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   1  <?php
   2  /**
   3   * Version of LockManager based on using DB table locks.
   4   *
   5   * This program is free software; you can redistribute it and/or modify
   6   * it under the terms of the GNU General Public License as published by
   7   * the Free Software Foundation; either version 2 of the License, or
   8   * (at your option) any later version.
   9   *
  10   * This program is distributed in the hope that it will be useful,
  11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13   * GNU General Public License for more details.
  14   *
  15   * You should have received a copy of the GNU General Public License along
  16   * with this program; if not, write to the Free Software Foundation, Inc.,
  17   * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18   * http://www.gnu.org/copyleft/gpl.html
  19   *
  20   * @file
  21   * @ingroup LockManager
  22   */
  23  
  24  /**
  25   * Version of LockManager based on using named/row DB locks.
  26   *
  27   * This is meant for multi-wiki systems that may share files.
  28   *
  29   * All lock requests for a resource, identified by a hash string, will map
  30   * to one bucket. Each bucket maps to one or several peer DBs, each on their
  31   * own server, all having the filelocks.sql tables (with row-level locking).
  32   * A majority of peer DBs must agree for a lock to be acquired.
  33   *
  34   * Caching is used to avoid hitting servers that are down.
  35   *
  36   * @ingroup LockManager
  37   * @since 1.19
  38   */
  39  abstract class DBLockManager extends QuorumLockManager {
  40      /** @var array Map of DB names to server config */
  41      protected $dbServers; // (DB name => server config array)
  42      /** @var BagOStuff */
  43      protected $statusCache;
  44  
  45      protected $lockExpiry; // integer number of seconds
  46      protected $safeDelay; // integer number of seconds
  47  
  48      protected $session = 0; // random integer
  49      /** @var array Map Database connections (DB name => Database) */
  50      protected $conns = array();
  51  
  52      /**
  53       * Construct a new instance from configuration.
  54       *
  55       * @param array $config Paramaters include:
  56       *   - dbServers   : Associative array of DB names to server configuration.
  57       *                   Configuration is an associative array that includes:
  58       *                     - host        : DB server name
  59       *                     - dbname      : DB name
  60       *                     - type        : DB type (mysql,postgres,...)
  61       *                     - user        : DB user
  62       *                     - password    : DB user password
  63       *                     - tablePrefix : DB table prefix
  64       *                     - flags       : DB flags (see DatabaseBase)
  65       *   - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
  66       *                   each having an odd-numbered list of DB names (peers) as values.
  67       *                   Any DB named 'localDBMaster' will automatically use the DB master
  68       *                   settings for this wiki (without the need for a dbServers entry).
  69       *                   Only use 'localDBMaster' if the domain is a valid wiki ID.
  70       *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  71       *                   This tells the DB server how long to wait before assuming
  72       *                   connection failure and releasing all the locks for a session.
  73       */
  74  	public function __construct( array $config ) {
  75          parent::__construct( $config );
  76  
  77          $this->dbServers = isset( $config['dbServers'] )
  78              ? $config['dbServers']
  79              : array(); // likely just using 'localDBMaster'
  80          // Sanitize srvsByBucket config to prevent PHP errors
  81          $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  82          $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  83  
  84          if ( isset( $config['lockExpiry'] ) ) {
  85              $this->lockExpiry = $config['lockExpiry'];
  86          } else {
  87              $met = ini_get( 'max_execution_time' );
  88              $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  89          }
  90          $this->safeDelay = ( $this->lockExpiry <= 0 )
  91              ? 60 // pick a safe-ish number to match DB timeout default
  92              : $this->lockExpiry; // cover worst case
  93  
  94          foreach ( $this->srvsByBucket as $bucket ) {
  95              if ( count( $bucket ) > 1 ) { // multiple peers
  96                  // Tracks peers that couldn't be queried recently to avoid lengthy
  97                  // connection timeouts. This is useless if each bucket has one peer.
