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File: simple_controller.php

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File: simple_controller.php
Role: Example script
Content type: text/plain
Description: shows how to attach a controller to started pseudo-threads.
Class: Thread
A class to implement multi-threaded applications
Author: By
Last change: updated to 1.1
Date: 15 years ago
Size: 9,071 bytes
 

 

Contents

Class file image Download
<?php
/**
 * PHP_Fork class usage examples
 * ==================================================================================
 * NOTE: In real world you surely want to keep each class into
 * a separate file, then include() it into your application.
 * For this examples is more useful to keep all_code_into_one_file,
 * so that each example shows a unique feature of the PHP_Fork framework.
 * ==================================================================================
 * simple_controller.php
 *
 * This example shows how to attach a controller to started pseudo-threads
 * Forked processes can sometime die or defunct for many reasons...
 * Without a controller process that periodically check thread status we
 * can not ensure that started threads are still alive into system
 * Here we have n executeThreads and a controllerThread that check all them
 * when the controller detect that a thread is died it try to respawn it.
 *
 * ATTENTION: this example often fails on Cygwin platform, probably due to some bugs
 * into ipc implementations that prevent the shared memory to be totally released
 * when a process die.
 *
 * ==================================================================================
 *
 * Copyright (c) 2003-2002 by Luca Mariano (luca.mariano@email.it)
 * http://www.lucamariano.it
 *
 * This program is free software. You can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License.
 */
// Import of base class
require_once ("../Fork.php");
// number of executeThreads we want
define ("NUM_THREAD", 2);
// max delay (seconds) that controller can accept from child's ping
define ("CTRL_MAX_IDLE", 3);
// controller will check threads status every CTRL_POLLING_INTERVAL secs.
define ("CTRL_POLLING_INTERVAL", 5);
// The same as previos examples, with the add of the controller ping...
class executeThread extends PHP_Fork {
    var
$counter;

    function
executeThread($name)
    {
       
$this->PHP_Fork($name);
       
$this->counter = 0;
    }

    function
run()
    {
        while (
true) {
           
// setVariable is a method inherited from PHP_Fork super class
            // it sets a variable that can be accessed thru its name
            // by parent process
           
$this->setVariable('counter', $this->counter++);
           
/**
             * While using the controller, every child must notify to controller that it's alive
             * The frequency of this notify must be set according to the parameter $maxIdleTime
             * (controllerThread constructor, default is 60 sec.)
             * Typically executeThreads runs an infinite loop making something useful; you should
             * calculate a reasonable time for one loop, then set the controller's $maxIdleTime
             * to a superior value.
             * Into the while(true) { } loop of the thread insert a call to the "setAlive" method
             * so that controller can detect properly the status of child processes.
             */
           
$this->setAlive();
           
sleep(1);
        }
    }

    function
getCounter()
    {
       
// parent process can call this facility method
        // in order to get back the actual value of the counter
       
return $this->getVariable('counter');
    }
}

class
controllerThread extends PHP_Fork {
    var
$_sleepInt;
    var
$_executeThreadPool;
    var
$_maxIdleTime;
    var
$_respawnThread;

   
/**
     * controllerThread::controllerThread()
     *
     * @param $name
     * @param $executeThreadPool
     * @param $maxIdleTime
     * @param $interval
     * @return
     */
   
function controllerThread($name, &$executeThreadPool, $maxIdleTime = 60, $interval = 60)
    {
       
$this->PHP_Fork($name);
       
$this->_sleepInt = $interval;
       
$this->_executeThreadPool = &$executeThreadPool;
       
$this->_maxIdleTime = $maxIdleTime;
       
$this->_respawnThread = array();

       
$this->setVariable('_executeThreadPool', $this->_executeThreadPool);
    }

    function
run()
    {
        while (
true) {
           
$this->_detectDeadChilds();
           
$this->_respawnDeadChilds();

           
sleep($this->_sleepInt);
        }
    }
    function
stopAllThreads()
    {
       
$this->_executeThreadPool = $this->getThreadPool();
        foreach(
$this->_executeThreadPool as $thread) {
           
$thread->stop();
            echo
"Stopped " . $thread->getName() . "\n";
        }
        unset(
$this->_executeThreadPool);
       
