I have implemented a command in my Symfony setup which grabs a job from the DB and then processes it.
How can I run multiple instances of command at once, to get through jobs quicker. I know that multithreading is not supported in PHP but seeing as the command is called from the shell, I was wondering if there was a workaround.
Call command using:
app/console job:process
The way I would solve this is to use a work queue with multiple workers. It's easier to manage and scale than manually running multiple processes and worrying about concurrency.
The simplest general-purpose queue I've found for working with php/symfony is beanstalkd which you can integrate into symfony2 with the LeezyPheanstalkBundle
Command, acting as a worker. And then a shell script to make sure that no workers were becoming zombies. Thanks!In general, I'd suggest using enqueue library. You can choose from a variety of transports available, from the simplest like filesystem and Doctrine DBAL to real once like RabbitMQ and Amazon SQS.
Regarding the consumers, you need sort of process manager. There several options:
http://supervisord.org/ - You need extra service. It has to be configured properly.
A pure PHP process manager like this. Based on Symfony process component and pure PHP code. It can handle process reboot, correct exit on sigterm signal and a lot more.
A php\swoole process manager like this. It requires a swoole PHP extension but it is performance is amazing.
I have written a blog post on how to solve this exact problem. https://plume.baucum.me/~/Absolutely/running-multiple-processes-simultaneously-in-a-symfony-command
It is much too long to rehash everything here, but the basic concept is that your command optionally takes in the job's ID. The command will check if the ID was given. If not then it will grab all the jobs from the DB, loop over them, and recall itself with the job ID parameter. As each command is kicked off you store it in an array, and if the array is too big you sleep, for rate throttling. As commands finish you remove them from the array.
When the command is ran with the job ID it will create a lock using Symfony's lock component so that a job cannot accidentally be processed two times at once. It is important that you unlock the job when it either finishes or errors out. Once it has the ID and the lock it will then call whatever code you have written to actually process the job.
Using this technique I have taken commands that took hours to run, as it synchronously went through each task, into taking only minutes. Make sure to try different throttles to balance resource utilization and time it takes to execute your task.
