Azure Application Gateway
An Azure service that provides a platform-managed, scalable, and highly available application delivery controller as a service.
Azure - Server Error: 502 - Web server received an invalid response while acting as a gateway or proxy server
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Quickspin Colombia
6
Reputation points
When I configured my application gateway, I get the error "Server Error: 502 - Web server received an invalid response while acting as a gateway or proxy server".
I have checked that NSG, UDR, and Custom DNS is not blocking access to backend pool members, any pointers to where else I can look how to get rid of this?
Azure Application Gateway
{count} vote
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GitaraniSharma-MSFT 50,187 Reputation points Microsoft Employee Moderator2022-05-26T13:26:28.383+00:00 Hello @Quickspin Colombia ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand you configured an Azure Application gateway and getting the error "Server Error: 502 - Web server received an invalid response while acting as a gateway or proxy server". You have checked that NSG, UDR, and Custom DNS is not blocking access to backend pool members and need guidance on proceeding further.
Could you please provide the below details?
- What is configured in the application gateway backend pool - VM or webapp?
- Did you check if your back-end instances can respond to a ping from another VM in the same VNet?
- And how about the probe - is it a default probe or custom probe? And whether the probe can reach the backend instances.
You can follow the below troubleshooting doc for 502 errors in Application gateway:
https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-troubleshooting-502I would also advise you to check the Details column on the Backend Health tab of your Application gateway and see if you are receiving any of the error messages listed in the below article and follow the recommended solution:
https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshootingRegards,
Gita -
GitaraniSharma-MSFT 50,187 Reputation points Microsoft Employee Moderator
2022-06-07T08:55:45.823+00:00 Hello @Quickspin Colombia , do you have any further updates on this issue?
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GitaraniSharma-MSFT 50,187 Reputation points Microsoft Employee Moderator
2022-06-09T09:45:39.32+00:00 Hello @Quickspin Colombia , do you have any updates on this issue?
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Jorge Ricardo Pacheco Cruz 21 Reputation points2022-09-15T17:46:10.24+00:00 Hello, exactly the same thing just happened to me, all the applications worked fine, and out of nowhere everything stopped working, without moving anything now the site does not work, is there anything that can solve the error?
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Jorge Ricardo Pacheco Cruz 21 Reputation points
2022-09-15T17:46:26.337+00:00 Hello, exactly the same thing just happened to me, all the applications worked fine, and out of nowhere everything stopped working, without moving anything now the site does not work, is there anything that can solve the error?
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Quickspin Colombia 6 Reputation points
2022-09-29T06:54:12.637+00:00 In my case it was that default health probe couldnt reach my back-end server.
I used the guide here: https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-troubleshooting-502 to solve the error. Good luck!
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Tola Chhoeun 1 Reputation point2022-12-08T05:27:00.083+00:00 Same problem here. I got the same problem when rolling out a new build from the Azure CI/CD process yesterday.
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GitaraniSharma-MSFT 50,187 Reputation points Microsoft Employee Moderator
2022-12-08T13:15:52.667+00:00 Hello @Tola Chhoeun ,
What is the status of the backend health in your Application gateway?
Refer : https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshootingAlso, did you refer the bad gateway errors troubleshooting doc to validate all your configuration?
Refer : https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-troubleshooting-502Regards,
Gita
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