PHP Resque Worker (and Enqueue)

PHP Resque is a Redis-backed library for creating background jobs, placing those jobs on one or more queues, and processing them later.

Background

Resque was pioneered by GitHub, and written in Ruby. What you're seeing here started life as an almost direct port of the Resque worker and enqueue system to PHP.

For more information on Resque, visit the official GitHub project: https://github.com/resque/resque

For further information, see the launch post on the GitHub blog: http://github.com/blog/542-introducing-resque

The PHP port does NOT include its own web interface for viewing queue stats, as the data is stored in the exact same expected format as the Ruby version of Resque.

The PHP port provides much the same features as the Ruby version:

• Workers can be distributed between multiple machines
• Includes support for priorities (queues)
• Resilient to memory leaks (forking)
• Expects failure

It also supports the following additional features:

• Has the ability to track the status of jobs
• Will mark a job as failed, if a forked child running a job does not exit with a status code as 0
• Has built in support for setUp and tearDown methods, called pre and post jobs

Additionally it includes php-resque-scheduler, a PHP port of resque-scheduler, which adds support for scheduling items in the future to Resque. It has been designed to be an almost direct-copy of the Ruby plugin

At the moment, php-resque-scheduler only supports delayed jobs, which is the ability to push a job to the queue and have it run at a certain timestamp, or in a number of seconds. Support for recurring jobs (similar to CRON) is planned for a future release.

This port was originally made by Chris Boulton, with maintenance by the community. See https://github.com/chrisboulton/php-resque for more on that history.

Requirements

• PHP 5.3+
• Redis 2.2+
• Optional but Recommended: Composer

Getting Started

The easiest way to work with php-resque is when it's installed as a Composer package inside your project. Composer isn't strictly required, but makes life a lot easier.

If you're not familiar with Composer, please see http://getcomposer.org/.

1. Run composer require resque/php-resque.

2. If you haven't already, add the Composer autoload to your project's initialization file. (example)

require 'vendor/autoload.php';

Jobs

Queueing Jobs

Jobs are queued as follows:

// Required if redis is located elsewhere
Resque\Resque::setBackend('localhost:6379');

$args = array(
          'name' => 'Chris'
        );
Resque\Resque::enqueue('default', 'My_Job', $args);

Defining Jobs

Each job should be in its own class, and include a perform method.

class My_Job
{
    public function perform()
    {
        // Work work work
        echo $this->args['name'];
    }
}

When the job is run, the class will be instantiated and any arguments will be set as an array on the instantiated object, and are accessible via $this->args.

Any exception thrown by a job will result in the job failing - be careful here and make sure you handle the exceptions that shouldn't result in a job failing.

Jobs can also have setUp and tearDown methods. If a setUp method is defined, it will be called before the perform method is run. The tearDown method, if defined, will be called after the job finishes.

class My_Job
{
    public function setUp()
    {
        // ... Set up environment for this job
    }

    public function perform()
    {
        // .. Run job
    }

    public function tearDown()
    {
        // ... Remove environment for this job
    }
}

Dequeueing Jobs

This method can be used to conveniently remove a job from a queue.

// Removes job class 'My_Job' of queue 'default'
Resque\Resque::dequeue('default', ['My_Job']);

// Removes job class 'My_Job' with Job ID '087df5819a790ac666c9608e2234b21e' of queue 'default'
Resque\Resque::dequeue('default', ['My_Job' => '087df5819a790ac666c9608e2234b21e']);

// Removes job class 'My_Job' with arguments of queue 'default'
Resque\Resque::dequeue('default', ['My_Job' => array('foo' => 1, 'bar' => 2)]);

// Removes multiple jobs
Resque\Resque::dequeue('default', ['My_Job', 'My_Job2']);

If no jobs are given, this method will dequeue all jobs matching the provided queue.

// Removes all jobs of queue 'default'
Resque\Resque::dequeue('default');

Tracking Job Statuses

php-resque has the ability to perform basic status tracking of a queued job. The status information will allow you to check if a job is in the queue, is currently being run, has finished, or has failed.

To track the status of a job, pass true as the fourth argument to Resque\Resque::enqueue. A token used for tracking the job status will be returned:

$token = Resque\Resque::enqueue('default', 'My_Job', $args, true);
echo $token;

To fetch the status of a job:

$status = new Resque\Job\Status($token);
echo $status->get(); // Outputs the status

Job statuses are defined as constants in the Resque\Job\Status class. Valid statuses include:

• Resque\Job\Status::STATUS_WAITING - Job is still queued
• Resque\Job\Status::STATUS_RUNNING - Job is currently running
• Resque\Job\Status::STATUS_FAILED - Job has failed
• Resque\Job\Status::STATUS_COMPLETE - Job is complete
• false - Failed to fetch the status; is the token valid?

Statuses are available for up to 24 hours after a job has completed or failed, and are then automatically expired. A status can also forcefully be expired by calling the stop() method on a status class.

