MediaWiki 1.15.0

[autoinstallsdev/mediawiki.git] / includes / ForkController.php

diff --git a/includes/ForkController.php b/includes/ForkController.php
new file mode 100644 (file)
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--- /dev/null
+++ b/includes/ForkController.php
@@ -0,0 +1,160 @@
+<?php
+
+/**
+ * Class for managing forking command line scripts.
+ * Currently just does forking and process control, but it could easily be extended 
+ * to provide IPC and job dispatch.
+ *
+ * This class requires the posix and pcntl extensions.
+ */
+class ForkController {
+       var $children = array();
+       var $termReceived = false;
+       var $flags = 0, $procsToStart = 0;
+
+       static $restartableSignals = array(
+               SIGFPE,
+               SIGILL,
+               SIGSEGV,
+               SIGBUS,
+               SIGABRT,
+               SIGSYS,
+               SIGPIPE,
+               SIGXCPU,
+               SIGXFSZ,
+       );
+
+       /**
+        * Pass this flag to __construct() to cause the class to automatically restart
+        * workers that exit with non-zero exit status or a signal such as SIGSEGV.
+        */
+       const RESTART_ON_ERROR = 1;
+
+       public function __construct( $numProcs, $flags = 0 ) {
+               if ( php_sapi_name() != 'cli' ) {
+                       throw new MWException( "MultiProcess cannot be used from the web." );
+               }
+               $this->procsToStart = $numProcs;
+               $this->flags = $flags;
+       }
+
+       /**
+        * Start the child processes. 
+        *
+        * This should only be called from the command line. It should be called 
+        * as early as possible during execution.
+        *
+        * This will return 'child' in the child processes. In the parent process, 
+        * it will run until all the child processes exit or a TERM signal is 
+        * received. It will then return 'done'.
+        */
+       public function start() {
+               // Trap SIGTERM
+               pcntl_signal( SIGTERM, array( $this, 'handleTermSignal' ), false );
+
+               do {
+                       // Start child processes
+                       if ( $this->procsToStart ) {
+                               if ( $this->forkWorkers( $this->procsToStart ) == 'child' ) {
+                                       return 'child';
+                               }
+                               $this->procsToStart = 0;
+                       }
+
+                       // Check child status
+                       $status = false;
+                       $deadPid = pcntl_wait( $status );
+
+                       if ( $deadPid > 0 ) {
+                               // Respond to child process termination
+                               unset( $this->children[$deadPid] );
+                               if ( $this->flags & self::RESTART_ON_ERROR ) {
+                                       if ( pcntl_wifsignaled( $status ) ) {
+                                               // Restart if the signal was abnormal termination
+                                               // Don't restart if it was deliberately killed
+                                               $signal = pcntl_wtermsig( $status );
+                                               if ( in_array( $signal, self::$restartableSignals ) ) { 
+                                                       echo "Worker exited with signal $signal, restarting\n";
+                                                       $this->procsToStart++;
+                                               }
+                                       } elseif ( pcntl_wifexited( $status ) ) {
+                                               // Restart on non-zero exit status
+                                               $exitStatus = pcntl_wexitstatus( $status );
+                                               if ( $exitStatus > 0 ) {
+                                                       echo "Worker exited with status $exitStatus, restarting\n";
+                                                       $this->procsToStart++;
+                                               }
+                                       }
+                               }
+                               // Throttle restarts
+                               if ( $this->procsToStart ) {
+                                       usleep( 500000 );
+                               }
+                       }
+
+                       // Run signal handlers
+                       if ( function_exists( 'pcntl_signal_dispatch' ) ) {
+                               pcntl_signal_dispatch();
+                       } else {
+                               declare (ticks=1) { $status = $status; } 
+                       }
+                       // Respond to TERM signal
+                       if ( $this->termReceived ) {
+                               foreach ( $this->children as $childPid => $unused ) {
+                                       posix_kill( $childPid, SIGTERM );
+                               }
+                               $this->termReceived = false;
+                       }
+               } while ( count( $this->children ) );
+               pcntl_signal( SIGTERM, SIG_DFL );
+               return 'done';
+       }
+
+       protected function prepareEnvironment() {
+               global $wgCaches, $wgMemc;
+               // Don't share DB or memcached connections
+               wfGetLBFactory()->destroyInstance();
+               $wgCaches = array();
+               unset( $wgMemc );
+       }
+
+       /**
+        * Fork a number of worker processes.
+        */
+       protected function forkWorkers( $numProcs ) {
+               global $wgMemc, $wgCaches, $wgMainCacheType;
+       
+               $this->prepareEnvironment();
+
+               // Create the child processes
+               for ( $i = 0; $i < $numProcs; $i++ ) {
+                       // Do the fork
+                       $pid = pcntl_fork();
+                       if ( $pid === -1 || $pid === false ) {
+                               echo "Error creating child processes\n";
+                               exit( 1 );
+                       }
+
+                       if ( !$pid ) {
+                               $this->initChild();
+                               return 'child';
+                       } else {
+                               // This is the parent process
+                               $this->children[$pid] = true;
+                       }
+               }
+
+               return 'parent';
+       }
+
+       protected function initChild() {
+               global $wgMemc, $wgMainCacheType;
+               $wgMemc = wfGetCache( $wgMainCacheType );
+               $this->children = null;
+               pcntl_signal( SIGTERM, SIG_DFL );               
+       }
+
+       protected function handleTermSignal( $signal ) {
+               $this->termReceived = true;
+       }
+}