Building off config-specific Prometheus refresh metrics from an earlier
PR (https://github.com/prometheus/prometheus/pull/17138), this deletes
refresh metrics like `prometheus_sd_refresh_duration_seconds` and
`prometheus_sd_refresh_failures_total` when the underlying scrape job
configuration is removed on reload. This reduces un-needed cardinality
from scrape job specific metrics while still preserving metrics that
indicate overall health of a service discovery engine.
For example,
`prometheus_sd_refresh_failures_total{config="linode-servers",mechanism="linode"} 1`
will no longer be exported by Prometheus when the `linode-servers`
scrape job for the Linode service provider is removed. The generic,
service discovery specific `prometheus_sd_linode_failures_total` metric
will persist however.
* fix: add targetsMtx lock for targets access
* test: validate refresh/discover metrics are gone
* ref: combine sdMetrics and refreshMetrics
Good idea from @bboreham to combine sdMetrics and refreshMetrics!
They're always passed around together and don't have much of a
reason not to be combined. mechanismMetrics makes it clear what kind of
metrics this is used for (service discovery mechanisms).
---------
Signed-off-by: Will Bollock <wbollock@linode.com>
Adds a `config` label (similar to `prometheus_sd_discovered_targets`) to
refresh metrics to help identify the source of refresh issues or
performance stats. In particular for HTTP SD, it can be common to have
multiple disparate HTTP SD sources that should be identified and not
lumped together. For example if one HTTP SD service has failures, that
should be evident in its own time series seperate from other HTTP SD
sources.
`config` seemed more appropriate than `endpoint` as a general standard
for `prometheus_sd` metrics.
Docs were also updated for HTTP SD to point at the new refresh metrics
rather than the older metrics.
Signed-off-by: Will Bollock <wbollock@linode.com>
