write_prometheus plugin: New plugin for exposing metrics to Prometheus.

[collectd.git] / src / collectd.conf.pod

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index c21dac9..dcf6c36 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -8148,6 +8148,41 @@ want to use authentication all three fields must be set.
 
 =back
 
+=head2 Plugin C<write_prometheus>
+
+The I<write_prometheus plugin> implements a tiny webserver that can be scraped
+using I<Prometheus>.
+
+B<Options:>
+
+=over 4
+
+=item B<Port> I<Port>
+
+Port the embedded webserver should listen on. Defaults to B<9103>.
+
+=item B<StalenessDelta> I<Seconds>
+
+Time in seconds after which I<Prometheus> considers a metric "stale" if it
+hasn't seen any update for it. This value must match the setting in Prometheus.
+It defaults to B<300> seconds (5 minutes), same as Prometheus.
+
+B<Background:>
+
+I<Prometheus> has a global setting, C<StalenessDelta>, which controls after
+which time a metric without updates is considered "stale". This setting
+effectively puts an upper limit on the interval in which metrics are reported.
+
+When the I<write_prometheus plugin> encounters a metric with an interval
+exceeding this limit, it will inform you, the user, and provide the metric to
+I<Prometheus> B<without> a timestamp. That causes I<Prometheus> to consider the
+metric "fresh" each time it is scraped, with the time of the scrape being
+considered the time of the update. The result is that there appear more
+datapoints in I<Prometheus> than were actually created, but at least the metric
+doesn't disappear periodically.
+
+=back
+
 =head2 Plugin C<write_http>
 
 This output plugin submits values to an HTTP server using POST requests and