deadlock in pyomo tee using highs with multiprocessing

[maurerle]

Summary

We have an issue where are solving multiple independent problems at the same time using pyomo and highs.

This somehow leads to the error message Significant delay observed waiting to join reader threads, possible output stream deadlock and a deadlock.

Steps to reproduce the issue

Sorry, no MWE for now, I hope to get feedback on what the cause of this could.

$ command1 [options]
$ command2 [options]
...

# example.py
import pyomo.environ
...

Error Message

$ # Output message here, including entire stack trace, if available

Information on your system

Pyomo version: 6.8.2
Python version: 3.12
Operating system: Debian 12
How Pyomo was installed (PyPI, conda, source): pip
Solver (if applicable): pyhighs/HiGHs

Additional information

This occurs when using multiprocessing equally well as when using two terminals to start two optimizations at the same time

[maurerle]

I suspect this issue has to do with FINE, which tries to use tee on all outputs and therefore generates this issue.

I am trying to add proper HiGHs support to FINE here: FZJ-IEK3-VSA/FINE#65

[mrmundt]

This is most likely related to/similar to #3084 - we have a PR open for that. Would you mind trying that branch (#3449)?

[ChriKo97]

#3449 is not working for me

[mrmundt]

@maurerle - We cannot recreate this without a MWE. Can you please provide us with one?