Obtaining job PID

You can obtain the PID of the actual process doing the work through Resque\Job\PID. On a forking OS this will be the PID of the forked process.

CAUTION: on a non-forking OS, the PID returned will be of the worker itself.

echo Resque\Job\PID::get($token);

Function returns 0 if the perform hasn't started yet, or if it has already ended.

Delayed Jobs

To quote the documentation for the Ruby resque-scheduler:

Delayed jobs are one-off jobs that you want to be put into a queue at some point in the future. The classic example is sending an email:

require 'Resque.php';
require 'Scheduler.php';

$in = 3600;
$args = array('id' => $user->id);
Resque\Scheduler::enqueueIn($in, 'email', 'SendFollowUpEmail', $args);

The above will store the job for 1 hour in the delayed queue, and then pull the job off and submit it to the email queue in Resque for processing as soon as a worker is available.

Instead of passing a relative time in seconds, you can also supply a timestamp as either a DateTime object or integer containing a UNIX timestamp to the enqueueAt method:

require 'Resque.php';
require 'Scheduler.php';

$time = 1332067214;
Resque\Scheduler::enqueueAt($time, 'email', 'SendFollowUpEmail', $args);

$datetime = new DateTime('2012-03-18 13:21:49');
Resque\Scheduler::enqueueAt($datetime, 'email', 'SendFollowUpEmail', $args);

NOTE: resque-scheduler does not guarantee a job will fire at the time supplied. At the time supplied, resque-scheduler will take the job out of the delayed queue and push it to the appropriate queue in Resque. Your next available Resque worker will pick the job up. To keep processing as quick as possible, keep your queues as empty as possible.

Workers

Workers work in the exact same way as the Ruby workers. For complete documentation on workers, see the original documentation.

A basic "up-and-running" bin/resque file is included that sets up a running worker environment. (vendor/bin/resque when installed via Composer)

The exception to the similarities with the Ruby version of resque is how a worker is initially setup. To work under all environments, not having a single environment such as with Ruby, the PHP port makes no assumptions about your setup.

To start a worker, it's very similar to the Ruby version:

$ QUEUE=file_serve php bin/resque

It's your responsibility to tell the worker which file to include to get your application underway. You do so by setting the APP_INCLUDE environment variable:

$ QUEUE=file_serve APP_INCLUDE=../application/init.php php bin/resque

Pro tip: Using Composer? More than likely, you don't need to worry about APP_INCLUDE, because hopefully Composer is responsible for autoloading your application too!

Getting your application underway also includes telling the worker your job classes, by means of either an autoloader or including them.

Alternately, you can always include('bin/resque') from your application and skip setting APP_INCLUDE altogether. Just be sure the various environment variables are set (setenv) before you do.

Logging

The port supports the same environment variables for logging to STDOUT. Setting VERBOSE will print basic debugging information and VVERBOSE will print detailed information.

$ VERBOSE=1 QUEUE=file_serve bin/resque
$ VVERBOSE=1 QUEUE=file_serve bin/resque

Priorities and Queue Lists

Similarly, priority and queue list functionality works exactly the same as the Ruby workers. Multiple queues should be separated with a comma, and the order that they're supplied in is the order that they're checked in.

As per the original example:

$ QUEUE=file_serve,warm_cache bin/resque

The file_serve queue will always be checked for new jobs on each iteration before the warm_cache queue is checked.

Running All Queues

All queues are supported in the same manner and processed in alphabetical order:

$ QUEUE='*' bin/resque

Running Multiple Workers

Multiple workers can be launched simultaneously by supplying the COUNT environment variable:

$ COUNT=5 bin/resque

Be aware, however, that each worker is its own fork, and the original process will shut down as soon as it has spawned COUNT forks. If you need to keep track of your workers using an external application such as monit, you'll need to work around this limitation.

Custom prefix

When you have multiple apps using the same Redis database it is better to use a custom prefix to separate the Resque data:

$ PREFIX=my-app-name bin/resque

Setting Redis backend

When you have the Redis database on a different host than the one the workers are running, you must set the REDIS_BACKEND environment variable:

$ REDIS_BACKEND=my-redis-ip:my-redis-port bin/resque

Forking

Similarly to the Ruby versions, supported platforms will immediately fork after picking up a job. The forked child will exit as soon as the job finishes.

The difference with php-resque is that if a forked child does not exit nicely (PHP error or such), php-resque will automatically fail the job.

Signals

Signals also work on supported platforms exactly as in the Ruby version of Resque:

• QUIT - Wait for job to finish processing then exit
• TERM / INT - Immediately kill job then exit
• USR1 - Immediately kill job but don't exit
• USR2 - Pause worker, no new jobs will be processed
• CONT - Resume worker.

Process Titles/Statuses

The Ruby version of Resque has a nifty feature whereby the process title of the worker is updated to indicate what the worker is doing, and any forked children also set their process title with the job being run. This helps identify running processes on the server and their resque status.

