I maintain a game server and unruly players frequently crash the application. My moderation team needs the ability to restart the server process, but allowing ssh access would be impractical/insecure, so im using shell exec to pass the needed commands to restart the server process from a web based interface. The problem is, the shell session doesnt detatch properly and thus php maintains its session untill it finally times out and closes the session/stops the server process.
Here's how I'm calling shell_exec:
$command='nohup java -jar foobar_server.jar';
shell_exec($command);
shell_exec will wait until the command you've executed returns (e.g. drops back to a shell prompt). If you want to run that as a background task, so shelL_exec returns immediately, then do
$command='nohup java -jar foobar_server.jar &';
^--- run in background
Of course, that assumes you're doing this on a unix/linux host. For windows, it'd be somewhat different.
If you try this you'd see it won't work. To fully detach in PHP you must also do stdout redirection else shell_exec will hang even with '&'.
This is what you'd really want:
shell_exec('java -jar foobar_server.jar >/dev/null 2>&1 &');
But to take this one step further, I would get rid of the web interface and make this a one-minute interval cronjob which first checks if the process is running, and if it's not start a new instance:
#!/bin/bash
if ! pidof foobar_server.jar; then
java -jar foobar_server.jar >/tmp/foobar_server.log 2>&1 &;
fi
And have that run every minute, if it finds a running process it does nothing, else it starts a new instance. Worst case scenerio after a server crash is 59 seconds downtime.
Cheers
Related
I'm in a school project and we use a process of collecting tweets through a stream set up with PHP. I usually run it in background through the terminal with a command like:
nohup ./mystream.php 2>&1 &
This stream is supposed to be on at all times and thus I would like to make sure that this process starts up whenever the system reboots. How would I do that in Ubuntu?
You would make it part of a script that runs doing startup. We have done this with things like Upstart which replaces the sbin/init/ daemon. Here is an example script -
start on filesystem and net-device-up IFACE=eth0
respawn
exec /usr/bin/php -f /path/to/your/process.php
I'm starting my php script in the following way:
bash
cd 'path'
php -f 'scriptname'.php
There is no output while the php script is running.
After a time, the php script responds with:
Killed
My idea is that it reached the memory_limit: ini_set('memory_limit', '40960M');
Increasing the memory limit seemed to solve the problem, but it only increased the edge.
What exactly does that Killed phrase mean?
Your process is killed. There could be a multitude of reasons, but it's easy to discard some of the more obvious.
php limits: if you run into a php limit, you'll get an error in the logfile, and probably on the commandline as well. This normally does not print 'killed'
the session-is-ended-issues: if you still have your session, then your session is obvioiusly not ended, so disregard all the nohup and & stuff
If your server is starved for resources (no memory, no swap), the kernel might kill your process. This is probably what's happening.
In anycase: your process is getting send a signal that it should stop. Normally only a couple of 'things' can do this
your account (e.g. you kill the process)
an admin user (e.g. root)
the kernel when it is really needing your memory for itself.
maybe some automated process, for instance, if you live on a shared server and you take up more then your share of resources.
references: Who "Killed" my process and why?
You could be running out of memory in the PHP script. Here is how to reproduce that error:
I'm doing this example on Ubuntu 12.10 with PHP 5.3.10:
Create this PHP script called m.php and save it:
<?php
function repeat(){
repeat();
}
repeat();
?>
Run it:
el#apollo:~/foo$ php m.php
Killed
The program takes 100% CPU for about 15 seconds then stops. Look at dmesg | grep php and there are clues:
el#apollo:~/foo$ dmesg | grep php
[2387779.707894] Out of memory: Kill process 2114 (php) score 868 or
sacrifice child
So in my case, the PHP program printed "Killed" and halted because it ran out of memory due to an infinite loop.
Solutions:
Increase the amount of RAM available.
Break down the problem set into smaller chunks that operate sequentially.
Rewrite the program so it has a much smaller memory requirements.
