includes/libs/lockmanager/LockManager.php

   1 <?php
   2 /**
   3  * @defgroup LockManager Lock management
   4  * @ingroup FileBackend
   5  */
   6 use Psr\Log\LoggerInterface;
   7 use Wikimedia\WaitConditionLoop;
   8
   9 /**
  10  * Resource locking handling.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  25  * http://www.gnu.org/copyleft/gpl.html
  26  *
  27  * @file
  28  * @ingroup LockManager
  29  */
  30
  31 /**
  32  * @brief Class for handling resource locking.
  33  *
  34  * Locks on resource keys can either be shared or exclusive.
  35  *
  36  * Implementations must keep track of what is locked by this process
  37  * in-memory and support nested locking calls (using reference counting).
  38  * At least LOCK_UW and LOCK_EX must be implemented. LOCK_SH can be a no-op.
  39  * Locks should either be non-blocking or have low wait timeouts.
  40  *
  41  * Subclasses should avoid throwing exceptions at all costs.
  42  *
  43  * @ingroup LockManager
  44  * @since 1.19
  45  */
  46 abstract class LockManager {
  47         /** @var LoggerInterface */
  48         protected $logger;
  49
  50         /** @var array Mapping of lock types to the type actually used */
  51         protected $lockTypeMap = [
  52                 self::LOCK_SH => self::LOCK_SH,
  53                 self::LOCK_UW => self::LOCK_EX, // subclasses may use self::LOCK_SH
  54                 self::LOCK_EX => self::LOCK_EX
  55         ];
  56
  57         /** @var array Map of (resource path => lock type => count) */
  58         protected $locksHeld = [];
  59
  60         protected $domain; // string; domain (usually wiki ID)
  61         protected $lockTTL; // integer; maximum time locks can be held
  62
  63         /** @var string Random 32-char hex number */
  64         protected $session;
  65
  66         /** Lock types; stronger locks have higher values */
  67         const LOCK_SH = 1; // shared lock (for reads)
  68         const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
  69         const LOCK_EX = 3; // exclusive lock (for writes)
  70
  71         /** @var int Max expected lock expiry in any context */
  72         const MAX_LOCK_TTL = 7200; // 2 hours
  73
  74         /**
  75          * Construct a new instance from configuration
  76          *
  77          * @param array $config Parameters include:
  78          *   - domain  : Domain (usually wiki ID) that all resources are relative to [optional]
  79          *   - lockTTL : Age (in seconds) at which resource locks should expire.
  80          *               This only applies if locks are not tied to a connection/process.
  81          */
  82         public function __construct( array $config ) {
  83                 $this->domain = isset( $config['domain'] ) ? $config['domain'] : 'global';
  84                 if ( isset( $config['lockTTL'] ) ) {
  85                         $this->lockTTL = max( 5, $config['lockTTL'] );
  86                 } elseif ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' ) {
  87                         $this->lockTTL = 3600;
  88                 } else {
  89                         $met = ini_get( 'max_execution_time' ); // this is 0 in CLI mode
  90                         $this->lockTTL = max( 5 * 60, 2 * (int)$met );
  91                 }
  92
  93                 // Upper bound on how long to keep lock structures around. This is useful when setting
  94                 // TTLs, as the "lockTTL" value may vary based on CLI mode and app server group. This is
  95                 // a "safe" value that can be used to avoid clobbering other locks that use high TTLs.
