Spawn

An simply uv_spawn or proc-open wrapper API to execute and manage a Pool of child-processes, achieving parallel/asynchronous PHP for Blocking I/O.

Table of Contents

• Installation
• Usage
• Channels Transfer messages between Child and Parent
• Event hooks
• Parallel
• Parallel Configuration
• Behind the curtains
• Differences with original author's "Spatie/Async"
• How to integrate into your project/package
• Error handling
• Contributing
• License

This package uses features of libuv, the PHP extension ext-uv of the Node.js library. It's uv_spawn function is used to launch processes. The performance it a much better alternative to pcntl-extension, or the use of proc_open. This package will fallback to use [symfony/process], if libuv is not installed.

This package is part of our symplely/coroutine package for handling any blocking i/o process, that can not be handled by Coroutine natively.

To learn more about libuv features read the online tutorial book.

The terminology in versions 3x and above was changed to be inline with ext-parallel extension usage, and to behave as a Thread, but without many of that library extension's limitations.

The Channeled and Future classes are both designed in a way to be extend from to create your own implementation of a Parallel based library. Currently libuv will be required to get full benefits of the implementation.

Installation

composer require symplely/spawn

This package will use libuv features if available. Do one of the following to install.

For Debian like distributions, Ubuntu...

apt-get install libuv1-dev php-pear -y

For RedHat like distributions, CentOS...

yum install libuv-devel php-pear -y

Now have Pecl auto compile, install, and setup.

pecl channel-update pecl.php.net
pecl install uv-beta

For Windows there is good news, native async thru libuv has arrived.

Windows builds for stable PHP versions are available from PECL.

Directly download latest from https://windows.php.net/downloads/pecl/releases/uv/

Extract libuv.dll to same directory as PHP binary executable, and extract php_uv.dll to ext\ directory.

Enable extension php_sockets.dll and php_uv.dll in php.ini

cd C:\Php
Invoke-WebRequest "https://windows.php.net/downloads/pecl/releases/uv/0.2.4/php_uv-0.2.4-7.2-ts-vc15-x64.zip" -OutFile "php_uv-0.2.4.zip"
#Invoke-WebRequest "https://windows.php.net/downloads/pecl/releases/uv/0.2.4/php_uv-0.2.4-7.3-nts-vc15-x64.zip" -OutFile "php_uv-0.2.4.zip"
#Invoke-WebRequest "https://windows.php.net/downloads/pecl/releases/uv/0.2.4/php_uv-0.2.4-7.4-ts-vc15-x64.zip" -OutFile "php_uv-0.2.4.zip"
7z x -y php_uv-0.2.4.zip libuv.dll php_uv.dll
copy php_uv.dll ext\php_uv.dll
del php_uv.dll
del php_uv-0.2.4.zip
echo extension=php_sockets.dll >> php.ini
echo extension=php_uv.dll >> php.ini

Usage

include 'vendor/autoload.php';

use Async\Spawn\Spawn;

// Shows output by default and Channel instance is extracted from args.
$future = \parallel($function, ...$args)
// Shows output by default, turns on yield usage, can include additional file, and the Channel instance is extracted from args.
$future = \paralleling($function, $includeFile, ...$args)
// Or Does not show output by default and channel instance has to be explicitly passed in.
$future = \spawn($function, $timeout, $channel)
// Or Show output by default and channel instance has to be explicitly passed in.
$future = \spawning($function, $timeout, $channel)
// Or
$future = Spawn::create(function () use ($thing) {
    // Do a thing
    }, $timeout, $channel)
    ->then(function ($output) {
        // Handle success
    })->catch(function (\Throwable $exception) {
        // Handle exception
});

// Wait for `Future` to terminate. Note this should only be executed for local testing only.
// Use "How to integrate into your project/package" section instead.
// Second option can be used to set to display child output, default is false
\spawn_run($future, true);
// Or same as
$future->displayOn()->run();
// Or
$future->run();

Channels Transfer messages between Child and Parent

The feature has been completely redesigned to behave similar to PHP ext-parallel extension.

