Worker pcntl_wait to non-blocking loop

[Rockstar04]

Putting the thread to sleep with pcntl_wait no longer allows signals to be captured (PHP 5 >= 5.3.0). This PR puts pcntl_wait into a while loop waiting for the child to exit, and allows signals like USR1 to be used again (pcntl_signal_dispatch being called inside the loop).

My only concern would be compatibility with PHP< 5.3.0

http://www.php.net/manual/en/function.pcntl-signal.php#114575
http://www.php.net/manual/en/function.pcntl-signal-dispatch.php

[Rockstar04]

It looks like #83 could also solve this problem, but I have not personally tested that PR

[danhunsaker]

I have tested #83, heavily, but that's beside the point.

My concern with this is that a while loop for this will quickly consume CPU, as there's nothing to keep the loop from moving as quickly as it can. Pegging the CPU in the worker would prevent the child from having any CPU to work with, causing all kinds of problems for the jobs. I'm sure that didn't happen in your tests, but this is the kind of thing that is heavily system-dependent, so it could easily be a problem in a different configuration.

It'll be tricky to figure out a better workaround... Honestly, ignoring signals during pcntl_wait sounds like a pretty big bug to me, so it would be preferable for the pcntl extension to be fixed instead, but we'll still need to work around the broken version(s).

As to #83, it's only real problem is that there are too many things I fixed in a single PR. And now I'd have to rebase it to get it working again.

[Rockstar04]

Would a micro sleep like you used in #83 be an acceptable hack then?

Sent from my Droid 4

[danhunsaker]

Email replies to GitHub issues are UGLY...

Yes, given that's the entire reason I put the micro sleep in there to begin with. :-)

[Rockstar04]

Sorry I wasn’t trying to imply #83 was not well tested, only that I had not confirmed if it properly responded to signals.

I just pushed a commit that adds a half second delay in checking for new signals

[Rockstar04]

Are jobs that are killed with a USR1 supposed to be added to the failed job queue?

[danhunsaker]

This is a good question...