Killed is what bash says when a process exits after a SIGKILL, it's not related to putty.
Terminated is what bash says when a process exits after a a SIGTERM.
You are not running into PHP limits, you may be running into a different problem, see:
Return code when OOM killer kills a process
http://en.wikipedia.org/wiki/Nohup
Try using nohup before your command.
nohup catches the hangup signal while the ampersand doesn't (except the shell is confgured that way or doesn't send SIGHUP at all).
Normally, when running a command using & and exiting the shell afterwards, the shell will terminate the sub-command with the hangup signal (kill -SIGHUP ). This can be prevented using nohup, as it catches the signal and ignores it so that it never reaches the actual application.
In case you're using bash, you can use the command shopt | grep hupon to find out whether your shell sends SIGHUP to its child processes or not. If it is off, processes won't be terminated, as it seems to be the case for you.
There are cases where nohup does not work, for example when the process you start reconnects the NOHUP signal.
nohup php -f 'yourscript'.php
If you are already taking care of php.ini settings related with script memory and timeout then may be its linux ssh connection which terminating in active session or some thing like that.
You can use 'nohup' linux command run a command immune to hangups
shell> nohup php -f 'scriptname'.php
Edit:- You can close your session by adding '&' at end of command:-
shell> nohup php -f 'scriptname'.php &> /dev/null &
'&' operater at end of any comand in linux move that command in background
In a apcahe server i want to run a PHP scripts as cron which starts a php file in background and exits just after starting of the file and doesn't wait for the script to complete as that script will take around 60 minutes to complete.how this can be done?
You should know that there is no threads in PHP.
But you can execute programs and detach them easily if you're running on Unix/linux system.
$command = "/usr/bin/php '/path/to/your/php/to/execute.php'";
exec("{$command} > /dev/null 2>&1 & echo -n \$!");
May do the job. Let's explain a bit :
exec($command);
Executes /usr/bin/php '/path/to/your/php/to/execute.php' : your script is launched but Apache will awaits the end of the execution before executing next code.
> /dev/null
will redirect standard output (ie. your echo, print etc) to a virtual file (all outputs written in it are lost).
2>&1
will redirect error output to standard output, writting in the same virtual and non-existing file. This avoids having logs into your apache2/error.log for example.
&
is the most important thing in your case : it will detach your execution of $command : so exec() will immediatly release your php code execution.
echo -n \$!
will give PID of your detached execution as response : it will be returned by exec() and makes you able to work with it (such as, put this pid into a database and kill it after some time to avoid zombies).
You need to use "&" symbol to run program as background proccess.
$ php -f file.php &
Thats will run this command in background.
You may wright sh script
#!/bin/bash
php -f file.php &
And run this script from crontab.
This may not be the best solution to your specific problem. But for the record, there is Threads in PHP.
https://github.com/krakjoe/pthreads
I'm assuming you know how to use threads, this is very young code that I wrote myself, but if you have experience with threads and mutex and the like you should be able to solve your problem using this extension.
This is clearly a shameless plug of my own project, and if the user doesn't have the access required to install extensions then it won't help him, but many people find stackoverflow and it will solve other problems no doubt ...
I've created a php script that allows me to click a button to restart a PHP script. However, I'm not sure the best way to do it. Here's a snapshot of it: http://i51.tinypic.com/2niz32o.png
I currently have this:
if(isset($_POST['login_restart']))
{
$command = exec("/usr/bin/php /var/www/html/login_server.php >/dev/null &");
$pid = exec("nohup $command > /dev/null 2>&1 & echo $!");
$info = "Login server started...PID: $pid";
}
However, that doesn't seem to work. I need it so when the "Restart" button is pressed, it starts the login server, and keeps it running. I've been using the screen function in SSH, however, I don't want to have to keep logging into SSH to restart the login server. I want to somehow use a process ID so I can check to see if the script is running, and if it's not, it'll allow me to click the "Restart" button.
Thanks.
Is there a particular reason that you want to do this manually and not automatically? Is it not the case that the server should always be restarted?