  98                  try {
  99                      $this->statusCache = ObjectCache::newAccelerator( array() );
 100                  } catch ( MWException $e ) {
 101                      trigger_error( __CLASS__ .
 102                          " using multiple DB peers without apc, xcache, or wincache." );
 103                  }
 104                  break;
 105              }
 106          }
 107  
 108          $this->session = wfRandomString( 31 );
 109      }
 110  
 111      // @todo change this code to work in one batch
 112  	protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 113          $status = Status::newGood();
 114          foreach ( $pathsByType as $type => $paths ) {
 115              $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 116          }
 117  
 118          return $status;
 119      }
 120  
 121  	protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 122          return Status::newGood();
 123      }
 124  
 125      /**
 126       * @see QuorumLockManager::isServerUp()
 127       * @param string $lockSrv
 128       * @return bool
 129       */
 130  	protected function isServerUp( $lockSrv ) {
 131          if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 132              return false; // recent failure to connect
 133          }
 134          try {
 135              $this->getConnection( $lockSrv );
 136          } catch ( DBError $e ) {
 137              $this->cacheRecordFailure( $lockSrv );
 138  
 139              return false; // failed to connect
 140          }
 141  
 142          return true;
 143      }
 144  
 145      /**
 146       * Get (or reuse) a connection to a lock DB
 147       *
 148       * @param string $lockDb
 149       * @return DatabaseBase
 150       * @throws DBError
 151       */
 152  	protected function getConnection( $lockDb ) {
 153          if ( !isset( $this->conns[$lockDb] ) ) {
 154              $db = null;
 155              if ( $lockDb === 'localDBMaster' ) {
 156                  $lb = wfGetLBFactory()->getMainLB( $this->domain );
 157                  $db = $lb->getConnection( DB_MASTER, array(), $this->domain );
 158              } elseif ( isset( $this->dbServers[$lockDb] ) ) {
 159                  $config = $this->dbServers[$lockDb];
 160                  $db = DatabaseBase::factory( $config['type'], $config );
 161              }
 162              if ( !$db ) {
 163                  return null; // config error?
 164              }
 165              $this->conns[$lockDb] = $db;
 166              $this->conns[$lockDb]->clearFlag( DBO_TRX );
 167              # If the connection drops, try to avoid letting the DB rollback
 168              # and release the locks before the file operations are finished.
 169              # This won't handle the case of DB server restarts however.
 170              $options = array();
 171              if ( $this->lockExpiry > 0 ) {
 172                  $options['connTimeout'] = $this->lockExpiry;
 173              }
 174              $this->conns[$lockDb]->setSessionOptions( $options );
 175              $this->initConnection( $lockDb, $this->conns[$lockDb] );
 176          }
 177          if ( !$this->conns[$lockDb]->trxLevel() ) {
 178              $this->conns[$lockDb]->begin( __METHOD__ ); // start transaction
 179          }
 180  
 181          return $this->conns[$lockDb];
 182      }
 183  
 184      /**
 185       * Do additional initialization for new lock DB connection
 186       *
 187       * @param string $lockDb
 188       * @param DatabaseBase $db
 189       * @throws DBError
 190       */
 191  	protected function initConnection( $lockDb, DatabaseBase $db ) {
 192      }
 193  
 194      /**
 195       * Checks if the DB has not recently had connection/query errors.
 196       * This just avoids wasting time on doomed connection attempts.
