Appropiate Coro/AnyEvent model?

[Marc Lehmann]

AnyEvent/Coro using 100% cpu without doing anything usually happens when
you have no watchers left and ask them to wait for events - this results
in a livelock (or deadlock if you prefer).

On Sun, Nov 17, 2013 at 09:08:12PM +0100, Mark Lawrence <nomad at null.net> wrote:
> >     $self->{interrupt} = rouse_cb;
> >     AE::io $self->{child_stdout}, 0, $self->{interrupt};

Here you create a watcher and imemdiately destroy it (it's never stored).
What you want is either:

   {
      $self->{interrupt} = rouse_cb;
      my $w = AE::io $self->{child_stdout}, 0, $self->{interrupt};
      Coro::rouse_wait;
   }

Or you can use Coro::AnyEvent for more convenience:

   Coro::AnyEvent::readable $self->{child_stdout};

I haven't closely looked at your code to se eif its true, but when you
want to exec a child, maybe AnyEvent::Util::run could simplify the job (it
can "send" the output to a handler or a scalar).

> The last thing I want to be doing inside the do_stuff() subroutine is
> waiting on possible errors. There is nothing event based about that
> approach.  Waiting on (normal) input (hence the use of Coro) is however
> fine.

You could use a timeout, and with Coro::Anyevent that's rather simply:

   Coro::AnyEvent::readable $self->{child_stdout}, 60
      or die "no child data received in 60s\n";

> After all of that I guess I can phrase my question better now: Can a
> coro thread stop itself?

Yes, terminate, cancel, die, return from toplevel would all stop it in
some way or another. Your problem is likely elsewhere (i.e. in the events
part).

> Possibly related to this whole issue is the question of why
> Coro::Handle doesn't deal with errors the same way that
> AnyEvent::Handle does. I had been hoping that Coro::Handle would have
> an on_error => sub {} capability.

Coro::Handle isn't event based, it's supposed to emulate perl's
IO::Handle, to allow traditional code to (mostly) run unchanged.

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