IF my_custom_metric == 0
Scenario is as follows:
In the correct runtime my_custom_metric is 1, and MyServiceDown alert is green at Alert tab.
Then I set my_custom_metric 0 and Propetheus retrieves it as 0, which I can see at Graph -> Console tab.
MyServiceDown immediately becomes Pending (yellow) and after 15 seconds becomes Firing (red).
Then I "fix bug", my_custom_metric is 1 again, and MyServiceDown alert is green.
Here comes strange part. I break app second time so that my_custom_metric is 0 again. It is shown at Graph -> Console. But MyServiceDown alert never pending or firing. When I restart Prometheus everything works good, but only once.