App Server ARRAffinity lead to 'The resource you are looking for has been removed, had its name changed, or is temporarily unavailable'

Question

App Server ARRAffinity lead to 'The resource you are looking for has been removed, had its name changed, or is temporarily unavailable'

Edward Sun (US) 0

Access sub page will get 'The resource you are looking for has been removed, had its name changed, or is temporarily unavailable'

After further investigation we found it related to the Cookies: ARRAffinity and ARRAffinitySameSite, after remove these cookies the page will be available.

But after the two cookies add back again automatically, open new page still get the same error message.

I want to understand what happened in the Web App service and what will cause this issue?

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Answer 1

Hi @Edward Sun (US) thanks for the question.

When a client makes a request to an Azure App Service, the request is routed to one of the available instances of the app service. The ARRAffinity and ARRAffinitySameSite cookies are then set by the app service to ensure that subsequent requests from the same client are routed to the same instance.

There are a few reason why you're seeing the error message "The resource you are looking for has been removed, had its name changed, or is temporarily unavailable" when accessing a sub-page of your azure web application:

If the ARRAffinity and ARRAffinitySameSite cookies are being sent with subsequent requests from the same client, but are not being recognized by the app service, the request may be routed to a different instance, which may not have the session state for the client.
If the ARRAffinity cookies have a different domain value, the browser will take it as different cookies. This can cause issues if the first ARRAffinity value is invalid due to the instance being removed from the service plan (by scale in or UD walk), as the FrontEnd will try to find a new valid worker instance with a new ARRAffinity value for the client. However, this new ARRAffinity value will always be saved into the second subdomain’s cookies, which cannot be picked up by the App Service FrontEnd.

To troubleshoot this issue, you can try the following steps:

Ignore the domain name and keep only one ARRAffinity Cookies at the client side
Update the App Service FrontEnd to pick up the ARRAffinity, which has the same domain name as the request has.
If your app isn’t scaled to multiple instances, or doesn’t use in-process session, you can disable the affinity cookie from the App Service Configuration blade (under General Settings). See this SO thread

For more troubleshooting tips please see this blog post: Session lost due to ARRAffinity Cookies

Hope this helps. please let us know if you have further questions.

-Grace

Edward Sun (US) 0 Reputation points

2023-10-09T01:22:50+00:00

Thanks Grmacjon, we did not have multiple domains and Front Door service behind App Service. And after further investigation, I found we actually add web.config to disable the ARRAffinity like

<httpProtocol> <customHeaders> <add name="Arr-Disable-Session-Affinity" value="true" /> </customHeaders> </httpProtocol>

But we still get found ARRAffinity and ARRAffinitySameSite Cookie even after clear all data cache in browser.

So, if that means the possible reason was:

If the ARRAffinity and ARRAffinitySameSite cookies are being sent with subsequent requests from the same client, but are not being recognized by the app service, the request may be routed to a different instance, which may not have the session state for the client.
Grmacjon-MSFT 19,381 Reputation points Moderator

2023-10-12T01:08:47.1033333+00:00

@Edward Sun (US) thanks for the update. this is odd behavior especially since you already disable the ARRAffinity cookies in your web.config file. I bring this up with the engineering team internally to see if this is a known issue/bug and get back to you soon.
Edward Sun (US) 0 Reputation points

2023-10-23T01:20:01.5633333+00:00

Hi @Grmacjon-MSFT , is there any finding by engineering team?
We are currently seeking ways to prevent similar issues in the future. If you could provide us with more information, it would greatly assist us in identifying the necessary next steps.
Edward Sun (US) 0 Reputation points

2023-10-23T01:21:40.7+00:00

not able to add comment, try again.

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App Server ARRAffinity lead to 'The resource you are looking for has been removed, had its name changed, or is temporarily unavailable'

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