Fix leaking EventSourceDelegate and URLSession

[diederich]

Requirements

• [-] I have added test coverage for new or changed functionality
• [+] I have followed the repository's pull request submission guidelines (I ran swift test)
• [-] I have validated my changes against all supported platform versions

Describe the solution you've provided

I was looking for mem leaks today, and spot some coming from the EventSource here:

• leaking URLSessions (and everything that belongs to it, like certificates, ...)
• leaking the EventSourceDelegate class

To fix them:

• cleanup the EventSourceDelegate from not-required usage of self (it was mixed anyways, and only having the ones required helps a bit spotting self-captures
• fix ref-cycle self -> eventParser -> ConnectionHandler -> self
• fix URLSession not being cleaned up properly, which kept the delegate alive

Describe alternatives you've considered

n/a

[torchhound]

Hi @diederich thanks for contributing this patch! We will review and test it internally.

[diederich]

Thanks @torchhound!

[diederich]

@torchhound Again, thanks for looking into this. Any updates here? (We'd love to drop our custom dependency on the branch and go back to mainline)

[RyanYuan-Iconic]

Hi team, is there any update on this issue?

[fbarbat]

I hit this issue too. I had created this issue launchdarkly/ios-client-sdk#258 before finding this PR.

[DispoKen]

Hello, are there any updates on this issue? We noticed that this issue may have contributed to a spike in out-of-memory crashes that we observed last week. Is there an ETA for this?

[louis-launchdarkly]

Hello all on this thread and apologize for the slow response. Thank you for your contribution and reaching out on this issue - we have merged #36 with a bit more changes on top of this change. This should address the leaking issue.

This is still an issue for the iOS client-side SDK because we haven't adopted the change there yet. We still need more time to release a new version of the iOS client-side SDK, and I will give another update to this ticket when the new version of the iOS client-side SDK is available.

[DispoKen]

Thanks for the update @louis-launchdarkly, do you have a rough estimate when there will be a new update? I'm debating if I should fork LaunchDarkly with the fixes to address the memory leaks.