For a website, I need to be able to start and stop a daemon process. What I am currently doing is
exec("sudo /etc/init.d/daemonToStart start");
The daemon process is started, but Apache/PHP hangs. Doing a ps aux revealed that sudo itself changed into a zombie process, effectively killing all further progress. Is this normal behavior when trying to start a daeomon from PHP?
And yes, Apache has the right to execute the /etc/init.d/daemonToStart command. I altered the /etc/sudoers file to allow it to do so. No, I have not allowed Apache to be able to execute any kind of command, just a limited few to allow the website to work.
Anyway, going back to my question, is there a way to allow PHP to start daemons in a way that no zombie process is created? I ask this because when I do the reverse, stopping an already started daemon, works just fine.
Try appending > /dev/null 2>&1 & to the command.
So this:
exec("sudo /etc/init.d/daemonToStart > /dev/null 2>&1 &");
Just in case you want to know what it does/why:
> /dev/null - redirect STDOUT to /dev/null (blackhole it, in other words)
2>&1 - redirect STDERR to STDOUT (blackhole it as well)
& detach process and run in the background
I had the same problem.
I agree with DaveRandom, you have to suppress every output (stdout and stderr). But no need to launch in another process with the ending '&': the exec() function can't check the return code anymore, and returns ok even if there is an error...
And I prefer to store outputs in a temporary file, instead of 'blackhole'it.
Working solution:
$temp = tempnam(sys_get_temp_dir(), 'php');
exec('sudo /etc/init.d/daemonToStart >'.$temp.' 2>&1');
Just read file content after, and delete temporary file:
$output = explode("\n", file_get_contents($temp));
#unlink($temp);
I have never tried starting a daemon from PHP, but I have tried running other shell commands, with much trouble. Here are a few things I have tried, in the past:
As per DaveRandom's answer, append /dev/null 2>&1 & to the end of your command. This will redirect errors to standard output. You can then use this output to debug.
Make sure your webserver's user's PATH contains all referenced binaries inside your daemon script. You can do this by calling exec('echo $PATH; whoami;). This will tell you the user PHP is running under, and it's current PATH variable.
Related
I have a process intensive task that I would like to run in the background.
The user clicks on a page, the PHP script runs, and finally, based on some conditions, if required, then it has to run a shell script, E.G.:
shell_exec('php measurePerformance.php 47 844 email#yahoo.com');
Currently I use shell_exec, but this requires the script to wait for an output. Is there any way to execute the command I want without waiting for it to complete?
How about adding.
"> /dev/null 2>/dev/null &"
shell_exec('php measurePerformance.php 47 844 email#yahoo.com > /dev/null 2>/dev/null &');
Note this also gets rid of the stdio and stderr.
This will execute a command and disconnect from the running process. Of course, it can be any command you want. But for a test, you can create a php file with a sleep(20) command it.
exec("nohup /usr/bin/php -f sleep.php > /dev/null 2>&1 &");
You can also give your output back to the client instantly and continue processing your PHP code afterwards.
This is the method I am using for long-waiting Ajax calls which would not have any effect on client side:
ob_end_clean();
ignore_user_abort();
ob_start();
header("Connection: close");
echo json_encode($out);
header("Content-Length: " . ob_get_length());
ob_end_flush();
flush();
// execute your command here. client will not wait for response, it already has one above.
You can find the detailed explanation here: http://oytun.co/response-now-process-later
On Windows 2003, to call another script without waiting, I used this:
$commandString = "start /b c:\\php\\php.EXE C:\\Inetpub\\wwwroot\\mysite.com\\phpforktest.php --passmsg=$testmsg";
pclose(popen($commandString, 'r'));
This only works AFTER giving changing permissions on cmd.exe - add Read and Execute for IUSR_YOURMACHINE (I also set write to Deny).
Use PHP's popen command, e.g.:
pclose(popen("start c:\wamp\bin\php.exe c:\wamp\www\script.php","r"));
This will create a child process and the script will excute in the background without waiting for output.
