opentelemetry-instrumentation-starlette: fix memory leak and double middleware

[anuraaga]

Description

Fixes memory leak from using set, which prevents __del__, which means starlette apps can never be garbage collected.

Fixes adding two middlewares if instrument_app is called with auto instrumentation active

/cc @xrmx

Type of change

• [] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Unit tests of latest and oldest

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[xrmx]

@anuraaga this is ready to review since you fixed the testcase right?

[anuraaga]

FYI @codefromthecrypt

[anuraaga]

@anuraaga this is ready to review since you fixed the testcase right?

Yup should be ok now

[anuraaga]

Oh no, I didn't check existing PRs before making this one and now see @MattiasDC's #3456 is quite similar. I found the tests seem to pass fine for the current baseline version so didn't raise it here which is the main difference. Feel free to reject this PR as a duplicate and get that one in instead though, then I can send another one with just the WeakSet and other fixes which should still apply.

[emdneto]

@anuraaga Thank you for the fix! To be fair with the already opened PR #3456 I would suggest that we proceed with #3456 and later you can modify your PR with the changes you are proposing here (weakset and the fix for the already instrumented flag)

[emdneto]

@anuraaga #3456 was merged.

[anuraaga]

Thanks @emdneto have rebased this PR