My architecture is composed of the following :
A supervisor controller that makes sure n instances of the same PHP scripts are running (and restart them when there are not).
The script is a while loop that waits for a job from Beanstalk and process it when it arrive. After a certain number of loops (defined), the script exit, in order to be reloaded by supervisorctl (I do that because PHP tends to be instable in the long run).
When I push some changes, I have to wait that the "workers" have finished the number of expected loop to be restarted and then take into consideration the new changes.
Is there a way to fasten this ?
Thank you for your help.
Maybe simply decoupling the loop from the code that ingest the jobs + using process control extension can help, check this out: http://www.hackingwithphp.com/16/1/8/running-programs-in-the-current-process-space
(Sorry if I'm making wrong assumptions here, I don't have enough Karma to ask questions through comments)
Related
I am trying to start a linux shell script from PHP5 that will run for 24hours, but I want the webpage to return within seconds. I though this could be solved by making a script spawning of the task, but it does not seem to work.
I have been searching around for a solution or a "one shot / fire and forget" option for a couple of days without any luck.
The following example shows the problem.
In PHP 5 I make one of the following call (tried a lot it this point)
passthru("dummy_script.sh");
or
system("dummy_script.sh");
or
shell_exec("dummy_script.sh");
The dummy script look the following:
#!/bin/sh
{
while true
do
sleep 1
done
} &
I can see the that process gets started, but the webpage does not return before I make a 'killall dummy_script.sh'. If I run the script manually in a terminal it return immediately and spawns of the loop.
Does anyone know a way here I can spawn of the task without making the webpage wait it ?
Hope you guys can help me out, it would be most appreciated.
To answer your question:
You may start looking at pcntl_fork. Or you may check this. Basically, you are using the native fork to fork the long running process so your php frontend does not have to wait.
If you're feeling adventurous, you may put your "job" (your request to this long running process) in a DB. A cron job then checks the DB for incoming requests and it is the one that executes that process.
Another method is to use resque, but don't bother at this point.
I've previously used Gearman along with supervisor to manage jobs.
In this case we are using Amazon SQS which I have spent some time trying to get my head around.
I have set up a separate micro instance from our main webserver to use as an Image processing server (purely for testing at the moment, it will be upgraded and become part of a cluster before this implementation goes live)
On this micro instance I have installed PHP and ImageMagick in order to perform the image processing.
I have also written a worker script which receives the messages from Amazon SQS.
All works perfectly, however I need this script to run over and over again in order to continuously check for messages.
I don't like the thought of running a continuous loop so have started to look at other methods with little success.
So my question is what is generally considered the best practice way to do this?
I am worried about memory since PHP wasn't really designed for this, therefore it feels like running the script for a while, then stopping and restarting it might be my best bet.
I have experience using supervisor (to ensure that gearman workers kept running) and am wondering if I could simply use that to continuously execute the simple php script over and over?
My thoughts are as follows:
Set up SQS long polling so that the script checks for 20 seconds.
Use a while loop with a 20 second sleep to keep this script running for say an hour at a time
Have all this run through supervisor. When the hour is up and the loop is complete, allow the script to exit.
Supervisor should then automatically restart it
Does this sound viable? Is there a better way? What is generally considered the best practice for receiving SQS messages in PHP?
Thanks in advance
In supervisord you can set autorestart to true to have it run your command over and over again. See: http://supervisord.org/configuration.html#program-x-section-settings
Overall, using an endless while loop is perfectly fine, PHP will free your objects correctly and keep memory in check if written correctly. It can run for years without leaks (if there's a leak, you probably created it yourself, so review your code).
How do I stop a Supervisord process without killing the program it's controlling? might be of interest to you; the OP had a similar setup, with autorestart and wanted to add graceful shutdowns to it.
I'm developing a PHP-service which does numerous operations per customer, and I want this to run continuously. I've already taken a look at cron, but as far as I understood cron made it possible to run the code on set times. This can be a bit dangerous since we are dependant that the code has finished running before it starts over, and the time for each run may vary as the customer base increases. So refresh, cron or other timed intervals cant be done, as far as I'm aware.
So I'm wondering if you know any solutions where I can restart my service when it is finished, and under no circumstances make the re-run before all the code have been executed?
I'm sorry if this is answered before or is easily found on Google, I have tried to find something, but to no avail.
Edit: I could set timed intervals to be 1 hour, to be absolutely sure, but I want as little time as possible between each run.
Look at this:
http://www.godlikemouse.com/2011/03/31/php-daemons-tutorial/
What you need is a daemon that keeps running. There are more solutions than this while loop.
The following I once used in a project: http://kvz.io/blog/2009/01/09/create-daemons-in-php/ , it's also a package for PEAR: http://pear.php.net/package/System_Daemon
For more information, see the following SO links:
What is a daemon: What is daemon? Their practical use? Usage with php?
How to use: PHP script that works forever :)
Have you tried runnning the PHP script as a process. This here has more details http://nsaunders.wordpress.com/2007/01/12/running-a-background-process-in-php/
If you do not want to learn how to code a daemon, I recommand using a software that manages processes in userland: Supervisor (http://supervisord.org/)
You just need to write a configuration file to specify which processes you want to run, and how.
