Listener.php

TLDR

This file defines a class called Listener in the Illuminate\Queue namespace. The Listener class is responsible for listening to a queue connection and running the worker process to process the jobs in the queue.

Methods

makeProcess

This method creates a new Symfony process for the worker.

listen

This method listens to the given queue connection and runs the worker process.

setOutputHandler

This method sets the output handler callback.

addEnvironment

This method adds the environment option to the given command.

createCommand

This method creates the command with the listener options.

runProcess

This method runs the given process.

handleWorkerOutput

This method handles output from the worker process.

memoryExceeded

This method determines if the memory limit has been exceeded.

stop

This method stops listening and exits the script.

END

<?php

namespace Illuminate\Queue;

use Closure;
use Symfony\Component\Process\PhpExecutableFinder;
use Symfony\Component\Process\Process;

class Listener
{
    /**
     * The command working path.
     *
     * @var string
     */
    protected $commandPath;

    /**
     * The environment the workers should run under.
     *
     * @var string
     */
    protected $environment;

    /**
     * The amount of seconds to wait before polling the queue.
     *
     * @var int
     */
    protected $sleep = 3;

    /**
     * The number of times to try a job before logging it failed.
     *
     * @var int
     */
    protected $maxTries = 0;

    /**
     * The output handler callback.
     *
     * @var \Closure|null
     */
    protected $outputHandler;

    /**
     * Create a new queue listener.
     *
     * @param  string  $commandPath
     * @return void
     */
    public function __construct($commandPath)
    {
        $this->commandPath = $commandPath;
    }

    /**
     * Get the PHP binary.
     *
     * @return string
     */
    protected function phpBinary()
    {
        return (new PhpExecutableFinder)->find(false);
    }

    /**
     * Get the Artisan binary.
     *
     * @return string
     */
    protected function artisanBinary()
    {
        return defined('ARTISAN_BINARY') ? ARTISAN_BINARY : 'artisan';
    }

    /**
     * Listen to the given queue connection.
     *
     * @param  string  $connection
     * @param  string  $queue
     * @param  \Illuminate\Queue\ListenerOptions  $options
     * @return void
     */
    public function listen($connection, $queue, ListenerOptions $options)
    {
        $process = $this->makeProcess($connection, $queue, $options);

        while (true) {
            $this->runProcess($process, $options->memory);

            if ($options->rest) {
                sleep($options->rest);
            }
        }
    }

    /**
     * Create a new Symfony process for the worker.
     *
     * @param  string  $connection
     * @param  string  $queue
     * @param  \Illuminate\Queue\ListenerOptions  $options
     * @return \Symfony\Component\Process\Process
     */
    public function makeProcess($connection, $queue, ListenerOptions $options)
    {
        $command = $this->createCommand(
            $connection,
            $queue,
            $options
        );

        // If the environment is set, we will append it to the command array so the
        // workers will run under the specified environment. Otherwise, they will
        // just run under the production environment which is not always right.
        if (isset($options->environment)) {
            $command = $this->addEnvironment($command, $options);
        }

        return new Process(
            $command,
            $this->commandPath,
            null,
            null,
            $options->timeout
        );
    }

    /**
     * Add the environment option to the given command.
     *
     * @param  array  $command
     * @param  \Illuminate\Queue\ListenerOptions  $options
     * @return array
     */
    protected function addEnvironment($command, ListenerOptions $options)
    {
        return array_merge($command, ["--env={$options->environment}"]);
    }

    /**
     * Create the command with the listener options.
     *
     * @param  string  $connection
     * @param  string  $queue
     * @param  \Illuminate\Queue\ListenerOptions  $options
     * @return array
     */
    protected function createCommand($connection, $queue, ListenerOptions $options)
    {
        return array_filter([
            $this->phpBinary(),
            $this->artisanBinary(),
            'queue:work',
            $connection,
            '--once',
            "--name={$options->name}",
            "--queue={$queue}",
            "--backoff={$options->backoff}",
            "--memory={$options->memory}",
            "--sleep={$options->sleep}",
            "--tries={$options->maxTries}",
            $options->force ? '--force' : null,
        ], function ($value) {
            return ! is_null($value);
        });
    }

    /**
     * Run the given process.
     *
     * @param  \Symfony\Component\Process\Process  $process
     * @param  int  $memory
     * @return void
     */
    public function runProcess(Process $process, $memory)
    {
        $process->run(function ($type, $line) {
            $this->handleWorkerOutput($type, $line);
        });

        // Once we have run the job we'll go check if the memory limit has been exceeded
        // for the script. If it has, we will kill this script so the process manager
        // will restart this with a clean slate of memory automatically on exiting.
        if ($this->memoryExceeded($memory)) {
            $this->stop();
        }
    }

    /**
     * Handle output from the worker process.
     *
     * @param  int  $type
     * @param  string  $line
     * @return void
     */
    protected function handleWorkerOutput($type, $line)
    {
        if (isset($this->outputHandler)) {
            call_user_func($this->outputHandler, $type, $line);
        }
    }

    /**
     * Determine if the memory limit has been exceeded.
     *
     * @param  int  $memoryLimit
     * @return bool
     */
    public function memoryExceeded($memoryLimit)
    {
        return (memory_get_usage(true) / 1024 / 1024) >= $memoryLimit;
    }

    /**
     * Stop listening and bail out of the script.
     *
     * @return void
     */
    public function stop()
    {
        exit;
    }

    /**
     * Set the output handler callback.
     *
     * @param  \Closure  $outputHandler
     * @return void
     */
    public function setOutputHandler(Closure $outputHandler)
    {
        $this->outputHandler = $outputHandler;
    }
}