note 99416 added to function.pcntl-fork

When dealing with fork in a web server environment a bit annoying situation can occur if you are not waiting for your child processes (for instance you do some long processing in the background) and you need to return some output to the browser (for example fork result) and finish work with parent. Your parent is not actually finished (even if you call exit() function), it just returns output to the web server and waits for a new connection. This behavior leads to a lot of zombie processes in server's process table, because operating system waits until parent will call wait() function and get child's exit value. But you are finished your work with parent. It is almost impossible to call wait() function during next requests to the web server because there is a lot of php-cgi or forked httpd processes which are not parents of your zombie childs. But we can finish parent right after the fork. After webserver's process kill, webserver will detect that child is dead and it will spawn new copy. Tested on Apache prefork and Nginx+spawn_fcgi. <?php $pid = pcntl_fork(); if ($pid == -1) { throw new Exception('could not fork'); } else if ($pid) { //we are the parent echo 'Forked successfully'; flush(); //Kill parent process now (self) to prevent zombie creation. posix_kill(posix_getpid(), SIGTERM); exit; } else { //we are the child //Do some time-consuming job //When fork() function is called operating system clones whole process - in case of Apache its child, in case of CGI SAPI php-cgi process and usual exit don't work and process will stuck in the memory. But we can kill own process. //Kill self posix_kill(posix_getpid(), SIGTERM); //Usual exit don't work exit; } ?> ---- Server IP: 69.147.83.197 Probable Submitter: 77.68.106.226 ---- Manual Page -- http://www.php.net/manual/en/function.pcntl-fork.php Edit -- https://master.php.net/note/edit/99416 Del: integrated -- https://master.php.net/note/delete/99416/integrated Del: useless -- https://master.php.net/note/delete/99416/useless Del: bad code -- https://master.php.net/note/delete/99416/bad+code Del: spam -- https://master.php.net/note/delete/99416/spam Del: non-english -- https://master.php.net/note/delete/99416/non-english Del: in docs -- https://master.php.net/note/delete/99416/in+docs Del: other reasons-- https://master.php.net/note/delete/99416 Reject -- https://master.php.net/note/reject/99416 Search -- https://master.php.net/manage/user-notes.php