Run php script as daemon process

Question

I need to run a php script as daemon process (wait for instructions and do stuff). cron job will not do it for me because actions need to be taken as soon as instruction arrives. I know PHP is not really the best option for daemon processes due to memory management issues, but due to various reasons I have to use PHP in this case. I came across a tool by libslack called Daemon (http://libslack.org/daemon) it seems to help me manage daemon processes, but there hasn't been any updates in the last 5 years, so I wonder if you know some other alternatives suitable for my case. Any information will be really appreciated.

Answer 1

I wrote and deployed a simple php-daemon, code is online here

https://github.com/jmullee/PhpUnixDaemon

Features: privilege dropping, signal handling, logging

I used it in a queue-handler (use case: trigger a lengthy operation from a web page, without making the page-generating php wait, i.e. launch an asynchronous operation) https://github.com/jmullee/PhpIPCMessageQueue

Answer 2

There is more than one way to solve this problem.

I do not know the specifics but perhaps there is another way to trigger the PHP process. For instance if you need the code to run based on events in a SQL database you could setup a trigger to execute your script. This is really easy to do under PostgreSQL: http://www.postgresql.org/docs/current/static/external-pl.html .

Honestly I think your best bet is to create a Damon process using nohup. nohup allows the command to continue to execute even after the user has logged out:

nohup php myscript.php &

There is however a very serious problem. As you said PHP's memory manager is complete garbage, it was built with the assumption that a script is only executing for a few seconds and then exists. Your PHP script will start to use GIGABYTES of memory after only a few days. You MUST ALSO create a cron script that runs every 12 or maybe 24 hours that kills and re-spawns your php script like this:

killall -3 php
nohup php myscript.php &

But what if the script was in the middle of a job? Well kill -3 is an interrupt, its the same as doing a ctrl+c on the CLI. Your php script can catch this interrupt and exit gracefully using the PHP pcntl library: http://php.oregonstate.edu/manual/en/function.pcntl-signal.php

Here is an example:

function clean_up() {
  GLOBAL $lock;
  mysql_close();
  fclose($lock)
  exit();
}
pcntl_signal(SIGINT, 'clean_up');

The idea behind the $lock is that the PHP script can open a file with a fopen("file","w");. Only one process can have a write lock on a file, so using this you can make sure that only one copy of your PHP script is running.

Good Luck!

Answer 3

Kevin van Zonneveld wrote a very nice detailed article on this, in his example he makes use of the System_Daemon PEAR package (last release date on 2009-09-02).

Answer 4

I run a large number of PHP daemons.

I agree with you that PHP is not the best (or even a good) language for doing this, but the daemons share code with the web-facing components so overall it is a good solution for us.

We use daemontools for this. It is smart, clean and reliable. In fact we use it for running all of our daemons.

You can check this out at http://cr.yp.to/daemontools.html.

EDIT: A quick list of features.

• Automatically starts the daemon on reboot
• Automatically restart dameon on failure
• Logging is handled for you, including rollover and pruning
• Management interface: 'svc' and 'svstat'
• UNIX friendly (not a plus for everyone perhaps)

Answer 5

As others have already mentioned, running PHP as a daemon is quite easy, and can be done using a single line of command. But the actual problem is keeping it running and managing it. I've had the same problem quite some time ago and although there are plenty of solutions already available, most of them have lots of dependencies or are difficult to use and not suitable for basic usages. I wrote a shell script that can manage a any process/application including PHP cli scripts. It can be set as a cronjob to start the application and will contain the application and manage it. If it's executed again, for example via the same cronjob, it check if the app is running or not, if it does then simply exits and let its previous instance continue managing the application.

I uploaded it to github, feel free to use it : https://github.com/sinasalek/EasyDeamonizer

EasyDeamonizer

Simply watches over your application (start, restart, log, monitor, etc). a generic script to make sure that your appliation remains running properly. Intentionally it uses process name instread of pid/lock file to prevent all its side effects and keep the script as simple and as stirghforward as possible, so it always works even when EasyDaemonizer itself is restarted. Features

• Starts the application and optionally a customized delay for each start
• Makes sure that only one instance is running
• Monitors CPU usage and restarts the app automatically when it reaches the defined threshold
• Setting EasyDeamonizer to run via cron to run it again if it's halted for any reason
• Logs its activity

Answer 6

You could start your php script from the command line (i.e. bash) by using

nohup php myscript.php &

the & puts your process in the background.

Edit:
Yes, there are some drawbacks, but not possible to control? That's just wrong.
A simple kill processid will stop it. And it's still the best and simplest solution.