X-Git-Url: https://scripts.mit.edu/gitweb/autoinstallsdev/mediawiki.git/blobdiff_plain/74c929b24b048c9f1e31e17db757ae4195cd7673..dc9cc5d707f5a612938cc9371614cc41c328fda2:/includes/ForkController.php

diff --git a/includes/ForkController.php b/includes/ForkController.php
new file mode 100644
index 00000000..09e1788b
--- /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;
+	}
+}