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Re: Detecting thread exits

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Elizabeth Mattijsen
January 24, 2005 08:41
Re: Detecting thread exits
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At 11:18 AM -0500 1/24/05, Eric Garland wrote:
>I'm setting up a Boss/Worker threaded program that runs for a very 
>long time.  There are times where a worker thread will run into 
>errors and exit.  The obvios solution would be to prevent that from 
>happening but I would like to create a fault tolerant framework that 
>doesn't tip over at the slightest hint of a problem.  I would like 
>to have the Boss detect when a worker exits and restart a worker 
>thread in its place.
>So far, I find no functions that will determine if a thread has 
>exited outside of join().  The obvious issue with join is that it 
>blocks so I need a join thread for each worker thread so that I can 
>send a message back to the Boss to restart the thread.  This seems 
>to wildly increase the memory usage.   There are large shared data 
>structures in this program and it already seems to be at the memory 
>limits of the machine without these join threads.

You might want to have a look at Thread::Running on CPAN, by yours truly.

>Is there a way to remove the shared variables from the join threads 
>so that they take up as little memory as possible?

Not sure what you mean by that.

>Better yet, is there a way to detect thread deaths outside of a 
>dedicated join thread, perhaps a $thread->ready_for_join() type 
>function or a $thread->join_non_blocking() or even a 

 From the pod of Thread::Running:

        Thread::Running - provide non-blocking check whether threads are run-

            use Thread::Running;      # exports running(), exited() and tojoin()
            use Thread::Running qw(running);   # only exports running()
            use Thread::Running ();   # threads methods only

            my $thread = threads->new( sub { whatever } );
            while ($thread->running) {
            # do your stuff

            $_->join foreach threads->tojoin;

            until (threads->exited( $tid )) {
            # do your stuff

            sleep 1 while threads->running;

Hope this is what you're looking for.


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