 197       *
 198       * @param string $lockDb
 199       * @return bool
 200       */
 201  	protected function cacheCheckFailures( $lockDb ) {
 202          return ( $this->statusCache && $this->safeDelay > 0 )
 203              ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 204              : true;
 205      }
 206  
 207      /**
 208       * Log a lock request failure to the cache
 209       *
 210       * @param string $lockDb
 211       * @return bool Success
 212       */
 213  	protected function cacheRecordFailure( $lockDb ) {
 214          return ( $this->statusCache && $this->safeDelay > 0 )
 215              ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 216              : true;
 217      }
 218  
 219      /**
 220       * Get a cache key for recent query misses for a DB
 221       *
 222       * @param string $lockDb
 223       * @return string
 224       */
 225  	protected function getMissKey( $lockDb ) {
 226          $lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
 227          return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 228      }
 229  
 230      /**
 231       * Make sure remaining locks get cleared for sanity
 232       */
 233  	function __destruct() {
 234          $this->releaseAllLocks();
 235          foreach ( $this->conns as $db ) {
 236              $db->close();
 237          }
 238      }
 239  }
 240  
 241  /**
 242   * MySQL version of DBLockManager that supports shared locks.
 243   * All locks are non-blocking, which avoids deadlocks.
 244   *
 245   * @ingroup LockManager
 246   */
 247  class MySqlLockManager extends DBLockManager {
 248      /** @var array Mapping of lock types to the type actually used */
 249      protected $lockTypeMap = array(
 250          self::LOCK_SH => self::LOCK_SH,
 251          self::LOCK_UW => self::LOCK_SH,
 252          self::LOCK_EX => self::LOCK_EX
 253      );
 254  
 255      /**
 256       * @param string $lockDb
 257       * @param DatabaseBase $db
 258       */
 259  	protected function initConnection( $lockDb, DatabaseBase $db ) {
 260          # Let this transaction see lock rows from other transactions
 261          $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
 262      }
 263  
 264      /**
 265       * Get a connection to a lock DB and acquire locks on $paths.
 266       * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
 267       *
 268       * @see DBLockManager::getLocksOnServer()
 269       * @param string $lockSrv
 270       * @param array $paths
 271       * @param string $type
 272       * @return Status
 273       */
 274  	protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
 275          $status = Status::newGood();
 276  
 277          $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
 278  
 279          $keys = array(); // list of hash keys for the paths
 280          $data = array(); // list of rows to insert
 281          $checkEXKeys = array(); // list of hash keys that this has no EX lock on
 282          # Build up values for INSERT clause
 283          foreach ( $paths as $path ) {
 284              $key = $this->sha1Base36Absolute( $path );
 285              $keys[] = $key;
 286              $data[] = array( 'fls_key' => $key, 'fls_session' => $this->session );
 287              if ( !isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 288                  $checkEXKeys[] = $key;
 289              }
 290          }
 291  
 292          # Block new writers (both EX and SH locks leave entries here)...
 293          $db->insert( 'filelocks_shared', $data, __METHOD__, array( 'IGNORE' ) );
 294          # Actually do the locking queries...
 295          if ( $type == self::LOCK_SH ) { // reader locks
 296              $blocked = false;
 297              # Bail if there are any existing writers...
 298              if ( count( $checkEXKeys ) ) {
 299                  $blocked = $db->selectField( 'filelocks_exclusive', '1',
 300                      array( 'fle_key' => $checkEXKeys ),
 301                      __METHOD__
 302                  );
 303              }
 304              # Other prospective writers that haven't yet updated filelocks_exclusive
 305              # will recheck filelocks_shared after doing so and bail due to this entry.
 306          } else { // writer locks
 307              $encSession = $db->addQuotes( $this->session );
 308              # Bail if there are any existing writers...
 309              # This may detect readers, but the safe check for them is below.
 310              # Note: if two writers come at the same time, both bail :)
 311              $blocked = $db->selectField( 'filelocks_shared', '1',
 312                  array( 'fls_key' => $keys, "fls_session != $encSession" ),
 313                  __METHOD__
 314              );
 315              if ( !$blocked ) {
 316                  # Build up values for INSERT clause
 317                  $data = array();
 318                  foreach ( $keys as $key ) {
 319                      $data[] = array( 'fle_key' => $key );
 320                  }
 321                  # Block new readers/writers...
 322                  $db->insert( 'filelocks_exclusive', $data, __METHOD__ );
 323                  # Bail if there are any existing readers...
