API management service ClientConnectionFailure at forward-request

6
votes

I have a Azure function calling Service fabric API using HttpClient API exposed in API management service. But the API management service logs shows that the API call failed with the problem ID "ClientConnectionFailure at forward-request".

On the client side I receive System.Net.Sockets.SocketException with error message "The operation was canceled. Unable to read data from the transport connection: The I/O operation has been aborted because of either a thread exit or an application request. The I/O operation has been aborted because of either a thread exit or an application request"

What are the possible reasons for this failure? How to fix it? Unfortunately I couldn't find enough documentation on this?

2
azureazure-api-management
HI. Check your API by running on Postman with same payload and setup. Check the direct link first , after that link with APIM. Compare the time that took by this API. – Inzi
Look like it got timeout. try thsi, docs.microsoft.com/en-us/azure/api-management/… – Inzi
From APIM point of view client (the one making a call to APIM) is breaking connection. – Vitaliy Kurokhtin
Actually the issue was with backend API. The backend API threw an unhandled c# application exception but my expectation was that API management gateway forwards the same exception to the client but API management threw misleading exceptions like ClientConnectionFailure at forward-request and Timeout etc. Not sure why is this behaviour? – PNDev

2 Answers

4
votes

First you have to understand that in APIM we have client which could be your browser or any other tool, the APIM proxy that forwards the requests to the back-end and the back-end that hosts your application.

The reason behind the client connection failure is that the client drops the connection before receiving the response from the APIM proxy.

Two reasons might cause the client to drop the connection

  1. The APIM gateway takes long time to respond due to heavy load at the APIM gateway or the back-end the APIM instance points to (proxying) is unable to handle the amount of requests forwarded by the APIM gateway (unable to keep up with the apim service load) so the client times out while waiting for a response or sometimes while still sending the request.

  2. The client drops the connection for any reason while receiving the response from the APIM proxy.

You have to identify what reason is causing this and based on that you need to react by either fixing your client or to scale-up your APIM or your back-end.

0
votes

I had similar issue. In my case sales force is the client and I have observed this error often. Sales forces closes connection if it does not get a response within 5 seconds of call. This fails the request at APIM level and error "ClientConnectionFailure at forward-request" is observed.

Please check for how long does you'r client wait for the response. If APIM takes longer than that is the same issue.

to cater this you need to either increase wait time at client side or work on improving response time of APIM.