See the Channel page for real examples.

include 'vendor/autoload.php';

use Async\Spawn\Channeled as Channel;

$channel = Channel::make("io");

// Shows output by default and Channel instance is extracted for args.
$future = parallel(function ($channel) {
  $channel = Channel::open($channel);

  for ($count = 0; $count <= 10; $count++) {
    $channel->send($count);
  }

  echo 'pingpangpong';
  $channel->send(false);

  return 'return whatever';
}, (string) $channel);

while (($value = $channel->recv()) !== false) {
  var_dump($value);
}

echo \spawn_output($future); // pingpangpong
// Or
echo \spawn_result($future); // return whatever
// Or
echo $future->getResult(); // return whatever

Event hooks

When creating asynchronous processes, you'll get an instance of FutureInterface returned. You can add the following event callback hooks on a Future process.

// Shows output by default and Channel instance is extracted for args.
$future = parallel($function, ...$args)
// Or
$future = spawn($function, $timeout, $channel)
// Or
$future = Spawn::create(function () {
        // The second argument is optional, Defaults no timeout,
        // it sets The maximum amount of time a process may take to finish in seconds
        // The third is the Channel instance pass to Future subprocess.

        return `whatever`|Object|Closure|; // `whatever` will be encoded, then decoded by parent.
    }, int $timeout = 0 , $input = null)
    ->then(function ($result) {
        // On success, `$result` is returned by the process.
    })
    ->catch(function ($exception) {
        // When an exception is thrown from within a process, it's caught and passed here.
    })
    ->timeout(function () {
        // When an timeout is reached, it's caught and passed here.
    })
    ->progress(function ($type, $data) {
        // Live progressing of output: `$type, $data` is returned by the Future process.
        // $type is `ERR` for stderr, or `OUT` for stdout.
    })
    ->signal($signal, function ($signal) {
        // The process will be sent termination `signal` and stopped.
        // When an signal is triggered, it's caught and passed here.
        // This feature is only available using `libuv`.
    });

->then(function ($result) {
    // On success, `$result` is returned by the Future process or callable you passed.
        //
    }, function ($catchException) {
        //
    }, function ($progressOutput) {
        //
    }
);

// To turn on displaying of child output.
->displayOn();

// Stop displaying child output.
->displayOff();

// A `Future` process can be retried.
->restart();

// Wait for `Future` to terminate. Note this should only be executed for local testing only.
// Use "How to integrate into your project/package" section instead.
->run();

Parallel

The Parallel class is used to manage a Pool of Future's. The same Event hooks and Error handling are available.

include 'vendor/autoload.php';

use Async\Spawn\Parallel;

$parallel = new Parallel();

foreach ($things as $thing) {
        // the second argument `optional`, can set the maximum amount of time a process may take to finish in seconds.
    $parallel->add(function () use ($thing) {
        // Do a thing
    }, $optional)->then(function ($output) {
        // Handle success
        // On success, `$output` is returned by the process or callable you passed to the queue.
    })->catch(function (\Throwable $exception) {
        // Handle exception
        // When an exception is thrown from within a process, it's caught and passed here.
    });
}

// Wait for Parallel `Future` Pool to terminate. Note this should only be executed for local testing only.
// Use "How to integrate into your project/package" section instead.
$parallel->wait();

Parallel Configuration

You're free to create as many parallel process pools as you want, each parallel pool has its own queue of processes it will handle.

A parallel pool is configurable by the developer:

use Async\Spawn\Parallel;

$parallel = (new Parallel())

// The maximum amount of processes which can run simultaneously.
    ->concurrency(20)

// Configure how long the loop should sleep before re-checking the process statuses in milliseconds.
    ->sleepTime(50000);

Behind the curtains

This package using uv_spawn, and proc_open as a fallback, to create and manage a pool of child processes in PHP. By creating child processes on the fly, we're able to execute PHP scripts in parallel. This parallelism can improve performance significantly when dealing with multiple Synchronous I/O tasks, which don't really need to wait for each other.

By giving these tasks a separate process to run on, the underlying operating system can take care of running them in parallel.

The Parallel class provided by this package takes care of handling as many processes as you want by scheduling and running them when it's possible. When multiple processes are spawned, each can have a separate time to completion.

Waiting for all processes is done by using uv_run, or basic child process polling which will monitor until all processes are finished.

When a process is finished, its success event is triggered, which you can hook into with the ->then() function. When a process fails, an error event is triggered, which you can hook into with the ->catch() function. When a process times out, an timeout event is triggered, which you can hook into with the ->timeout() function.