 324                  $blocked = $db->selectField( 'filelocks_shared', '1',
 325                      array( 'fls_key' => $keys, "fls_session != $encSession" ),
 326                      __METHOD__
 327                  );
 328              }
 329          }
 330  
 331          if ( $blocked ) {
 332              foreach ( $paths as $path ) {
 333                  $status->fatal( 'lockmanager-fail-acquirelock', $path );
 334              }
 335          }
 336  
 337          return $status;
 338      }
 339  
 340      /**
 341       * @see QuorumLockManager::releaseAllLocks()
 342       * @return Status
 343       */
 344  	protected function releaseAllLocks() {
 345          $status = Status::newGood();
 346  
 347          foreach ( $this->conns as $lockDb => $db ) {
 348              if ( $db->trxLevel() ) { // in transaction
 349                  try {
 350                      $db->rollback( __METHOD__ ); // finish transaction and kill any rows
 351                  } catch ( DBError $e ) {
 352                      $status->fatal( 'lockmanager-fail-db-release', $lockDb );
 353                  }
 354              }
 355          }
 356  
 357          return $status;
 358      }
 359  }
 360  
 361  /**
 362   * PostgreSQL version of DBLockManager that supports shared locks.
 363   * All locks are non-blocking, which avoids deadlocks.
 364   *
 365   * @ingroup LockManager
 366   */
 367  class PostgreSqlLockManager extends DBLockManager {
 368      /** @var array Mapping of lock types to the type actually used */
 369      protected $lockTypeMap = array(
 370          self::LOCK_SH => self::LOCK_SH,
 371          self::LOCK_UW => self::LOCK_SH,
 372          self::LOCK_EX => self::LOCK_EX
 373      );
 374  
 375  	protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
 376          $status = Status::newGood();
 377          if ( !count( $paths ) ) {
 378              return $status; // nothing to lock
 379          }
 380  
 381          $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
 382          $bigints = array_unique( array_map(
 383              function ( $key ) {
 384                  return wfBaseConvert( substr( $key, 0, 15 ), 16, 10 );
 385              },
 386              array_map( array( $this, 'sha1Base16Absolute' ), $paths )
 387          ) );
 388  
 389          // Try to acquire all the locks...
 390          $fields = array();
 391          foreach ( $bigints as $bigint ) {
 392              $fields[] = ( $type == self::LOCK_SH )
 393                  ? "pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
 394                  : "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
 395          }
 396          $res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
 397          $row = (array)$res->fetchObject();
 398  
 399          if ( in_array( 'f', $row ) ) {
 400              // Release any acquired locks if some could not be acquired...
 401              $fields = array();
 402              foreach ( $row as $kbigint => $ok ) {
 403                  if ( $ok === 't' ) { // locked
 404                      $bigint = substr( $kbigint, 1 ); // strip off the "K"
 405                      $fields[] = ( $type == self::LOCK_SH )
 406                          ? "pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
 407                          : "pg_advisory_unlock({$db->addQuotes( $bigint )})";
 408                  }
 409              }
 410              if ( count( $fields ) ) {
 411                  $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
 412              }
 413              foreach ( $paths as $path ) {
 414                  $status->fatal( 'lockmanager-fail-acquirelock', $path );
 415              }
 416          }
 417  
 418          return $status;
 419      }
 420  
 421      /**
 422       * @see QuorumLockManager::releaseAllLocks()
 423       * @return Status
 424       */
 425  	protected function releaseAllLocks() {
 426          $status = Status::newGood();
 427  
 428          foreach ( $this->conns as $lockDb => $db ) {
 429              try {
 430                  $db->query( "SELECT pg_advisory_unlock_all()", __METHOD__ );
 431              } catch ( DBError $e ) {
 432                  $status->fatal( 'lockmanager-fail-db-release', $lockDb );
 433              }
 434          }
 435  
 436          return $status;
 437      }
 438  }