Question

I have a php script that divides a task into multiple parts and runs each part in a separate child process. The code looks like this:

foreach($users as $k => $arr) {
  if(($pid = pcntl_fork()) === -1) continue;
  if($pid) {
      pcntl_wait($status,WNOHANG);
      continue;
  }
  ob_start();
  posix_setsid();
  dbConnect();
  // do stuff to data
  exit();
}

I’m running this script using crontab on a Debian server, but the problem is some processes keep running and reserve memory. After a while the server’s memory is flooded.
I need to find a way to make sure all processes finish correctly.

Answer 1

I think the issue is the use of WNOHANG in the pcntl_wait call. This means the pcntl_wait function exist before the child process – which you want, in order to be able to fork the other child processes concurrently. But it has the side-effect that the main parent finishes before some of the children. This link http://www.devshed.com/c/a/PHP/Managing-Standalone-Scripts-in-PHP/2/ describes how to loop using pcntl_wait with WNOHANG until all children complete.