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On Sat, 27 Jun 2020 19:40:53 GMT, John Neffenger
<github.com+1413266+jgn...@openjdk.org> wrote:
>> OK, that seems fine then. I'll take a closer look and then finish my review.
>
>> OK, that seems fine then. I'll take a closer look and then finish my review.
>
> Actually, I think you may be right, though. Sorry for replying before looking
> into it. I now think the
> `ScheduledThreadPoolExecutor` should be shut down, but let me look into it a
> bit more this afternoon before your final
> review. Thanks! The new `ScheduledThreadPoolExecutor` is ~complicated~
> flexible! 😄
I think the code in the `_stop` method is correct after all.
The `MonocleTimer` class is written to allow for multiple calls to the pair of
`_start` and `_stop` methods (even
though I don't think that ever happens), and the static
`ScheduledThreadPoolExecutor`, named `scheduler`, is created
only once and reused on subsequent calls.
Changing the `_stop` method to call `task.cancel(true)` still leaves the timer
thread running, which prevents the
JavaFX application from exiting when the timer thread is a user thread.
Furthermore, whether it's a user or daemon thread, if the call to
`task.cancel(true)` happens to run exactly when the
periodic task is *in progress*, the `timerRunnable` lambda in `QuantumToolkit`
prints the stack trace when it catches
the `InterruptedException`.
java.lang.InterruptedException:
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit
.lambda$runToolkit$12(QuantumToolkit.java:345)
at java.base/java.util.concurrent.Executors$RunnableAdapter
.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask
.runAndReset(FutureTask.java:305)
at
java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask
.run(ScheduledThreadPoolExecutor.java:305)
at java.base/java.util.concurrent.ThreadPoolExecutor
.runWorker(ThreadPoolExecutor.java:1130)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker
.run(ThreadPoolExecutor.java:630)
at java.base/java.lang.Thread
.run(Thread.java:832)
So the call to `task.cancel(false)` is correct.
Changing the `_stop` method to shut down the `scheduler` will terminate the
associated thread, regardless of its daemon
status, but a subsequent call to `_start` will throw a
`RejectedExecutionException` when trying to schedule the timer
task:
java.util.concurrent.RejectedExecutionException:
Task
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@b1fe89
[Not completed, task = java.util.concurrent.Executors$RunnableAdapter@1f85c96
[Wrapped task =
com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$111/0x34563828@141859b]]
rejected from java.util.concurrent.ScheduledThreadPoolExecutor@55f462
[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed
tasks = 0]
at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy
.rejectedExecution(ThreadPoolExecutor.java:2057)
at java.base/java.util.concurrent.ThreadPoolExecutor
.reject(ThreadPoolExecutor.java:827)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor
.delayedExecute(ScheduledThreadPoolExecutor.java:340)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor
.scheduleAtFixedRate(ScheduledThreadPoolExecutor.java:632)
at javafx.graphics/com.sun.glass.ui.monocle.MonocleTimer
._start(MonocleTimer.java:64)
at javafx.graphics/com.sun.glass.ui.Timer
.start(Timer.java:96)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit
.runToolkit(QuantumToolkit.java:384)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit
.lambda$startup$10(QuantumToolkit.java:280)
at javafx.graphics/com.sun.glass.ui.Application
.lambda$run$1(Application.java:153)
at javafx.graphics/com.sun.glass.ui.monocle.RunnableProcessor
.runLoop(RunnableProcessor.java:92)
at javafx.graphics/com.sun.glass.ui.monocle.RunnableProcessor
.run(RunnableProcessor.java:51)
at java.base/java.lang.Thread
.run(Thread.java:832)
So if we want `MonocleTimer` to reuse a single `ScheduledThreadPoolExecutor`
object, I think the only way to make sure
that its timer thread exits when the application exits is to set its daemon
status to `true`.
-------------
PR: https://git.openjdk.java.net/jfx/pull/256
