Azure App Service health check alert not firing

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I have an app service with provides a health check endpoint. I have enabled "Health check" on this service and provided the health check endpoint path. I have validated the endpoint in a browser and it is reachable. When everything is running it is reporting a value for the metric of 100. I have set up an alert rule on this metric in Application Insights and tried Average and Min in this rule (< 100). When I kill or stop the service the rule never fires.

It is stated here that this should be possible but I have not found a way to do this: https://azure.github.io/AppService/2020/08/24/healthcheck-on-app-service.html#alerts

Also I'm not sure what the 100 even is: %?

In the chart when I hover over the last few minutes it doesn't show a numeric value but rather "--". Which is probably why the rule doesn't fire. Anyone got this working? Is it a bug?

azure-web-app-service azure-application-insights azure
2 Answers

Just to report back, this seems to be working as expected now. It also depends on the type of "unhealthiness" of the service. If you stop the service manually it doesn't fire as it is then a planned stop. If you kill the main process then the service is automatically restarted (as it is seemingly implemented with docker and the main process is the entrypoint). If however you do something for the server to report downness (5XX status code for example on the health endpoint) then it works as expected. The metrics are recorded correctly and thus metric graphs are correct. Alerting on such metrics also works then.

user_29395700
user_124270360
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