow_coredumps(TRUE);
+}
+
+static void main_init(void)
+{
+	void **sets = master_service_settings_get_others(master_service);
+	stats_settings = sets[0];
+
+	stats_startup_time = ioloop_time;
+	stats_metrics = stats_metrics_init(stats_settings);
+	stats_event_categories_init();
+	client_readers_init();
+	client_writers_init();
+	client_http_init(stats_settings);
+	stats_services_init();
+}
+
+static void main_deinit(void)
+{
+	stats_services_deinit();
+	client_readers_deinit();
+	client_writers_deinit();
+	client_http_deinit();
+	stats_event_categories_deinit();
+	stats_metrics_deinit(&stats_metrics);
+}
+
+int main(int argc, char *argv[])
+{
+	const struct setting_parser_info *set_roots[] = {
+		&stats_setting_parser_info,
+		NULL
+	};
+	const enum master_service_flags service_flags =
+		MASTER_SERVICE_FLAG_NO_SSL_INIT |
+		MASTER_SERVICE_FLAG_DONT_SEND_STATS |
+		MASTER_SERVICE_FLAG_NO_IDLE_DIE |
+		MASTER_SERVICE_FLAG_UPDATE_PROCTITLE;
+	const char *error;
+
+	master_service = master_service_init("stats", service_flags,
+					     &argc, &argv, "");
+	if (master_getopt(master_service) > 0)
+		return FATAL_DEFAULT;
+	if (master_service_settings_read_simple(master_service, set_roots,
+						&error) < 0)
+		i_fatal("Error reading configuration: %s", error);
+	master_service_init_log(master_service);
+	master_service_set_die_callback(master_service, stats_die);
+
+	main_preinit();
+
+	main_init();
+	master_service_init_finish(master_service);
+	master_service_run(master_service, client_connected);
+	main_deinit();
+	master_service_deinit(&master_service);
+        return 0;
+}
diff --git a/src/stats/stats-common.h b/src/stats/stats-common.h
new file mode 100644
index 0000000..09af424
--- /dev/null
+++ b/src/stats/stats-common.h
@@ -0,0 +1,10 @@
+#ifndef STATS_COMMON_H
+#define STATS_COMMON_H
+
+#include "lib.h"
+#include "stats-settings.h"
+
+extern struct stats_metrics *stats_metrics;
+extern time_t stats_startup_time;
+
+#endif
diff --git a/src/stats/stats-event-category.c b/src/stats/stats-event-category.c
new file mode 100644
index 0000000..cb01e8b
--- /dev/null
+++ b/src/stats/stats-event-category.c
@@ -0,0 +1,32 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "stats-event-category.h"
+
+static pool_t categories_pool;
+
+void stats_event_category_register(const char *name,
+				   struct event_category *parent)
+{
+	struct event_category *category =
+		p_new(categories_pool, struct event_category, 1);
+	category->parent = parent;
+	category->name = p_strdup(categories_pool, name);
+
+	/* Create a temporary event to register the category. A bit slower
+	   than necessary, but this code won't be called often. */
+	struct event *event = event_create(NULL);
+	struct event_category *categories[] = { category, NULL };
+	event_add_categories(event, categories);
+	event_unref(&event);
+}
+
+void stats_event_categories_init(void)
+{
+	categories_pool = pool_alloconly_create("categories", 1024);
+}
+
+void stats_event_categories_deinit(void)
+{
+	pool_unref(&categories_pool);
+}
diff --git a/src/stats/stats-event-category.h b/src/stats/stats-event-category.h
new file mode 100644
index 0000000..b56fc91
--- /dev/null
+++ b/src/stats/stats-event-category.h
@@ -0,0 +1,12 @@
+#ifndef STATS_EVENT_CATEGORY_H
+#define STATS_EVENT_CATEGORY_H
+
+/* Register a new event category if it doesn't already exist.
+   parent may be NULL. */
+void stats_event_category_register(const char *name,
+				   struct event_category *parent);
+
+void stats_event_categories_init(void);
+void stats_event_categories_deinit(void);
+
+#endif
diff --git a/src/stats/stats-metrics.c b/src/stats/stats-metrics.c
new file mode 100644
index 0000000..b582bb4
--- /dev/null
+++ b/src/stats/stats-metrics.c
@@ -0,0 +1,765 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "array.h"
+#include "str.h"
+#include "str-sanitize.h"
+#include "stats-dist.h"
+#include "time-util.h"
+#include "event-filter.h"
+#include "event-exporter.h"
+#include "stats-settings.h"
+#include "stats-metrics.h"
+#include "settings-parser.h"
+
+#include <ctype.h>
+
+#define LOG_EXPORTER_LONG_FIELD_TRUNCATE_LEN 1000
+
+struct stats_metrics {
+	pool_t pool;
+	struct event_filter *filter; /* stats & export */
+	ARRAY(struct exporter *) exporters;
+	ARRAY(struct metric *) metrics;
+};
+
+static void
+stats_metric_event(struct metric *metric, struct event *event, pool_t pool);
+static struct metric *
+stats_metric_sub_metric_alloc(struct metric *metric, const char *name, pool_t pool);
+static void stats_metric_free(struct metric *metric);
+
+static void stats_exporters_add_set(struct stats_metrics *metrics,
+				    const struct stats_exporter_settings *set)
+{
+	struct exporter *exporter;
+
+	exporter = p_new(metrics->pool, struct exporter, 1);
+	exporter->name = p_strdup(metrics->pool, set->name);
+	exporter->transport_args = p_strdup(metrics->pool, set->transport_args);
+	exporter->transport_timeout = set->transport_timeout;
+	exporter->time_format = set->parsed_time_format;
+
+	/* TODO: The following should be plugable.
+	 *
+	 * Note: Make sure to mirror any changes to the below code in
+	 * stats_exporter_settings_check().
+	 */
+	if (strcmp(set->format, "none") == 0) {
+		exporter->format = event_export_fmt_none;
+		exporter->format_mime_type = "application/octet-stream";
+	} else if (strcmp(set->format, "json") == 0) {
+		exporter->format = event_export_fmt_json;
+		exporter->format_mime_type = "application/json";
+	} else if (strcmp(set->format, "tab-text") == 0) {
+		exporter->format = event_export_fmt_tabescaped_text;
+		exporter->format_mime_type = "text/plain";
+	} else {
+		i_unreached();
+	}
+
+	/* TODO: The following should be plugable.
+	 *
+	 * Note: Make sure to mirror any changes to the below code in
+	 * stats_exporter_settings_check().
+	 */
+	if (strcmp(set->transport, "drop") == 0) {
+		exporter->transport = event_export_transport_drop;
+	} else if (strcmp(set->transport, "http-post") == 0) {
+		exporter->transport = event_export_transport_http_post;
+	} else if (strcmp(set->transport, "log") == 0) {
+		exporter->transport = event_export_transport_log;
+		exporter->format_max_field_len =
+			LOG_EXPORTER_LONG_FIELD_TRUNCATE_LEN;
+	} else {
+		i_unreached();
+	}
+
+	exporter->transport_args = set->transport_args;
+
+	array_push_back(&metrics->exporters, &exporter);
+}
+
+static struct metric *
+stats_metric_alloc(pool_t pool, const char *name,
+		   const struct stats_metric_settings *set,
+		   const char *const *fields)
+{
+	struct metric *metric = p_new(pool, struct metric, 1);
+	metric->name = p_strdup(pool, name);
+	metric->set = set;
+	metric->duration_stats = stats_dist_init();
+	metric->fields_count = str_array_length(fields);
+	if (metric->fields_count > 0) {
+		metric->fields = p_new(pool, struct metric_field,
+				       metric->fields_count);
+		for (unsigned int i = 0; i < metric->fields_count; i++) {
+			metric->fields[i].field_key = p_strdup(pool, fields[i]);
+			metric->fields[i].stats = stats_dist_init();
+		}
+	}
+	return metric;
+}
+
+static void stats_metrics_add_set(struct stats_metrics *metrics,
+				  const struct stats_metric_settings *set)
+{
+	struct exporter *exporter;
+	struct metric *metric;
+	const char *const *fields;
+	const char *const *tmp;
+
+	fields = t_strsplit_spaces(set->fields, " ");
+	metric = stats_metric_alloc(metrics->pool, set->metric_name, set, fields);
+
+	if (array_is_created(&set->parsed_group_by))
+		metric->group_by = array_get(&set->parsed_group_by,
+					     &metric->group_by_count);
+
+	array_push_back(&metrics->metrics, &metric);
+
+	event_filter_merge_with_context(metrics->filter, set->parsed_filter, metric);
+
+	/*
+	 * Metrics may also be exported - make sure exporter info is set
+	 */
+
+	if (set->exporter[0] == '\0')
+		return; /* not exported */
+
+	array_foreach_elem(&metrics->exporters, exporter) {
+		if (strcmp(set->exporter, exporter->name) == 0) {
+			metric->export_info.exporter = exporter;
+			break;
+		}
+	}
+
+	if (metric->export_info.exporter == NULL)
+		i_panic("Could not find exporter (%s) for metric (%s)",
+			set->exporter, set->metric_name);
+
+	/* Defaults */
+	metric->export_info.include = EVENT_EXPORTER_INCL_NONE;
+
+	tmp = t_strsplit_spaces(set->exporter_include, " ");
+	for (; *tmp != NULL; tmp++) {
+		if (strcmp(*tmp, "name") == 0)
+			metric->export_info.include |= EVENT_EXPORTER_INCL_NAME;
+		else if (strcmp(*tmp, "hostname") == 0)
+			metric->export_info.include |= EVENT_EXPORTER_INCL_HOSTNAME;
+		else if (strcmp(*tmp, "timestamps") == 0)
+			metric->export_info.include |= EVENT_EXPORTER_INCL_TIMESTAMPS;
+		else if (strcmp(*tmp, "categories") == 0)
+			metric->export_info.include |= EVENT_EXPORTER_INCL_CATEGORIES;
+		else if (strcmp(*tmp, "fields") == 0)
+			metric->export_info.include |= EVENT_EXPORTER_INCL_FIELDS;
+		else
+			i_warning("Ignoring unknown exporter include '%s'", *tmp);
+	}
+}
+
+static struct stats_metric_settings *
+stats_metric_settings_dup(pool_t pool, const struct stats_metric_settings *src)
+{
+	struct stats_metric_settings *set = p_new(pool, struct stats_metric_settings, 1);
+
+	set->metric_name = p_strdup(pool, src->metric_name);
+	set->description = p_strdup(pool, src->description);
+	set->fields = p_strdup(pool, src->fields);
+	set->group_by = p_strdup(pool, src->group_by);
+	set->filter = p_strdup(pool, src->filter);
+	set->exporter = p_strdup(pool, src->exporter);
+	set->exporter_include = p_strdup(pool, src->exporter_include);
+
+	return set;
+}
+
+static struct metric *
+stats_metrics_find(struct stats_metrics *metrics,
+		   const char *name, unsigned int *idx_r)
+{
+	struct metric *const *m;
+	array_foreach(&metrics->metrics, m) {
+		if (strcmp((*m)->name, name) == 0) {
+			*idx_r = array_foreach_idx(&metrics->metrics, m);
+			return *m;
+		}
+	}
+	return NULL;
+}
+
+static bool
+stats_metrics_check_for_exporter(struct stats_metrics *metrics, const char *name)
+{
+	struct exporter *exporter;
+
+	/* Allow registering metrics with empty/missing exporters. */
+	if (name[0] == '\0')
+		return TRUE;
+
+	if (!array_is_created(&metrics->exporters))
+		return FALSE;
+
+	bool is_found = FALSE;
+	array_foreach_elem(&metrics->exporters, exporter) {
+		if (strcmp(exporter->name, name) == 0) {
+			is_found = TRUE;
+			break;
+		}
+	}
+
+	return is_found;
+}
+
+bool stats_metrics_add_dynamic(struct stats_metrics *metrics,
+			       struct stats_metric_settings *set,
+			       const char **error_r)
+{
+	unsigned int existing_idx ATTR_UNUSED;
+	if (stats_metrics_find(metrics, set->metric_name, &existing_idx) != NULL) {
+		*error_r = "Metric already exists";
+		return FALSE;
+	}
+
+	struct stats_metric_settings *_set =
+		stats_metric_settings_dup(metrics->pool, set);
+	if (!stats_metric_setting_parser_info.check_func(_set, metrics->pool, error_r))
+		return FALSE;
+
+	if (!stats_metrics_check_for_exporter(metrics, set->exporter)) {
+		*error_r = t_strdup_printf("Exporter '%s' does not exist.",
+					   set->exporter);
+		return FALSE;
+	}
+
+	stats_metrics_add_set(metrics, _set);
+	return TRUE;
+}
+
+bool stats_metrics_remove_dynamic(struct stats_metrics *metrics,
+				  const char *name)
+{
+	unsigned int m_idx;
+	bool ret = FALSE;
+	struct metric *m = stats_metrics_find(metrics, name, &m_idx);
+	if (m != NULL) {
+		array_delete(&metrics->metrics, m_idx, 1);
+		ret = event_filter_remove_queries_with_context(metrics->filter, m);
+		stats_metric_free(m);
+	}
+	return ret;
+}
+
+static void
+stats_metrics_add_from_settings(struct stats_metrics *metrics,
+				const struct stats_settings *set)
+{
+	/* add all the exporters first */
+	if (!array_is_created(&set->exporters)) {
+		p_array_init(&metrics->exporters, metrics->pool, 0);
+	} else {
+		struct stats_exporter_settings *exporter_set;
+
+		p_array_init(&metrics->exporters, metrics->pool,
+			     array_count(&set->exporters));
+		array_foreach_elem(&set->exporters, exporter_set)
+			stats_exporters_add_set(metrics, exporter_set);
+	}
+
+	/* then add all the metrics */
+	if (!array_is_created(&set->metrics)) {
+		p_array_init(&metrics->metrics, metrics->pool, 0);
+	} else {
+		struct stats_metric_settings *metric_set;
+
+		p_array_init(&metrics->metrics, metrics->pool,
+			     array_count(&set->metrics));
+		array_foreach_elem(&set->metrics, metric_set) T_BEGIN {
+			stats_metrics_add_set(metrics, metric_set);
+		} T_END;
+	}
+}
+
+struct stats_metrics *stats_metrics_init(const struct stats_settings *set)
+{
+	struct stats_metrics *metrics;
+	pool_t pool = pool_alloconly_create("stats metrics", 1024);
+
+	metrics = p_new(pool, struct stats_metrics, 1);
+	metrics->pool = pool;
+	metrics->filter = event_filter_create();
+	stats_metrics_add_from_settings(metrics, set);
+	return metrics;
+}
+
+static void stats_metric_free(struct metric *metric)
+{
+	struct metric *sub_metric;
+	stats_dist_deinit(&metric->duration_stats);
+	for (unsigned int i = 0; i < metric->fields_count; i++)
+		stats_dist_deinit(&metric->fields[i].stats);
+	if (!array_is_created(&metric->sub_metrics))
+		return;
+	array_foreach_elem(&metric->sub_metrics, sub_metric)
+		stats_metric_free(sub_metric);
+}
+
+static void stats_export_deinit(void)
+{
+	/* no need for event_export_transport_drop_deinit() - no-op */
+	event_export_transport_http_post_deinit();
+	/* no need for event_export_transport_log_deinit() - no-op */
+}
+
+void stats_metrics_deinit(struct stats_metrics **_metrics)
+{
+	struct stats_metrics *metrics = *_metrics;
+	struct metric *metric;
+
+	*_metrics = NULL;
+
+	stats_export_deinit();
+
+	array_foreach_elem(&metrics->metrics, metric)
+		stats_metric_free(metric);
+	event_filter_unref(&metrics->filter);
+	pool_unref(&metrics->pool);
+}
+
+static void stats_metric_reset(struct metric *metric)
+{
+	struct metric *sub_metric;
+	stats_dist_reset(metric->duration_stats);
+	for (unsigned int i = 0; i < metric->fields_count; i++)
+		stats_dist_reset(metric->fields[i].stats);
+	if (!array_is_created(&metric->sub_metrics))
+		return;