$this->_executeThreadPool = array();
       
$this->setVariable('_executeThreadPool', $this->_executeThreadPool);
    }

    function
getThreadPool()
    {
        return
$this->getVariable('_executeThreadPool');
    }


    function
_detectDeadChilds()
    {
       
// check every executethread to see if it is alive...
       
foreach ($this->_executeThreadPool as $idx => $executeThread) {
            if (
$executeThread->getLastAlive() > $this->_maxIdleTime) {
               
// this thread is not responding, probably [defunct]
               
$threadName = $executeThread->getName();
                print
time() . "-" . $this->getName() . "-" . $threadName . " seems to be died...\n";
               
// so let's kill it...
               
$executeThread->stop();

                unset(
$executeThread);
               
// remove this thread from the pool
               
array_splice($this->_executeThreadPool, $idx, 1);
               
// and add them to the "to be respawned" thread list...
               
$this->_respawnThread[] = $threadName;
               
// stop this foreach
               
break;
            }
        }
    }

    function
_respawnDeadChilds()
    {
        foreach (
$this->_respawnThread as $idx => $threadName) {
           
$n = &new executeThread ($threadName);
           
// usually we try to start a Thread without this check
            // if Shared Memory Area is not ready, the start() method
            // die, so the process is destroyed. When respawing a dead child
            // this is not useful, because die() will cause the controller itself
            // to die!
            // So let's check if IPC is ok before call the start() method.
           
if ($n->_ipc_is_ok) {
               
$n->start();
               
$this->_executeThreadPool[] = &$n;
                print
time() . "-" . $this->getName() . "- New instance of " . $threadName . " successfully spawned (PID=" . $n->getPid() . ")\n";
               
array_splice($this->_respawnThread, $idx, 1);
               
$this->setVariable('_executeThreadPool', $this->_executeThreadPool);
            } else {
                print
time() . "-" . $this->getName() . "-" . "Unable to create IPC segment...\n";
            }
        }
    }
}

/**
 * Functions used by the console
 */
function _getInputCLI()
{
   
$opt = _read();
   
$opt = strtoupper (trim($opt));
    return
$opt;
}

function
_read()
{
   
$fp = fopen("php://stdin", "r");
   
$input = fgets($fp, 255);
   
fclose($fp);

    return
$input;
}

/**
 * Main program. Bring up two instances of the executeThread class that
 * runs concurrently. It's a multi-thread app with a few lines of code!!!
 * executeThread does nothing interesting, it simply has a counter and increment
 * this counter each second... (see class definition at top of this file)
 */
for ($i = 0;$i < NUM_THREAD;$i++) {
   
$executeThread[$i] = &new executeThread ("executeThread-" . $i);
   
$executeThread[$i]->start();
    echo
"Started " . $executeThread[$i]->getName() . " with PID " . $executeThread[$i]->getPid() . "...\n";
}

$ctrl = new controllerThread("controllerThread", $executeThread, CTRL_MAX_IDLE, CTRL_POLLING_INTERVAL);
$ctrl->start();
print
"Started " . $ctrl->getName() . " with PID " . $ctrl->getPid() . "...\n\n";

echo
"This is the main process.\nPress [X] to terminate, [G] to read thread's counter.\nTo test the controller respawn functionality, simply kill one (or more) executeThread (kill -9 [pid]). The controller should detect the died child & respawn it very soon...\n";

/**
 * Console simple listener
 */
while (true) {
    echo
">";

   
$opt = _getInputCLI();
    echo
"\n";
    switch (
$opt) {
        case
"X":
           
// when using the controller we cannot traverse the $executeThread array
            // because it only contains the original pool of thread.
            // if a thread dies, the controller respawn it and updates it's own
            // thread pool. The method stopAllThreads() stops all running threads.
           
$ctrl->stopAllThreads();
           
// stop the controller itself
           
$ctrl->stop();
            print
"Stopped " . $ctrl->getName() . "\n";
            exit;
            break;

        case
"G":
               
$pool = $ctrl->getThreadPool();
                foreach (
$pool as $thread) {
                   
//print_r($thread);
                   
echo $thread->getName() . " returns " . $thread->getCounter() . "\n";
                    }
            break;

    }
}

?>