HTTP 504 and message successful

[#1]

Hi API Experts,

Please can you provide guidance for the issue I am facing in following scenario related to APIGEE(On Premise)

Scenario is : Source system access APIGEE API and the protocol is SOAP. APIGEE forwards the message to Target application.

In the above scenario sometimes Source system is getting HTTP 504 error when trying to post the message via API. In the API dashboard I can see Proxy error as well. However even after getting HTTP 504 error the message is being transferred by the API to target system. So this is giving wrong signal to source application, they are thinking message didn't reach target application as they got HTTP 504 error and they are trying to repost the same message again. In such scenario it is creating duplicate messages in target system.

1. Firstly, how can we handle the above situation?
2. Secondly, How can we ensure that message is not forwarded to target application when APIGEE sends HTTP 504
3. Finally, Where can I find the logs for such error?

Thanks