* Alerting: Fix alert flapping in the alertmanager
fixes a bug that caused Alerts that are evaluated at low intervals (sub 1 minute), to flap in the Alertmanager.
Mostly due to a combination of `EndsAt` and resend delay.
The Alertmanager uses `EndsAt` as a heuristic to know whenever it should resolve a firing alert, in the case that it hasn't heard
back from the alert generation system.
Because grafana sent the alert with an `EndsAt` which is equal to the `For` of the alert itself,
and we had a hard-coded 1 minute re-send delay (only applicable to firing alerts) this meant that a firing alert would resolve in the Alertmanager before we re-notify that it still firing.
This commit, increases the `EndsAt` by 3x the the resend delay or alert interval (depending on which one is higher). The resendDelay has been decreased to 30 seconds.
* Expand the value of math and reduce expressions in annotations and labels
This commit makes it possible to use the values of reduce and math
expressions in annotations and labels via their RefIDs. It uses the
Stringer interface to ensure that "{{ $values.A }}" still prints the
value in decimal format while also making the labels for each RefID
available with "{{ $values.A.Labels }}" and the float64 value with
"{{ $values.A.Value }}"
When, and currently only when using a classic condition, evaluation information is added (which is like the EvalMatches from dashboard alerting).
This is returned via the API and can be included in notifications by reading the `__value__` label attached `.Alerts` in the template. It is a string.
* Fix fialure when adding state annotations
* Fix get org rules API
Do not fail response if user has no access to view a namespace.
Do not include the namespace in the response instead.
* lint
* set processing time
* merge labels and set on response
* use state cache for adding alerts to rules
* minor cleanup
* add support for NoData and Error results
* rename test
* bring in changes from other PRs tha have been merged
* pr feedback
* add integration test
* close state tracker cleanup on context.Done
* fixup test
* rename state tracker
* set EvaluationDuration on Result
* default labels set as constants
* separate cache and state from manager
* use RWMutex in cache