Then the iterations will update that process's status and move on.

Differences with original author's "Spatie/Async"

This package differs from original author's spatie/async implementations:

• The Runnable class is Future with expanded capabilities.
• The Pool class is Parallel with some features extracted into another class FutureHandler.
• The ParentRuntime class is Spawn that can accept a string command line action to execute, returns a Future.
• The async function is spawn with additional spawning that will display any child process output.
• Removed output limit, no timeout unless set per Future, added all Symfony Process features.
• Not Linux or CLI only, runs the same in Web environment under Windows and Apple macOS too.
• Added a Event Loop library libuv support, it's now the main usage model, fallback to proc-open Process if not installed.
• Libuv allows more direct Channel message exchange, same is done with proc-open but is limited.

Todo: Move in all ext-parallel like functionality from external Coroutine library.

A previous PR of a fork was submitted addressing real Windows support.

How to integrate into your project/package

When you include this library into your project, you can't execute functions/methods spawn_wait(), spawn_run(), wait() or run() directly. They are for mainly testing this library locally. You will need to adapt to or create a custom event loop routine.

The Parallel class has a getFutureHandler() method that returns a FutureHandler instance. The FutureHandler has two methods processing() and isEmpty() that you will need to call within your custom loop routine. These two calls are the same ones the wait() method calls onto within a while loop with additional sleepingTime().

The processing() method will monitor/check the Future's state status and execute any appropriate event callback handler. The FutureHandler class can accept/handle a custom Event Loop that has executeTask(event callback, future) and isPcntl() methods defined. The custom Event Loop object should be supplied to Parallel instantiation.

A basic setup to add to your Event Loop

use Async\Spawn\Parallel;
use Async\Spawn\FutureHandler;
use Async\Spawn\FutureInterface;
use Async\Spawn\ParallelInterface;

class setupLoop
{
  /**
   * @var Parallel
   */
  protected $parallel;

  /**
   * @var FutureHandler
   */
  protected $future = null;

  public function __construct() {
    $this->parallel = new Parallel($this);
    $this->future = $this->parallel->getFutureHandler();
  }

  public function addFuture($callable, int $timeout = 0, bool $display = false, $channel = null): FutureInterface {
    $future = $this->parallel->add($callable, $timeout, $channel);
    return $display ? $future->displayOn() : $future;
  }

  public function getParallel(): ParallelInterface {
    return $this->parallel;
  }

  /**
   * Check for pending I/O events, signals, futures, streams/sockets/fd activity, timers or etc...
   */
  protected function hasEvents(): bool {
    return !$this->future->isEmpty() || !$this->ActionEventsCheckers->isEmpty();
  }

  public function runLoop() {
    while ($this->hasEvents()) {
      $this->future->processing();
      if ($this->waitForAction());
        $this->DoEventActions();
    }
  }

  public function executeTask($event, $parameters = null) {
    $this->DoEventActions($event, $parameters);
    // Or just
    // if (\is_callable($event))
       // $event($parameters);
  }

  public function isPcntl(): bool {}
}

This library uses opis/closure package for closure/callable serialization. For any function or class methods to be accessible in a Future child process you must make changes to your composer.json to insure it's picked up. The composer.json file should contain a pointer to some file with functions you always need, and insure all new classes/namespaces are within added. You can't just make local named functions or classes on the fly and expect them to be available.

// composer.json
"autoload": {
    "files": [
        "Extra/functions.php"
    ],
    "psr-4": {
        "Name\\Space\\": ["Folder/"],
        "Extra\\Name\\Spaces\\": ["Extra/"]
    }
},

// functions.php
if (!\function_exists('___marker')) {
  //
  // All additional extra functions needed in a `Future` process...
  //

  function ___marker()
  {
    return true;
  }
}

Error handling

If an Exception or Error is thrown from within a child process, it can be caught per process by specifying a callback in the ->catch() method.

If there's no error handler added, the error will be thrown in the parent process.

If the child process would unexpectedly stop without throwing an Throwable, the output written to stderr will be wrapped and thrown as Async\Spawn\SpawnError in the parent process.

Contributing

Contributions are encouraged and welcome; I am always happy to get feedback or pull requests on Github :) Create Github Issues for bugs and new features and comment on the ones you are interested in.

License

The MIT License (MIT). Please see License File for more information.