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From Siegfried Goeschl <siegfried.goes...@it20one.at>
Subject Re: ExecuteWatchdog does not really terminate the "hung" process?
Date Mon, 22 Jun 2009 17:19:27 GMT
Hi Ernest,

this is a lurking developer .... :-)

+) killing your top-level process has not the semantics you would expect
(see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4770092) - so
under Windows it would never kill your "ping" process

+) it seems that the new ProcessBuilder does not help either (see
http://stackoverflow.com/questions/801609/java-processbuilder-process-destroy-not-killing-child-processes-in-winxp)

+) we have a test case
"DefaultExecutorTest#testExecuteAsyncWithTooLateUserTermination" which
kills a process using Watchdog - please note that we carefully avoided
to create s subprocess here since we rely on built-in shell commands -
we always try to prove that our code works ... :-)

+) which leaves the question why your thread waits for the whole 10
seconds - need to investigate that

Cheers,

Siegfried Goeschl



Mishkin, Ernest wrote:
> Hello,
>
> I have a simple test case which involves starting a .bat file which
> tries to simulate a process "stuck for N seconds" by executing
> ping -n %1 -w 1000 127.0.0.1
>
> I invoke this from java using DefaultExcutor, passing "10" as an
> argument to .bat file (so that it will run 10 approx. 1 sec pings
> resulting in close to 10 sec wait).
> I'm also setting ExecuteWatchdog with a 2 sec timeout.
> Problem is, my execute call does not return until ~ 10 seconds later, as
> measured by System.currentTimeMillis().
> The watchdog confirms that it "killed" the process however the expected
> behavior is that execute() call gets interrupted after 2 secs and it
> wasn't.
>
> The complete source code is attached. 
>
> Please help me understand: am I missing something fundamental, have I
> found an issue, or something else?
>
>
> If developer(s) are lurking on this list, I'd like to mention that it
> seems like when ExecuteWatchdog detects a timeout it should interrupt
> the "primary" thread (the one which runs code from
> DefaultExecutor::executeInternal, in particular the lines below:
>             try {
>                 exitValue = process.waitFor();
>             } catch (InterruptedException e) {
>                 process.destroy();
>             }
> process.waitFor() blocks, and it seems that when process.destroy() is
> called from the watchdog thread the other thread which is stuck in
> process.waitFor() is not released.
> That's why having DefaultWatchdog maintain a reference to the executor's
> thread and interrupt()'ing it might be helpful.
>
>
>
> Sincerely,
> Ernest Mishkin
>  
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