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| 1 | <?php |
| 2 | /** |
| 3 | * This program is free software; you can redistribute it and/or modify |
| 4 | * it under the terms of the GNU General Public License as published by |
| 5 | * the Free Software Foundation; either version 2 of the License, or |
| 6 | * (at your option) any later version. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 16 | * http://www.gnu.org/copyleft/gpl.html |
| 17 | * |
| 18 | * @file |
| 19 | */ |
| 20 | |
| 21 | namespace MediaWiki\Maintenance; |
| 22 | |
| 23 | use MediaWiki\MediaWikiServices; |
| 24 | use ObjectCache; |
| 25 | use RedisConnectionPool; |
| 26 | use RuntimeException; |
| 27 | |
| 28 | /** |
| 29 | * Manage forking inside CLI maintenance scripts. |
| 30 | * |
| 31 | * Only handles forking and process control. In the future, this could |
| 32 | * be extended to provide IPC and job dispatch. |
| 33 | * |
| 34 | * This class requires the posix and pcntl extensions. |
| 35 | * |
| 36 | * @ingroup Maintenance |
| 37 | */ |
| 38 | class ForkController { |
| 39 | /** @var array|null */ |
| 40 | protected $children = []; |
| 41 | |
| 42 | /** @var int */ |
| 43 | protected $childNumber = 0; |
| 44 | |
| 45 | /** @var bool */ |
| 46 | protected $termReceived = false; |
| 47 | |
| 48 | /** @var int */ |
| 49 | protected $flags = 0; |
| 50 | |
| 51 | /** @var int */ |
| 52 | protected $procsToStart = 0; |
| 53 | |
| 54 | protected static $RESTARTABLE_SIGNALS = []; |
| 55 | |
| 56 | /** |
| 57 | * Pass this flag to __construct() to cause the class to automatically restart |
| 58 | * workers that exit with non-zero exit status or a signal such as SIGSEGV. |
| 59 | */ |
| 60 | private const RESTART_ON_ERROR = 1; |
| 61 | |
| 62 | /** |
| 63 | * @param int $numProcs The number of worker processes to fork |
| 64 | * @param int $flags |
| 65 | */ |
| 66 | public function __construct( $numProcs, $flags = 0 ) { |
| 67 | if ( !wfIsCLI() ) { |
| 68 | throw new RuntimeException( "MediaWiki\Maintenance\ForkController cannot be used from the web." ); |
| 69 | } elseif ( !extension_loaded( 'pcntl' ) ) { |
| 70 | throw new RuntimeException( |
| 71 | 'MediaWiki\Maintenance\ForkController requires pcntl extension to be installed.' |
| 72 | ); |
| 73 | } elseif ( !extension_loaded( 'posix' ) ) { |
| 74 | throw new RuntimeException( |
| 75 | 'MediaWiki\Maintenance\ForkController requires posix extension to be installed.' |
| 76 | ); |
| 77 | } |
| 78 | $this->procsToStart = $numProcs; |
| 79 | $this->flags = $flags; |
| 80 | |
| 81 | // Define this only after confirming PCNTL support |
| 82 | self::$RESTARTABLE_SIGNALS = [ |
| 83 | SIGFPE, SIGILL, SIGSEGV, SIGBUS, |
| 84 | SIGABRT, SIGSYS, SIGPIPE, SIGXCPU, SIGXFSZ, |
| 85 | ]; |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Start the child processes. |
| 90 | * |
| 91 | * This should only be called from the command line. It should be called |
| 92 | * as early as possible during execution. |
| 93 | * |
| 94 | * This will return 'child' in the child processes. In the parent process, |
| 95 | * it will run until all the child processes exit or a TERM signal is |
| 96 | * received. It will then return 'done'. |
| 97 | * @return string |
| 98 | */ |
| 99 | public function start() { |
| 100 | // Trap SIGTERM |
| 101 | pcntl_signal( SIGTERM, [ $this, 'handleTermSignal' ], false ); |
| 102 | |
| 103 | do { |
| 104 | // Start child processes |
| 105 | if ( $this->procsToStart ) { |
| 106 | if ( $this->forkWorkers( $this->procsToStart ) == 'child' ) { |
| 107 | return 'child'; |
| 108 | } |
| 109 | $this->procsToStart = 0; |
| 110 | } |
| 111 | |
| 112 | // Check child status |
