Make IOServerSocketChannel#accept cancelable
#31
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| test("IOServerSocketChannel.accept is cancelable") { | ||
| // note that this test targets IOServerSocketChannel#accept, | ||
| // not the underlying AsynchronousSocketChannel#accept implementation | ||
| IOServerSocketChannel | ||
| .open | ||
| .evalTap(_.bind(new InetSocketAddress(0))) | ||
| .flatMap(_.accept) | ||
| .use_ | ||
| .timeout(100.millis) | ||
| .intercept[TimeoutException] | ||
| } |
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I could reproduce this issue on the JVM as well. It's not an issue with our implementation in epollcat, it's an issue with the fact that accept is not cancelable.
| IO.async { cb => | ||
| IO(ch.accept(null, toHandler(cb))) | ||
| // it seems the only way to cancel accept is to close the socket :( | ||
| .as(Some(IO(ch.close()))) | ||
| } |
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The fundamental issue is that there is no good way with the JDK APIs to cancel a pending accept (which is really dumb to be honest). Some googling suggested that closing the channel is the only way to do so.
This is very ugly, but it is good enough for our tests ... I think.
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LGTM.
I think the close() is entirely good, not just good enough. What would one do
with the now messed-up listen socket anyway? Like a mayfly, its purpose was
singular and brief.
I think in C one would send a signal, yeech!
Thank you for fixing this.
Would you like to try it out or are you sufficiently satisfied?
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Thanks! If you're happy I'm happy :) |
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I think I will be causing enough failures over the near future that I well |
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I think this also ends Issue #28. I ran this PR in my "provoke connect' failure X86_64 environment This leaves Issue #20 as still relevant but at lesser severity. |
Fixes #21. I think :)
This was more of a problem with our tests than the actual implementation. But it definitely warrants discussion.
The reason for the hang was that Cats Effect will never "fire-and-forget" by default: if there is an error, it will cancel other running fibers (aka green threads) and wait for their cancellation. If an action is not cancelable, then it will wait until that action either completes or errors before canceling that fiber.
Since
acceptwas not cancelable if fell into this trap.