The Pool class

(PECL pthreads >= 2.0.0)

Introduction

A Pool is a container for, and controller of, an adjustable number of Workers.

Pooling provides a higher level abstraction of the Worker functionality, including the management of references in the way required by pthreads.

Class synopsis

class Pool {

/* Properties */

protected $size;

protected $class;

protected $workers;

protected $ctor;

protected $last;

/* Methods */

public __construct(int $size, string $class = ?, array $ctor = ?)

public collect(Callable $collector = ?): int

public resize(int $size): void

public shutdown(): void

public submit(Threaded $task): int

public submitTo(int $worker, Threaded $task): int

}

Properties

size: maximum number of Workers this Pool can use
class: the class of the Worker
workers: references to Workers
ctor: the arguments for constructor of new Workers
last: offset in workers of the last Worker used

Pool::collect — Collect references to completed tasks
Pool::__construct — Creates a new Pool of Workers
Pool::resize — Resize the Pool
Pool::shutdown — Shutdown all workers
Pool::submit — Submits an object for execution
Pool::submitTo — Submits a task to a specific worker for execution

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User Contributed Notes 4 notes

down

meadowsjared at gmail dot com ¶

3 years ago

In this example, it shows how to use a pool to get an array of results, using pThreads v3.2.1 and php 7.3.23

<?php
class TestWork extends Threaded {
//updated version that works with pThreads v3.2.1 and php 7.3.23
    protected $complete;
    //$pData is the data sent to your worker thread to do it's job.
    public function __construct($pData) {
        //transfer all the variables to local variables
        $this->complete = false;
        $this->testData = $pData;
    }
    //This is where all of your work will be done.
    public function run() {
        usleep(2000000); //sleep 2 seconds to simulate a large job
        $this->complete = true;
    }
    public function isDone() {
        return $this->complete;
    }
}
class ExamplePool extends Pool {
    public $data = array(); // used to return data after we're done
    private $numTasks = 0; // counter used to know when we're done
    /**
     * override the submit function from the parent
     * to keep track of our jobs
     */
    public function submit(Threaded $task) {
        $this->numTasks++;
        parent::submit($task);
    }
    /**
     * used to wait until all workers are done
     */
    public function process() {
        // Run this loop as long as we have
        // jobs in the pool
        while (count($this->data) < $this->numTasks) {
            $this->collect(function (TestWork $task) {
                // If a task was marked as done, collect its results
                if ($task->isDone()) {
                    $tmpObj = new stdclass();
                    $tmpObj->complete = $task->complete;
                    //this is how you get your completed data back out [accessed by $pool->process()]
                    $this->data[] = $tmpObj;
                }
                return $task->isDone();
            });
        }
        // All jobs are done
        // we can shutdown the pool
        $this->shutdown();
        return $this->data;
    }
}
$pool = new ExamplePool(3);
$testData = 'asdf';
for($i=0;$i<5;$i++) {
    $pool->submit(new TestWork($testData));
}
$retArr = $pool->process(); //get all of the results
echo '<pre>';
print_r($retArr); //return the array of results (and maybe errors)
echo '</pre>';
?>

down

meadowsjared at gmail dot com ¶

8 years ago

Please note, when using the collect function, it's important that you extend the pool class so you can keep checking for finished threads until they're all done.

<?php
class TestWork extends Threaded {
    protected $complete;
    //$pData is the data sent to your worker thread to do it's job.
    public function __construct($pData){
        //transfer all the variables to local variables
        $this->complete = false;
        $this->testData = $pData;
    }
    //This is where all of your work will be done.
    public function run(){
        usleep(2000000); //sleep 2 seconds to simulate a large job
        $this->complete = true;
    }
    public function isGarbage() {
        return $this->complete;
    }
}
class ExamplePool extends Pool
{
    public $data = array();
    public function process()
    {
        // Run this loop as long as we have
        // jobs in the pool
        while (count($this->work)) {
            $this->collect(function (TestWork $task) {
                // If a task was marked as done
                // collect its results
                if ($task->isGarbage()) {
                    $tmpObj = new stdclass();
                    $tmpObj->complete = $task->complete;
                    //this is how you get your completed data back out [accessed by $pool->process()]
                    $this->data[] = $tmpObj;
                }
                return $task->isGarbage();
            });
        }
        // All jobs are done
        // we can shutdown the pool
        $this->shutdown();
        return $this->data;
    }
}
$pool = new ExamplePool(3);
$testData = 'asdf';
for($i=0;$i<5;$i++) {
    $pool->submit(new TestWork($testData));
}
$retArr = $pool->process(); //get all of the results
echo '<pre>';
print_r($retArr); //return the array of results (and maybe errors)
echo '</pre>';
?>

down

olavk ¶

9 years ago

Simple example with Collectable (basically Thread meant for Pool) and Pool

<?php

class job extends Collectable {
  public $val;

  public function __construct($val){
    // init some properties
    $this->val = $val;
  }
  public function run(){
    // do some work
    $this->val = $this->val . file_get_contents('http://www.example.com/', null, null, 3, 20);
    $this->setGarbage();
  }
}

