worker: fix interaction of terminate() with messaging port #37319
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When a Worker is terminated, its own handle and the public `MessagePort` are `.ref()`’ed, so that all relevant events, including the `'exit'` events, end up being received. However, this is problematic if messages end up being queued from the Worker between the beginning of the `.terminate()` call and its completion, and there are no `'message'` event handlers present at that time. In that situation, currently the messages would not end up being processed, and since the MessagePort is still `.ref()`’ed, it would keep the event loop alive indefinitely. To fix this: - Make sure that all messages end up being received by `drainMessagePort()`, including cases in which the port had been stopped (i.e. there are no `'message'` listeners) and cases in which we exceed the limit for messages being processed in one batch. - Unref the Worker’s internal ports manually after the Worker has exited. Either of these solutions should be solving this on its own, but I think it makes sense to make sure that both of them happen during cleanup.
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When a Worker is terminated, its own handle and the public `MessagePort` are `.ref()`’ed, so that all relevant events, including the `'exit'` events, end up being received. However, this is problematic if messages end up being queued from the Worker between the beginning of the `.terminate()` call and its completion, and there are no `'message'` event handlers present at that time. In that situation, currently the messages would not end up being processed, and since the MessagePort is still `.ref()`’ed, it would keep the event loop alive indefinitely. To fix this: - Make sure that all messages end up being received by `drainMessagePort()`, including cases in which the port had been stopped (i.e. there are no `'message'` listeners) and cases in which we exceed the limit for messages being processed in one batch. - Unref the Worker’s internal ports manually after the Worker has exited. Either of these solutions should be solving this on its own, but I think it makes sense to make sure that both of them happen during cleanup. PR-URL: #37319 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Rich Trott <[email protected]>
targos
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Feb 28, 2021
When a Worker is terminated, its own handle and the public `MessagePort` are `.ref()`’ed, so that all relevant events, including the `'exit'` events, end up being received. However, this is problematic if messages end up being queued from the Worker between the beginning of the `.terminate()` call and its completion, and there are no `'message'` event handlers present at that time. In that situation, currently the messages would not end up being processed, and since the MessagePort is still `.ref()`’ed, it would keep the event loop alive indefinitely. To fix this: - Make sure that all messages end up being received by `drainMessagePort()`, including cases in which the port had been stopped (i.e. there are no `'message'` listeners) and cases in which we exceed the limit for messages being processed in one batch. - Unref the Worker’s internal ports manually after the Worker has exited. Either of these solutions should be solving this on its own, but I think it makes sense to make sure that both of them happen during cleanup. PR-URL: #37319 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Rich Trott <[email protected]>
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When a Worker is terminated, its own handle and the public
MessagePortare.ref()’ed, so that all relevant events,including the
'exit'events, end up being received.However, this is problematic if messages end up being queued
from the Worker between the beginning of the
.terminate()calland its completion, and there are no
'message'event handlerspresent at that time. In that situation, currently the messages
would not end up being processed, and since the MessagePort
is still
.ref()’ed, it would keep the event loop aliveindefinitely.
To fix this:
drainMessagePort(), including cases in which the port hadbeen stopped (i.e. there are no
'message'listeners) andcases in which we exceed the limit for messages being processed
in one batch.
has exited.
Either of these solutions should be solving this on its own,
but I think it makes sense to make sure that both of them
happen during cleanup.
@nodejs/workers