I am new to Python programming and having a problem with a multithreaded program (using the "threading" module) that runs fine at the beginning, but after a while starts repeatedly printing "IOStream.flush timed out" errors.
I am not even sure how to debug such an error, because I don't know what line is causing it. I read a bit about this error and saw that it might be related to memory consumption, so I tried profiling my program using a memory profiler on the Spyder IDE. Nothing jumped out at me, however (although I admit that I am not sure what to look for when it comes to Python memory leaks).
A few more observations:
I have an outer loop that runs my function over a large number of files. The files are just number data with the same formatting (they are quite large though and there is download latency, which is why I have made my application multithreaded so that each thread works on different files). If I have a long list of files, the problem occurs. If I shorten the list, the program concludes without problem. I am not sure why that is, although if it is some kind of memory leak then I would assume when I run the program longer, the problem grows until it reaches some kind of memory limit.
Normally, I use 128 threads in the program. If I reduce the number of threads to 48 or less, the program works fine and completes correctly. So clearly the problem is caused by multithreading (I'm using the "threading" module). This makes it a bit trickier to debug and figure out what is causing the problem. It seems something around 64 threads starts causing problems.
The program never explicitly crashes out. Once it gets to the point where it has this error, it just keeps repeatedly printing "IOStream.flush timed out". I have to close the Spyder IDE to stop it (Restart kernel doesn't work).
Right before this error happens, the program appears to stall. At least no more "prints" happen to the console (the various threads are all printing debug information to the screen). The last lines printed are standard debugging/status print statements that usually work when the number of threads is reduced or the number of files to process is decreased.
I have no idea how to debug this and get to the bottom of the problem. Any suggestions on how to get to the bottom of this would be much appreciated. Thanks in advance!
Specs:
- Python 3.8.8
- Spyder 4.2.5
- Windows 10