// At most 3 threads will work at once
$p = new Pool(3);

$tasks = array(
  new job('0'),
  new job('1'),
  new job('2'),
  new job('3'),
  new job('4'),
  new job('5'),
  new job('6'),
  new job('7'),
  new job('8'),
  new job('9'),
  new job('10'),
);
// Add tasks to pool queue
foreach ($tasks as $task) {
  $p->submit($task);
}

// shutdown will wait for current queue to be completed
$p->shutdown();
// garbage collection check / read results
$p->collect(function($checkingTask){
  echo $checkingTask->val;
  return $checkingTask->isGarbage();
});

?>

down

-5

fajan ¶

10 years ago

Example class to demonstrate usage of Pool/Worker mechanism, also to show a few tricks & hints ;)
<?php
class Config extends Threaded{    // shared global object
    protected $val=0, $val2=0;
    protected function inc(){++$this->val;}    // protected synchronizes by-object
    public function inc2(){++$this->val2;}    // no synchronization
}
class WorkerClass extends Worker{
    protected static $worker_id_next = -1;
    protected $worker_id;
    protected $config;
    public function __construct($config){
        $this->worker_id = ++static::$worker_id_next;    // static members are not avalable in thread but are in 'main thread'
        $this->config = $config;
    }
    public function run(){
        global $config;
        $config = $this->config;    // NOTE: setting by reference WON'T work
        global $worker_id;
        $worker_id = $this->worker_id;
        echo "working context {$worker_id} is created!\n";
        //$this->say_config();    // globally synchronized function.
    }
    protected function say_config(){    // 'protected' is synchronized by-object so WON'T work between multiple instances
        global $config;        // you can use the shared $config object as synchronization source.
        $config->synchronized(function() use (&$config){    // NOTE: you can use Closures here, but if you attach a Closure to a Threaded object it will be destroyed as can't be serialized
            var_dump($config);
        });
    }
}
class Task extends Stackable{    // Stackable still exists, it's just somehow dissappeared from docs (probably by mistake). See older version's docs for more details.
    protected $set;
    public function __construct($set){
        $this->set = $set;
    }
    public function run(){
        global $worker_id;
        echo "task is running in {$worker_id}!\n";
        usleep(mt_rand(1,100)*100);
        $config = $this->getConfig();
        $val = $config->arr->shift();
        $config->arr[] = $this->set;
        for ($i = 0 ; $i < 1000; ++$i){
            $config->inc();
            $config->inc2();
        }
    }
    public function getConfig(){
        global $config;    // WorkerClass set this on thread's scope, can be reused by Tasks for additional asynch data source. (ie: connection pool or taskqueue to demultiplexer)
        return $config;
    }
}

$config = new Config;
$config->arr = new \Threaded();
$config->arr->merge(array(1,2,3,4,5,6));
class PoolClass extends Pool{
    public function worker_list(){
        if ($this->workers !== null)
            return array_keys($this->workers);
        return null;
    }
}
$pool = new PoolClass(3, 'WorkerClass', [$config] );
$pool->worker_list();
//$pool->submitTo(0,new Task(-10));    // submitTo DOES NOT try to create worker

$spammed_id = -1;
for ($i = 1; $i <= 100; ++$i){    // add some jobs
    if ($spammed_id == -1 && ($x = $pool->worker_list())!= null && @$x[2]){
        $spammed_id = $x[2];
        echo "spamming worker {$spammed_id} with lots of tasks from now on\n";
    }
    if ($spammed_id != -1 && ($i % 5) == 0)    // every 5th job is routed to one worker, so it has 20% of the total jobs (with 3 workers it should do ~33%, not it has (33+20)%, so only delegate to worker if you plan to do balancing as well... )
        $pool->submitTo($spammed_id,new Task(10*$i));    
    else
        $pool->submit(new Task(10*$i));
}
$pool->shutdown();
var_dump($config); // "val" is exactly 100000, "val2" is probably a bit less
// also: if you disable the spammer, you'll that the order of the "arr" is random.
?>

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The Pool class

Introduction

Class synopsis

Properties

Table of Contents

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User Contributed Notes 4 notes