VanillaEventLoop erroneously calls close() if an EventHandler happens to implement Closeable about chronicle-threads HOT 6 CLOSED

The current rule is that loopFinished is called exactly once and then close is called exactly once on an event handler when it is either removed from an event loop, or the event loop is stopped.
Please review EventGroupTest - this enforces this contract.
It needs to be better documented - will do so tomorrow.

from chronicle-threads.

Ok. What is the rationale of having two different methods being invoked on the same event?

loopFinished() {
  a();
}

close() {
 b()
}

But instead we might as well just have:

close() {
  a();
  b();
}

from chronicle-threads.

@minborg there is some history here - OpenHFT/Chronicle-Network#45

In a nutshell, you can't rely on close() to release resources because the action method may still be executing in another thread.

We could make a rule that if an EventHandler implements Closeable then it is only allowed to be called by the event loop? Then we could do away with loopFinished.

from chronicle-threads.

In general, we should have a consistent life-cycle for both the EventLoop and EventHandler. Either an EventHandler is managed by an EventLoop or by its creating entity. This is of particular importance in this case because of thread visibility issues.

Letting the EventLoop invoke close() creates a dissonance in my opinion as the EventHandler is created by another entity using another thread but then handed over to the EventLoop. Either the creating entity should invoke close() or the EventLoop should create the EventHandler, potentially via a provided Supplier<EventHandler>.

I think it would be more consistent to let the creating entity manage the lifecycle of the EventHandler and remove the magic invocation of close() and instead have:

• onAdded()
• onRemoved()

which are invoked exactly one time by the EventLoop (using.the event loop's thread). These methods can then be used to initialize and clean up the EventHandler with no concurrency issues.

from chronicle-threads.

The behaviour for closeable is that should expect to be called one or more times and ignore any duplicates. SimpleCloseable can assist.

from chronicle-threads.

Released in Chronicle-Threads-2.20.43, BOM-2.20.67

from chronicle-threads.