Sure, for windows you can use:
$WshShell = new COM("WScript.Shell");
$oExec = $WshShell->Run("C:/path/to/php-win.exe -f C:/path/to/script.php", 0, false);
Note:
If you get a COM error, add the extension to your php.ini and restart apache:
[COM_DOT_NET]
extension=php_com_dotnet.dll
If it's off of a web page, I recommend generating a signal of some kind (dropping a file in a directory, perhaps) and having a cron job pick up the work that needs to be done. Otherwise, we're likely to get into the territory of using pcntl_fork() and exec() from inside an Apache process, and that's just bad mojo.
That will work but you will have to be careful not to overload your server because it will create a new process every time you call this function which will run in background. If only one concurrent call at the same time then this workaround will do the job.
If not then I would advice to run a message queue like for instance beanstalkd/gearman/amazon sqs.
I have a simple question, i searched and I couldn't find a solution.
I have a simple shell script that run a small php code every 2 seconds, I wrote it and save as a file:
$ cat every-2-seconds.sh
#!/bin/bash
while true
do
php /home/account/domains/domain.co.il/public_html/my-php-script.php
sleep 2
done
Now, i need that this script will always run on background, but I also need that it will run on startup, Just like a service, it should always run in background, and I never want to start it manually (of course, if something happen and it will stop, i should be able to start it manually)
I heard about nohup, but its not a service right? and I can start it on startup.. :(
Can you help me on this??
You can make your script run with this line of code (assuming you are in the directory with your script)
nohup every-2-seconds.sh &
The & will run this as a background task and nohup will keep the process running even after you've disconnected from your session.
To handle starting it on reboot you need to add this command to your crontab
crontab -e
#reboot /path/to/every-2-seconds.sh > /dev/null
In the crontab you need to specify the full path. You can change /dev/null to the file you want output to go to (assuming you want the output)
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 have a process intensive task that I would like to run in the background.
The user clicks on a page, the PHP script runs, and finally, based on some conditions, if required, then it has to run a shell script, E.G.:
shell_exec('php measurePerformance.php 47 844 email#yahoo.com');
Currently I use shell_exec, but this requires the script to wait for an output. Is there any way to execute the command I want without waiting for it to complete?
How about adding.
"> /dev/null 2>/dev/null &"
shell_exec('php measurePerformance.php 47 844 email#yahoo.com > /dev/null 2>/dev/null &');
Note this also gets rid of the stdio and stderr.
This will execute a command and disconnect from the running process. Of course, it can be any command you want. But for a test, you can create a php file with a sleep(20) command it.
exec("nohup /usr/bin/php -f sleep.php > /dev/null 2>&1 &");
You can also give your output back to the client instantly and continue processing your PHP code afterwards.
This is the method I am using for long-waiting Ajax calls which would not have any effect on client side:
ob_end_clean();
ignore_user_abort();
ob_start();
header("Connection: close");
echo json_encode($out);
header("Content-Length: " . ob_get_length());
ob_end_flush();
flush();
// execute your command here. client will not wait for response, it already has one above.
You can find the detailed explanation here: http://oytun.co/response-now-process-later
On Windows 2003, to call another script without waiting, I used this:
$commandString = "start /b c:\\php\\php.EXE C:\\Inetpub\\wwwroot\\mysite.com\\phpforktest.php --passmsg=$testmsg";
pclose(popen($commandString, 'r'));
This only works AFTER giving changing permissions on cmd.exe - add Read and Execute for IUSR_YOURMACHINE (I also set write to Deny).
Use PHP's popen command, e.g.:
pclose(popen("start c:\wamp\bin\php.exe c:\wamp\www\script.php","r"));
This will create a child process and the script will excute in the background without waiting for output.
Sure, for windows you can use:
$WshShell = new COM("WScript.Shell");
$oExec = $WshShell->Run("C:/path/to/php-win.exe -f C:/path/to/script.php", 0, false);
Note:
If you get a COM error, add the extension to your php.ini and restart apache:
[COM_DOT_NET]
extension=php_com_dotnet.dll
If it's off of a web page, I recommend generating a signal of some kind (dropping a file in a directory, perhaps) and having a cron job pick up the work that needs to be done. Otherwise, we're likely to get into the territory of using pcntl_fork() and exec() from inside an Apache process, and that's just bad mojo.
That will work but you will have to be careful not to overload your server because it will create a new process every time you call this function which will run in background. If only one concurrent call at the same time then this workaround will do the job.
If not then I would advice to run a message queue like for instance beanstalkd/gearman/amazon sqs.