Problem Application Gateway Timeout

Question

Hello,

After configuring the application gateway with my domain, I'm encountering a persistent 504 timeout error. The home page loads, but I receive a timeout exactly 20 seconds after I'm trying to logging in to the website.

I discovered that the default backend timeout setting is 20 seconds, so I increased it to 200 seconds and also set the IP idle timeout to 20 minutes. However, the error still occurs after 20 seconds.

It seems the backend timeout setting is not taking effect the new changes. Any assistance would be greatly appreciated.

Answer 1

@Hatem BENNACEUR

Thank you for reaching out.

I understand you are facing 504 timeout error after 20 seconds for your Azure Application Gateway even when you have increased the default backend timeout setting value to 200 seconds.

Based on your observation above I think the issue can be because of the timeout set at the backend. It will help if you can check if the 504 response was sent out by the backend in this instance. As documented here

If your backend server is IIS, see Default Limits for Web Sites to set the timeout value. Refer to the connectionTimeout attribute for details. Ensure the connection timeout in IIS matches or does not exceed the timeout set in the backend setting.

nginx

If the backend server is nginx or nginx ingress controller, and if it has upstream servers, ensure the value of nginx:proxy_read_timeout matches or does not exceed with the timeout set in the backend setting.

You can also take help of Diagnostic logging for Azure Application Gateway and check the Access logs for any error codes received.

Hope this helps! Please let me know if the issue still persists and we gladly continue with our discussion. Thank you!

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