Metrics for DataSource

[mdeinum]

Currently the metrics provided are repository based or for the web request. It would be nice if we could also get some metrics about the datasources, like in DropWizard. It would be nice if we could get an overview of the min/max connecties, current open connecties and pool usage/saturation. Those metrics can help to tune the datasource configuration for live systems (and could be a trigger if the open connections or pool usage go upto 100%).

[snicoll]

There are two ways we can implement this. Either we update the DatasourceHealthIndicator to provide this information (alongside the version and the status of the connection) or we add it to the metrics endpoint.

If we want to add it to the metrics endpoint, then we need to rework a bit how PublicMetrics works because it's hard to customize it. I would see a composite similar to what we have done for the health endpoint.

What do you guys think?