+	array_foreach_elem(&metric->sub_metrics, sub_metric)
+		stats_metric_reset(sub_metric);
+}
+
+void stats_metrics_reset(struct stats_metrics *metrics)
+{
+	struct metric *metric;
+
+	array_foreach_elem(&metrics->metrics, metric)
+		stats_metric_reset(metric);
+}
+
+struct event_filter *
+stats_metrics_get_event_filter(struct stats_metrics *metrics)
+{
+	return metrics->filter;
+}
+
+static struct metric *
+stats_metric_find_sub_metric(struct metric *metric,
+			     const struct metric_value *value)
+{
+	struct metric *sub_metrics;
+
+	/* lookup sub-metric */
+	array_foreach_elem(&metric->sub_metrics, sub_metrics) {
+		switch (sub_metrics->group_value.type) {
+		case METRIC_VALUE_TYPE_STR:
+			if (memcmp(sub_metrics->group_value.hash, value->hash,
+				   SHA1_RESULTLEN) == 0)
+				return sub_metrics;
+			break;
+		case METRIC_VALUE_TYPE_INT:
+			if (sub_metrics->group_value.intmax == value->intmax)
+				return sub_metrics;
+			break;
+		case METRIC_VALUE_TYPE_BUCKET_INDEX:
+			if (sub_metrics->group_value.intmax == value->intmax)
+				return sub_metrics;
+			break;
+		}
+	}
+	return NULL;
+}
+
+static struct metric *
+stats_metric_sub_metric_alloc(struct metric *metric, const char *name, pool_t pool)
+{
+	struct metric *sub_metric;
+	ARRAY_TYPE(const_string) fields;
+	t_array_init(&fields, metric->fields_count);
+	for (unsigned int i = 0; i < metric->fields_count; i++)
+		array_append(&fields, &metric->fields[i].field_key, 1);
+	array_append_zero(&fields);
+	sub_metric = stats_metric_alloc(pool, metric->name, metric->set,
+					array_idx(&fields, 0));
+	sub_metric->sub_name = p_strdup(pool, str_sanitize_utf8(name, 32));
+	array_append(&metric->sub_metrics, &sub_metric, 1);
+	return sub_metric;
+}
+
+static bool
+stats_metric_group_by_discrete(const struct event_field *field,
+			       struct metric_value *value_r)
+{
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+		value_r->type = METRIC_VALUE_TYPE_STR;
+		/* use sha1 of value to avoid excessive memory usage in case the
+		   actual value is quite long */
+		sha1_get_digest(field->value.str, strlen(field->value.str),
+				value_r->hash);
+		return TRUE;
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		value_r->type = METRIC_VALUE_TYPE_INT;
+		value_r->intmax = field->value.intmax;
+		return TRUE;
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+		return FALSE;
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		return FALSE;
+	}
+
+	i_unreached();
+}
+
+/* convert the value to a bucket index */
+static bool
+stats_metric_group_by_quantized(const struct event_field *field,
+				struct metric_value *value_r,
+				const struct stats_metric_settings_group_by *group_by)
+{
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		return FALSE;
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		break;
+	}
+
+	value_r->type = METRIC_VALUE_TYPE_BUCKET_INDEX;
+
+	for (unsigned int i = 0; i < group_by->num_ranges; i++) {
+		if ((field->value.intmax <= group_by->ranges[i].min) ||
+		    (field->value.intmax > group_by->ranges[i].max))
+			continue;
+
+		value_r->intmax = i;
+		return TRUE;
+	}
+
+	i_panic("failed to find a matching bucket for '%s'=%jd",
+		group_by->field, field->value.intmax);
+}
+
+/* convert value to a bucket label */
+static const char *
+stats_metric_group_by_quantized_label(const struct event_field *field,
+				      const struct stats_metric_settings_group_by *group_by,
+				      const size_t bucket_index)
+{
+	const struct stats_metric_settings_bucket_range *range = &group_by->ranges[bucket_index];
+	const char *name = group_by->field;
+	const char *label;
+
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		i_unreached();
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		break;
+	}
+
+	if (range->min == INTMAX_MIN)
+		label = t_strdup_printf("%s_ninf_%jd", name, range->max);
+	else if (range->max == INTMAX_MAX)
+		label = t_strdup_printf("%s_%jd_inf", name, range->min + 1);
+	else
+		label = t_strdup_printf("%s_%jd_%jd", name,
+					range->min + 1, range->max);
+
+	return label;
+}
+
+static bool
+stats_metric_group_by_get_value(const struct event_field *field,
+				const struct stats_metric_settings_group_by *group_by,
+				struct metric_value *value_r)
+{
+	switch (group_by->func) {
+	case STATS_METRIC_GROUPBY_DISCRETE:
+		if (!stats_metric_group_by_discrete(field, value_r))
+			return FALSE;
+		return TRUE;
+	case STATS_METRIC_GROUPBY_QUANTIZED:
+		if (!stats_metric_group_by_quantized(field, value_r, group_by))
+			return FALSE;
+		return TRUE;
+	}
+
+	i_panic("unknown group-by function %d", group_by->func);
+}
+
+static const char *
+stats_metric_group_by_get_label(const struct event_field *field,
+				const struct stats_metric_settings_group_by *group_by,
+				const struct metric_value *value)
+{
+	switch (group_by->func) {
+	case STATS_METRIC_GROUPBY_DISCRETE:
+		i_unreached();
+	case STATS_METRIC_GROUPBY_QUANTIZED:
+		return stats_metric_group_by_quantized_label(field, group_by,
+							     value->intmax);
+	}
+
+	i_panic("unknown group-by function %d", group_by->func);
+}
+
+static const char *
+stats_metric_group_by_value_label(const struct event_field *field,
+				  const struct stats_metric_settings_group_by *group_by,
+				  const struct metric_value *value)
+{
+	switch (value->type) {
+	case METRIC_VALUE_TYPE_STR:
+		return field->value.str;
+	case METRIC_VALUE_TYPE_INT:
+		return dec2str(field->value.intmax);
+	case METRIC_VALUE_TYPE_BUCKET_INDEX:
+		return stats_metric_group_by_get_label(field, group_by, value);
+	}
+	i_unreached();
+}
+
+static struct metric *
+stats_metric_get_sub_metric(struct metric *metric,
+			    const struct event_field *field,
+			    const struct metric_value *value,
+			    pool_t pool)
+{
+	struct metric *sub_metric;
+
+	sub_metric = stats_metric_find_sub_metric(metric, value);
+	if (sub_metric != NULL)
+		return sub_metric;
+
+	T_BEGIN {
+		const char *value_label =
+			stats_metric_group_by_value_label(field,
+				&metric->group_by[0], value);
+		sub_metric = stats_metric_sub_metric_alloc(metric, value_label,
+							   pool);
+	} T_END;
+	if (metric->group_by_count > 1) {
+		sub_metric->group_by_count = metric->group_by_count - 1;
+		sub_metric->group_by = &metric->group_by[1];
+	}
+	sub_metric->group_value.type = value->type;
+	sub_metric->group_value.intmax = value->intmax;
+	memcpy(sub_metric->group_value.hash, value->hash, SHA1_RESULTLEN);
+	return sub_metric;
+}
+
+static void
+stats_metric_group_by_field(struct metric *metric, struct event *event,
+			    const struct event_field *field, pool_t pool)
+{
+	struct metric *sub_metric;
+	struct metric_value value;
+
+	if (!stats_metric_group_by_get_value(field, &metric->group_by[0], &value))
+		return;
+
+	if (!array_is_created(&metric->sub_metrics))
+		p_array_init(&metric->sub_metrics, pool, 8);
+	sub_metric = stats_metric_get_sub_metric(metric, field, &value, pool);
+
+	/* sub-metrics are recursive, so each sub-metric can have additional
+	   sub-metrics. */
+	stats_metric_event(sub_metric, event, pool);
+}
+
+static void
+stats_event_get_strlist(struct event *event, const char *name,
+			ARRAY_TYPE(const_string) *strings)
+{
+	if (event == NULL)
+		return;
+
+	const struct event_field *field =
+		event_find_field_nonrecursive(event, name);
+	if (field != NULL) {
+		const char *str;
+		array_foreach_elem(&field->value.strlist, str)
+			array_push_back(strings, &str);
+	}
+	stats_event_get_strlist(event_get_parent(event), name, strings);
+}
+
+static void
+stats_metric_group_by(struct metric *metric, struct event *event, pool_t pool)
+{
+	const struct event_field *field =
+		event_find_field_recursive(event, metric->group_by[0].field);
+
+	/* ignore missing field */
+	if (field == NULL)
+		return;
+
+	if (field->value_type != EVENT_FIELD_VALUE_TYPE_STRLIST)
+		stats_metric_group_by_field(metric, event, field, pool);
+	else {
+		/* Handle each string in strlist separately. The strlist needs
+		   to be combined from the event and its parents, as well as
+		   the global event and its parents. */
+		ARRAY_TYPE(const_string) strings;
+
+		t_array_init(&strings, 8);
+		stats_event_get_strlist(event, metric->group_by[0].field,
+					&strings);
+		stats_event_get_strlist(event_get_global(),
+					metric->group_by[0].field, &strings);
+
+		struct event_field str_field = {
+			.value_type = EVENT_FIELD_VALUE_TYPE_STR,
+		};
+		const char *str;
+
+		/* sort strings so duplicates can be easily skipped */
+		array_sort(&strings, i_strcmp_p);
+		array_foreach_elem(&strings, str) {
+			if (str_field.value.str == NULL ||
+			    strcmp(str_field.value.str, str) != 0) {
+				str_field.value.str = str;
+				stats_metric_group_by_field(metric, event,
+							    &str_field, pool);
+			}
+		}
+	}
+}
+
+static void
+stats_metric_event_field(struct event *event, const char *fieldname,
+			 struct stats_dist *stats)
+{
+	const struct event_field *field =
+		event_find_field_recursive(event, fieldname);
+	intmax_t num = 0;
+
+	if (field == NULL)
+		return;
+
+	switch (field->value_type) {
+	case EVENT_FIELD_VALUE_TYPE_STR:
+	case EVENT_FIELD_VALUE_TYPE_STRLIST:
+		break;
+	case EVENT_FIELD_VALUE_TYPE_INTMAX:
+		num = field->value.intmax;
+		break;
+	case EVENT_FIELD_VALUE_TYPE_TIMEVAL:
+		num = field->value.timeval.tv_sec * 1000000ULL +
+			field->value.timeval.tv_usec;
+		break;
+	}
+
+	stats_dist_add(stats, num);
+}
+
+static void
+stats_metric_event(struct metric *metric, struct event *event, pool_t pool)
+{
+	/* duration is special - we always add it */
+	stats_metric_event_field(event, STATS_EVENT_FIELD_NAME_DURATION,
+				 metric->duration_stats);
+
+	for (unsigned int i = 0; i < metric->fields_count; i++)
+		stats_metric_event_field(event,
+					 metric->fields[i].field_key,
+					 metric->fields[i].stats);
+
+	if (metric->group_by != NULL)
+		stats_metric_group_by(metric, event, pool);
+}
+
+static void
+stats_export_event(struct metric *metric, struct event *oldevent)
+{
+	const struct metric_export_info *info = &metric->export_info;
+	const struct exporter *exporter = info->exporter;
+	struct event *event;
+
+	i_assert(exporter != NULL);
+
+	event = event_flatten(oldevent);
+
+	T_BEGIN {
+		buffer_t *buf;
+
+		buf = t_buffer_create(128);
+
+		exporter->format(metric, event, buf);
+		exporter->transport(exporter, buf);
+	} T_END;
+
+	event_unref(&event);
+}
+
+void stats_metrics_event(struct stats_metrics *metrics, struct event *event,
+			 const struct failure_context *ctx)
+{
+	struct event_filter_match_iter *iter;
+	struct metric *metric;
+	uintmax_t duration;
+
+	/* Note: Adding the field here means that it will get exported
+	   below.  This is necessary to allow group-by functions to quantize
+	   based on the event duration. */
+	event_get_last_duration(event, &duration);
+	event_add_int(event, STATS_EVENT_FIELD_NAME_DURATION, duration);
+
+	/* process stats & exports */
+	iter = event_filter_match_iter_init(metrics->filter, event, ctx);
+	while ((metric = event_filter_match_iter_next(iter)) != NULL) T_BEGIN {
+		/* every metric is fed into stats */
+		stats_metric_event(metric, event, metrics->pool);
+
+		/* some metrics are exported */
+		if (metric->export_info.exporter != NULL)
+			stats_export_event(metric, event);
+	} T_END;
+	event_filter_match_iter_deinit(&iter);
+}
+
+struct stats_metrics_iter {
+	struct stats_metrics *metrics;
+	unsigned int idx;
+};
+
+struct stats_metrics_iter *
+stats_metrics_iterate_init(struct stats_metrics *metrics)
+{
+	struct stats_metrics_iter *iter;
+
+	iter = i_new(struct stats_metrics_iter, 1);
+	iter->metrics = metrics;
+	return iter;
+}
+
+const struct metric *stats_metrics_iterate(struct stats_metrics_iter *iter)
+{
+	struct metric *const *metrics;
+	unsigned int count;
+
+	metrics = array_get(&iter->metrics->metrics, &count);
+	if (iter->idx >= count)
+		return NULL;
+	return metrics[iter->idx++];
+}
+
+void stats_metrics_iterate_deinit(struct stats_metrics_iter **_iter)
+{
+	struct stats_metrics_iter *iter = *_iter;
+
+	*_iter = NULL;
+	i_free(iter);
+}
diff --git a/src/stats/stats-metrics.h b/src/stats/stats-metrics.h
new file mode 100644
index 0000000..6d7d745
--- /dev/null
+++ b/src/stats/stats-metrics.h
@@ -0,0 +1,134 @@
+#ifndef STATS_METRICS_H
+#define STATS_METRICS_H
+
+#include "stats-settings.h"
+#include "sha1.h"
+
+#define STATS_EVENT_FIELD_NAME_DURATION "duration"
+
+struct metric;
+struct stats_metrics;
+
+struct exporter {
+	const char *name;
+
+	/*
+	 * serialization format options
+	 *
+	 * the "how do we encode the event before sending it" knobs
+	 */
+	enum event_exporter_time_fmt time_format;
+
+	/* Max length for string field values */
+	size_t format_max_field_len;
+
+	/* function to serialize the event */
+	void (*format)(const struct metric *, struct event *, buffer_t *);
+
+	/* mime type for the format */
+	const char *format_mime_type;
+
+	/*
+	 * transport options
+	 *
+	 * the "how do we get the event to the external location" knobs
+	 */
+	const char *transport_args;
+	unsigned int transport_timeout;
+
+	/* function to send the event */
+	void (*transport)(const struct exporter *, const buffer_t *);
+};
+
+struct metric_export_info {
+	const struct exporter *exporter;
+
+	enum event_exporter_includes {
+		EVENT_EXPORTER_INCL_NONE       = 0,
+		EVENT_EXPORTER_INCL_NAME       = 0x01,
+		EVENT_EXPORTER_INCL_HOSTNAME   = 0x02,
+		EVENT_EXPORTER_INCL_TIMESTAMPS = 0x04,
+		EVENT_EXPORTER_INCL_CATEGORIES = 0x08,
+		EVENT_EXPORTER_INCL_FIELDS     = 0x10,
+	} include;
+};
+
+struct metric_field {
+	const char *field_key;
+	struct stats_dist *stats;
+};
+
+enum metric_value_type {
+	METRIC_VALUE_TYPE_STR,
+	METRIC_VALUE_TYPE_INT,
+	METRIC_VALUE_TYPE_BUCKET_INDEX,
+};
+
+struct metric_value {
+	enum metric_value_type type;
+	unsigned char hash[SHA1_RESULTLEN];
+	intmax_t intmax;
+};
+
+struct metric {
+	const struct stats_metric_settings *set;
+	const char *name;
+	/* When this metric is a sub-metric, then this is the
+	   suffix for name and any sub_names before it.
