This is a follow-up on the `go fix` run in commit
0210c5fd92.
That commit recorded the automated updates.
This one applies further simplifications that are mechanical and do not
involve logic changes, but are outside of what `go fix` did.
It also removes some now-obsolete comments and statements.
The openmetrics format doesn't support empty newlines or miscellaneous
comments, and the Prometheus parser has become more strict over time,
which is now causing scraping errors.
This patch fixes those issues by adjusting to the stricter openmetrics
format.
Thanks to Jakub Ječmínek for reporting this issue!
The openmetrics proposed standard says we should use the
`application/openmetrics-text` content type when exporting the metrics.
Currently we use `text/plain` for backwards compatibility with
Prometheus, but the new content type is apparently supported since 2018,
so it should be safe to update to match the current proposed standard.
This patch makes chasquid's monitoring server expose an OpenMetrics
metrics endpoint.
It adds a new package "expvarom" which implements an HTTP handler that
exports expvar variables in the OpenMetrics text format.
Then, the handler is registered by the monitoring server at /metrics
(where most things expect it to be).
The existing exported variables are also extended with descriptions,
which is optional, but improves the readability of the metrics.
Alberto Bertogli