4 files changed, 136 insertions, 0 deletions
diff --git a/web/api/formatters/value/Makefile.am b/web/api/formatters/value/Makefile.am
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--- /dev/null
+++ b/web/api/formatters/value/Makefile.am
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+AUTOMAKE_OPTIONS = subdir-objects
+MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
+
+dist_noinst_DATA = \
+    README.md \
+    $(NULL)
diff --git a/web/api/formatters/value/README.md b/web/api/formatters/value/README.md
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+++ b/web/api/formatters/value/README.md
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+<!--
+title: "Value formatter"
+custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/formatters/value/README.md
+-->
+
+# Value formatter
+
+The Value formatter presents [results of database queries](/web/api/queries/README.md) as a single value.
+
+To calculate the single value to be returned, it sums the values of all dimensions.
+
+The Value formatter respects the following API `&options=`:
+
+| option    | supported | description |
+|:----:     |:-------:  |:----------  |
+| `percent` | yes       | to replace all values with their percentage over the row total|
+| `abs`     | yes       | to turn all values positive, before using them |
+| `min2max` | yes       | to return the delta from the minimum value to the maximum value (across dimensions)|
+
+The Value formatter is not exposed by the API by itself.
+Instead it is used by the [`ssv`](/web/api/formatters/ssv/README.md) formatter
+and [health monitoring queries](/health/README.md).
+
+[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fweb%2Fapi%2Fformatters%2Fvalue%2FREADME&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)
diff --git a/web/api/formatters/value/value.c b/web/api/formatters/value/value.c
new file mode 100644
index 0000000..aea6c16
--- /dev/null
+++ b/web/api/formatters/value/value.c
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "value.h"
+
+
+inline calculated_number rrdr2value(RRDR *r, long i, RRDR_OPTIONS options, int *all_values_are_null) {
+    rrdset_check_rdlock(r->st);
+
+    long c;
+    RRDDIM *d;
+
+    calculated_number *cn = &r->v[ i * r->d ];
+    RRDR_VALUE_FLAGS *co = &r->o[ i * r->d ];
+
+    calculated_number sum = 0, min = 0, max = 0, v;
+    int all_null = 1, init = 1;
+
+    calculated_number total = 1;
+    int set_min_max = 0;
+    if(unlikely(options & RRDR_OPTION_PERCENTAGE)) {
+        total = 0;
+        for(c = 0, d = r->st->dimensions; d && c < r->d ;c++, d = d->next) {
+            calculated_number n = cn[c];
+
+            if(likely((options & RRDR_OPTION_ABSOLUTE) && n < 0))
+                n = -n;
+
+            total += n;
+        }
+        // prevent a division by zero
+        if(total == 0) total = 1;
+        set_min_max = 1;
+    }
+
+    // for each dimension
+    for(c = 0, d = r->st->dimensions; d && c < r->d ;c++, d = d->next) {
+        if(unlikely(r->od[c] & RRDR_DIMENSION_HIDDEN)) continue;
+        if(unlikely((options & RRDR_OPTION_NONZERO) && !(r->od[c] & RRDR_DIMENSION_NONZERO))) continue;
+
+        calculated_number n = cn[c];
+
+        if(likely((options & RRDR_OPTION_ABSOLUTE) && n < 0))
+            n = -n;
+
+        if(unlikely(options & RRDR_OPTION_PERCENTAGE)) {
+            n = n * 100 / total;
+
+            if(unlikely(set_min_max)) {
+                r->min = r->max = n;
+                set_min_max = 0;
+            }
+
+            if(n < r->min) r->min = n;
+            if(n > r->max) r->max = n;
+        }
+
+        if(unlikely(init)) {
+            if(n > 0) {
+                min = 0;
+                max = n;
+            }
+            else {
+                min = n;
+                max = 0;
+            }
+            init = 0;
+        }
+
+        if(likely(!(co[c] & RRDR_VALUE_EMPTY))) {
+            all_null = 0;
+            sum += n;
+        }
+
+        if(n < min) min = n;
+        if(n > max) max = n;
+    }
+
+    if(unlikely(all_null)) {
+        if(likely(all_values_are_null))
+            *all_values_are_null = 1;
+        return 0;
+    }
+    else {
+        if(likely(all_values_are_null))
+            *all_values_are_null = 0;
+    }
+
+    if(options & RRDR_OPTION_MIN2MAX)
+        v = max - min;
+    else
+        v = sum;
+
+    return v;
+}
diff --git a/web/api/formatters/value/value.h b/web/api/formatters/value/value.h
new file mode 100644
index 0000000..d9e981f
--- /dev/null
+++ b/web/api/formatters/value/value.h
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_API_FORMATTER_VALUE_H
+#define NETDATA_API_FORMATTER_VALUE_H
+
+#include "../rrd2json.h"
+
+extern calculated_number rrdr2value(RRDR *r, long i, RRDR_OPTIONS options, int *all_values_are_null);
+
+#endif //NETDATA_API_FORMATTER_VALUE_H