+
+	   So if we have
+
+	   struct metric imap_command {
+	       event_name = imap_command_finished
+	       group_by = cmd_name
+	   }
+
+	   The metric.name will always be imap_command and for each sub-metric
+	   metric.sub_name will be whatever the cmd_name is, such as 'select'.
+
+	   This is a display name and does not guarantee uniqueness.
+	*/
+	const char *sub_name;
+
+	/* Timing for how long the event existed */
+	struct stats_dist *duration_stats;
+
+	unsigned int fields_count;
+	struct metric_field *fields;
+
+	unsigned int group_by_count;
+	const struct stats_metric_settings_group_by *group_by;
+	struct metric_value group_value;
+	ARRAY(struct metric *) sub_metrics;
+
+	struct metric_export_info export_info;
+};
+
+bool stats_metrics_add_dynamic(struct stats_metrics *metrics,
+			       struct stats_metric_settings *set,
+			       const char **error_r);
+
+bool stats_metrics_remove_dynamic(struct stats_metrics *metrics,
+				  const char *name);
+
+struct stats_metrics *stats_metrics_init(const struct stats_settings *set);
+void stats_metrics_deinit(struct stats_metrics **metrics);
+
+/* Reset all metrics */
+void stats_metrics_reset(struct stats_metrics *metrics);
+
+/* Returns event filter created from the stats_settings. */
+struct event_filter *
+stats_metrics_get_event_filter(struct stats_metrics *metrics);
+
+/* Update metrics with given event. */
+void stats_metrics_event(struct stats_metrics *metrics, struct event *event,
+			 const struct failure_context *ctx);
+
+/* Iterate through all the tracked metrics. */
+struct stats_metrics_iter *
+stats_metrics_iterate_init(struct stats_metrics *metrics);
+const struct metric *stats_metrics_iterate(struct stats_metrics_iter *iter);
+void stats_metrics_iterate_deinit(struct stats_metrics_iter **iter);
+
+#endif
diff --git a/src/stats/stats-service-openmetrics.c b/src/stats/stats-service-openmetrics.c
new file mode 100644
index 0000000..371e8d9
--- /dev/null
+++ b/src/stats/stats-service-openmetrics.c
@@ -0,0 +1,826 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "dovecot-version.h"
+#include "str.h"
+#include "array.h"
+#include "json-parser.h"
+#include "ioloop.h"
+#include "ostream.h"
+#include "stats-dist.h"
+#include "http-server.h"
+#include "client-http.h"
+#include "stats-settings.h"
+#include "stats-metrics.h"
+#include "stats-service-private.h"
+
+#define OPENMETRICS_CONTENT_VERSION "0.0.1"
+
+#ifdef DOVECOT_REVISION
+#define OPENMETRICS_BUILD_INFO \
+	"version=\""DOVECOT_VERSION"\"," \
+	"revision=\""DOVECOT_REVISION"\""
+#else
+#define OPENMETRICS_BUILD_INFO \
+	"version=\""DOVECOT_VERSION"\""
+#endif
+
+enum openmetrics_metric_type {
+	OPENMETRICS_METRIC_TYPE_COUNT,
+	OPENMETRICS_METRIC_TYPE_DURATION,
+	OPENMETRICS_METRIC_TYPE_FIELD,
+	OPENMETRICS_METRIC_TYPE_HISTOGRAM,
+};
+
+enum openmetrics_request_state {
+	OPENMETRICS_REQUEST_STATE_INIT = 0,
+	OPENMETRICS_REQUEST_STATE_METRIC,
+	OPENMETRICS_REQUEST_STATE_METRIC_HEADER,
+	OPENMETRICS_REQUEST_STATE_SUB_METRICS,
+	OPENMETRICS_REQUEST_STATE_METRIC_BODY,
+	OPENMETRICS_REQUEST_STATE_FINISHED,
+};
+
+struct openmetrics_request_sub_metric {
+	size_t labels_pos;
+	const struct metric *metric;
+	unsigned int sub_index;
+};
+
+struct openmetrics_request {
+	struct ostream *output;
+
+	enum openmetrics_request_state state;
+	struct stats_metrics_iter *stats_iter;
+	const struct metric *metric;
+	enum openmetrics_metric_type metric_type;
+	string_t *labels;
+	size_t labels_pos;
+	unsigned int field_pos;
+	ARRAY(struct openmetrics_request_sub_metric) sub_metric_stack;
+
+	bool has_submetric:1;
+};
+
+/* https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels:
+
+   Every time series is uniquely identified by its metric name and optional
+   key-value pairs called labels.
+
+   The metric name specifies the general feature of a system that is measured
+   (e.g. http_requests_total - the total number of HTTP requests received). It
+   may contain ASCII letters and digits, as well as underscores and colons. It
+   must match the regex [a-zA-Z_:][a-zA-Z0-9_:]*.
+ */
+
+static bool openmetrics_check_name(const char *name)
+{
+	const unsigned char *p, *pend;
+
+	p = (const unsigned char *)name;
+	pend = p + strlen(name);
+
+	if (p == pend)
+		return FALSE;
+
+	if (!(*p >= 'a' && *p <= 'z') && !(*p >= 'A' && *p <= 'Z') &&
+	    *p != '_' && *p != ':')
+		return FALSE;
+	p++;
+	while (p < pend) {
+		if (!(*p >= 'a' && *p <= 'z') && !(*p >= 'A' && *p <= 'Z') &&
+		    !(*p >= '0' && *p <= '9') && *p != '_' && *p != ':')
+			return FALSE;
+		p++;
+	}
+	return TRUE;
+}
+
+static void openmetrics_export_dovecot(string_t *out)
+{
+	i_assert(stats_startup_time <= ioloop_time);
+	str_append(out, "# HELP process_start_time_seconds "
+			"Timestamp of service start\n");
+	str_append(out, "# TYPE process_start_time_seconds gauge\n");
+	str_printfa(out, "process_start_time_seconds %"PRIdTIME_T"\n",
+		    stats_startup_time);
+
+	str_append(out, "# HELP dovecot_build "
+			"Dovecot build information\n");
+	str_append(out, "# TYPE dovecot_build info\n");
+	str_append(out, "dovecot_build_info{"OPENMETRICS_BUILD_INFO"} 1\n");
+}
+
+static void openmetrics_export_eof(string_t *out)
+{
+	str_append(out, "# EOF\n");
+}
+
+static void
+openmetrics_export_metric_value(struct openmetrics_request *req, string_t *out,
+				const struct metric *metric)
+{
+	const struct metric_field *field;
+	/* Metric name */
+	str_append(out, "dovecot_");
+	str_append(out, req->metric->name);
+	switch (req->metric_type) {
+	case OPENMETRICS_METRIC_TYPE_COUNT:
+		if (req->metric->group_by != NULL && str_len(req->labels) == 0)
+			str_append(out, "_count");
+		else
+			str_append(out, "_total");
+		break;
+	case OPENMETRICS_METRIC_TYPE_DURATION:
+		if (req->metric->group_by != NULL && str_len(req->labels) == 0)
+			str_append(out, "_duration_seconds_sum");
+		else
+			str_append(out, "_duration_seconds_total");
+		break;
+	case OPENMETRICS_METRIC_TYPE_FIELD:
+		field = &metric->fields[req->field_pos];
+		if (req->metric->group_by != NULL && str_len(req->labels) == 0)
+			str_printfa(out, "_%s_sum", field->field_key);
+		else
+			str_printfa(out, "_%s_total", field->field_key);
+		break;
+	case OPENMETRICS_METRIC_TYPE_HISTOGRAM:
+		i_unreached();
+	}
+	/* Labels */
+	if (str_len(req->labels) > 0) {
+		str_append_c(out, '{');
+		str_append_str(out, req->labels);
+		str_append_c(out, '}');
+	}
+	/* Value */
+	switch (req->metric_type) {
+	case OPENMETRICS_METRIC_TYPE_COUNT:
+		str_printfa(out, " %u\n",
+			    stats_dist_get_count(metric->duration_stats));
+		break;
+	case OPENMETRICS_METRIC_TYPE_DURATION:
+		/* Convert from microseconds to seconds */
+		str_printfa(out, " %.6f\n",
+			    stats_dist_get_sum(metric->duration_stats)/1e6F);
+		break;
+	case OPENMETRICS_METRIC_TYPE_FIELD:
+		field = &metric->fields[req->field_pos];
+		str_printfa(out, " %"PRIu64"\n",
+			    stats_dist_get_sum(field->stats));
+		break;
+	case OPENMETRICS_METRIC_TYPE_HISTOGRAM:
+		i_unreached();
+	}
+}
+
+static const struct metric *
+openmetrics_find_histogram_bucket(const struct metric *metric,
+				 unsigned int index)
+{
+	struct metric *sub_metric;
+
+	if (!array_is_created(&metric->sub_metrics))
+		return NULL;
+
+	array_foreach_elem(&metric->sub_metrics, sub_metric) {
+		if (sub_metric->group_value.type !=
+		    METRIC_VALUE_TYPE_BUCKET_INDEX)
+			continue;
+		if (sub_metric->group_value.intmax == index)
+			return sub_metric;
+	}
+
+	return NULL;
+}
+
+static void
+openmetrics_export_histogram_bucket(struct openmetrics_request *req,
+				    string_t *out, const struct metric *metric,
+				    intmax_t bucket_limit, int64_t count)
+{
+	/* Metric name */
+	str_append(out, "dovecot_");
+	str_append(out, metric->name);
+	str_append(out, "_bucket");
+	/* Labels */
+	str_append_c(out, '{');
+	if (str_len(req->labels) > 0) {
+		str_append_str(out, req->labels);
+		str_append_c(out, ',');
+	}
+	if (bucket_limit == INTMAX_MAX)
+		str_append(out, "le=\"+Inf\"");
+	else if (strcmp(metric->group_by->field,
+			STATS_EVENT_FIELD_NAME_DURATION) == 0) {
+		/* Convert from microseconds to seconds */
+		str_printfa(out, "le=\"%.6f\"", bucket_limit/1e6F);
+	} else {
+		str_printfa(out, "le=\"%jd\"", bucket_limit);
+	}
+	str_printfa(out, "} %"PRIu64"\n", count);
+}
+
+static void
+openmetrics_export_histogram(struct openmetrics_request *req, string_t *out,
+			     const struct metric *metric)
+{
+	const struct stats_metric_settings_group_by *group_by =
+		metric->group_by;
+	float sum = 0;
+	uint64_t count = 0;
+
+	/* Buckets */
+	for (unsigned int i = 0; i < group_by->num_ranges; i++) {
+		const struct metric *sub_metric =
+			openmetrics_find_histogram_bucket(metric, i);
+
+		if (sub_metric != NULL) {
+			sum += stats_dist_get_sum(sub_metric->duration_stats);
+			count += stats_dist_get_count(sub_metric->duration_stats);
+		}
+
+		openmetrics_export_histogram_bucket(req, out, metric,
+						    group_by->ranges[i].max,
+						    count);
+	}
+
+	/* There is either no data in histogram, which adding the optional
+	   sum and count metrics doesn't add any new information or
+	   these have already been exported for submetrics. */
+	if (count == 0)
+		return;
+
+	/* Sum */
+	str_append(out, "dovecot_");
+	str_append(out, metric->name);
+	str_append(out, "_sum");
+	/* Labels */
+	if (str_len(req->labels) > 0) {
+		str_append_c(out, '{');
+		str_append_str(out, req->labels);
+		str_append_c(out, '}');
+	}
+	if (strcmp(metric->group_by->field,
+		   STATS_EVENT_FIELD_NAME_DURATION) == 0) {
+		/* Convert from microseconds to seconds */
+		sum /= 1e6F;
+	}
+	str_printfa(out, " %.6f\n", sum);
+	/* Count */
+	str_append(out, "dovecot_");
+	str_append(out, metric->name);
+	str_append(out, "_count");
+	/* Labels */
+	if (str_len(req->labels) > 0) {
+		str_append_c(out, '{');
+		str_append_str(out, req->labels);
+		str_append_c(out, '}');
+	}
+	str_printfa(out, " %"PRIu64"\n", count);
+}
+
+static void
+openmetrics_export_metric_header(struct openmetrics_request *req, string_t *out)
+{
+	const struct metric *metric = req->metric;
+	const struct metric_field *field;
+
+	/* Description */
+	str_append(out, "# HELP dovecot_");
+	str_append(out, metric->name);
+	switch (req->metric_type) {
+	case OPENMETRICS_METRIC_TYPE_COUNT:
+		str_append(out, " Total number of all events of this kind");
+		break;
+	case OPENMETRICS_METRIC_TYPE_DURATION:
+		str_append(out, "_duration_seconds Total duration of all events of this kind");
+		break;
+	case OPENMETRICS_METRIC_TYPE_FIELD:
+		field = &metric->fields[req->field_pos];
+		str_printfa(out, "_%s Total of field value for events of this kind",
+			    field->field_key);
+		break;
+	case OPENMETRICS_METRIC_TYPE_HISTOGRAM:
+		str_append(out, " Histogram");
+		break;
+	}
+	if (*metric->set->description != '\0') {
+		str_append(out, " of ");
+		str_append(out, metric->set->description);
+	}
+	str_append_c(out, '\n');
+	/* Type */
+	str_append(out, "# TYPE dovecot_");
+	str_append(out, metric->name);
+	switch (req->metric_type) {
+	case OPENMETRICS_METRIC_TYPE_COUNT:
+		str_append(out, " counter\n");
+		break;
+	case OPENMETRICS_METRIC_TYPE_DURATION:
+		str_append(out, "_duration_seconds counter\n");
+		break;
+	case OPENMETRICS_METRIC_TYPE_FIELD:
+		field = &metric->fields[req->field_pos];
+		str_printfa(out, "_%s counter\n", field->field_key);
+		break;
+	case OPENMETRICS_METRIC_TYPE_HISTOGRAM:
+		str_append(out, " histogram\n");
+		break;
+	}
+}
+
+static void
+openmetrics_export_submetric(struct openmetrics_request *req, string_t *out,
+			     const struct metric *metric)
+{
+	/* This metric may be a submetric and therefore have a label
+	   associated with it. */
+	if (metric->sub_name != NULL) {
+		str_append_c(req->labels, '"');
+		json_append_escaped(req->labels, metric->sub_name);
+		str_append_c(req->labels, '"');
+	}
+
+	if (req->metric_type == OPENMETRICS_METRIC_TYPE_HISTOGRAM) {
+		if (metric->group_by == NULL ||
+		    metric->group_by[0].func != STATS_METRIC_GROUPBY_QUANTIZED)
+			return;
+
+		openmetrics_export_histogram(req, out, metric);
+		return;
+	}
+
+	openmetrics_export_metric_value(req, out, metric);
+
+	req->has_submetric = TRUE;
+}
+
+static const struct metric *
+openmetrics_export_sub_metric_get(struct openmetrics_request_sub_metric *reqsm)
+{
+	if (reqsm->sub_index >= array_count(&reqsm->metric->sub_metrics))
+		return NULL;
+
+	return array_idx_elem(&reqsm->metric->sub_metrics, reqsm->sub_index);
+}
+
+static const struct metric *
+openmetrics_export_sub_metric_get_next(
+	struct openmetrics_request_sub_metric *reqsm)
+{
+	/* Get the next valid sub-metric */
+	reqsm->sub_index++;
+	return openmetrics_export_sub_metric_get(reqsm);
+}
+
+static struct openmetrics_request_sub_metric *
+openmetrics_export_sub_metric_down(struct openmetrics_request *req)
+{
+	struct openmetrics_request_sub_metric *reqsm =
+		array_back_modifiable(&req->sub_metric_stack);
+	const struct metric *sub_metric;
+
+	/* Descend further into sub-metric tree */
+
+	if (reqsm->metric->group_by == NULL ||
+	    !openmetrics_check_name(reqsm->metric->group_by->field) ||
+	    !array_is_created(&reqsm->metric->sub_metrics) ||
+	    array_count(&reqsm->metric->sub_metrics) == 0)
+		return NULL;
+	if (reqsm->metric->group_by[0].func == STATS_METRIC_GROUPBY_QUANTIZED) {
+		/* Never descend into quantized group_by sub-metrics.
