Tidy up PlainListenableActionFuture #68735
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As of elastic#53261 today `PlainListenableActionFuture` is the sole implementation of `ListenableActionFuture`, the reason for the `Plain...` prefix is now lost. It also heavily uses variable shadowing in its implementation which makes it quite hard to read, uses a mix of `volatile` fields and mutexes, and keeps hold of the deferred listeners even after completion. Finally it does not have many tests. This commit drops the unnecessary interface and renames the class to simply `ListenableActionFuture`. It reworks the implementation to avoid shadowing variables, drops the deferred listeners on completion, and moves to an entirely mutex-based implementation. Finally, it adds another test that it works as advertised.
DaveCTurner added :Core/Infra/Core 
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| Pinging @elastic/es-core-infra (Team:Core/Infra) |
DaveCTurner commented Feb 9, 2021
| synchronized (this) { | ||
| executedListeners = true; | ||
| } | ||
| Object listeners = this.listeners; |
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This is the only volatile read outside of the mutex, but we just had the mutex anyway, may as well move this up a line and drop the volatile.
| if (executedListeners) { | ||
| executeImmediate = true; | ||
| } else { | ||
| Object listeners = this.listeners; |
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Reworked this to have better names and to use final variables throughout, which introduces one extra local variable but makes it all a lot clearer.
| | ||
| @Override | ||
| public void addListener(final ActionListener<T> listener) { | ||
| internalAddListener(listener); |
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The only caller of internalAddListener, inlined it.
henningandersen approved these changes Feb 9, 2021
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Nice cleanup, LGTM.
DaveCTurner deleted the 2021-02-09-PlainListenableActionFuture-refactoring branch DaveCTurner added a commit that referenced this pull request Feb 9, 2021
As of #53261 today `PlainListenableActionFuture` is the sole implementation of `ListenableActionFuture`, the reason for the `Plain...` prefix is now lost. It also heavily uses variable shadowing in its implementation which makes it quite hard to read, uses a mix of `volatile` fields and mutexes, and keeps hold of the deferred listeners even after completion. Finally it does not have many tests. This commit drops the unnecessary interface and renames the class to simply `ListenableActionFuture`. It reworks the implementation to avoid shadowing variables, drops the deferred listeners on completion, and moves to an entirely mutex-based implementation. Finally, it adds another test that it works as advertised.
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As of #53261 today
PlainListenableActionFutureis the soleimplementation of
ListenableActionFuture, the reason for thePlain...prefix is now lost. It also heavily uses variable shadowingin its implementation which makes it quite hard to read, uses a mix of
volatilefields and mutexes, and keeps hold of the deferred listenerseven after completion. Finally it does not have many tests.
This commit drops the unnecessary interface and renames the class to
simply
ListenableActionFuture. It reworks the implementation to avoidshadowing variables, drops the deferred listeners on completion, and
moves to an entirely mutex-based implementation. Finally, it adds
another test that it works as advertised.