[Spce-user] How to switch to Prometheus backend?

[Guillem Jover]

Hi!

On Wed, 2022-06-29 at 21:48:58 +0200, Henk wrote:
> I have a recently installed a system with mr 9.5.4 which runs the new
> Prometheus backend, but an older system I upgraded to the same version is
> still running the old one. I cannot find an update script or any instruction
> in the manual, only the backend and Influxdb_migrated settings.

Hmm, right, the initial intention was to try to provide some migration
script, but migrating the metrics data is very hard and rather
infeasible, given that InfluxDB can store non-numbers as values, while
prometheus cannot, and those would need to be mapped one-by-one somehow
into labels, which can be very tedious (if possible at all). The
resulting script ended up being trivial as it consisted of just changing
a config option, so we stopped installing it.

> What is the procedure to migrate to Prometheus?

Taking into account that the metrics data will not be migrated, doing:

  # ngcpcfg set /etc/ngcp-config/config.yml monitoring.backend=prometheus
  # ngcpcfg apply "Migrate to prometheus as backend"

would switch the monitoring backend. The «influxdb_migrated» settings
controls whether the InfluxDB daemon will still run, in case you want
to query its historical metrics. If you do not care about those (at
least for now), you can set that to «yes» (you can always set it back
to «no» as long as you have not removed the InfluxDB database if you
need to access those old metrics again).

I'll add some notes into the handbook, along the above lines.

Thanks,
Guillem