+		   Histograms are exported as a single blob. */
+		return NULL;
+	}
+
+	/* Find sub-metric to descend into */
+	sub_metric = openmetrics_export_sub_metric_get(reqsm);
+	if (sub_metric == NULL) {
+		/* None valid */
+		return NULL;
+	}
+
+	if (str_len(req->labels) > 0)
+		str_append_c(req->labels, ',');
+	str_append(req->labels, reqsm->metric->group_by->field);
+	str_append_c(req->labels, '=');
+	reqsm->labels_pos = str_len(req->labels);
+
+	/* Descend */
+	reqsm = array_append_space(&req->sub_metric_stack);
+	reqsm->metric = sub_metric;
+
+	return reqsm;
+}
+
+static struct openmetrics_request_sub_metric *
+openmetrics_export_sub_metric_up_next(struct openmetrics_request *req)
+{
+	struct openmetrics_request_sub_metric *reqsm;
+	const struct metric *sub_metric = NULL;
+
+	/* Ascend to next sub-metric of an ancestor */
+
+	while (array_count(&req->sub_metric_stack) > 1) {
+		/* Ascend */
+		array_pop_back(&req->sub_metric_stack);
+		reqsm = array_back_modifiable(&req->sub_metric_stack);
+		str_truncate(req->labels, reqsm->labels_pos);
+
+		/* Find next sub-metric */
+		sub_metric = openmetrics_export_sub_metric_get_next(reqsm);
+		if (sub_metric != NULL) {
+			/* None valid */
+			break;
+		}
+	}
+	if (sub_metric == NULL) {
+		/* End of sub-metric tree */
+		return NULL;
+	}
+
+	/* Descend */
+	reqsm = array_append_space(&req->sub_metric_stack);
+	reqsm->metric = sub_metric;
+	return reqsm;
+}
+
+static struct openmetrics_request_sub_metric *
+openmetrics_export_sub_metric_current(struct openmetrics_request *req)
+{
+	struct openmetrics_request_sub_metric *reqsm;
+
+	/* Get state for current sub-metric */
+
+	if (!array_is_created(&req->sub_metric_stack))
+		i_array_init(&req->sub_metric_stack, 8);
+	if (array_count(&req->sub_metric_stack) >= 2) {
+		/* Already walking the sub-metric tree */
+		return array_back_modifiable(&req->sub_metric_stack);
+	}
+
+	/* Start tree walking */
+
+	reqsm = array_append_space(&req->sub_metric_stack);
+	reqsm->metric = req->metric;
+	reqsm->labels_pos = str_len(req->labels);
+
+	return openmetrics_export_sub_metric_down(req);
+}
+
+static bool
+openmetrics_export_sub_metrics(struct openmetrics_request *req, string_t *out)
+{
+	struct openmetrics_request_sub_metric *reqsm = NULL;
+
+	if (!array_is_created(&req->metric->sub_metrics))
+		return TRUE;
+
+	reqsm = openmetrics_export_sub_metric_current(req);
+	if (reqsm == NULL) {
+		/* No valid sub-metrics to export */
+		return TRUE;
+	}
+	openmetrics_export_submetric(req, out, reqsm->metric);
+
+	/* Try do descend into sub-metrics tree for next sub-metric to export.
+	 */
+	reqsm = openmetrics_export_sub_metric_down(req);
+	if (reqsm == NULL) {
+		/* Sub-metrics of this metric exhausted; ascend to the next
+		   parent sub-metric.
+		 */
+		reqsm = openmetrics_export_sub_metric_up_next(req);
+	}
+
+	if (reqsm == NULL) {
+		/* Finished */
+		array_clear(&req->sub_metric_stack);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+static void
+openmetrics_export_metric_body(struct openmetrics_request *req, string_t *out)
+{
+	openmetrics_export_metric_value(req, out, req->metric);
+}
+
+static int
+openmetrics_send_buffer(struct openmetrics_request *req, buffer_t *buffer)
+{
+	ssize_t sent;
+
+	if (buffer->used == 0)
+		return 1;
+
+	sent = o_stream_send(req->output, buffer->data, buffer->used);
+	if (sent < 0)
+		return -1;
+
+	/* Max buffer size is enormous */
+	i_assert((size_t)sent == buffer->used);
+
+	if (o_stream_get_buffer_used_size(req->output) >= IO_BLOCK_SIZE)
+		return 0;
+	return 1;
+}
+
+static bool openmetrics_export_has_histogram(struct openmetrics_request *req)
+{
+	const struct metric *metric = req->metric;
+	unsigned int i;
+
+	if (metric->group_by_count == 0) {
+		/* No group_by */
+		return FALSE;
+	}
+
+	/* We can only support quantized group_by when it is the last group
+	   item. */
+	for (i = 0; i < (metric->group_by_count - 1); i++) {
+		if (metric->group_by[i].func ==
+		    STATS_METRIC_GROUPBY_QUANTIZED)
+			return FALSE;
+	}
+
+	return (metric->group_by[metric->group_by_count - 1].func ==
+		STATS_METRIC_GROUPBY_QUANTIZED);
+}
+
+static void openmetrics_export_next(struct openmetrics_request *req)
+{
+	/* Determine what to export next. */
+	switch (req->metric_type) {
+	case OPENMETRICS_METRIC_TYPE_COUNT:
+		/* Continue with duration output for this metric. */
+		req->metric_type = OPENMETRICS_METRIC_TYPE_DURATION;
+		req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		break;
+	case OPENMETRICS_METRIC_TYPE_DURATION:
+		if (openmetrics_export_has_histogram(req)) {
+			/* Continue with histogram output for this metric. */
+			req->metric_type = OPENMETRICS_METRIC_TYPE_HISTOGRAM;
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		} else if (req->metric->fields_count > 0) {
+			req->field_pos = 0;
+			req->metric_type = OPENMETRICS_METRIC_TYPE_FIELD;
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		} else {
+			/* No histogram; continue with next metric */
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC;
+		}
+		break;
+	case OPENMETRICS_METRIC_TYPE_FIELD:
+		req->field_pos++;
+		if (req->field_pos < req->metric->fields_count) {
+			req->metric_type = OPENMETRICS_METRIC_TYPE_FIELD;
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		} else {
+			/* all fields consumed */
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC;
+		}
+		break;
+	case OPENMETRICS_METRIC_TYPE_HISTOGRAM:
+		if (req->metric->fields_count > 0) {
+			/* Continue with fields */
+			req->field_pos = 0;
+			req->metric_type = OPENMETRICS_METRIC_TYPE_FIELD;
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		} else {
+			/* Continue with next metric */
+			req->state = OPENMETRICS_REQUEST_STATE_METRIC;
+		}
+		break;
+	}
+}
+
+static void
+openmetrics_export_continue(struct openmetrics_request *req, string_t *out)
+{
+	switch (req->state) {
+	case OPENMETRICS_REQUEST_STATE_INIT:
+		/* Export the Dovecot base metrics. */
+		i_assert(req->stats_iter == NULL);
+		req->stats_iter = stats_metrics_iterate_init(stats_metrics);
+		openmetrics_export_dovecot(out);
+		req->state = OPENMETRICS_REQUEST_STATE_METRIC;
+		break;
+	case OPENMETRICS_REQUEST_STATE_METRIC:
+		/* Export the next metric. */
+		i_assert(req->stats_iter != NULL);
+		do {
+			req->metric = stats_metrics_iterate(req->stats_iter);
+		} while (req->metric != NULL &&
+			 !openmetrics_check_name(req->metric->name));
+		if (req->metric == NULL) {
+			/* Finished exporting metrics. */
+			req->state = OPENMETRICS_REQUEST_STATE_FINISHED;
+			break;
+		}
+
+		if (req->labels == NULL)
+			req->labels = str_new(default_pool, 32);
+		else
+			str_truncate(req->labels, 0);
+		req->labels_pos = 0;
+
+		/* Start with count output for this metric if the type
+		   is not histogram. If the metric is of type histogram,
+		   start with quantiles. */
+		if (openmetrics_export_has_histogram(req))
+			req->metric_type = OPENMETRICS_METRIC_TYPE_HISTOGRAM;
+		else
+			req->metric_type = OPENMETRICS_METRIC_TYPE_COUNT;
+		req->state = OPENMETRICS_REQUEST_STATE_METRIC_HEADER;
+		/* Fall through */
+	case OPENMETRICS_REQUEST_STATE_METRIC_HEADER:
+		/* Export the HELP/TYPE header for the current metric */
+		str_truncate(req->labels, req->labels_pos);
+		req->has_submetric = FALSE;
+		if (array_is_created(&req->sub_metric_stack))
+			array_clear(&req->sub_metric_stack);
+		openmetrics_export_metric_header(req, out);
+		req->state = OPENMETRICS_REQUEST_STATE_SUB_METRICS;
+		break;
+	case OPENMETRICS_REQUEST_STATE_SUB_METRICS:
+		/* Export the sub-metrics for the current metric. This will
+		   return for each sub-metric, so that the out string buffer
+		   stays small. */
+		if (!openmetrics_export_sub_metrics(req, out))
+			break;
+		/* All sub-metrics written. */
+		req->state = OPENMETRICS_REQUEST_STATE_METRIC_BODY;
+		break;
+	case OPENMETRICS_REQUEST_STATE_METRIC_BODY:
+		/* Export the body of the current metric. */
+		str_truncate(req->labels, req->labels_pos);
+		if (req->metric_type == OPENMETRICS_METRIC_TYPE_HISTOGRAM)
+			openmetrics_export_histogram(req, out, req->metric);
+		else
+			openmetrics_export_metric_body(req, out);
+		openmetrics_export_next(req);
+		break;
+	case OPENMETRICS_REQUEST_STATE_FINISHED:
+		i_unreached();
+	}
+}
+
+static void openmetrics_handle_write_error(struct openmetrics_request *req)
+{
+	i_info("openmetrics: write(%s) failed: %s",
+	       o_stream_get_name(req->output),
+	       o_stream_get_error(req->output));
+	o_stream_destroy(&req->output);
+}
+
+static void openmetrics_request_deinit(struct openmetrics_request *req)
+{
+	stats_metrics_iterate_deinit(&req->stats_iter);
+	str_free(&req->labels);
+	array_free(&req->sub_metric_stack);
+}
+
+static int openmetrics_export(struct openmetrics_request *req)
+{
+	string_t *out;
+	int ret;
+
+	ret = o_stream_flush(req->output);
+	if (ret < 0) {
+		openmetrics_handle_write_error(req);
+		return -1;
+	}
+	if (ret == 0) {
+		/* Output stream buffer needs to be flushed further */
+		return 0;
+	}
+
+	if (req->state == OPENMETRICS_REQUEST_STATE_FINISHED) {
+		/* All metrics were exported already, so we can finish the
+		   HTTP request now. */
+		o_stream_destroy(&req->output);
+		return 1;
+	}
+
+	/* Export metrics into a string buffer and write that buffer to the
+	   output stream after each (sub-)metric, so that the string buffer
+	   stays small. The output stream buffer can grow bigger, but writing is
+	   stopped for later resumption when the output stream buffer has grown
+	   beyond an optimal size. */
+	out = t_str_new(1024);
+	for (;;) {
+		str_truncate(out, 0);
+
+		openmetrics_export_continue(req, out);
+
+		ret = openmetrics_send_buffer(req, out);
+		if (ret < 0) {
+			openmetrics_handle_write_error(req);
+			return -1;
+		}
+		if (req->state == OPENMETRICS_REQUEST_STATE_FINISHED) {
+			/* Finished export of metrics, but the output stream
+			   buffer may still contain data. */
+			break;
+		}
+		if (ret == 0) {
+			/* Output stream buffer is filled up beyond the optimal
+			   size; wait until we can write more. */
+			return ret;
+		}
+	}
+
+	/* Send EOF */
+	str_truncate(out, 0);
+	openmetrics_export_eof(out);
+        ret = openmetrics_send_buffer(req, out);
+        if (ret < 0) {
+            openmetrics_handle_write_error(req);
+            return -1;
+        }
+
+	/* Cleanup everything except the output stream */
+	openmetrics_request_deinit(req);
+
+	/* Finished; flush output */
+	ret = o_stream_finish(req->output);
+	if (ret < 0) {
+		openmetrics_handle_write_error(req);
+		return -1;
+	}
+	return ret;
+}
+
+static void openmetrics_request_destroy(struct openmetrics_request *req)
+{
+	o_stream_destroy(&req->output);
