Something I recently learned about with FME is that each HTTPCaller seems to equate to one session - there are most likely a lot of cases where this isn’t true but I had some weird issues recently where a series of calls working intermittently. 

The process was creating a document container and then uploading files into it and then closing the container. 

I used 3 separate HTTPCallers for this. When testing from FME desktop it worked sometimes and others it didn’t work. I spent a tonne of time trying to debug what was wrong in my POST. Finally it seemed like it was working, I published to Server and directly had issues again. 

Looking into the Debug logs I noticed that with each new instance of the HTTPCaller there was a new connection to the service BUT that connection was going to a different IP. The host was using a load balancer to handle API requests. 

Turns out my container was being created on one server and my follow up requests were hitting the other server.

After I fed everything though a single HTTPCaller the problem went away.

Creating a session in python is pretty standard and I was wondering how FME handles sessions. To me it seeems like it’s one session per HTTPCaller.

Has anyone else got any more insight?