I'm experimenting with PHP's pcntl_* functions using the PHP cgi ... I've
never written a daemon before, and there doesn't seem to be a lot of
information out there about how to do this with the pcntl functions.
So, I've read what I can find on the subject as it deals with UNIX
programming. The goal is a script that will run forever, checking a "job
queue" ... If jobs are waiting, use pcntl_fork() to handle the jobs.
To this end, I've come up with this pseudo-code ... Before going WAY off in
this direction, I'd like to submit this for comments by those who've had
more experience with this sort of thing.
------------------
// run forever if necessary
set_time_limit(0);
// detatch from the controlling terminal
if (!posix_setsid()) {
die('could not detach from terminal');
}
// setup signal handlers
pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGHUP, "sig_handler");
// loop forever waiting on jobs
while(1) {
// check queue for pending jobs
// (db lookup omitted, let's assume jobs are waiting)
$jobs_waiting = true;
if($jobs_waiting) {
$pid = pcntl_fork();
if($pid == -1) {
die('could not fork');
} else if ($pid) {
// parent
// call waitpid to reap children that
// have already terminated
do {
$tpid = pcntl_waitpid(-1,$status,WNOHANG);
if($tpid == -1)
die('error occurred while waiting for child');
} while (!$tpid);
} else {
// child
// perform task on jobs waiting
// when job(s) complete, quit
exit();
}
}
// wait two seconds before checking queue again
sleep(2);
unset($jobs_waiting);
}
function sig_handler($signo) {
// blah blah
}
--------------------
I am open to suggestions or comments on this approach! Please let me know if
you think this looks nuts.
Thanks,
Clay
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