|
|
|
|
Bookmark this on Delicious
Share on Facebook
 Slashdot It!
Digg pcntl_wait
Waits on or returns the status of a forked child
(PHP 5)
The wait function suspends execution of the current process until a child has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function. If a child has already exited by the time of the call (a so-called "zombie" process), the function returns immediately. Any system resources used by the child are freed. Please see your system's wait(2) man page for specific details as to how wait works on your system.
Note:
This function is equivalent to calling pcntl_waitpid()
with a Parameters
Return Valuespcntl_wait() returns the process ID of the child which exited, -1 on error or zero if WNOHANG was provided as an option (on wait3-available systems) and no child was available. Code Examples / Notes » pcntl_waitfederico
This a simple multi process application where you can choose the maximun process that can run at the same time. This is useful when you need to limit the fork of process. When the MAXPROCESS is reached the program wait on pcntl_wait() <? DEFINE(MAXPROCESS,25); for ($i=0;$i<100;$i++){ $pid = pcntl_fork(); if ($pid == -1) { die("could not fork"); } elseif ($pid) { echo "I'm the Parent $i\n"; $execute++; if ($execute>=MAXPROCESS){ pcntl_wait($status); $execute--; } } else { echo "I am the child, $i pid = $pid \n"; sleep(rand(1,3)); echo "Bye Bye from $i\n"; exit; } } ?> thomas dot nicolai
The code before isnt working for me cause the children are correctly started but not refreshed after they died. So keep in mind to use this instead and use the signal handler to know when a child exits to know when you have to start a new one. I added a few lines to the posting from {andy at cbeyond dot net} cause his post wasnt working for me as well (PHP5.1). Same effect like the one below. <?php declare(ticks = 1); $max=5; $child=0; // function for signal handler function sig_handler($signo) { global $child; switch ($signo) { case SIGCHLD: echo "SIGCHLD received\n"; $child--; } } // install signal handler for dead kids pcntl_signal(SIGCHLD, "sig_handler"); while (1){ $child++; $pid=pcntl_fork(); if ($pid == -1) { die("could not fork"); } else if ($pid) { // we are the parent if ( $child >= $max ){ pcntl_wait($status); $child++; } } else { // we are the child echo "\t Starting new child | now we de have $child child processes\n"; // presumably doing something interesting sleep(rand(3,5)); exit; } } ?> thisisroot
Below is a simple example of forking some children and timing the total duration (useful for stress tests). <?php $isParent = true; $children = array(); $start = microtime( true); /* Fork you! * (Sorry, I had to) */ $ceiling = $CONCURRENCY - 1; for ( $i = 0; (( $i < $ceiling) && ( $isParent)); $i++) { $pid = pcntl_fork(); if ( $pid === 0) { $isParent = false; } elseif ( $pid != -1) { $children[] = $pid; } } /* Process body */ echo "Do stuff here\n"; /* Cleanup */ if ( $isParent) { $status = null; while ( count( $children)) { pcntl_wait( $status); array_pop( $children); } echo "Completed in " . ( microtime( true) - $start) . " seconds.\n"; } ?> |