+	openmetrics_request_deinit(req);
+}
+
+static void
+stats_service_openmetrics_request(void *context ATTR_UNUSED,
+				  struct http_server_request *hsreq,
+				  const char *sub_path)
+{
+	const struct http_request *hreq = http_server_request_get(hsreq);
+	struct http_server_response *hsresp;
+	struct openmetrics_request *req;
+	pool_t pool;
+
+	if (strcmp(hreq->method, "OPTIONS") == 0) {
+		hsresp = http_server_response_create(hsreq, 200, "OK");
+		http_server_response_add_header(hsresp, "Allow", "GET");
+		http_server_response_submit(hsresp);
+		return;
+	}
+	if (strcmp(hreq->method, "GET") != 0) {
+		http_server_request_fail_bad_method(hsreq, "GET");
+		return;
+	}
+	if (*sub_path != '\0') {
+		http_server_request_fail(hsreq, 404, "Not Found");
+		return;
+	}
+
+	pool = http_server_request_get_pool(hsreq);
+	req = p_new(pool, struct openmetrics_request, 1);
+
+	http_server_request_set_destroy_callback(
+		hsreq, openmetrics_request_destroy, req);
+
+	hsresp = http_server_response_create(hsreq, 200, "OK");
+	http_server_response_add_header(
+		hsresp, "Content-Type",
+		"application/openmetrics-text; version="OPENMETRICS_CONTENT_VERSION"; "
+		"charset=utf-8");
+
+	req->output = http_server_response_get_payload_output(
+		hsresp, SIZE_MAX, FALSE);
+
+	o_stream_set_flush_callback(req->output, openmetrics_export, req);
+	o_stream_set_flush_pending(req->output, TRUE);
+}
+
+void stats_service_openmetrics_init(void)
+{
+	struct stats_metrics_iter *iter;
+	const struct metric *metric;
+
+	iter = stats_metrics_iterate_init(stats_metrics);
+	while ((metric = stats_metrics_iterate(iter)) != NULL) {
+		if (!openmetrics_check_name(metric->name)) {
+			i_warning(
+				"stats: openmetrics: "
+				"Metric `%s' is not valid for OpenMetrics"
+				"(invalid metric name; skipped)",
+				metric->name);
+		}
+	}
+	stats_metrics_iterate_deinit(&iter);
+
+	stats_http_resource_add("/metrics", "OpenMetrics",
+				stats_service_openmetrics_request, NULL);
+}
diff --git a/src/stats/stats-service-private.h b/src/stats/stats-service-private.h
new file mode 100644
index 0000000..5f5ab20
--- /dev/null
+++ b/src/stats/stats-service-private.h
@@ -0,0 +1,8 @@
+#ifndef STATS_SERVICE_PRIVATE_H
+#define STATS_SERVICE_PRIVATE_H
+
+#include "stats-service.h"
+
+void stats_service_openmetrics_init(void);
+
+#endif
diff --git a/src/stats/stats-service.c b/src/stats/stats-service.c
new file mode 100644
index 0000000..fa67864
--- /dev/null
+++ b/src/stats/stats-service.c
@@ -0,0 +1,15 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "http-server.h"
+#include "stats-service-private.h"
+
+void stats_services_init(void)
+{
+	 stats_service_openmetrics_init();
+}
+
+void stats_services_deinit(void)
+{
+	/* Nothing yet */
+}
diff --git a/src/stats/stats-service.h b/src/stats/stats-service.h
new file mode 100644
index 0000000..fab477b
--- /dev/null
+++ b/src/stats/stats-service.h
@@ -0,0 +1,7 @@
+#ifndef STATS_SERVICE_H
+#define STATS_SERVICE_H
+
+void stats_services_init(void);
+void stats_services_deinit(void);
+
+#endif
diff --git a/src/stats/stats-settings.c b/src/stats/stats-settings.c
new file mode 100644
index 0000000..f75a737
--- /dev/null
+++ b/src/stats/stats-settings.c
@@ -0,0 +1,538 @@
+/* Copyright (c) 2009-2018 Dovecot authors, see the included COPYING file */
+
+#include "stats-common.h"
+#include "buffer.h"
+#include "settings-parser.h"
+#include "service-settings.h"
+#include "stats-settings.h"
+#include "array.h"
+
+/* <settings checks> */
+#include "event-filter.h"
+#include <math.h>
+/* </settings checks> */
+
+static bool stats_metric_settings_check(void *_set, pool_t pool, const char **error_r);
+static bool stats_exporter_settings_check(void *_set, pool_t pool, const char **error_r);
+static bool stats_settings_check(void *_set, pool_t pool, const char **error_r);
+
+/* <settings checks> */
+static struct file_listener_settings stats_unix_listeners_array[] = {
+	{ "stats-reader", 0600, "", "" },
+	{ "stats-writer", 0660, "", "$default_internal_group" },
+	{ "login/stats-writer", 0600, "$default_login_user", "" },
+};
+static struct file_listener_settings *stats_unix_listeners[] = {
+	&stats_unix_listeners_array[0],
+	&stats_unix_listeners_array[1],
+	&stats_unix_listeners_array[2],
+};
+static buffer_t stats_unix_listeners_buf = {
+	{ { stats_unix_listeners, sizeof(stats_unix_listeners) } }
+};
+/* </settings checks> */
+
+struct service_settings stats_service_settings = {
+	.name = "stats",
+	.protocol = "",
+	.type = "",
+	.executable = "stats",
+	.user = "$default_internal_user",
+	.group = "",
+	.privileged_group = "",
+	.extra_groups = "",
+	.chroot = "",
+
+	.drop_priv_before_exec = FALSE,
+
+	.process_min_avail = 0,
+	.process_limit = 1,
+	.client_limit = 0,
+	.service_count = 0,
+	.idle_kill = UINT_MAX,
+	.vsz_limit = UOFF_T_MAX,
+
+	.unix_listeners = { { &stats_unix_listeners_buf,
+			      sizeof(stats_unix_listeners[0]) } },
+	.inet_listeners = ARRAY_INIT,
+};
+
+/*
+ * event_exporter { } block settings
+ */
+
+#undef DEF
+#define DEF(type, name) \
+	SETTING_DEFINE_STRUCT_##type(#name, name, struct stats_exporter_settings)
+
+static const struct setting_define stats_exporter_setting_defines[] = {
+	DEF(STR, name),
+	DEF(STR, transport),
+	DEF(STR, transport_args),
+	DEF(TIME_MSECS, transport_timeout),
+	DEF(STR, format),
+	DEF(STR, format_args),
+	SETTING_DEFINE_LIST_END
+};
+
+static const struct stats_exporter_settings stats_exporter_default_settings = {
+	.name = "",
+	.transport = "",
+	.transport_args = "",
+	.transport_timeout = 250, /* ms */
+	.format = "",
+	.format_args = "",
+};
+
+const struct setting_parser_info stats_exporter_setting_parser_info = {
+	.defines = stats_exporter_setting_defines,
+	.defaults = &stats_exporter_default_settings,
+
+	.type_offset = offsetof(struct stats_exporter_settings, name),
+	.struct_size = sizeof(struct stats_exporter_settings),
+
+	.parent_offset = SIZE_MAX,
+	.check_func = stats_exporter_settings_check,
+};
+
+/*
+ * metric { } block settings
+ */
+
+#undef DEF
+#define DEF(type, name) \
+	SETTING_DEFINE_STRUCT_##type(#name, name, struct stats_metric_settings)
+
+static const struct setting_define stats_metric_setting_defines[] = {
+	DEF(STR, metric_name),
+	DEF(STR, fields),
+	DEF(STR, group_by),
+	DEF(STR, filter),
+	DEF(STR, exporter),
+	DEF(STR, exporter_include),
+	DEF(STR, description),
+	SETTING_DEFINE_LIST_END
+};
+
+static const struct stats_metric_settings stats_metric_default_settings = {
+	.metric_name = "",
+	.fields = "",
+	.filter = "",
+	.exporter = "",
+	.group_by = "",
+	.exporter_include = STATS_METRIC_SETTINGS_DEFAULT_EXPORTER_INCLUDE,
+	.description = "",
+};
+
+const struct setting_parser_info stats_metric_setting_parser_info = {
+	.defines = stats_metric_setting_defines,
+	.defaults = &stats_metric_default_settings,
+
+	.type_offset = offsetof(struct stats_metric_settings, metric_name),
+	.struct_size = sizeof(struct stats_metric_settings),
+
+	.parent_offset = SIZE_MAX,
+	.check_func = stats_metric_settings_check,
+};
+
+/*
+ * top-level settings
+ */
+
+#undef DEF
+#define DEF(type, name) \
+	SETTING_DEFINE_STRUCT_##type(#name, name, struct stats_settings)
+#undef DEFLIST_UNIQUE
+#define DEFLIST_UNIQUE(field, name, defines) \
+	{ .type = SET_DEFLIST_UNIQUE, .key = name, \
+	  .offset = offsetof(struct stats_settings, field), \
+	  .list_info = defines }
+
+static const struct setting_define stats_setting_defines[] = {
+	DEF(STR, stats_http_rawlog_dir),
+
+	DEFLIST_UNIQUE(metrics, "metric", &stats_metric_setting_parser_info),
+	DEFLIST_UNIQUE(exporters, "event_exporter", &stats_exporter_setting_parser_info),
+	SETTING_DEFINE_LIST_END
+};
+
+const struct stats_settings stats_default_settings = {
+	.stats_http_rawlog_dir = "",
+
+	.metrics = ARRAY_INIT,
+	.exporters = ARRAY_INIT,
+};
+
+const struct setting_parser_info stats_setting_parser_info = {
+	.module_name = "stats",
+	.defines = stats_setting_defines,
+	.defaults = &stats_default_settings,
+
+	.type_offset = SIZE_MAX,
+	.struct_size = sizeof(struct stats_settings),
+
+	.parent_offset = SIZE_MAX,
+	.check_func = stats_settings_check,
+};
+
+/* <settings checks> */
+static bool parse_format_args_set_time(struct stats_exporter_settings *set,
+				       enum event_exporter_time_fmt fmt,
+				       const char **error_r)
+{
+	if ((set->parsed_time_format != EVENT_EXPORTER_TIME_FMT_NATIVE) &&
+	    (set->parsed_time_format != fmt)) {
+		*error_r = t_strdup_printf("Exporter '%s' specifies multiple "
+					   "time format args", set->name);
+		return FALSE;
+	}
+
+	set->parsed_time_format = fmt;
+
+	return TRUE;
+}
+
+static bool parse_format_args(struct stats_exporter_settings *set,
+			      const char **error_r)
+{
+	const char *const *tmp;
+
+	/* Defaults */
+	set->parsed_time_format = EVENT_EXPORTER_TIME_FMT_NATIVE;
+
+	tmp = t_strsplit_spaces(set->format_args, " ");
+
+	/*
+	 * If the config contains multiple types of the same type (e.g.,
+	 * both time-rfc3339 and time-unix) we fail the config check.
+	 *
+	 * Note: At the moment, we have only time-* tokens.  In the future
+	 * when we have other tokens, they should be parsed here.
+	 */
+	for (; *tmp != NULL; tmp++) {
+		enum event_exporter_time_fmt fmt;
+
+		if (strcmp(*tmp, "time-rfc3339") == 0) {
+			fmt = EVENT_EXPORTER_TIME_FMT_RFC3339;
+		} else if (strcmp(*tmp, "time-unix") == 0) {
+			fmt = EVENT_EXPORTER_TIME_FMT_UNIX;
+		} else {
+			*error_r = t_strdup_printf("Unknown exporter format "
+						   "arg: %s", *tmp);
+			return FALSE;
+		}
+
+		if (!parse_format_args_set_time(set, fmt, error_r))
+			return FALSE;
+	}
+
+	return TRUE;
+}
+
+static bool stats_exporter_settings_check(void *_set, pool_t pool ATTR_UNUSED,
+					  const char **error_r)
+{
+	struct stats_exporter_settings *set = _set;
+	bool time_fmt_required;
+
+	if (set->name[0] == '\0') {
+		*error_r = "Exporter name can't be empty";
+		return FALSE;
+	}
+
+	/* TODO: The following should be plugable.
+	 *
+	 * Note: Make sure to mirror any changes to the below code in
+	 * stats_exporters_add_set().
+	 */
+	if (set->format[0] == '\0') {
+		*error_r = "Exporter format name can't be empty";
+		return FALSE;
+	} else if (strcmp(set->format, "none") == 0) {
+		time_fmt_required = FALSE;
+	} else if (strcmp(set->format, "json") == 0) {
+		time_fmt_required = TRUE;
+	} else if (strcmp(set->format, "tab-text") == 0) {
+		time_fmt_required = TRUE;
+	} else {
+		*error_r = t_strdup_printf("Unknown exporter format '%s'",
+					   set->format);
+		return FALSE;
+	}
+
+	/* TODO: The following should be plugable.
+	 *
+	 * Note: Make sure to mirror any changes to the below code in
+	 * stats_exporters_add_set().
