tree 68d9d35e3ea87bacedeae312b9f92e0858e73a86
parent e70b34d0361f29ac5a5dd99c179ef8c8443ce53b
author mammadli.khazar <mammadli.khazar@cloudera.com> 1665495703 +0200
committer Alexey Serbin <alexey@apache.org> 1668051752 +0000

KUDU-3375 Expose Prometheus Metrics in Kudu

This patch introduces an endpoint which emits server level metrics in
Prometheus Text Explosion format for Kudu. The endpoint can be found at
/metrics_prometheus path of the webserver.

More information on the Prometheus format can be found at:
https://prometheus.io/docs/instrumenting/exposition_formats

Prefix kudu_ has been added to all of the metric names according to
Prometheus naming convention to specify the domain and differentiate
from any other metrics belonging to different services. Following the
kudu_ prefix either master_ or tserver_ prefix is attached based on the
server type that is exposing the metrics. In order to differentiate
between different master and tablet servers running on the same host
Prometheus automatically attaches an instance label which holds the
"hostname:portname".

eg: kudu_master_metric{instance="localhost:8765", job="kudu-master", unit_type="unit"}

Not all of the Kudu metric names follow the Prometheus metric naming
recommendations which state metric units should be attached at the end
of the metric name. In Kudu some metrics have these units at the end of
the metric name, some in the middle of the metric and for some metrics
it is unclear what the metric unit is just by looking at the metric
name. Due to this and also because Kudu supports more Metric Units
than base Prometheus Metric units, metric units are represented as
Prometheus labels for each metric. This also makes it possible to keep
time based units more accurate as Milliseconds, Nanoseconds and etc.
do not need to be converted to seconds which is the base time unit in
Prometheus.

More information on Prometheus Metric units and naming conventions
can be found at:
https://prometheus.io/docs/practices/naming/#metric-names

Tested by feeding all of the generated metrics to a prometheus server
running on localhost. Added unit tests to each metric type.

Change-Id: I4b2d01bd56f6f0f1b6f31cbce15e671d16521739
Reviewed-on: http://gerrit.cloudera.org:8080/19133
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <alexey@apache.org>