Countdown latch for std #1404
Countdown latch for std #1404
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| import java.util.concurrent.TimeoutException | ||
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| class CountDownLatchSpec extends BaseSpec { | ||
| sequential |
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why are these sequential?
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Because I copied the header from QueueSpec 😂 I'm not actually sure why it needs sequential either?
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yeah I would remove it unless someone else has a reason for it. I vaguely recall one place where it was actually needed, but then I think it spread through copy-paste
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Only the laws tests need sequential. Everything else can be in parallel for maximum speeds. :-)
| case Awaiting(n, signal) => | ||
| if (n > 1) (Awaiting(n - 1, signal), F.unit) else (Done(), signal.complete(()).void) | ||
| case d @ Done() => (d, F.unit) | ||
| }.flatten |
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let's make this uncancelable
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Oh good point! Just to check my understanding: if we observed cancellation after modify and before flatten then we would have transitioned to the Done state without ever unblocking the fibers by completing the signal?
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exactly. You can solve it by adding an onCancel that checks the state yada-yada, but because complete is not a long-lived operation, it's overwhelmingly better to just make the whole thing uncancelable (since modify is already uncancelable anyway)
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| /** | ||
| * Concurrency abstraction that supports semantically blocking | ||
| * until n latches are released |
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Worth adding a comment about this being one-shot (in slightly less concise terms :) )
| name: String, | ||
| constructor: Int => IO[CountDownLatch[IO]]): Fragments = { | ||
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| s"$name - raise an exception when constructed with negative initial latches" in real { |
TimWSpence
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