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-rw-r--r--src/proxymap/proxymap.c38
1 files changed, 35 insertions, 3 deletions
diff --git a/src/proxymap/proxymap.c b/src/proxymap/proxymap.c
index abdcf3a..c0af411 100644
--- a/src/proxymap/proxymap.c
+++ b/src/proxymap/proxymap.c
@@ -37,7 +37,7 @@
/* .IP \(bu
/* To provide single-updater functionality for lookup tables
/* that do not reliably support multiple writers (i.e. all
-/* file-based tables).
+/* file-based tables that are not based on \fBlmdb\fR).
/* .PP
/* The \fBproxymap\fR(8) server implements the following requests:
/* .IP "\fBopen\fR \fImaptype:mapname flags\fR"
@@ -752,8 +752,10 @@ static void post_jail_init(char *service_name, char **unused_argv)
if (strcmp(service_name, MAIL_SERVICE_PROXYWRITE) == 0)
proxy_writer = 1;
else if (strcmp(service_name, MAIL_SERVICE_PROXYMAP) != 0)
- msg_fatal("service name must be one of %s or %s",
- MAIL_SERVICE_PROXYMAP, MAIL_SERVICE_PROXYMAP);
+ msg_fatal("invalid service name: \"%s\" - "
+ "service name must be \"%s\" or \"%s\"",
+ service_name, MAIL_SERVICE_PROXYWRITE,
+ MAIL_SERVICE_PROXYMAP);
/*
* Pre-allocate buffers.
@@ -841,6 +843,36 @@ int main(int argc, char **argv)
*/
MAIL_VERSION_STAMP_ALLOCATE;
+ /*
+ * XXX When invoked with the master.cf service name "proxywrite", the
+ * proxymap daemon will allow update requests. To update a table that is
+ * not multi-writer safe (for example, some versions of Berkeley DB), the
+ * "proxywrite" service should run as a single updater (i.e. a process
+ * limit of 1, which could be enforced below by requesting
+ * CA_MAIL_SERVER_SOLITARY).
+ *
+ * In the default master.cf file, the "proxywrite" service has a process
+ * limit of 1. Assuming that updates will be rare, this process limit
+ * will suffice. Latency-sensitive services such as postscreen must not
+ * use the proxywrite service (in fact, postscreen has a latency check
+ * built-in).
+ *
+ * Optimizing for multi-writer operation would suffer from all kinds of
+ * complexity that would make it hard to use:
+ *
+ * - The master daemon specifies the "proxywrite" service name with the -n
+ * command-line option. This information is not known here, before the
+ * multi_server_main() call. The multi_server_main() function could
+ * reveal process limit information to its call-back functions, and leave
+ * single-updater enforcement to its call-back functions.
+ *
+ * - If we really want multi-writer update support, the "proxywrite" service
+ * would have to parse the $proxy_write_maps value, and permit
+ * multi-writer operation only if all tables are multi-writer safe. That
+ * would require a new dict(3) method, to query each lookup table
+ * implementation if it is multi-writer safe, without instantiating a
+ * lookup table client.
+ */
multi_server_main(argc, argv, proxymap_service,
CA_MAIL_SERVER_STR_TABLE(str_table),
CA_MAIL_SERVER_POST_INIT(post_jail_init),