Checking if process still running?

Question

As a way to build a poor-man\'s watchdog and make sure an application is restarted in case it crashes (until I figure out why), I need to write a PHP CLI script that will be

Answer 1

I didn't see this mentioned here, but here's another approach taking the second grep out of the equation, i use this with alot of my PHP scripts and should work universally

exec("ps aux | grep -i '[l]ighttpd -D'", $pids);
if(empty($pids)) {
        print "Lighttpd not running!\n";
} else {
        print "Lighttpd OK\n";
}

Enjoy.

Answer 2

Try this one

function processExists ($pid) {
    return file_exists("/proc/{$pid}");
}

Function checks whether process file is exists in /proc/ root directory. Works for Linux only

Answer 3

I'd use pgrep to do this (caution, untested code):

exec("pgrep lighttpd", $pids);
if(empty($pids)) {

    // lighttpd is not running!
}

I have a bash script that does something similar (but with SSH tunnels):

#!/bin/sh

MYSQL_TUNNEL="ssh -f -N -L 33060:127.0.0.1:3306 tunnel@db"
RSYNC_TUNNEL="ssh -f -N -L 8730:127.0.0.1:873 tunnel@db"

# MYSQL
if [ -z `pgrep -f -x "$MYSQL_TUNNEL"` ] 
then
    echo Creating tunnel for MySQL.
    $MYSQL_TUNNEL
fi

# RSYNC
if [ -z `pgrep -f -x "$RSYNC_TUNNEL"` ]
then
    echo Creating tunnel for rsync.
    $RSYNC_TUNNEL
fi

You could alter this script with the commands that you want to monitor.

Answer 4

You can try this, which combines bits of those two approaches:

function processExists($processName) {
    $exists= false;
    exec("ps -A | grep -i $processName | grep -v grep", $pids);
    if (count($pids) > 0) {
        $exists = true;
    }
    return $exists;
}

If that doesn't work, you may want to just try running the ps command on your system and seeing what output it gives.

Answer 5

If you're doing it in php, why not use php code:

In the running program:

define('PIDFILE', '/var/run/myfile.pid');

file_put_contents(PIDFILE, posix_getpid());
function removePidFile() {
    unlink(PIDFILE);
}
register_shutdown_function('removePidFile');   

Then, in the watchdog program, all you need to do is:

function isProcessRunning($pidFile = '/var/run/myfile.pid') {
    if (!file_exists($pidFile) || !is_file($pidFile)) return false;
    $pid = file_get_contents($pidFile);
    return posix_kill($pid, 0);
}

Basically, posix_kill has a special signal 0 that doesn't actually send a signal to the process, but it does check to see if a signal can be sent (the process is actually running).

And yes, I do use this quite often when I need long running (or at least watchable) php processes. Typically I write init scripts to start the PHP program, and then have a cron watchdog to check hourly to see if it's running (and if not restart it)...

Answer 6

The main problem is the if you run a php script, the exec command will be run as the web-servers user (www-data); this user can't see pid's from other users, unless you use "pidof"

<?php
//##########################################
// desc: Diese PHP Script zeig euch ob ein Prozess läuft oder nicht
// autor: seevenup
// version: 1.3
// info: Da das exec kommando als apache user (www-data) ausgefuert
//       wird, muss pidof benutzt werden da es prozesse von
//       anderen usern anzeigen kann
//##########################################

if (!function_exists('server_status')) {
        function server_status($string,$name) {
                $pid=exec("pidof $name");
                exec("ps -p $pid", $output);

                if (count($output) > 1) {
                        echo "$string: <font color='green'><b>RUNNING</b></font><br>";
                }
                else {
                        echo "$string: <font color='red'><b>DOWN</b></font><br>";
                }
        }
}

//Beispiel "Text zum anzeigen", "Prozess Name auf dem Server"
server_status("Running With Rifles","rwr_server");
server_status("Starbound","starbound_server");
server_status("Minecraft","minecarf");
?>

More information about the script here http://umbru.ch/?p=328