Azure Front Door Unavailable after deployment

Kumar 0

We have set up the Azure Front door for our web application and recently we made some code changes to the application and during the deployment the Front Door is unavailable and it 's been 2 days and it is still not up and in Unavailable state. The web application is up and running.

Usually when there is a deployment the Front Door will be Degraded / Unavailable for few minutes and will be up. But this time it still shows as Unavailable.

How can we isolate the issue if this is because of code changes to the web application the Front door is unavailable or any other issue with Front door ?

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GitaraniSharma-MSFT 46,761 Reputation points Microsoft Employee

2023-01-18T21:08:44.1233333+00:00

Hello @Kumar ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

Could you please confirm if the Azure Front Door is actually working despite the unavailable notification from the resource health? Or the Front Door itself is not working?

Could you also confirm if the health probes for the Azure Front Door is disabled?

Regards,
Gita
Kumar 0 Reputation points

2023-01-20T13:38:02.5666667+00:00
@GitaraniSharma-MSFT Can you please provide some screenshots for the following questions where should I have to look into it in Azure Portal?

Could you please confirm if the Azure Front Door is actually working despite the unavailable notification from the resource health? Or the Front Door itself is not working?

Could you also confirm if the health probes for the Azure Front Door is disabled?
GitaraniSharma-MSFT 46,761 Reputation points Microsoft Employee

2023-01-20T19:12:14.93+00:00
@Kumar ,

Could you please confirm if the Azure Front Door is actually working despite the unavailable notification from the resource health? Or the Front Door itself is not working? --> By this question, I meant if you are able to access your application using the Azure Front Door's URL or not. Sometimes, the resource health may show the AFD as unavailable, but the application may still work. So, I wanted to understand if it is just the resource health which is showing AFD as unavailable or the Front Door as well is down.

Could you also confirm if the health probes for the Azure Front Door is disabled? In Azure Front Door Standard/Premium, you can check the health probe in your configured origin group as below: In Azure Front Door Classic, you can check the health probe in your configured backend pool as below:
Kumar 0 Reputation points

2023-01-24T08:57:58.3466667+00:00

@GitaraniSharma-MSFT Thank you for those details. The Azure Front Door is now up, before it is up the web application is also running without any issue.
We have disabled Health probes for the Azure Front Door.
Should you recommend to enable Health probes for the Azure Front Door ?
GitaraniSharma-MSFT 46,761 Reputation points Microsoft Employee

2023-01-24T11:45:00.9566667+00:00

Hello @Kumar ,

Your Front Door was showing unavailable with the following summary: "One or more of your Front Door backends are responding with errors to health probes". And this generally happens when the backend application is not responding with a 200 OK Status to the Front Door health probes.

Refer: https://learn.microsoft.com/en-us/azure/frontdoor/health-probes

NOTE: A 200 OK status code indicates the backend is healthy. Everything else is considered a failure. If for any reason (including network failure) a valid HTTP response isn't received for a probe, the probe is counted as a failure.

You mentioned that you have disabled the health probes for the Azure Front Door.

Could you please confirm if the health probe for your Front door was enabled before and you have disabled it now? Or it was always in disabled status?

Also, you mentioned that "The Azure Front Door is now up, before it is up the web application is also running without any issue."

Could you please confirm if you are referring to the resource health here or the actual Front Door service?

My understanding is that the application was working via Front Door without any issue even when the Front Door Resource health was showing unavailable, meaning the Front Door was working despite showing unavailable in the resource health section., is that correct?

When I say resource health, I'm referring to the below:

Regards,
Gita
Kumar 0 Reputation points

2023-01-24T12:43:30.28+00:00

@GitaraniSharma-MSFT The health probes for the Azure Front Door was disabled long back ago and I have not enabled / disabled after I receive unavailable notification.
We have configured Resource Health Alerts and received notification and then I noticed the FD is unavailable in following places
Service Health - > Resource Health - > Selected subscription and Resource Type as Front Door

Front Door and CDN Profiles -> Resource Health

My understanding is that the application was working via Front Door without any issue even when the Front Door Resource health was showing unavailable, meaning the Front Door was working despite showing unavailable in the resource health section. CORRECT

Can you share above image again as it is not showing ?
GitaraniSharma-MSFT 46,761 Reputation points Microsoft Employee

2023-01-25T14:14:27.78+00:00

@Kumar , without checking the backend logs, it is difficult to find the root cause of this issue. If the health probes were disabled on the Front Door, then the resource health shouldn't report health probe errors. However, as per the Azure Resource Health team, the health probe mentioned here is not related to the health signal which are constantly sent out to check the health of your individual cloud resources.

Refer: Refer: https://learn.microsoft.com/en-us/azure/service-health/resource-health-overview

https://learn.microsoft.com/en-us/azure/service-health/resource-health-faq#what-health-checks-are-performed-by-resource-health-

So, I believe after the code changes to the application, the backend application was not responding to these health signals (as I mentioned above, this is different from the Azure Front Door health probes) and hence you received an alert for same.

You can find the list of all the checks executed through resource health by resource types in the below doc:

https://learn.microsoft.com/en-us/azure/service-health/resource-health-checks-resource-types

If you are looking for RCA (Root Cause Analysis), then I would suggest opening a support request, where the team can look into the backend logs and try to find out what exactly happened in that time frame. Hence, if you have a support plan, I request you file a support ticket, else please do let us know, we will try and help you get a one-time free technical support.

Regards,
Gita