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

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2. 2
   Hello.
   Eric Mann
   Director of Engineering, Vacasa
   

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4. 4
   In 2012, I had to build a way for the
   “Save PDF” button on this screen
   to work. It required building a
   PDF in the background and
   would sometimes take up to
   5 minutes to work.
   Doing things asynchronously
   was hard!
   

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5. 5
   Report generation
   PubSub events
   Parallel I/O
   Parallel data access
   

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6. 6
   Pseudo-cron (WordPress native and tools like wp-async-task)
   

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10. 10
    Pseudo-cron (WordPress native and tools like wp-async-task)
    Mechanical Turk-like job systems
    Using another language entirely
    

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12. 12
    Lorem ipsum dolor sit amet, consectetur
    adipiscing elit. Fusce elit ex, consequat et
    tincidunt non, pharetra non risus. Quisque ut
    leo pretium, eleifend lectus in, ultrices diam.
    Quisque ac congue urna, non finibus orci.
    Concurrent
    Parallel (not covered today)
    Concurrent Parallel
    Image by Joe Armstrong - https://joearms.github.io/published/2013-04-05-concurrent-and-parallel-programming.html
    

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13. 13
    Lorem ipsum dolor sit amet, consectetur
    adipiscing elit. Fusce elit ex, consequat et
    tincidunt non, pharetra non risus. Quisque ut
    leo pretium, eleifend lectus in, ultrices diam.
    Quisque ac congue urna, non finibus orci.
    Concurrent
    Parallel (not covered today)
    Concurrent Parallel
    Image by Joe Armstrong - https://joearms.github.io/published/2013-04-05-concurrent-and-parallel-programming.html
    

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    // 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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17. 17
    // app.php
    $client = new GearmanClient();
    $client->addServer('localhost', 4730);
    $job = $client->doBackground('import', $file . '|:|' . $email);
    $db->record($job);
    

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    $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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    $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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23. 23
    $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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25. 25
    —Promises/A+
    

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26. 26
    use Amp\Loop;
    function asyncMultiply($x, $y)
    {
    $deferred = new Amp\Deferred;
    Amp\Loop::delay(1000, function () use ($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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27. 27
    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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    class WorkerThread extends Thread
    {
    private $workerId;
    public function __construct($id)
    {
    $this->workerId = $id;
    }
    public function run()
    {
    // Do some heavy processing
    }
    }
    

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    $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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    Thread::run(function (Channel $channel) {
    printf("Received: %s\n", yield $channel->receive());
    print "Sleeping for 3 seconds...\n";
    sleep(3); // Blocking call in thread.
    yield $channel->send("Data sent from child.");
    print "Sleeping for 2 seconds...\n";
    sleep(2); // Blocking call in thread.
    return 42;
    });
    

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    Loop::run(function () {
    $timer = Loop::repeat(1000, function () {
    static $i;
    $i = $i ? ++$i : 1;
    print "Demonstrating a live parent for the {$i}th time.\n";
    });
    try {
    // Do stuff
    } finally {
    Loop::cancel();
    }
    });
    

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    Loop::run(function () {
    // Timer
    try {
    $context = yield Thread::run() // Child
    print "Waiting 2 seconds to send start data...\n";
    yield new Delayed(2000);
    yield $context->send("Start data");
    printf("Received: %s\n", yield $context->receive());
    printf("Thread ended: %d\n", yield $context->join());
    } finally {
    Loop::cancel();
    }
    });
    

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    Powers things like PDF conversion, video transpiling, APNS
    Powers cross-app messaging in load balanced environments
    Power concurrent data migrations for large data sources
    Powers task management in a performance, scalable, managed fashion
    

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    Look at what the other communities are doing – we often 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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