  96                 $this->lockTTL = min( $this->lockTTL, self::MAX_LOCK_TTL );
  97
  98                 $random = [];
  99                 for ( $i = 1; $i <= 5; ++$i ) {
 100                         $random[] = mt_rand( 0, 0xFFFFFFF );
 101                 }
 102                 $this->session = md5( implode( '-', $random ) );
 103
 104                 $this->logger = isset( $config['logger'] ) ? $config['logger'] : new \Psr\Log\NullLogger();
 105         }
 106
 107         /**
 108          * Lock the resources at the given abstract paths
 109          *
 110          * @param array $paths List of resource names
 111          * @param int $type LockManager::LOCK_* constant
 112          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.21)
 113          * @return StatusValue
 114          */
 115         final public function lock( array $paths, $type = self::LOCK_EX, $timeout = 0 ) {
 116                 return $this->lockByType( [ $type => $paths ], $timeout );
 117         }
 118
 119         /**
 120          * Lock the resources at the given abstract paths
 121          *
 122          * @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
 123          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.21)
 124          * @return StatusValue
 125          * @since 1.22
 126          */
 127         final public function lockByType( array $pathsByType, $timeout = 0 ) {
 128                 $pathsByType = $this->normalizePathsByType( $pathsByType );
 129
 130                 $status = null;
 131                 $loop = new WaitConditionLoop(
 132                         function () use ( &$status, $pathsByType ) {
 133                                 $status = $this->doLockByType( $pathsByType );
 134
 135                                 return $status->isOK() ?: WaitConditionLoop::CONDITION_CONTINUE;
 136                         },
 137                         $timeout
 138                 );
 139                 $loop->invoke();
 140
 141                 return $status;
 142         }
 143
 144         /**
 145          * Unlock the resources at the given abstract paths
 146          *
 147          * @param array $paths List of paths
 148          * @param int $type LockManager::LOCK_* constant
 149          * @return StatusValue
 150          */
 151         final public function unlock( array $paths, $type = self::LOCK_EX ) {
 152                 return $this->unlockByType( [ $type => $paths ] );
 153         }
 154
 155         /**
 156          * Unlock the resources at the given abstract paths
 157          *
 158          * @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
 159          * @return StatusValue
 160          * @since 1.22
 161          */
 162         final public function unlockByType( array $pathsByType ) {
 163                 $pathsByType = $this->normalizePathsByType( $pathsByType );
 164                 $status = $this->doUnlockByType( $pathsByType );
 165
 166                 return $status;
 167         }
 168
 169         /**
 170          * Get the base 36 SHA-1 of a string, padded to 31 digits.
 171          * Before hashing, the path will be prefixed with the domain ID.
 172          * This should be used internally for lock key or file names.
 173          *
 174          * @param string $path
 175          * @return string
 176          */
 177         final protected function sha1Base36Absolute( $path ) {
 178                 return Wikimedia\base_convert( sha1( "{$this->domain}:{$path}" ), 16, 36, 31 );
 179         }
 180
 181         /**
 182          * Get the base 16 SHA-1 of a string, padded to 31 digits.
 183          * Before hashing, the path will be prefixed with the domain ID.
 184          * This should be used internally for lock key or file names.
 185          *
 186          * @param string $path
 187          * @return string
 188          */
 189         final protected function sha1Base16Absolute( $path ) {
 190                 return sha1( "{$this->domain}:{$path}" );
 191         }
 192
 193         /**
 194          * Normalize the $paths array by converting LOCK_UW locks into the
 195          * appropriate type and removing any duplicated paths for each lock type.
 196          *
 197          * @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
 198          * @return array
 199          * @since 1.22
 200          */
 201         final protected function normalizePathsByType( array $pathsByType ) {
 202                 $res = [];
 203                 foreach ( $pathsByType as $type => $paths ) {
 204                         $res[$this->lockTypeMap[$type]] = array_unique( $paths );
 205                 }
 206
 207                 return $res;
 208         }
 209
 210         /**
 211          * @see LockManager::lockByType()
 212          * @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
 213          * @return StatusValue
 214          * @since 1.22
 215          */
 216         protected function doLockByType( array $pathsByType ) {
 217                 $status = StatusValue::newGood();
 218                 $lockedByType = []; // map of (type => paths)
 219                 foreach ( $pathsByType as $type => $paths ) {
 220                         $status->merge( $this->doLock( $paths, $type ) );
 221                         if ( $status->isOK() ) {
 222                                 $lockedByType[$type] = $paths;
 223                         } else {
 224                                 // Release the subset of locks that were acquired
 225                                 foreach ( $lockedByType as $lType => $lPaths ) {
 226                                         $status->merge( $this->doUnlock( $lPaths, $lType ) );
 227                                 }
 228                                 break;
 229                         }
 230                 }
 231
 232                 return $status;
 233         }
 234
 235         /**
 236          * Lock resources with the given keys and lock type
 237          *
 238          * @param array $paths List of paths
 239          * @param int $type LockManager::LOCK_* constant
 240          * @return StatusValue
 241          */
 242         abstract protected function doLock( array $paths, $type );
 243
 244         /**
 245          * @see LockManager::unlockByType()
 246          * @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
 247          * @return StatusValue
 248          * @since 1.22
 249          */
 250         protected function doUnlockByType( array $pathsByType ) {
 251                 $status = StatusValue::newGood();
 252                 foreach ( $pathsByType as $type => $paths ) {
 253                         $status->merge( $this->doUnlock( $paths, $type ) );
 254                 }
 255
 256                 return $status;
 257         }
 258
 259         /**
 260          * Unlock resources with the given keys and lock type
 261          *
 262          * @param array $paths List of paths
 263          * @param int $type LockManager::LOCK_* constant
 264          * @return StatusValue
 265          */
 266         abstract protected function doUnlock( array $paths, $type );
 267 }