includes/libs/lockmanager/DBLockManager.php

   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 to one bucket.
  30  * Each bucket maps to one or several peer DBs, each on their own server.
  31  * A majority of peer DBs must agree for a lock to be acquired.
  32  *
  33  * Caching is used to avoid hitting servers that are down.
  34  *
  35  * @ingroup LockManager
  36  * @since 1.19
  37  */
  38 abstract class DBLockManager extends QuorumLockManager {
  39         /** @var array[]|IDatabase[] Map of (DB names => server config or IDatabase) */
  40         protected $dbServers; // (DB name => server config array)
  41         /** @var BagOStuff */
  42         protected $statusCache;
  43
  44         protected $lockExpiry; // integer number of seconds
  45         protected $safeDelay; // integer number of seconds
  46         /** @var IDatabase[] Map Database connections (DB name => Database) */
  47         protected $conns = [];
  48
  49         /**
  50          * Construct a new instance from configuration.
  51          *
  52          * @param array $config Parameters include:
  53          *   - dbServers   : Associative array of DB names to server configuration.
  54          *                   Configuration is an associative array that includes:
  55          *                     - host        : DB server name
  56          *                     - dbname      : DB name
  57          *                     - type        : DB type (mysql,postgres,...)
  58          *                     - user        : DB user
  59          *                     - password    : DB user password
  60          *                     - tablePrefix : DB table prefix
  61          *                     - flags       : DB flags; bitfield of IDatabase::DBO_* constants
  62          *   - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
  63          *                   each having an odd-numbered list of DB names (peers) as values.
  64          *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  65          *                   This tells the DB server how long to wait before assuming
  66          *                   connection failure and releasing all the locks for a session.
  67          *   - srvCache    : A BagOStuff instance using APC or the like.
  68          */
  69         public function __construct( array $config ) {
  70                 parent::__construct( $config );
  71
  72                 $this->dbServers = $config['dbServers'];
  73                 // Sanitize srvsByBucket config to prevent PHP errors
  74                 $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  75                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  76
  77                 if ( isset( $config['lockExpiry'] ) ) {
  78                         $this->lockExpiry = $config['lockExpiry'];
  79                 } else {
  80                         $met = ini_get( 'max_execution_time' );
  81                         $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  82                 }
  83                 $this->safeDelay = ( $this->lockExpiry <= 0 )
  84                         ? 60 // pick a safe-ish number to match DB timeout default
  85                         : $this->lockExpiry; // cover worst case
  86
  87                 // Tracks peers that couldn't be queried recently to avoid lengthy
  88                 // connection timeouts. This is useless if each bucket has one peer.
  89                 $this->statusCache = isset( $config['srvCache'] )
  90                         ? $config['srvCache']
  91                         : new HashBagOStuff();
  92         }
  93
  94         /**
  95          * @TODO change this code to work in one batch
  96          * @param string $lockSrv
  97          * @param array $pathsByType
  98          * @return StatusValue
  99          */
 100         protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 101                 $status = StatusValue::newGood();
 102                 foreach ( $pathsByType as $type => $paths ) {
 103                         $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 104                 }
 105
 106                 return $status;
 107         }
 108
 109         abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
 110
 111         protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 112                 return StatusValue::newGood();
 113         }
 114
 115         /**
 116          * @see QuorumLockManager::isServerUp()
 117          * @param string $lockSrv
 118          * @return bool
 119          */
 120         protected function isServerUp( $lockSrv ) {
 121                 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 122                         return false; // recent failure to connect
 123                 }
 124                 try {
 125                         $this->getConnection( $lockSrv );
 126                 } catch ( DBError $e ) {
 127                         $this->cacheRecordFailure( $lockSrv );
 128
 129                         return false; // failed to connect
 130                 }
 131
 132                 return true;
 133         }
 134
 135         /**
 136          * Get (or reuse) a connection to a lock DB
 137          *
 138          * @param string $lockDb
 139          * @return IDatabase
 140          * @throws DBError
 141          * @throws UnexpectedValueException
 142          */
 143         protected function getConnection( $lockDb ) {
 144                 if ( !isset( $this->conns[$lockDb] ) ) {
 145                         if ( $this->dbServers[$lockDb] instanceof IDatabase ) {
 146                                 // Direct injected connection hande for $lockDB
 147                                 $db = $this->dbServers[$lockDb];
 148                         } elseif ( is_array( $this->dbServers[$lockDb] ) ) {
 149                                 // Parameters to construct a new database connection
 150                                 $config = $this->dbServers[$lockDb];
 151                                 $db = Database::factory( $config['type'], $config );
 152                         } else {
 153                                 throw new UnexpectedValueException( "No server called '$lockDb'." );
 154                         }
 155
 156                         $db->clearFlag( DBO_TRX );
 157                         # If the connection drops, try to avoid letting the DB rollback
 158                         # and release the locks before the file operations are finished.
 159                         # This won't handle the case of DB server restarts however.
 160                         $options = [];
 161                         if ( $this->lockExpiry > 0 ) {
 162                                 $options['connTimeout'] = $this->lockExpiry;
 163                         }
 164                         $db->setSessionOptions( $options );
 165                         $this->initConnection( $lockDb, $db );
 166
 167                         $this->conns[$lockDb] = $db;
 168                 }
 169
 170                 return $this->conns[$lockDb];
 171         }
 172
 173         /**
 174          * Do additional initialization for new lock DB connection
 175          *
 176          * @param string $lockDb
 177          * @param IDatabase $db
 178          * @throws DBError
 179          */
 180         protected function initConnection( $lockDb, IDatabase $db ) {
 181         }
 182
 183         /**
 184          * Checks if the DB has not recently had connection/query errors.
 185          * This just avoids wasting time on doomed connection attempts.
 186          *
 187          * @param string $lockDb
 188          * @return bool
 189          */
 190         protected function cacheCheckFailures( $lockDb ) {
 191                 return ( $this->safeDelay > 0 )
 192                         ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 193                         : true;
 194         }
 195
 196         /**
 197          * Log a lock request failure to the cache
 198          *
 199          * @param string $lockDb
 200          * @return bool Success
 201          */
 202         protected function cacheRecordFailure( $lockDb ) {
 203                 return ( $this->safeDelay > 0 )
 204                         ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 205                         : true;
 206         }
 207
 208         /**
 209          * Get a cache key for recent query misses for a DB
 210          *
 211          * @param string $lockDb
 212          * @return string
 213          */
 214         protected function getMissKey( $lockDb ) {
 215                 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 216         }
 217
 218         /**
 219          * Make sure remaining locks get cleared for sanity
 220          */
 221         function __destruct() {
 222                 $this->releaseAllLocks();
 223                 foreach ( $this->conns as $db ) {
 224                         $db->close();
 225                 }
 226         }
 227 }