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We got some IoT devices connecting with an Azure App Service through an Azure Application gateway. The mobile connection has a limited data capacity each month and because of this we need the connection to be kept alive. But the connection drops after apx 50 seconds and the cost to re-open the connection or ping to keep it alive is too much.
According to this link: https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-faq the default is 75 seconds in the v2 SKU. How can I increase the 75 seconds or obtain a connection that is kept alive
@BBCDenmark,
The default is 75 seconds and that settings is not editable. I think your issue is caused by the Request timeout settings in the HTTP settings.
That is editable and default is 30 seconds. Can you check and change the settings and see if that fixes your issue?
Regards,
Karthik Srinivas
I tried to increase the timeout settings from 30 to 50 to 70 and it makes no difference. Still the same and the connection closes after apx. 50-54 seconds. The IoT device can "sleep" for hours before it sends a request to the backend / API. In this sleeping time the connection must continue to be open (if possible)
Application Gateway is a reverse proxy. So maintaining connections for hours are costly. So there is a timeout on the Public IP of Application Gateway, on the Frontend - 70 seconds which you mentioned and on the HTTP Settings which keeps the connection from the AppGW to the App Service open. If your connections are getting dropped at 50 seconds, then we need to find which connection is trigged. I mean is it the connection between AppGW and App Service or IOT and AppGW. That requires packet capture at all 3 end. I suggest you to raise a support to get the logs from AppGW and App Service to further troubleshoot.
Thank you very much for helping here. I will see what we can do with the logs.
Best regards Brian