[Question] How to customize (tag) HikariCP Micrometer pool metrics

[diogo-hs]

We're undergoing some changes in our multi-module Spring app, and I need to collect a few Micrometer HikariCP metrics (more specifically, the hikaricp_connections_active) in a customized way.

Currently, it tags the metrics per data source pool:

# TYPE hikaricp_connections_active gauge
hikaricp_connections_active{pool="reading-pool",} 0.0
hikaricp_connections_active{pool="writing-pool",} 0.0

We have several modules in the app, and I'd like to tag the connections per module as well, something like:

# TYPE hikaricp_connections_active gauge
hikaricp_connections_active{pool="reading-pool",module="a",} 0.0
hikaricp_connections_active{pool="writing-pool",module="a",} 0.0
hikaricp_connections_active{pool="reading-pool",module="b",} 0.0
hikaricp_connections_active{pool="writing-pool",module="b",} 0.0

Initially, I thought about creating my own IMetricsTracker along with an interceptor (to identify which module code is requesting a connection) to set the metric I need, but the problem is it's a Gauge, and it relies on PoolStats and all the machinery behind the HikariPool (especially the ConcurrentBag) to feed the pool stats.

I couldn't find any way to customize the Hikari pool metrics management classes (most of them are package-protected, I believe purposefully).

Has anyone ever had to do something like this? Any suggestion on what direction I could take here? I really appreciate your time and feedback! 🙏