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I deployed some changes to Azure Functions, but it looks like my endpoint is not reachable. For a while, I kept getting "Function host is not running" errors. Lately, the errors became "HTTP Error 500.37 - ANCM Failed to Start Within Startup Time Limit". How do I resolve this issue? I restarted my function app, but it didn't resolve anything.

EDIT: I looked at my activity log. I see a lot of errors like this:

Operation name 
SlotSwap 
Time stamp 
Fri Aug 14 2020 13:36:40 GMT-0500
(Central Daylight Time) 
Event initiated by 
SlotSwapJobProcessor

"Failed swapping site. Error: Cannot swap slots for site '...' because the warmup requests to application in '...' slot have timed out. Please check the application logs to determine what causes the timeouts."

and this:

Operation name
List Web Apps Functions Host Keys
Time stamp
Fri Aug 14 2020 17:27:49 GMT-0500 (Central Daylight Time)
Event initiated by
[email]
Error code
BadRequest
Message
Encountered an error (InternalServerError) from host runtime.

Everything was working up until today and I haven't made any changes to cause this issue.

user246392
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  • Because the problem you encountered is now running normally, you can rule out your code or release and other factors. – Jason Pan Aug 17 '20 at 01:23
  • It is recommended that you [raise a support ticket](https://learn.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request) to confirm your problem on the portal. – Jason Pan Aug 17 '20 at 01:24

1 Answers1

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I had a similar issue today. (I found this question by searching for List Web Apps Functions Host Keys). Restarting the function app seemed to solve the issue, but only for a few minutes. Then the function app would still produce the impossible to debug Function host is not running error. I was also seeing an OutOfMemoryException error message under the Overview in the Azure portal.

After some digging I realised that I had configured FUNCTIONS_EXTENSION_VERSION to beta (under Settings → Configuration in the Azure portal). I changed it to ~3 as suggested in the Azure Functions runtime versions overview. After changing the function app runtime version, it started to work again.

0xced
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  • Thanks. My extension version was 3. I think that this issue is generic and could be thrown for many reasons. Unfortunately, I deleted the function app and created one from scratch. I'm not sure how I'd have dealt with this if it had occurred in production. – user246392 Aug 20 '20 at 00:40
  • Also, I've had many issues with slots so far. For now, I've stopped using slots. – user246392 Aug 20 '20 at 00:41