MINOR: contrib/prometheus-exporter: filter exported metrics by scope
Now, the prometheus exporter parses the HTTP query-string to filter or to adapt
the exported metrics. In this first version, it is only possible select the
scopes of metrics to export. To do so, one or more parameters with "scope" as
name must be passed in the query-string, with one of those values: global,
frontend, backend, server or '*' (means all). A scope parameter with no value
means to filter out all scopes (nothing is returned). The scope parameters are
parsed in their appearance order in the query-string. So an empty scope will
reset all scopes already parsed. But it can be overridden by following scope
parameters in the query-string. By default everything is exported.
The filtering can also be done on prometheus scraping configuration, but general
aim is to optimise the source of data to improve load and scraping time. This is
particularly true for huge configuration with thousands of backends and servers.
Also note that this configuration was possible on the previous official haproxy
exporter but with even more parameters to select the needed metrics. Here we
thought it was sufficient to simply avoid a given type of metric. However, more
filters are still possible.
Thanks to William Dauchy. This patch is based on his work.
(cherry picked from commit 78407ce156b9dd317ae9f4becccd4afa3d5f8c56)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/contrib/prometheus-exporter/README b/contrib/prometheus-exporter/README
index 915fc7f..84ae8e2 100644
--- a/contrib/prometheus-exporter/README
+++ b/contrib/prometheus-exporter/README
@@ -50,6 +50,30 @@
through the stats page. To give a comparison order, quick benchmarks shown that
a PROMEX dump is 5x slower and 20x more verbose than a CSV export.
+
+metrics filtering
+-------------------
+
+It is possible to dynamically select the metrics to export if you don't use all
+of them passing parameters in the query-string.
+
+* Filtering on scopes
+
+The metrics may be filtered by scopes. Multiple parameters with "scope" as name
+may be passed in the query-string to filter exported metrics, with one of those
+values: global, frontend, backend, server or '*' (means all). A scope parameter
+with no value means to filter out all scopes (nothing is returned). The scope
+parameters are parsed in their appearance order in the query-string. So an empty
+scope will reset all scopes already parsed. But it can be overridden by
+following scope parameters in the query-string. By default everything is
+exported. Here are examples:
+
+ /metrics?scope=server # ==> server metrics will be exported
+ /metrics?scope=frontend&scope=backend # ==> Frontend and backend metrics will be exported
+ /metrics?scope=*&scope= # ==> no metrics will be exported
+ /metrics?scope=&scope=global # ==> global metrics will be exported
+
+
Exported metrics
------------------