Adding a listener or wasm-id label to the Prometheus stats

[iMaxGit]

Hi,

we use different listeners in our envoy configuration. To be able to track coraza interventions on a per listener level for better visibility in the prometheus stats, it would be useful to add an additional label to identify the corresponding wasm instance. The listener name would be most helpful in our case, but also the wasm-id should work, if this is easier/quicker to implement, as we can configure it accordingly in our envoy configuration.

[jcchavezs]

Indeed necessary. Up for a PR?

[iMaxGit]

I am not a (Go) programmer, but I assume it would not be too complicated to do. I will give it a try and submit it for review once I have working implementation.

[iMaxGit]

@jcchavezs I had a look at the data accessible by the wasm plugin and I could not find an option to retrieve the listener name or wasm plugin name. If there is a way to get those, please let me know.
If this is not possible then I would suggest to use an additional configuration option, like "stats_prefix" for example. I was pondering using the vm-id, as it is already available to the plugin. However, this might not be practical as it could impact efficiency, as it would prohibit running the plugin from two different listeners or filter chains in the same vm context, if the vm-id is different. Using an additional "stats_prefix" option would give the freedom to separate or consolidate different instances as one sees fit from a statistics point of view.

Any thoughts?