Prometheus restores alert state between restarts and updates. For each rule, it looks at the alerts that are meant to be active and then queries the `ALERTS_FOR_STATE` series for _each_ alert within the rules.
If the alert rule has 120 instances (or series) it'll execute the same query with slightly different labels.
This PR changes the approach so that we only query once per alert rule and then match the corresponding alert that we're about to restore against the series-set. While the approach might use a bit more memory at start-up (if even?) the restore proccess is only ran once per restart so I'd consider this a big win.
This builds on top of #13974
Signed-off-by: gotjosh <josue.abreu@gmail.com>
When a rule group changes or prometheus is restarted we need to ensure we restore the active alerts that were firing for a corresponding rule, for that Prometheus uses the `ALERTS_FOR_STATE` series to query the previous state and restore it. If a given rule has high cardinality (think 100s of 1000s for series) this proccess can take a bit of time - this is the first of a series of PRs to improve this problem and I'd like to start with exposing the time it takes to restore a rule group as a gauge.
Signed-off-by: gotjosh <josue.abreu@gmail.com>
Rule warnings are logged with numDropped=N while every other component uses num_dropped=N:
```
notifier/notifier.go: level.Warn(n.logger).Log("msg", "Alert batch larger than queue capacity, dropping alerts", "num_dropped", d)
notifier/notifier.go: level.Warn(n.logger).Log("msg", "Alert notification queue full, dropping alerts", "num_dropped", d)
storage/remote/write_handler.go: _ = level.Warn(h.logger).Log("msg", "Error on ingesting out-of-order exemplars", "num_dropped", outOfOrderExemplarErrs)
rules/group.go: level.Warn(logger).Log("msg", "Error on ingesting out-of-order result from rule evaluation", "num_dropped", numOutOfOrder)
rules/group.go: level.Warn(logger).Log("msg", "Error on ingesting too old result from rule evaluation", "num_dropped", numTooOld)
rules/group.go: level.Warn(logger).Log("msg", "Error on ingesting results from rule evaluation with different value but same timestamp", "num_dropped", numDuplicates)
scrape/scrape.go: level.Warn(sl.l).Log("msg", "Error on ingesting out-of-order samples", "num_dropped", appErrs.numOutOfOrder)
scrape/scrape.go: level.Warn(sl.l).Log("msg", "Error on ingesting samples with different value but same timestamp", "num_dropped", appErrs.numDuplicates)
scrape/scrape.go: level.Warn(sl.l).Log("msg", "Error on ingesting samples that are too old or are too far into the future", "num_dropped", appErrs.numOutOfBounds)
scrape/scrape.go: level.Warn(sl.l).Log("msg", "Error on ingesting out-of-order exemplars", "num_dropped", appErrs.numExemplarOutOfOrder)
```
Rename numDropped to num_dropped for consistency.
Signed-off-by: Łukasz Mierzwa <l.mierzwa@gmail.com>
Updated & added tests
Review feedback nits
Return empty map if not indeterminate
Use highWatermark to track inflight requests counter
Appease the linter
Clarify feature flag
Signed-off-by: Danny Kopping <danny.kopping@grafana.com>
