Is it possible that you have a mix of workspaces using Python 2 and 3?

There's a known issue with FME Server when a workspace requests a different Python version than the previously used Python version on the same engine.

More details here (also consider voting for the idea to improve this): https://knowledge.safe.com/idea/36272/allow-different-fme-cloud-python-interpreter.html

I am facing the same identical issue and I can guarantee I double, triple, quadruple checked the "different Python version than the previously used Python version on the same engine"

What FME Server version do you run?

Yes, the Engine should know to try to reload the correct python interpreter when there is a mismatch like this. This issue that you're seeing is a problem that was present in some of the earlier versions of the FME Server 2018 betas and we have fixed this for 2018.0 (build 18310 and newer) as well as 2018.1 build 18481 and newer (from the log file, it looks like you're seeing this on build 18459). With the fix, when an engine encounters a python version mismatch like this, it will automatically restart the engine so that it can load up the correct interpreter.

So FME Server should be able to reload the appropriate interpreter.

If you are stuck with an older version, just change in fmeServerConfig.txt:

MAX_TRANSACTION_RESULT_SUCCESSES=100 
MAX_TRANSACTION_RESULT_FAILURES=10 

both to 1. This forces the engines to restart after every process. (It takes only a fraction of a second, so in most cases no speed regression should occur).

Hi @tino, thanks a lot for your help. Investigating the issue I realised we are actually running on the version problem. I ignored the fact we have a shared FME server and some of my colleagues are still running workbenches with 2.7 interpreter set. So here is the thing, if someone else uploads a workbench on server with 2.7 and happens to run on the engine where the following one has 3.4+ then the second one will break, so the issue isn't much with the workspace that breaks but with the one that ran previously, even if it is from a different user and a different process. I got it now.

The inability for FME Server - in my case 2018.1.1.2 - to switch between Python versions (2.7/3.4) as required suggests a bug (unless it's explicitly not supported and then it should not allow the publish/scheduling).

Should this bug not be logged and fixed?

Error:

Hi, we also run into this (FME Server 2017.1.1). Not sure if upgrading is an option. The workspace I used that caused the error uses the JSON reader which apparently uses Python. Is there a possibility to force reloading Python in the workspace?