+	 */
+	if (set->transport[0] == '\0') {
+		*error_r = "Exporter transport name can't be empty";
+		return FALSE;
+	} else if (strcmp(set->transport, "drop") == 0 ||
+		   strcmp(set->transport, "http-post") == 0 ||
+		   strcmp(set->transport, "log") == 0) {
+		/* no-op */
+	} else {
+		*error_r = t_strdup_printf("Unknown transport type '%s'",
+					   set->transport);
+		return FALSE;
+	}
+
+	if (!parse_format_args(set, error_r))
+		return FALSE;
+
+	/* Some formats don't have a native way of serializing time stamps */
+	if (time_fmt_required &&
+	    set->parsed_time_format == EVENT_EXPORTER_TIME_FMT_NATIVE) {
+		*error_r = t_strdup_printf("%s exporter format requires a "
+					   "time-* argument", set->format);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+static bool parse_metric_group_by_common(const char *func,
+					 const char *const *params,
+					 intmax_t *min_r,
+					 intmax_t *max_r,
+					 intmax_t *other_r,
+					 const char **error_r)
+{
+	intmax_t min, max, other;
+
+	if ((str_array_length(params) != 3) ||
+	    (str_to_intmax(params[0], &min) < 0) ||
+	    (str_to_intmax(params[1], &max) < 0) ||
+	    (str_to_intmax(params[2], &other) < 0)) {
+		*error_r = t_strdup_printf("group_by '%s' aggregate function takes "
+					   "3 int args", func);
+		return FALSE;
+	}
+
+	if ((min < 0) || (max < 0) || (other < 0)) {
+		*error_r = t_strdup_printf("group_by '%s' aggregate function "
+					   "arguments must be >= 0", func);
+		return FALSE;
+	}
+
+	if (min >= max) {
+		*error_r = t_strdup_printf("group_by '%s' aggregate function "
+					   "min must be < max (%ju must be < %ju)",
+					   func, min, max);
+		return FALSE;
+	}
+
+	*min_r = min;
+	*max_r = max;
+	*other_r = other;
+
+	return TRUE;
+}
+
+static bool parse_metric_group_by_exp(pool_t pool, struct stats_metric_settings_group_by *group_by,
+				      const char *const *params, const char **error_r)
+{
+	intmax_t min, max, base;
+
+	if (!parse_metric_group_by_common("exponential", params, &min, &max, &base, error_r))
+		return FALSE;
+
+	if ((base != 2) && (base != 10)) {
+		*error_r = t_strdup_printf("group_by 'exponential' aggregate function "
+					   "base must be one of: 2, 10 (base=%ju)",
+					   base);
+		return FALSE;
+	}
+
+	group_by->func = STATS_METRIC_GROUPBY_QUANTIZED;
+
+	/*
+	 * Allocate the bucket range array and fill it in
+	 *
+	 * The first bucket is special - it contains everything less than or
+	 * equal to 'base^min'.  The last bucket is also special - it
+	 * contains everything greater than 'base^max'.
+	 *
+	 * The second bucket begins at 'base^min + 1', the third bucket
+	 * begins at 'base^(min + 1) + 1', and so on.
+	 */
+	group_by->num_ranges = max - min + 2;
+	group_by->ranges = p_new(pool, struct stats_metric_settings_bucket_range,
+				 group_by->num_ranges);
+
+	/* set up min & max buckets */
+	group_by->ranges[0].min = INTMAX_MIN;
+	group_by->ranges[0].max = pow(base, min);
+	group_by->ranges[group_by->num_ranges - 1].min = pow(base, max);
+	group_by->ranges[group_by->num_ranges - 1].max = INTMAX_MAX;
+
+	/* remaining buckets */
+	for (unsigned int i = 1; i < group_by->num_ranges - 1; i++) {
+		group_by->ranges[i].min = pow(base, min + (i - 1));
+		group_by->ranges[i].max = pow(base, min + i);
+	}
+
+	return TRUE;
+}
+
+static bool parse_metric_group_by_lin(pool_t pool, struct stats_metric_settings_group_by *group_by,
+				      const char *const *params, const char **error_r)
+{
+	intmax_t min, max, step;
+
+	if (!parse_metric_group_by_common("linear", params, &min, &max, &step, error_r))
+		return FALSE;
+
+	if ((min + step) > max) {
+		*error_r = t_strdup_printf("group_by 'linear' aggregate function "
+					   "min+step must be <= max (%ju must be <= %ju)",
+					   min + step, max);
+		return FALSE;
+	}
+
+	group_by->func = STATS_METRIC_GROUPBY_QUANTIZED;
+
+	/*
+	 * Allocate the bucket range array and fill it in
+	 *
+	 * The first bucket is special - it contains everything less than or
+	 * equal to 'min'.  The last bucket is also special - it contains
+	 * everything greater than 'max'.
+	 *
+	 * The second bucket begins at 'min + 1', the third bucket begins at
+	 * 'min + 1 * step + 1', the fourth at 'min + 2 * step + 1', and so on.
+	 */
+	group_by->num_ranges = (max - min) / step + 2;
+	group_by->ranges = p_new(pool, struct stats_metric_settings_bucket_range,
+				 group_by->num_ranges);
+
+	/* set up min & max buckets */
+	group_by->ranges[0].min = INTMAX_MIN;
+	group_by->ranges[0].max = min;
+	group_by->ranges[group_by->num_ranges - 1].min = max;
+	group_by->ranges[group_by->num_ranges - 1].max = INTMAX_MAX;
+
+	/* remaining buckets */
+	for (unsigned int i = 1; i < group_by->num_ranges - 1; i++) {
+		group_by->ranges[i].min = min + (i - 1) * step;
+		group_by->ranges[i].max = min + i * step;
+	}
+
+	return TRUE;
+}
+
+static bool parse_metric_group_by(struct stats_metric_settings *set,
+				  pool_t pool, const char **error_r)
+{
+	const char *const *tmp = t_strsplit_spaces(set->group_by, " ");
+
+	if (tmp[0] == NULL)
+		return TRUE;
+
+	p_array_init(&set->parsed_group_by, pool, str_array_length(tmp));
+
+	/* For each group_by field */
+	for (; *tmp != NULL; tmp++) {
+		struct stats_metric_settings_group_by group_by;
+		const char *const *params;
+
+		i_zero(&group_by);
+
+		/* <field name>:<aggregation func>... */
+		params = t_strsplit(*tmp, ":");
+
+		if (params[1] == NULL) {
+			/* <field name> - alias for <field>:discrete */
+			group_by.func = STATS_METRIC_GROUPBY_DISCRETE;
+		} else if (strcmp(params[1], "discrete") == 0) {
+			/* <field>:discrete */
+			group_by.func = STATS_METRIC_GROUPBY_DISCRETE;
+			if (params[2] != NULL) {
+				*error_r = "group_by 'discrete' aggregate function "
+					   "does not take any args";
+				return FALSE;
+			}
+		} else if (strcmp(params[1], "exponential") == 0) {
+			/* <field>:exponential:<min mag>:<max mag>:<base> */
+			if (!parse_metric_group_by_exp(pool, &group_by, &params[2], error_r))
+				return FALSE;
+		} else if (strcmp(params[1], "linear") == 0) {
+			/* <field>:linear:<min val>:<max val>:<step> */
+			if (!parse_metric_group_by_lin(pool, &group_by, &params[2], error_r))
+				return FALSE;
+		} else {
+			*error_r = t_strdup_printf("unknown aggregation function "
+						   "'%s' on field '%s'", params[1], params[0]);
+			return FALSE;
+		}
+
+		group_by.field = p_strdup(pool, params[0]);
+
+		array_push_back(&set->parsed_group_by, &group_by);
+	}
+
+	return TRUE;
+}
+
+static bool stats_metric_settings_check(void *_set, pool_t pool, const char **error_r)
+{
+	struct stats_metric_settings *set = _set;
+
+	if (set->metric_name[0] == '\0') {
+		*error_r = "Metric name can't be empty";
+		return FALSE;
+	}
+
+	if (set->filter[0] == '\0') {
+		*error_r = t_strdup_printf("metric %s { filter } is empty - "
+					   "will not match anything", set->metric_name);
+		return FALSE;
+	}
+
+	set->parsed_filter = event_filter_create_fragment(pool);
+	if (event_filter_parse(set->filter, set->parsed_filter, error_r) < 0)
+		return FALSE;
+
+	if (!parse_metric_group_by(set, pool, error_r))
+		return FALSE;
+
+	return TRUE;
+}
+
+static bool stats_settings_check(void *_set, pool_t pool ATTR_UNUSED,
+				 const char **error_r)
+{
+	struct stats_settings *set = _set;
+	struct stats_exporter_settings *exporter;
+	struct stats_metric_settings *metric;
+
+	if (!array_is_created(&set->metrics) || !array_is_created(&set->exporters))
+		return TRUE;
+
+	/* check that all metrics refer to exporters that exist */
+	array_foreach_elem(&set->metrics, metric) {
+		bool found = FALSE;
+
+		if (metric->exporter[0] == '\0')
+			continue; /* metric not exported */
+
+		array_foreach_elem(&set->exporters, exporter) {
+			if (strcmp(metric->exporter, exporter->name) == 0) {
+				found = TRUE;
+				break;
+			}
+		}
+
+		if (!found) {
+			*error_r = t_strdup_printf("metric %s refers to "
+						   "non-existent exporter '%s'",
+						   metric->metric_name,
+						   metric->exporter);
+			return FALSE;
+		}
+	}
+
+	return TRUE;
+}
+/* </settings checks> */
diff --git a/src/stats/stats-settings.h b/src/stats/stats-settings.h
new file mode 100644
index 0000000..54b7f9e
--- /dev/null
+++ b/src/stats/stats-settings.h
@@ -0,0 +1,125 @@
+#ifndef STATS_SETTINGS_H
+#define STATS_SETTINGS_H
+
+#define STATS_METRIC_SETTINGS_DEFAULT_EXPORTER_INCLUDE \
+	"name hostname timestamps categories fields"
+
+/* <settings checks> */
+/*
+ * We allow a selection of a timestamp format.
+ *
+ * The 'time-unix' format generates a number with the number of seconds
+ * since 1970-01-01 00:00 UTC.
+ *
+ * The 'time-rfc3339' format uses the YYYY-MM-DDTHH:MM:SS.uuuuuuZ format as
+ * defined by RFC 3339.
+ *
+ * The special native format (not explicitly selectable in the config, but
+ * default if no time-* token is used) uses the format's native timestamp
+ * format.  Note that not all formats have a timestamp data format.
+ *
+ * The native format and the rules below try to address the question: can a
+ * parser that doesn't have any knowledge of fields' values' types losslessly
+ * reconstruct the fields?
+ *
+ * For example, JSON only has strings and numbers, so it cannot represent a
+ * timestamp in a "context-free lossless" way.  Therefore, when making a
+ * JSON blob, we need to decide which way to serialize timestamps.  No
+ * matter how we do it, we incur some loss.  If a decoder sees 1557232304 in
+ * a field, it cannot be certain if the field is an integer that just
+ * happens to be a reasonable timestamp, or if it actually is a timestamp.
+ * Same goes with RFC3339 - it could just be that the user supplied a string
+ * that looks like a timestamp, and that string made it into an event field.
+ *
+ * Other common serialization formats, such as CBOR, have a lossless way of
+ * encoding timestamps.
+ *
+ * Note that there are two concepts at play: native and default.
+ *
+ * The rules for how the format's timestamp formats are used:
+ *
+ * 1. The default time format is the native format.
+ * 2. The native time format may or may not exist for a given format (e.g.,
+ *    in JSON)
+ * 3. If the native format doesn't exist and no time format was specified in
+ *    the config, it is a config error.
+ *
+ * We went with these rules because:
+ *
+ * 1. It prevents type information loss by default.
+ * 2. It completely isolates the policy from the algorithm.
+ * 3. It defers the decision whether each format without a native timestamp
+ *    type should have a default acting as native until after we've had some
+ *    operational experience.
+ * 4. A future decision to add a default (via 3. point) will be 100% compatible.
+ */
+enum event_exporter_time_fmt {
+	EVENT_EXPORTER_TIME_FMT_NATIVE = 0,
+	EVENT_EXPORTER_TIME_FMT_UNIX,
+	EVENT_EXPORTER_TIME_FMT_RFC3339,
+};
+/* </settings checks> */
+
+struct stats_exporter_settings {
+	const char *name;
+	const char *transport;
+	const char *transport_args;
+	unsigned int transport_timeout;
+	const char *format;
+	const char *format_args;
+
+	/* parsed values */
+	enum event_exporter_time_fmt parsed_time_format;
+};
+
+/* <settings checks> */
+enum stats_metric_group_by_func {
+	STATS_METRIC_GROUPBY_DISCRETE = 0,
+	STATS_METRIC_GROUPBY_QUANTIZED,
+};
+
+/*
+ * A range covering a stats bucket.  The the interval is half closed - the
+ * minimum is excluded and the maximum is included.  In other words: (min, max].
+ * Because we don't have a +Inf and -Inf, we use INTMAX_MIN and INTMAX_MAX
+ * respectively.
