Asynchronous Awesome

Sometimes, our use of PHP grows beyond the typical request/response cycle of dynamic page generation. Unfortunately, the threaded nature of PHP - and the stateless nature of the server - betrays any efforts to expand our utilization of the server. Image processing, video rendering, APNS (Apple Push Notification Service) integration - any of these can easily take longer than is reasonable for a simple page request.

Enter tools like message and job queues that empower daemonized PHP workers to handle data processing in the background. Yet further tools enable long-running event loops and asynchronous Promise-driven operations. PHP isn’t multi-threaded, but that doesn’t mean you’re limited to a single-thread paradigm. I will demonstrate various use cases necessitating asynchronous operations, then delve into the code and the tools that make these systems work. Every attendee will leave armed with new ways to think about the management of large data jobs in PHP and an understanding of the tools they can use to make it happen.

Transcript

1. Asynchronous
   Awesome
   Eric Mann
   

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4. Problems this Won’t Solve
   Report generation
   PubSub events
   Parallel I/O
   Parallel data access
   

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5. Naive Approaches to Async
   Pseudo-cron (WordPress native and tools like wp-async-task)
   Mechanical Turk-like job systems
   Using another language entirely
   

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6. There’s a Better Way
   

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7. Parallel vs Concurrent
   Concurrent
   Parallel (not covered today)
   Concurrent Parallel
   

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8. Concurrent and Parallel Programming - Joe Armstrong
   https://joearms.github.io/published/2013-04-05-concurrent-and-parallel-programming.html
   

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9. Tools Available
   Gearman
   RabbitMQ
   Amp (promises)
   pthreads
   

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10. Gearman
    

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11. Initialize a Standalone Worker
    // worker.php
    $importer = new PDFImporter();
    $worker = new GearmanWorker();
    $worker->addServer('localhost', 4730);
    $worker->addFunction('import', array($importer, 'import');
    while($worker->work());
    

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12. Dispatch Jobs to the Worker
    // app.php
    $client = new GearmanClient();
    $client->addServer('localhost', 4730);
    $job = $client->doBackground('import', $file . '|:|' . $email);
    $db->record($job);
    

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13. RabbitMQ
    

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15. Publish to the Queue
    $connection = new AMQPStreamConnection('localhost', 5672, 'u', 'p');
    $channel = $connection->channel();
    $channel->queue_declare('demo', false, false, false, false);
    $msg = new AMQPMessage('Hello World!');
    $channel->basic_publish($msg, '', 'demo');
    $channel->close();
    $connection->close();
    

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16. Consume from the Queue
    $connection = new AMQPStreamConnection('localhost', 5672, 'u', 'p');
    $channel = $connection->channel();
    $channel->queue_declare('demo', false, false, false, false);
    $cb = function($msg) {
    // Send Tweet with $msg contents
    }
    $channel->basic_consume('demo', '', false, true, false, false, $cb);
    while(count($channel->callbacks)) {
    $channel->wait();
    }
    

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18. Interact with Multiple Queues
    $channel->queue_declare('demo', false, false, false, false);
    $channel->queue_declare('demo-rc', false, false, false, false);
    $cb = function($msg) {
    // Send Tweet with $msg contents
    $result = new AMQPMessage( /* Tweet ID */ );
    $channel->basic_publish($result, '', 'demo-rc');
    }
    $channel->basic_consume('demo', '', false, true, false, false, $cb);
    while(count($channel->callbacks)) {
    $channel->wait();
    }
    

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19. Amp (promises)
    

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20. Deferred Empowers Async
    use Amp\Loop;
    function asyncMultiply($x, $y)
    {
    $deferred = new Amp\Deferred;
    // Resolve the async result one second from now
    Amp\Loop::delay(1000, function () use ($deferred, $x, $y) {
    $deferred->resolve($x * $y);
    });
    return $deferred->promise();
    }
    asyncMultiply(6, 7)->onResolve(function ($err, $result) {
    var_dump($result); // int(42)
    });
    

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21. Chain Multiple Promises Together
    Loop::run(function () {
    $httpClient = new Amp\Artax\DefaultClient();
    $uris = [
    "google" => "http://www.google.com",
    "bing" => "http://www.bing.com",
    ];
    $responses = yield array_map(function ($uri) use ($httpClient) {
    return $httpClient->request($uri);
    }, $uris);
    foreach ($responses as $key => $response) {
    printf("%s | %d\n", $key, $response->getStatus());
    }
    Loop::stop();
    });
    

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22. pthreads
    

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23. Create a Worker
    class WorkerThread extends Thread
    {
    private $workerId;
    public function __construct($id)
    {
    $this->workerId = $id;
    }
    public function run()
    {
    // Do some heavy processing
    }
    }
    

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24. Start the Workers
    $workers = [];
    foreach (range(0, 5) as $id) {
    $worker = new WorkerThread($id);
    $workers[] = $worker;
    $worker->start(); // Now they'll each run independently
    }
    foreach (range(0, 5) as $id) {
    $workers[$id]->join(); // Synchronously rejoin the main process
    }
    

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25. What Use is Any of This?
    Gearman – powers things like PDF conversion, video transpiling, APNS
    RabbitMQ – powers cross-app messaging in load balanced environments
    Promises – power concurrent data migrations for large data sources
    pthreads – powers task management in a performance, scalable, managed fashion
    

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26. Further Study
    The amphp/parallel library wraps pthreads entirely – use both at the same time!
    Look at what the Node community is doing – we have the same exact tools
    available, but a much larger community and lower barriers
    Challenge yourself to look at traditional programming problems from an
    asynchronous viewpoint – can things run faster in parallel?
    

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27. Questions?
    

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28. Thank you
    eric.mann@vacasa.com | 503.925.6266
    

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