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Diffstat (limited to 'www/wiki/includes/ForkController.php')
| -rw-r--r-- | www/wiki/includes/ForkController.php | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/www/wiki/includes/ForkController.php b/www/wiki/includes/ForkController.php new file mode 100644 index 00000000..cc16964e --- /dev/null +++ b/www/wiki/includes/ForkController.php @@ -0,0 +1,204 @@ +<?php +/** + * Class for managing forking command line scripts. + * + * 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, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * http://www.gnu.org/copyleft/gpl.html + * + * @file + */ +use MediaWiki\MediaWikiServices; + +/** + * 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. + * + * @ingroup Maintenance + */ +class ForkController { + protected $children = [], $childNumber = 0; + protected $termReceived = false; + protected $flags = 0, $procsToStart = 0; + + protected static $restartableSignals = [ + 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 ( !wfIsCLI() ) { + throw new MWException( "ForkController 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'. + * @return string + */ + public function start() { + // Trap SIGTERM + pcntl_signal( SIGTERM, [ $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++; + } else { + echo "Worker exited normally\n"; + } + } + } + // 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'; + } + + /** + * Get the number of the child currently running. Note, this + * is not the pid, but rather which of the total number of children + * we are + * @return int + */ + public function getChildNumber() { + return $this->childNumber; + } + + protected function prepareEnvironment() { + global $wgMemc; + // Don't share DB, storage, or memcached connections + MediaWikiServices::resetChildProcessServices(); + FileBackendGroup::destroySingleton(); + LockManagerGroup::destroySingletons(); + JobQueueGroup::destroySingletons(); + ObjectCache::clear(); + RedisConnectionPool::destroySingletons(); + $wgMemc = null; + } + + /** + * Fork a number of worker processes. + * + * @param int $numProcs + * @return string + */ + protected function forkWorkers( $numProcs ) { + $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(); + $this->childNumber = $i; + 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; + } +} |