Expose metrics

[martin31821]

Expose some information about the router itself, e.g.

• number per incoming/outgoing messages
• incoming/outgoing traffic (bytes/sec)
• number of successful and rejected authentications per authmethod
• number of successful/failed authorizations
• number of connected clients per authrole (maybe authid?)

Expose this either as prometheus compatible endpoint and/or directly as wamp topics/procedures.

@jwuensche

[johannwagner]

We talked about this issue.

We want to abstract the metrics to a prometheus format, which also should be published as a wamp message in the ee.* namespace.

The endpoint should be disableable.
The endpoint should be exposed at /metrics.

[fia0]

I've implemented the proposed metrics in a separate fork of mine, https://github.com/jwuensche/autobahnkreuz, which also requires a fork of nexus.

Though I've decided to expose the metrics as an API and use an exporter to make them scrapable for prometheus, to allow other applications to make use of the data.
It is currently not published as a wamp message.