includes/ForkController.php

   1 <?php
   2
   3 /**
   4  * Class for managing forking command line scripts.
   5  * Currently just does forking and process control, but it could easily be extended
   6  * to provide IPC and job dispatch.
   7  */
   8 class ForkController {
   9         var $children = array();
  10         var $termReceived = false;
  11
  12         public function __construct() {
  13                 if ( php_sapi_name() != 'cli' ) {
  14                         throw new MWException( "MultiProcess cannot be used from the web." );
  15                 }
  16         }
  17
  18         protected function prepareEnvironment() {
  19                 global $wgCaches, $wgMemc;
  20                 // Don't share DB or memcached connections
  21                 wfGetLBFactory()->destroyInstance();
  22                 $wgCaches = array();
  23                 unset( $wgMemc );
  24         }
  25
  26         /**
  27          * Fork a number of worker processes.
  28          *
  29          * This should only be called from the command line. It should be called
  30          * as early as possible during execution. It will return 'child' in the
  31          * child processes and 'parent' in the parent process. The parent process
  32          * should then call monitor().
  33          *
  34          * This function requires the posix and pcntl extensions.
  35          */
  36         public function forkWorkers( $numProcs ) {
  37                 global $wgMemc, $wgCaches, $wgMainCacheType;
  38
  39                 $this->prepareEnvironment();
  40
  41                 // Create the child processes
  42                 for ( $i = 0; $i < $numProcs; $i++ ) {
  43                         // Do the fork
  44                         $pid = pcntl_fork();
  45                         if ( $pid === -1 || $pid === false ) {
  46                                 echo "Error creating child processes\n";
  47                                 exit( 1 );
  48                         }
  49
  50                         if ( !$pid ) {
  51                                 $this->initChild();
  52                                 $this->children = null;
  53                                 return 'child';
  54                         } else {
  55                                 // This is the parent process
  56                                 $this->children[$pid] = true;
  57                         }
  58                 }
  59
  60                 return 'parent';
  61         }
  62
  63         /**
  64          * The parent process main loop
  65          */
  66         public function runParent() {
  67                 // Trap SIGTERM
  68                 pcntl_signal( SIGTERM, array( $this, 'handleTermSignal' ), false );
  69
  70                 do {
  71                         $status = false;
  72                         $deadPid = pcntl_wait( $status );
  73
  74                         if ( $deadPid > 0 ) {
  75                                 unset( $this->children[$deadPid] );
  76                         }
  77
  78                         // Run signal handlers
  79                         if ( function_exists( 'pcntl_signal_dispatch' ) ) {
  80                                 pcntl_signal_dispatch();
  81                         } else {
  82                                 declare (ticks=1) { $status = $status; }
  83                         }
  84                         // Respond to TERM signal
  85                         if ( $this->termReceived ) {
  86                                 foreach ( $this->children as $childPid => $unused ) {
  87                                         posix_kill( $childPid, SIGTERM );
  88                                 }
  89                                 $this->termReceived = false;
  90                         }
  91                 } while ( count( $this->children ) );
  92                 pcntl_signal( SIGTERM, SIG_DFL );
  93         }
  94
  95         protected function initChild() {
  96                 global $wgMemc, $wgMainCacheType;
  97                 $wgMemc = wfGetCache( $wgMainCacheType );
  98         }
  99
 100         protected function handleTermSignal( $signal ) {
 101                 $this->termReceived = true;
 102         }
 103 }