Fix accumulating memory issue

[Zain-Mahmoud]

Proposed Changes

This PR aims to fix the issue where repeated calls to the PyTA check_all() function cause the memory usage of the process to increase with each call (issue #646).

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[Zain-Mahmoud]

Investigation

import io
import tracemalloc
import python_ta

def run_runner():
    buf = io.StringIO()
    python_ta.check_all(output=buf)

tracemalloc.start()

for i in range(5000):
    run_runner()
    current = tracemalloc.get_traced_memory()
    print(f"{i} | {int(current[0] / 1024**2)} MB")

Running the above code snippet, we can see that the memory usage does in fact increase with each call:

0 | 42 MB
1 | 44 MB
2 | 46 MB
3 | 48 MB
4 | 49 MB
5 | 51 MB
6 | 53 MB
7 | 55 MB
8 | 56 MB
9 | 58 MB
...
91 | 121 MB
92 | 122 MB
93 | 124 MB
94 | 125 MB
95 | 127 MB
96 | 128 MB
97 | 130 MB
98 | 132 MB
99 | 133 MB
...

But there does seem to be some freeing of memory (approximately 20 or so MB) every ~20 calls.

I also checked both Pylint and Astroid's changelogs but I couldn't find any fixes related to any memory leak issues.

[david-yz-liu]

Thanks @Zain-Mahmoud. I did a bit of digging and found this pylint option: https://pylint.pycqa.org/en/latest/user_guide/configuration/all-options.html#clear-cache-post-run. Could you try to figure out how we can run PythonTA with this option enabled, and whether that fixes the issue?

[Zain-Mahmoud]

Hi @david-yz-liu
I tried using the clear-cache-post-run option after instantiating the linter but it doesn't seem like the issue has been fixed. I've also pushed the updated code I'm using.

[david-yz-liu]

Alright thanks @Zain-Mahmoud, I think we'll need to do some more research then. There are two tools that you can use to help with memory profiling in Python: tracemalloc, which is a Python built-in module, and memray, which is a third-party package. Please try using those to investigate which parts of the codebase may be resulting in issues.

BTW, you could also do some experimentation like commenting out particular components to see if that makes a difference.