It is extremely simple to configure and it is very adaptable (you can force having only one instance of your process, or instead have a fixed number of instances... etc).
It will also handle automatic restart in case your script crashes, and logging.
On the PHP side, just create a script that never quits, using a while(true) { ... } loop, and add an entry like this in supervisord's conf:
[program:your-script]
command=/usr/bin/php /path/to/your_script.php
I'm using that software in production for a few projects (to run ruby and php gearman asynchronous workers for websites).
Try to have a custom logic , where you can set the flag ON and OFF and in your CRON , you can check before running the code inside it. I wanted to suggested something like Queue based solution , once you get the entry , then run the logic of your processing . Which can be either daemon or cron. It will give more control if your task is OK to execute now . Edited it
I'm looking for some ideas to do the following. I need a PHP script to perform certain action for quite a long time. This is an extension for a CMS and this can't be anything else but PHP. It also can't be a command line script because it should be used by common people that will have only the standard means of the CMS. One of the options is having a cron job (most simple hostings have it) that will trigger the script often so that instead of working for a long time it could perform the action step by step preserving its state from one launch to the next one. This is not perfect but I can't see of any other solutions. If the script will be redirecting to itself server will interrupt it. What other options can suit?
Thanks everyone in advance!
What you're talking about is a daemon or long running program that waits for calls by client programs, performs and action, provides a response then keeps on waiting for more calls.
You might be familiar w/ these in the form of Apache & MySQL ;) Anyway PHP is generally OK in this regard, it does have the ability to function over raw sockets as well as fork sub-processes to handle multiple requests simultaneously.
Having said that PHP daemons are a tool where YMMV. Some folks will say they work great, other folks like me will say they have issues w/ interprocess communication and leaking memory even amidst plethora unset() calls.
Anyway you likely won't be able to deploy a daemon of any type on a shared hosting environment. You'll need to get a better server package or stick with a Cron based solution.
Here's a link about writing a PHP daemon.
Also, one more note. Daemons do crash from time to time and therefore you may still need to store state about whats going on, just in case someone trips over the power cord to your shared server :)
I would also suggest that you think about making it a daemon but if not then you can simply use
set_time_limit(0);
ignore_user_abort(true);
at the top to tell it not to time out and not to get interrupted by anything. Then call it from the cron to start it every day or whatever. I have this on many long processing daily tasks and it works great for me. However, it won't be able to easily talk to the outside world (other scripts can't query it or anything -- if that is what you want look into php services) so once you get it running make sure it will stop and have it print its progress to a logfile.
I am developing a website that requires a lot background processes for the site to run. For example, a queue, a video encoder and a few other types of background processes. Currently I have these running as a PHP cli script that contains:
while (true) {
// some code
sleep($someAmountOfSeconds);
}
Ok these work fine and everything but I was thinking of setting these up as a deamon which will give them an actual process id that I can monitor, also I can run them int he background and not have a terminal open all the time.
I would like to know if there is a better way of handling these? I was also thinking about cron jobs but some of these processes need to loop every few seconds.
Any suggestions?
Creating a daemon which you can make calls to and ask questions would seem the sensible option. Depends on wether your hoster permits such things, especially if you're requiring it to do work every few seconds, then definately an OS based service/daemon would seem far more sensible than anything else.
You could create a daemon in PHP, but in my experience this is a lot of hard work and the result is unreliable due to PHP's memory management and error handling.
I had the same problem, I wanted to write my logic in PHP but have it daemonised by a stable program that could restart the PHP script if it failed and so I wrote The Fat Controller.
It's written in C, runs as a daemon and can run PHP scripts, or indeed anything. If the PHP script ends for whatever reason, The Fat Controller will restart it. This means you don't have to take care of daemonising or error recovery - it's all handled for you.
The Fat Controller can also do lots of other things such as parallel processing which is ideal for queue processing, you can read about some potential use cases here:
http://fat-controller.sourceforge.net/use-cases.html
I've done this for 5 years using PHP to run background tasks and its no different to doing in any other language. Just use CRON and lock files. The lock file will prevent multiple instances of your script running.
Also its important to monitor your code and one check I always do to prevent stale lock files from preventing scripts to run is to have second CRON job to check if if the lock file is older than a few minutes and if an instance of the PHP script is running, if not it then removes the lock file.
Using this technique allows you to set your CRON to run the script every minute without issues.
Use the System::Daemon module from PEAR.
One solution (that I really need to try myself, as I may need it) is to use cron, but get the process to loop for five mins or so. Then, get cron to kick it off every five minutes. As one dies, the next one should be finishing (or close to finishing).
Bear in mind that the two may overlap a bit, and so you need to ensure that this doesn't cause a clash (e.g. writing to the same video file). Some simple inter-process communication may be useful, even if it is just writing to a PID file in the temp directory.
This approach is a bit low-tech but helps avoid PHP hanging onto memory over the longer term - sort of in-built task restarts!