Services: Fix memory leaks in watch mode - #504
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aomarks
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justinfagnani
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Nov 4, 2022
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Added a comment. It's the attempt after the final wait, where we don't wrap in a try so that the exception bubbles up.
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how often does this need all the retries to pass?
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In a single run I just did, one time needed 10, another needed 100.
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Fixes two memory leaks that affected watch mode:
An
abortpromise which always remained unresolved until wireit exited. This prevented both standard and service executions from ever being garbage collected, because they both awaited those promises indefinitely, even after those instances were stale.The fix was to replace the promise entirely with explicit
abort()methods, which turned out to be simpler and less error-prone anyway.The
Executorfor watch mode iteration N was holding references to all persistent services from watch mode iteration N-1, and so on all the way back through all iterations, because of thepreviousIterationServicesmap that we pass forward across iterations.The fix was to delete services from the map after we know they are adopted, breaking the reference chain.
This PR includes new garbage collection tests that use
FinalizationRegistryto keep track of how many instances ofExecutorsandExecutionsthere are after aglobal.gc(). I'm just running that on a single OS/node version on CI, since I think it might be slightly flaky, plus I think that's good enough anyway.In writing the GC tests, I also found a few other bugs with services -- some unhandled state transitions, and a timing issue where we weren't waiting for persistent services to be ready before indicating that the first phase of execution was done.
Part of #33