| 113 | $status = false; |
| 114 | $deadPid = pcntl_wait( $status ); |
| 115 | |
| 116 | if ( $deadPid > 0 ) { |
| 117 | // Respond to child process termination |
| 118 | unset( $this->children[$deadPid] ); |
| 119 | if ( $this->flags & self::RESTART_ON_ERROR ) { |
| 120 | if ( pcntl_wifsignaled( $status ) ) { |
| 121 | // Restart if the signal was abnormal termination |
| 122 | // Don't restart if it was deliberately killed |
| 123 | $signal = pcntl_wtermsig( $status ); |
| 124 | if ( in_array( $signal, self::$RESTARTABLE_SIGNALS ) ) { |
| 125 | echo "Worker exited with signal $signal, restarting\n"; |
| 126 | $this->procsToStart++; |
| 127 | } |
| 128 | } elseif ( pcntl_wifexited( $status ) ) { |
| 129 | // Restart on non-zero exit status |
| 130 | $exitStatus = pcntl_wexitstatus( $status ); |
| 131 | if ( $exitStatus != 0 ) { |
| 132 | echo "Worker exited with status $exitStatus, restarting\n"; |
| 133 | $this->procsToStart++; |
| 134 | } else { |
| 135 | echo "Worker exited normally\n"; |
| 136 | } |
| 137 | } |
| 138 | } |
| 139 | // Throttle restarts |
| 140 | if ( $this->procsToStart ) { |
| 141 | usleep( 500_000 ); |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | // Run signal handlers |
| 146 | if ( function_exists( 'pcntl_signal_dispatch' ) ) { |
| 147 | pcntl_signal_dispatch(); |
| 148 | } else { |
| 149 | declare( ticks=1 ) { |
| 150 | // @phan-suppress-next-line PhanPluginDuplicateExpressionAssignment |
| 151 | $status = $status; |
| 152 | } |
| 153 | } |
| 154 | // Respond to TERM signal |
| 155 | if ( $this->termReceived ) { |
| 156 | foreach ( $this->children as $childPid => $unused ) { |
| 157 | posix_kill( $childPid, SIGTERM ); |
| 158 | } |
| 159 | $this->termReceived = false; |
| 160 | } |
| 161 | } while ( count( $this->children ) ); |
| 162 | pcntl_signal( SIGTERM, SIG_DFL ); |
| 163 | return 'done'; |
| 164 | } |
| 165 | |
| 166 | /** |
| 167 | * Get the number of the child currently running. Note, this |
| 168 | * is not the pid, but rather which of the total number of children |
| 169 | * we are |
| 170 | * @return int |
| 171 | */ |
| 172 | public function getChildNumber() { |
| 173 | return $this->childNumber; |
| 174 | } |
| 175 | |
| 176 | protected function prepareEnvironment() { |
| 177 | // Don't share DB, storage, or memcached connections |
| 178 | MediaWikiServices::resetChildProcessServices(); |
| 179 | ObjectCache::clear(); |
| 180 | RedisConnectionPool::destroySingletons(); |
| 181 | } |
| 182 | |
| 183 | /** |
| 184 | * Fork a number of worker processes. |
| 185 | * |
| 186 | * @param int $numProcs |
| 187 | * @return string |
| 188 | */ |
| 189 | protected function forkWorkers( $numProcs ) { |
| 190 | $this->prepareEnvironment(); |
| 191 | |
| 192 | // Create the child processes |
| 193 | for ( $i = 0; $i < $numProcs; $i++ ) { |
| 194 | // Do the fork |
| 195 | $pid = pcntl_fork(); |
| 196 | if ( $pid === -1 ) { |
| 197 | echo "Error creating child processes\n"; |
| 198 | exit( 1 ); |
| 199 | } |
| 200 | |
| 201 | if ( !$pid ) { |
| 202 | $this->initChild(); |
| 203 | $this->childNumber = $i; |
| 204 | return 'child'; |
| 205 | } else { |
| 206 | // This is the parent process |
| 207 | $this->children[$pid] = true; |
| 208 | } |
| 209 | } |
| 210 | |
| 211 | return 'parent'; |
| 212 | } |
| 213 | |
| 214 | protected function initChild() { |
| 215 | $this->children = null; |
| 216 | pcntl_signal( SIGTERM, SIG_DFL ); |
| 217 | } |
| 218 | |
| 219 | protected function handleTermSignal( $signal ) { |
| 220 | $this->termReceived = true; |
| 221 | } |
| 222 | } |
| 223 | |
| 224 | /** @deprecated class alias since 1.40 */ |
| 225 | class_alias( ForkController::class, 'ForkController' ); |