Create a WFO metrics endpoint/exporter

[srichmond]

Background

The idea is to have a place were certain performance metrics are exposed so that they can be scraped and pushed to a TSDB.

Instant performance metrics:

• number of current workflow active
• number of current workflows active failed
• number of current tasks active
• number of current tasks active failed
• number of completed workflows (I am kind of unsure about this one)
• duration of completed workflows (same here)

long-term metrics:

• number of products
• number of subscriptions per state

These are the first things that pop up in my mind, I guess it could make sense to get some interesting stats about database usage but probably there are other ways to do it

Implementation

I guess a scraping endpoint that can be pointed at by a prometheus would work, but I also know that many of us use influxdb so this approach might be suboptimal. The idea came from the metric server in Proxomox where you can choose between graphite and influxdb.

I do not think this has to be something configurable via GUI.

[hanstrompert]

Probably better to use counters instead of gauges to be less interval dependent.