My advice would be to automate this, either by using cron to check the status of your script at regular intervals, or bash infinite loop script immortality.
First create a launcher script to invoke your PHP for convenience, and call it run_login_server.sh (don't forget to chmod +x it so it can be executed):
#!/bin/bash
/usr/bin/php /var/www/html_login_server.php > /dev/null
Then create login_server_daemon.sh to run your script in an infinite loop (again, chmod +x it to make it executable):
#!/bin/bash
while :
do
./run_login_server.sh # or any command line to be executed forever
done
N.B. I have not backgrounded the php process in the above bash script. It works, because the bash loop will call php each time, and the loop will only iterate again once php has died. Just execute login_server_daemon.sh to start the loop (either through an init service or in a detached screen session like you are using now).
If your PHP scripts hang, or you want to reload them because you have updated your code, you can simply kill the looped process–run_login_server.sh and the bash loop will respawn it.
It's as simple as killall run_login_server.sh, which you could do via php's exec. Note that you need to be careful about the user permissions of who has executed what: if you execute login_server_daemon.sh as your_username but php runs as php_username then php will not have permission to killall your process.
Finally, if you can't choose between cron and the script approaches, here are some factors to consider:
The script should live forever, and will only die if 1) explicitly killed, 2) bash somehow trips and dies on a while loop, which I doubt would happen, and 3) a machine-wide catastrophe happens, in which case your little bash script stopping is the least of your worries. A bonus with the script is that restart is immediate after php (or whatever you want to call in the infinite loop) dies.
cron has a the problem that it can only check once a minute at its most frequent setting, if you really care about immediate recovery. It has the additional annoyance that if you decide to stop the script, you also have to remove it from your crontab or it will just come back to life.
I need to have a script execute (bash or perl or php, any will do) another command and then exit, while the other command still runs and exits on its own. I could schedule via at command, but was curious if there was a easier way.
#!/bin/sh
your_cmd &
echo "started your_cmd, now exiting!"
Similar constructs exists for perl and php, but in sh/bash its very easy to run another command in the background and proceed.
edit
A very good source for generic process manipulation are all the start scripts under /etc/init.d. They do all sorts of neat tricks such as keep track of pids, executing basic start/stop/restart commands etc.
To run a command in the background, you can append an '&' to the command.
If you need the program to last past your login session, you can use nohup.
See this similar stackoverflow discussion: how to run a command in the background ...
The usual way to run a command and have it keep running when you log out is to use nohup(1). nohup prevents the given command from receiving the HUP signal when the shell exits. You also need to run in the background with the ampersand (&) command suffix.
$ nohup some_command arg1 arg2 &
&?
#!/usr/bin/bash
# command1.sh: execute command2.sh and exit
command2.sh &
I'm not entirely sure if this is what you are looking for, but you can background a process executed in a shell by appending the ampersand (&) symbol as the last character of the command.
So if you have script, a.sh
and a.sh needs to spawn a seperate process, like say execute the script b.sh, you'd:
b.sh &
So long as you mentioned Perl:
fork || exec "ls";
...where "ls" is anything at all. Repeat for as many commands as you need to fire off.
Most answers are correct in showing..
mycmd &
camh's answer goes further to keep it alive with nohup.
Going further with advanced topics...
mycmd1 &
mycmd2 &
mycmd3 &
wait
"wait" will block processing until the backgrounded tasks are all completed. This can be useful if response times are significant such as for off-system data collection. It helps if you an be sure they will complete.
How do I subsequently foreground a process?
If it is your intent to foreground a process on a subsequent logon, look into screen or tmux.
screen -dmS MVS ./mvs
or (Minecraft example).
screen -dm java -Xmx4096M -Xms1024M -jar server.jar nogui
You can then re-attach to the terminal upon subsequent login.
screen -r
The login that launches these need not be interactive, you can use ssh remotely (plink, Ansible, etc.) to spawn these in a "drive by" manner.