JMX Exporter - Caching rules pattern matching for mbeans

[Flavien Raynaud]

Hi there,

We have recently deployed the jmx_exporter to monitor our Kafka infrastructure using Prometheus.
When initially running the exporter (as a Java agent), we noticed collection time could be as high as 70 seconds on some of our Kafka brokers (partly due to the fact that Kafka exposes a lot of metrics on a per topic-partition basis and we have some large brokers), even after tweaking the configuration to only collect mbeans that were interesting to us.

After digging a bit into the codebase of the jmx_exporter and doing some profiling, we noticed most of the collection time was spent matching mbean names/values against regular expressions in the configuration. We have made changes internally to allow (via a feature-flag) to cache the result of these computations. With caching enabled, collection times went down from ~70 sec to ~3 sec. Note that this prevents having rules that take mbeans values in their pattern from being used (as only mbeans names are cached)

I would be happy to open a PR (and discuss potential implementation details) if you think this is a feature worth having in the upstream version of the jmx_exporter?

Cheers,
Flavien