+ */
+struct stats_metric_settings_bucket_range {
+	intmax_t min;
+	intmax_t max;
+};
+
+struct stats_metric_settings_group_by {
+	const char *field;
+	enum stats_metric_group_by_func func;
+	unsigned int num_ranges;
+	struct stats_metric_settings_bucket_range *ranges;
+};
+/* </settings checks> */
+
+struct stats_metric_settings {
+	const char *metric_name;
+	const char *description;
+	const char *fields;
+	const char *group_by;
+	const char *filter;
+
+	ARRAY(struct stats_metric_settings_group_by) parsed_group_by;
+	struct event_filter *parsed_filter;
+
+	/* exporter related fields */
+	const char *exporter;
+	const char *exporter_include;
+};
+
+struct stats_settings {
+	const char *stats_http_rawlog_dir;
+
+	ARRAY(struct stats_exporter_settings *) exporters;
+	ARRAY(struct stats_metric_settings *) metrics;
+};
+
+extern const struct setting_parser_info stats_setting_parser_info;
+extern const struct setting_parser_info stats_metric_setting_parser_info;
+
+#endif
diff --git a/src/stats/test-client-reader.c b/src/stats/test-client-reader.c
new file mode 100644
index 0000000..e9eed0c
--- /dev/null
+++ b/src/stats/test-client-reader.c
@@ -0,0 +1,235 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "test-stats-common.h"
+#include "master-service-private.h"
+#include "client-reader.h"
+#include "connection.h"
+#include "ostream.h"
+
+static struct connection_list *conn_list;
+
+struct test_connection {
+	struct connection conn;
+
+	unsigned int row_count;
+};
+
+static void test_reader_server_destroy(struct connection *conn)
+{
+	io_loop_stop(conn->ioloop);
+}
+
+static struct connection_settings client_set = {
+	.service_name_in = "stats-reader-server",
+	.service_name_out = "stats-reader-client",
+	.major_version = 2,
+	.minor_version = 0,
+	.allow_empty_args_input = TRUE,
+	.input_max_size = SIZE_MAX,
+	.output_max_size = SIZE_MAX,
+	.client = TRUE,
+};
+
+bool test_stats_callback(struct event *event,
+			 enum event_callback_type type ATTR_UNUSED,
+			 struct failure_context *ctx, const char *fmt ATTR_UNUSED,
+			 va_list args ATTR_UNUSED)
+{
+	if (stats_metrics != NULL) {
+		stats_metrics_event(stats_metrics, event, ctx);
+		struct event_filter *filter =
+			stats_metrics_get_event_filter(stats_metrics);
+		return !event_filter_match(filter, event, ctx);
+	}
+	return TRUE;
+}
+
+static const char *settings_blob_1 =
+"metric=test\n"
+"metric/test/metric_name=test\n"
+"metric/test/filter=event=test\n"
+"\n";
+
+static int test_reader_server_input_args(struct connection *conn ATTR_UNUSED,
+					 const char *const *args)
+{
+	if (args[0] == NULL)
+		return -1;
+
+	test_assert_strcmp(args[0], "test");
+	test_assert_strcmp(args[1], "1");
+
+	return 1;
+}
+
+static void test_dump_metrics(void)
+{
+	int fds[2];
+
+	test_assert(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0);
+
+	struct connection *conn = i_new(struct connection, 1);
+
+	struct ioloop *loop = io_loop_create();
+
+	client_reader_create(fds[1]);
+	connection_init_client_fd(conn_list, conn, "stats", fds[0], fds[0]);
+	o_stream_nsend_str(conn->output, "DUMP\tcount\n");
+
+	io_loop_run(loop);
+	connection_deinit(conn);
+	i_free(conn);
+
+	/* allow client-reader to finish up */
+	io_loop_set_running(loop);
+	io_loop_handler_run(loop);
+
+	io_loop_destroy(&loop);
+}
+
+static void test_client_reader(void)
+{
+	const struct connection_vfuncs client_vfuncs = {
+		.input_args = test_reader_server_input_args,
+		.destroy = test_reader_server_destroy,
+	};
+
+	test_begin("client reader");
+
+	/* register some stats */
+	test_init(settings_blob_1);
+
+	client_readers_init();
+	conn_list = connection_list_init(&client_set, &client_vfuncs);
+
+	/* push event in */
+	struct event *event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	test_event_send(event);
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	/* check output from reader */
+	test_dump_metrics();
+
+	test_deinit();
+
+	client_readers_deinit();
+	connection_list_deinit(&conn_list);
+
+	test_end();
+}
+
+static const char *settings_blob_2 =
+"metric=test\n"
+"metric/test/metric_name=test\n"
+"metric/test/filter=event=test\n"
+"metric/test/group_by=test_name\n"
+"\n";
+
+static int
+test_reader_server_input_args_group_by(struct connection *conn,
+				       const char *const *args)
+{
+	struct test_connection *tconn =
+		container_of(conn, struct test_connection, conn);
+
+	if (args[0] == NULL)
+		return -1;
+
+	tconn->row_count++;
+
+	if (tconn->row_count == 1) {
+		test_assert_strcmp(args[0], "test");
+		test_assert_strcmp(args[1], "1");
+	} else if (tconn->row_count == 2) {
+		test_assert_strcmp(args[0], "test_alpha");
+		test_assert_strcmp(args[1], "1");
+	}
+	return 1;
+}
+
+static void test_dump_metrics_group_by(void)
+{
+	int fds[2];
+
+	test_assert(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0);
+
+	struct test_connection *conn = i_new(struct test_connection, 1);
+
+	struct ioloop *loop = io_loop_create();
+
+	client_reader_create(fds[1]);
+	connection_init_client_fd(conn_list, &conn->conn, "stats", fds[0], fds[0]);
+	o_stream_nsend_str(conn->conn.output, "DUMP\tcount\n");
+
+	io_loop_run(loop);
+	connection_deinit(&conn->conn);
+	i_free(conn);
+
+	io_loop_set_running(loop);
+	io_loop_handler_run(loop);
+
+	io_loop_destroy(&loop);
+}
+
+static void test_client_reader_group_by(void)
+{
+	const struct connection_vfuncs client_vfuncs = {
+		.input_args = test_reader_server_input_args_group_by,
+		.destroy = test_reader_server_destroy,
+	};
+
+	test_begin("client reader (group by)");
+
+	/* register some stats */
+	test_init(settings_blob_2);
+
+	client_readers_init();
+	conn_list = connection_list_init(&client_set, &client_vfuncs);
+
+	/* push event in */
+	struct event *event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	event_add_str(event, "event_name", "alpha");
+	test_event_send(event);
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	/* check output from reader */
+	test_dump_metrics_group_by();
+
+	test_deinit();
+
+	client_readers_deinit();
+	connection_list_deinit(&conn_list);
+
+	test_end();
+}
+
+int main(void) {
+	/* fake master service to pretend destroying
+	   connections. */
+	struct master_service local_master_service = {
+		.stopping = TRUE,
+		.total_available_count = 100,
+		.service_count_left = 100,
+	};
+	void (*const test_functions[])(void) = {
+		test_client_reader,
+		test_client_reader_group_by,
+		NULL
+	};
+
+	master_service = &local_master_service;
+
+	int ret = test_run(test_functions);
+
+	return ret;
+}
diff --git a/src/stats/test-client-writer.c b/src/stats/test-client-writer.c
new file mode 100644
index 0000000..1256da9
--- /dev/null
+++ b/src/stats/test-client-writer.c
@@ -0,0 +1,152 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "test-stats-common.h"
+#include "master-service-private.h"
+#include "client-writer.h"
+#include "connection.h"
+#include "ostream.h"
+
+static struct event *last_sent_event = NULL;
+static bool recurse_back = FALSE;
+static struct connection_list *conn_list;
+
+static void test_writer_server_destroy(struct connection *conn)
+{
+	io_loop_stop(conn->ioloop);
+}
+
+static int test_writer_server_input_args(struct connection *conn,
+					 const char *const *args ATTR_UNUSED)
+{
+	/* check filter */
+	test_assert_strcmp(args[0], "FILTER");
+	test_assert_strcmp(args[1], "(event=\"test\")");
+	/* send commands now */
+	string_t *send_buf = t_str_new(128);
+	o_stream_nsend_str(conn->output, "CATEGORY\ttest\n");
+	str_printfa(send_buf, "BEGIN\t%"PRIu64"\t0\t0\t", last_sent_event->id);
+	event_export(last_sent_event, send_buf);
+	str_append_c(send_buf, '\n');
+	o_stream_nsend(conn->output, str_data(send_buf), str_len(send_buf));
+	str_truncate(send_buf, 0);
+	str_printfa(send_buf, "END\t%"PRIu64"\n", last_sent_event->id);
+	o_stream_nsend(conn->output, str_data(send_buf), str_len(send_buf));
+	/* disconnect immediately */
+	return -1;
+}
+
+static struct connection_settings client_set = {
+	.service_name_in = "stats-server",
+	.service_name_out = "stats-client",
+	.major_version = 4,
+	.minor_version = 0,
+
+	.input_max_size = SIZE_MAX,
+	.output_max_size = SIZE_MAX,
+	.client = TRUE,
+};
+
+static const struct connection_vfuncs client_vfuncs = {
+	.input_args = test_writer_server_input_args,
+	.destroy = test_writer_server_destroy,
+};
+
+static void test_write_one(struct event *event ATTR_UNUSED)
+{
+	int fds[2];
+
+	test_assert(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0);
+
+	struct connection *conn = i_new(struct connection, 1);
+
+	struct ioloop *loop = io_loop_create();
+
+	client_writer_create(fds[1]);
+	connection_init_client_fd(conn_list, conn, "stats", fds[0], fds[0]);
+
+	last_sent_event = event;
+	io_loop_run(loop);
+	last_sent_event = NULL;
+	connection_deinit(conn);
+	i_free(conn);
+
+	/* client-writer needs two loops to deinit */
+	io_loop_set_running(loop);
+	io_loop_handler_run(loop);
+	io_loop_set_running(loop);
+	io_loop_handler_run(loop);
+
+	io_loop_destroy(&loop);
+}
+
+bool test_stats_callback(struct event *event,
+			 enum event_callback_type type ATTR_UNUSED,
+			 struct failure_context *ctx ATTR_UNUSED,
+			 const char *fmt ATTR_UNUSED,
+			 va_list args ATTR_UNUSED)
+{
+	if (recurse_back)
+		return TRUE;
+
+	recurse_back = TRUE;
+	if (stats_metrics != NULL) {
+		test_write_one(event);
+	}
+	recurse_back = FALSE;
+
+	return TRUE;
+}
+
+static const char *settings_blob_1 =
+"metric=test\n"
+"metric/test/metric_name=test\n"
+"metric/test/filter=event=test\n"
+"\n";
+
+static void test_client_writer(void)
+{
+	test_begin("client writer");
+
+	/* register some stats */
+	test_init(settings_blob_1);
+
+	client_writers_init();
+	conn_list = connection_list_init(&client_set, &client_vfuncs);
+
+	/* push event in */
+	struct event *event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	test_event_send(event);
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	test_deinit();
+
+	client_writers_deinit();
+	connection_list_deinit(&conn_list);
+
+	test_end();
+}
+
+int main(void) {
+	/* fake master service to pretend destroying
+	   connections. */
+	struct master_service local_master_service = {
+		.stopping = TRUE,
+		.total_available_count = 100,
+		.service_count_left = 100,
+	};
+	void (*const test_functions[])(void) = {
+		test_client_writer,
+		NULL
+	};
+
+	master_service = &local_master_service;
+
+	int ret = test_run(test_functions);
+
+	return ret;
+}
diff --git a/src/stats/test-stats-common.c b/src/stats/test-stats-common.c
new file mode 100644
index 0000000..3e307a9
--- /dev/null
+++ b/src/stats/test-stats-common.c
@@ -0,0 +1,99 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "test-stats-common.h"
+#include <time.h>
+#include <unistd.h>
+
+struct event_category test_category = {
+	.name = "test",
+};
+
+struct event_category child_test_category = {
+	.name = "child",
+	.parent = &test_category,
+};
+
+pool_t test_pool;
+struct stats_metrics *stats_metrics = NULL;
+time_t stats_startup_time;
+
+static bool callback_added = FALSE;
+
+static struct stats_settings *read_settings(const char *settings)
+{
+	struct istream *is = test_istream_create(settings);
+	const char *error;
+	struct setting_parser_context *ctx =
+		settings_parser_init(test_pool, &stats_setting_parser_info, 0);
+	if (settings_parse_stream_read(ctx, is) < 0)
+		i_fatal("Failed to parse settings: %s",
+			settings_parser_get_error(ctx));
+	if (!settings_parser_check(ctx, test_pool, &error))
+		i_fatal("Failed to parse settings: %s",
+			error);
+	struct stats_settings *set = settings_parser_get(ctx);
+	settings_parser_deinit(&ctx);
+	i_stream_unref(&is);
+	return set;
+}
+
+void test_init(const char *settings_blob)
+{
+	if (!callback_added) {
+		event_register_callback(test_stats_callback);
+		callback_added = TRUE;
+	}
+
+	stats_event_categories_init();
+	test_pool = pool_alloconly_create(MEMPOOL_GROWING"test pool", 2048);
+	stats_startup_time = time(NULL);
+
+	/* register test categories */
+	stats_event_category_register(test_category.name, NULL);
+	stats_event_category_register(child_test_category.name,
+				      &test_category);
+	struct stats_settings *set = read_settings(settings_blob);
+	stats_metrics = stats_metrics_init(set);
+}
+
+void test_deinit(void)
+{
+	stats_metrics_deinit(&stats_metrics);
+	stats_event_categories_deinit();
+	pool_unref(&test_pool);
+}
+
+void test_event_send(struct event *event)
+{
+        struct failure_context ctx = {
+                .type = LOG_TYPE_DEBUG,
+        };
+
+	usleep(1); /* make sure duration>0 always */
+        event_send(event, &ctx, "hello");
+}
+
+uint64_t get_stats_dist_field(const char *metric_name, enum stats_dist_field field)
+{
+        struct stats_metrics_iter *iter =
+		stats_metrics_iterate_init(stats_metrics);
+        const struct metric *metric;
+        while((metric = stats_metrics_iterate(iter)) != NULL)
+                if (strcmp(metric->name, metric_name) == 0)
+                        break;
+
+        /* bug in test if not found */
+        i_assert(metric != NULL);
+
+        stats_metrics_iterate_deinit(&iter);
+
+        switch(field) {
+        case STATS_DIST_COUNT:
+                return stats_dist_get_count(metric->duration_stats);
+        case STATS_DIST_SUM:
+                return stats_dist_get_sum(metric->duration_stats);
+        default:
+                i_unreached();
+        }
+}
+
diff --git a/src/stats/test-stats-common.h b/src/stats/test-stats-common.h
new file mode 100644
index 0000000..86c03f4
--- /dev/null
+++ b/src/stats/test-stats-common.h