PHP does not have this functionality by default until 5.5.

A PECL module (http://pecl.php.net/package/proctitle) exists that adds this functionality to PHP before 5.5, so if you'd like process titles updated, install the PECL module as well. php-resque will automatically detect and use it.

Resque Scheduler

resque-scheduler requires a special worker that runs in the background. This worker is responsible for pulling items off the schedule/delayed queue and adding them to the queue for resque. This means that for delayed or scheduled jobs to be executed, that worker needs to be running.

A basic "up-and-running" bin/resque-scheduler file that sets up a running worker environment is included (vendor/bin/resque-scheduler when installed via composer). It accepts many of the same environment variables as the main workers for php-resque:

• REDIS_BACKEND - Redis server to connect to
• LOGGING - Enable logging to STDOUT
• VERBOSE - Enable verbose logging
• VVERBOSE - Enable very verbose logging
• INTERVAL - Sleep for this long before checking scheduled/delayed queues
• APP_INCLUDE - Include this file when starting (to launch your app)
• PIDFILE - Write the PID of the worker out to this file

It's easy to start the resque-scheduler worker using bin/resque-scheduler: $ php bin/resque-scheduler

Event/Hook System

php-resque has a basic event system that can be used by your application to customize how some of the php-resque internals behave.

You listen in on events (as listed below) by registering with Resque\Event and supplying a callback that you would like triggered when the event is raised:

Resque\Event::listen('eventName', [callback]);

[callback] may be anything in PHP that is callable by call_user_func_array:

• A string with the name of a function
• An array containing an object and method to call
• An array containing an object and a static method to call
• A closure (PHP 5.3+)

Events may pass arguments (documented below), so your callback should accept these arguments.

You can stop listening to an event by calling Resque\Event::stopListening with the same arguments supplied to Resque\Event::listen.

It is up to your application to register event listeners. When enqueuing events in your application, it should be as easy as making sure php-resque is loaded and calling Resque\Event::listen.

When running workers, if you run workers via the default bin/resque script, your APP_INCLUDE script should initialize and register any listeners required for operation. If you have rolled your own worker manager, then it is again your responsibility to register listeners.

A sample plugin is included in the extras directory.

Events

beforeFirstFork

Called once, as a worker initializes. Argument passed is the instance of Resque\Worker\ResqueWorker that was just initialized.

beforeFork

Called before php-resque forks to run a job. Argument passed contains the instance of Resque\JobHandler for the job about to be run.

beforeFork is triggered in the parent process. Any changes made will be permanent for as long as the worker lives.

afterFork

Called after php-resque forks to run a job (but before the job is run). Argument passed contains the instance of Resque\JobHandler for the job about to be run.

afterFork is triggered in the child process after forking out to complete a job. Any changes made will only live as long as the job is being processed.

beforePerform

Called before the setUp and perform methods on a job are run. Argument passed contains the instance of Resque\JobHandler for the job about to be run.

You can prevent execution of the job by throwing an exception of Resque\Exceptions\DoNotPerformException. Any other exceptions thrown will be treated as if they were thrown in a job, causing the job to fail.

afterPerform

Called after the perform and tearDown methods on a job are run. Argument passed contains the instance of Resque\JobHandler that was just run.

Any exceptions thrown will be treated as if they were thrown in a job, causing the job to be marked as having failed.

onFailure

Called whenever a job fails. Arguments passed (in this order) include:

• Exception - The exception that was thrown when the job failed
• Resque\JobHandler - The job that failed

beforeEnqueue

Called immediately before a job is enqueued using the Resque\Resque::enqueue method. Arguments passed (in this order) include:

• Class - string containing the name of the job to be enqueued
• Arguments - array of arguments for the job
• Queue - string containing the name of the queue the job is to be enqueued in
• ID - string containing the token of the job to be enqueued

You can prevent enqueing of the job by throwing an exception of Resque\Exceptions\DoNotCreateException.

afterEnqueue

Called after a job has been queued using the Resque\Resque::enqueue method. Arguments passed (in this order) include:

• Class - string containing the name of scheduled job
• Arguments - array of arguments supplied to the job
• Queue - string containing the name of the queue the job was added to
• ID - string containing the new token of the enqueued job

afterSchedule

Called after a job has been added to the schedule. Arguments passed are the timestamp, queue of the job, the class name of the job, and the job's arguments.

beforeDelayedEnqueue

Called immediately after a job has been pulled off the delayed queue and right before the job is added to the queue in resque. Arguments passed are the queue of the job, the class name of the job, and the job's arguments.

Step-By-Step

For a more in-depth look at what php-resque does under the hood (without needing to directly examine the code), have a look at HOWITWORKS.md.

Contributors

Project Creator

• @chrisboulton

Project Maintainers

• @danhunsaker
• @rajibahmed
• @steveklabnik

Others

• @acinader
• @ajbonner
• @andrewjshults
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