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Make Glean init in Kotlin fully async #672

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merged 4 commits into from
Feb 13, 2020

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Dexterp37
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@Dexterp37 Dexterp37 commented Jan 23, 2020

I tested this both using Fenix and the Glean SDK sample app: this seem to work as expected. Accumulated data is correctly accounted for and any pre-init dispatched piece of information is sent.

This PR additionally fixes some weird bugs we had in our testing code that made our tests hang forever under certain circumstances. Se the indivudual commit messages.

TODO

  • Take this for a manual QA, make sure it doesn't break
  • Think a bit more what changing flushQueuedInitialTasks implies
  • Test this in Fenix

// the @MainThread decorator and the `assertOnUiThread` call.
MainScope().launch {
ProcessLifecycleOwner.get().lifecycle.addObserver(gleanLifecycleObserver)
}
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Do we need to do this here, or could we do it outside of the coroutine (near the top where things like applicationContext are set?)

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I'm not sure yet, I don't think there's anything preventing us from moving it there, before the glean init even starts.

The only two reasons for not doing that would be:

  • we don't want to register this if the glean init fails;
  • we really want to test this in Fenix before making a call!

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Fair enough on both points. I think I was just coming at it from the angle of -- going off the main thread only to come back to it is more complicated. But, as you say, we don't really know until we try it in the context of Fenix.

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I'll make sure to try that first once I get rid of the failing test and have a proper Fenix build for testing!

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@Dexterp37 Dexterp37 Feb 12, 2020

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I tested that, but I think we should retain the current behaviour even just to make sure that we don't mistakenly register observers if init fails. Thoughts?

Note that this would also protect us against sudden/immediate going to background while initializing.

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That's a good point about not registering if we exit early for some other error during init. 👍 on this, then!

@Dexterp37 Dexterp37 force-pushed the faster_init branch 2 times, most recently from 588d246 to 9d7eadf Compare February 4, 2020 15:29
Our test code relies on `withTimeout*` and `while(true)`
in a few places to wait for things to happen. However,
having a timeout is not enough: if the coroutine is busy,
even if the timeout elapses, the work will not be interrupted.
That's because cancellation in Kotlin coroutines is cooperative,
see [the docs](https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/cancellation-and-timeouts.md#cancellation-is-cooperative)
for more details.

This commit uses cooperative cancellation so that tests will
break, instead of hanging forever.
Without the context, the Glean init would throw
an exception which would "hang" the dispatchers
in the next async tests.
@Dexterp37 Dexterp37 changed the title WIP: Make Glean init in Kotlin fully async Make Glean init in Kotlin fully async Feb 12, 2020
@Dexterp37 Dexterp37 marked this pull request as ready for review February 12, 2020 14:20
@auto-assign auto-assign bot requested a review from badboy February 12, 2020 14:20
@Dexterp37 Dexterp37 requested a review from mdboom February 12, 2020 14:20
@Dexterp37 Dexterp37 merged commit eeb82ab into mozilla:master Feb 13, 2020
@Dexterp37 Dexterp37 deleted the faster_init branch February 13, 2020 09:04
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3 participants