@@ -0,0 +1,36 @@
+#ifndef TEST_STATS_COMMON
+#define TEST_STATS_COMMON 1
+
+#include "stats-common.h"
+#include "event-filter.h"
+#include "istream.h"
+#include "settings-parser.h"
+#include "str.h"
+#include "test-common.h"
+#include "lib-event-private.h"
+#include "stats-dist.h"
+#include "stats-event-category.h"
+#include "stats-metrics.h"
+
+extern struct event_category test_category;
+extern struct event_category child_test_category;
+extern pool_t test_pool;
+
+bool test_stats_callback(struct event *event,
+			 enum event_callback_type type ATTR_UNUSED,
+			 struct failure_context *ctx, const char *fmt ATTR_UNUSED,
+			 va_list args ATTR_UNUSED);
+
+void test_init(const char *settings_blob);
+void test_deinit(void);
+
+void test_event_send(struct event *event);
+
+enum stats_dist_field {
+        STATS_DIST_COUNT,
+        STATS_DIST_SUM,
+};
+
+uint64_t get_stats_dist_field(const char *metric_name, enum stats_dist_field field);
+
+#endif
diff --git a/src/stats/test-stats-metrics.c b/src/stats/test-stats-metrics.c
new file mode 100644
index 0000000..c384014
--- /dev/null
+++ b/src/stats/test-stats-metrics.c
@@ -0,0 +1,449 @@
+/* Copyright (c) 2019 Dovecot authors, see the included COPYING file */
+
+#include "test-stats-common.h"
+#include "array.h"
+
+bool test_stats_callback(struct event *event,
+			 enum event_callback_type type ATTR_UNUSED,
+			 struct failure_context *ctx, const char *fmt ATTR_UNUSED,
+			 va_list args ATTR_UNUSED)
+{
+	if (stats_metrics != NULL) {
+		stats_metrics_event(stats_metrics, event, ctx);
+		struct event_filter *filter =
+			stats_metrics_get_event_filter(stats_metrics);
+		return !event_filter_match(filter, event, ctx);
+	}
+	return TRUE;
+}
+
+static const char *settings_blob_1 =
+"metric=test\n"
+"metric/test/metric_name=test\n"
+"metric/test/filter=event=test\n"
+"\n";
+
+static void test_stats_metrics(void)
+{
+	test_begin("stats metrics (event counting)");
+
+	/* register some stats */
+	test_init(settings_blob_1);
+
+	/* push event in */
+	struct event *event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	test_event_send(event);
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	test_deinit();
+	test_end();
+}
+
+static const char *settings_blob_2 =
+"metric=test\n"
+"metric/test/metric_name=test\n"
+"metric/test/filter=(event=test AND test_field=value)\n"
+"\n";
+
+static void test_stats_metrics_filter(void)
+{
+	test_begin("stats metrics (filter)");
+
+	test_init(settings_blob_2);
+
+	/* check filter */
+	struct event_filter *filter =
+		stats_metrics_get_event_filter(stats_metrics);
+	string_t *str_filter = t_str_new(64);
+	event_filter_export(filter, str_filter);
+	test_assert_strcmp("((event=\"test\" AND \"test_field\"=\"value\"))",
+			   str_c(str_filter));
+
+	/* send event */
+	struct event *event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	event_add_str(event, "test_field", "value");
+	test_event_send(event);
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	/* send another event */
+	event = event_create(NULL);
+	event_add_category(event, &test_category);
+	event_set_name(event, "test");
+	event_add_str(event, "test_field", "nother value");
+	e_debug(event, "test");
+	event_unref(&event);
+
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == 1);
+	test_assert(get_stats_dist_field("test", STATS_DIST_SUM) > 0);
+
+	test_deinit();
+	test_end();
+}
+
+static void test_stats_metrics_group_by_check_one(const struct metric *metric,
+						  const char *sub_name,
+						  unsigned int total_count,
+						  unsigned int submetric_count,
+						  unsigned int group_by_count,
+						  enum stats_metric_group_by_func group_by_func,
+						  const char *group_by_field,
+						  enum metric_value_type value_type)
+{
+	test_assert_strcmp(metric->name, "test");
+
+	if (sub_name != NULL)
+		test_assert_strcmp(metric->sub_name, sub_name);
+	else
+		test_assert(metric->sub_name == NULL);
+
+	test_assert(stats_dist_get_count(metric->duration_stats) == total_count);
+
+	if (submetric_count > 0) {
+		test_assert(array_is_created(&metric->sub_metrics));
+		test_assert(array_count(&metric->sub_metrics) == submetric_count);
+	} else {
+		test_assert(!array_is_created(&metric->sub_metrics));
+	}
+
+	if (group_by_count > 0) {
+		test_assert(metric->group_by_count == group_by_count);
+		i_assert(metric->group_by != NULL);
+		test_assert(metric->group_by[0].func == group_by_func);
+		test_assert_strcmp(metric->group_by[0].field, group_by_field);
+	} else {
+		test_assert(metric->group_by_count == 0);
+		test_assert(metric->group_by == NULL);
+	}
+
+	test_assert(metric->group_value.type == value_type);
+}
+
+#define DISCRETE_TEST_VAL_COUNT	3
+struct discrete_test {
+	const char *settings_blob;
+	unsigned int num_values;
+	const char *values_first[DISCRETE_TEST_VAL_COUNT];
+	const char *values_second[DISCRETE_TEST_VAL_COUNT];
+};
+
+static const struct discrete_test discrete_tests[] = {
+	{
+		"test_name sub_name",
+		3,
+		{ "eta", "kappa", "nu", },
+		{ "upsilon", "pi", "epsilon", },
+	},
+	{
+		"test_name:discrete sub_name:discrete",
+		3,
+		{ "apple", "bannana", "orange", },
+		{ "pie", "yoghurt", "cobbler", },
+	},
+	{
+		"test_name sub_name:discrete",
+		3,
+		{ "apollo", "gaia", "hermes", },
+		{ "thor", "odin", "loki", },
+	},
+};
+
+static void test_stats_metrics_group_by_discrete_real(const struct discrete_test *test)
+{
+	struct event *event;
+	unsigned int i, j;
+
+	test_begin(t_strdup_printf("stats metrics (discrete group by) - %s",
+				   test->settings_blob));
+
+	test_init(t_strdup_printf("metric=test\n"
+				  "metric/test/metric_name=test\n"
+				  "metric/test/filter=event=test\n"
+				  "metric/test/group_by=%s\n"
+				  "\n", test->settings_blob));
+
+	for (i = 0; i < test->num_values; i++) {
+		for (j = 0; j < test->num_values; j++) {
+			event = event_create(NULL);
+			event_add_category(event, &test_category);
+			event_set_name(event, "test");
+			event_add_str(event, "test_name", test->values_first[i]);
+			event_add_str(event, "sub_name", test->values_second[j]);
+			test_event_send(event);
+			event_unref(&event);
+		}
+	}
+
+	/* check total number of events */
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == test->num_values * test->num_values);
+
+	/* analyze the structure */
+	struct stats_metrics_iter *iter = stats_metrics_iterate_init(stats_metrics);
+	const struct metric *root_metric = stats_metrics_iterate(iter);
+	stats_metrics_iterate_deinit(&iter);
+
+	test_stats_metrics_group_by_check_one(root_metric,
+					      NULL,
+					      test->num_values * test->num_values,
+					      test->num_values,
+					      2, STATS_METRIC_GROUPBY_DISCRETE,
+					      "test_name", 0);
+
+	struct metric *const *first = array_idx(&root_metric->sub_metrics, 0);
+
+	/* examime each sub-metric */
+	for (i = 0; i < test->num_values; i++) {
+		test_stats_metrics_group_by_check_one(first[i],
+						      test->values_first[i],
+						      test->num_values,
+						      test->num_values,
+						      1, STATS_METRIC_GROUPBY_DISCRETE,
+						      "sub_name",
+						      METRIC_VALUE_TYPE_STR);
+
+		struct metric *const *second = array_idx(&first[i]->sub_metrics, 0);
+
+		/* examine each sub-sub-metric */
+		for (j = 0; j < test->num_values; j++) {
+			test_stats_metrics_group_by_check_one(second[j],
+							      test->values_second[j],
+							      1, 0, 0, 0, NULL,
+							      METRIC_VALUE_TYPE_STR);
+		}
+	}
+
+	test_deinit();
+	test_end();
+}
+
+static void test_stats_metrics_group_by_discrete(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < N_ELEMENTS(discrete_tests); i++)
+		test_stats_metrics_group_by_discrete_real(&discrete_tests[i]);
+}
+
+#define QUANTIZED_TEST_VAL_COUNT	15
+struct quantized_test {
+	const char *settings_blob;
+	unsigned int num_inputs;
+	intmax_t input_vals[QUANTIZED_TEST_VAL_COUNT];
+
+	unsigned int num_sub_metrics;
+
+	unsigned int num_ranges;
+	struct {
+		struct stats_metric_settings_bucket_range range;
+		intmax_t count;
+	} ranges[QUANTIZED_TEST_VAL_COUNT];
+};
+
+static const struct quantized_test quantized_tests[] = {
+	{
+		"linear:100:1000:100",
+		13,
+		{ 0, 50, 100, 101, 200, 201, 250, 301, 900, 901, 1000, 1001, 2000 },
+		7,
+		11,
+		{ { { INTMAX_MIN, 100 }, 3 },
+		  { { 100, 200 }, 2 },
+		  { { 200, 300 }, 2 },
+		  { { 300, 400 }, 1 },
+		  { { 400, 500 }, 0 },
+		  { { 500, 600 }, 0 },
+		  { { 600, 700 }, 0 },
+		  { { 700, 800 }, 0 },
+		  { { 800, 900 }, 1 },
+		  { { 900, 1000 }, 2 },
+		  { { 1000, INTMAX_MAX }, 2 },
+		}
+	},
+	{
+		/* start at 0 */
+		"exponential:0:6:10",
+		12,
+		{ 0, 5, 10, 11, 100, 101, 500, 1000, 1001, 1000000, 1000001, 2000000 },
+		7,
+		8,
+		{ { { INTMAX_MIN, 1 }, 1 },
+		  { { 1, 10 }, 2 },
+		  { { 10, 100 }, 2 },
+		  { { 100, 1000 }, 3 },
+		  { { 1000, 10000 }, 1 },
+		  { { 10000, 100000 }, 0 },
+		  { { 100000, 1000000 }, 1 },
+		  { { 1000000, INTMAX_MAX }, 2 },
+		}
+	},
+	{
+		/* start at 0 */
+		"exponential:0:6:2",
+		9,
+		{ 0, 1, 2, 4, 5, 20, 64, 65, 100 },
+		7,
+		8,
+		{ { { INTMAX_MIN, 1 }, 2 },
+		  { { 1, 2 }, 1 },
+		  { { 2, 4 }, 1 },
+		  { { 4, 8 }, 1 },
+		  { { 8, 16 }, 0 },
+		  { { 16, 32 }, 1 },
+		  { { 32, 64 }, 1 },
+		  { { 64, INTMAX_MAX }, 2 },
+		}
+	},
+	{
+		/* start at >0 */
+		"exponential:2:6:10",
+		12,
+		{ 0, 5, 10, 11, 100, 101, 500, 1000, 1001, 1000000, 1000001, 2000000 },
+		5,
+		6,
+		{ { { INTMAX_MIN, 100 }, 5 },
+		  { { 100, 1000 }, 3 },
+		  { { 1000, 10000 }, 1 },
+		  { { 10000, 100000 }, 0 },
+		  { { 100000, 1000000 }, 1 },
+		  { { 1000000, INTMAX_MAX }, 2 },
+		}
+	},
+	{
+		/* start at >0 */
+		"exponential:2:6:2",
+		9,
+		{ 0, 1, 2, 4, 5, 20, 64, 65, 100 },
+		5,
+		6,
+		{ { { INTMAX_MIN, 4 }, 4 },
+		  { { 4, 8 }, 1 },
+		  { { 8, 16 }, 0 },
+		  { { 16, 32 }, 1 },
+		  { { 32, 64 }, 1 },
+		  { { 64, INTMAX_MAX }, 2 },
+		}
+	},
+};
+
+static void test_stats_metrics_group_by_quantized_real(const struct quantized_test *test)
+{
+	unsigned int i;
+
+	test_begin(t_strdup_printf("stats metrics (quantized group by) - %s",
+				   test->settings_blob));
+
+	test_init(t_strdup_printf("metric=test\n"
+				  "metric/test/metric_name=test\n"
+				  "metric/test/filter=event=test\n"
+				  "metric/test/group_by=test_name foobar:%s\n"
+				  "\n", test->settings_blob));
+
+	struct event *event;
+
+	for (i = 0; i < test->num_inputs; i++) {
+		event = event_create(NULL);
+		event_add_category(event, &test_category);
+		event_set_name(event, "test");
+		event_add_str(event, "test_name", "alpha");
+		event_add_int(event, "foobar", test->input_vals[i]);
+		test_event_send(event);
+		event_unref(&event);
+	}
+
+	/* check total number of events */
+	test_assert(get_stats_dist_field("test", STATS_DIST_COUNT) == test->num_inputs);
+
+	/* analyze the structure */
+	struct stats_metrics_iter *iter = stats_metrics_iterate_init(stats_metrics);
+	const struct metric *root_metric = stats_metrics_iterate(iter);
+	stats_metrics_iterate_deinit(&iter);
+
+	test_stats_metrics_group_by_check_one(root_metric, NULL, test->num_inputs,
+					      1, 2, STATS_METRIC_GROUPBY_DISCRETE,
+					      "test_name", 0);
+
+	/* examine first level sub-metric */
+	struct metric *const *first = array_idx(&root_metric->sub_metrics, 0);
+	test_stats_metrics_group_by_check_one(first[0],
+					      "alpha",
+					      test->num_inputs,
+					      test->num_sub_metrics,
+					      1,
+					      STATS_METRIC_GROUPBY_QUANTIZED,
+					      "foobar",
+					      METRIC_VALUE_TYPE_STR);
+
+	/* check the ranges */
+	test_assert(first[0]->group_by[0].num_ranges == test->num_ranges);
+	for (i = 0; i < test->num_ranges; i++) {
+		test_assert(first[0]->group_by[0].ranges[i].min == test->ranges[i].range.min);
+		test_assert(first[0]->group_by[0].ranges[i].max == test->ranges[i].range.max);
+	}
+
+	/* examine second level sub-metrics */
+	struct metric *const *second = array_idx(&first[0]->sub_metrics, 0);
+
+	for (i = 0; i < test->num_sub_metrics; i++) {
+		const char *sub_name;
+		intmax_t range_idx;
+
+		/* we check these first, before we use the value below */
+		test_assert(second[i]->group_value.type == METRIC_VALUE_TYPE_BUCKET_INDEX);
+		test_assert(second[i]->group_value.intmax < test->num_ranges);
+
+		range_idx = second[i]->group_value.intmax;
+
+		/* construct the expected sub-metric name */
+		if (test->ranges[range_idx].range.min == INTMAX_MIN) {
+			sub_name = t_strdup_printf("foobar_ninf_%jd",
+						   test->ranges[range_idx].range.max);
+		} else if (test->ranges[range_idx].range.max == INTMAX_MAX) {
+			sub_name = t_strdup_printf("foobar_%jd_inf",
+						   test->ranges[range_idx].range.min + 1);
+		} else {
+			sub_name = t_strdup_printf("foobar_%jd_%jd",
+						   test->ranges[range_idx].range.min + 1,
+						   test->ranges[range_idx].range.max);
+		}
+
+		test_stats_metrics_group_by_check_one(second[i],
+						      sub_name,
+						      test->ranges[second[i]->group_value.intmax].count,
+						      0, 0, 0, NULL,
+						      METRIC_VALUE_TYPE_BUCKET_INDEX);
+	}
+
+	test_deinit();
+	test_end();
+}
+
+static void test_stats_metrics_group_by_quantized(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < N_ELEMENTS(quantized_tests); i++)
+		test_stats_metrics_group_by_quantized_real(&quantized_tests[i]);
+}
+
+int main(void) {
+	void (*const test_functions[])(void) = {
+		test_stats_metrics,
+		test_stats_metrics_filter,
+		test_stats_metrics_group_by_discrete,
+		test_stats_metrics_group_by_quantized,
+		NULL
+	};
+
+	int ret = test_run(test_functions);
+
+	return ret;
+}