Using psutil to investigate “Too many open files”#

I was getting this intermittent error running my Datasette test suite:

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OSError: [Errno 24] Too many open files

To figure out what was going on, I used the psutil package and its open_files() method.

Here’s the documentation for psutil.Process.open_files.

I ran pip install psutil in my virtual environment.

Then I ran pytest --pdb to drop into a Python debugger when a test failed.

In the debugger I ran this:

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import psutil
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for f in psutil.Process().open_files(): print(f)

This showed the current list of open files for that process, which gave me some clues to help me start resolving the problem.