Possible memory leak in nodejs interception

Describe the bug

A clear and concise description of what the bug is.

I have a simple repo with 16 test files where every test file does the same thing of firing a simple fetch call and asserting for the response from the MSW handler. But when we run all the test files one after the other the heap usage keeps increasing. But when I comment the MSW server instantiation and other MSW related code heap memory stays constant.

Environment

• msw: 0.28.2
• nodejs: v12.14.0
• npm: 6.13.4

Please also provide your browser version.

To Reproduce

Steps to reproduce the behavior:

1. Clone the repo https://github.com/mathanpec/msw-memory-leak-test
2. Do yarn install
3. Execute node --expose-gc ./node_modules/.bin/jest --silent --runInBand --detectOpenHandles --logHeapUsage
4. I am specifically doing node --expose-gc and running GC in the AfterAll step to make sure there are no unused memory is left between test files.

Expected behavior

Memory heap should be consistent between every file runs or there should be a very minimal change. Check the following screenshot from the same repo without MSW server initialisation and handlers

[mathanpec]

Hi @kettanaito,

So I tried profiling the runs and this is what I could find,

You can see ClientRequestOverride is being referenced recursively and when I looked at the code, http.ClientRequest is being monkey patched here but its not being set back to the original reference anywhere. This could be one possible cause but I am not very sure though.

[kettanaito]

Hey, @mathanpec. I’ve commented on the pull request. Will have to check it out and get back to you. Thank you for your work on this, it looks great!