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
  47         protected $session = 0; // random integer
  48         /** @var IDatabase[] Map Database connections (DB name => Database) */
  49         protected $conns = [];
  50
  51         /**
  52          * Construct a new instance from configuration.
  53          *
  54          * @param array $config Parameters include:
  55          *   - dbServers   : Associative array of DB names to server configuration.
  56          *                   Configuration is an associative array that includes:
  57          *                     - host        : DB server name
  58          *                     - dbname      : DB name
  59          *                     - type        : DB type (mysql,postgres,...)
  60          *                     - user        : DB user
  61          *                     - password    : DB user password
  62          *                     - tablePrefix : DB table prefix
  63          *                     - flags       : DB flags (see DatabaseBase)
  64          *   - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
  65          *                   each having an odd-numbered list of DB names (peers) as values.
  66          *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  67          *                   This tells the DB server how long to wait before assuming
  68          *                   connection failure and releasing all the locks for a session.
  69          *   - srvCache    : A BagOStuff instance using APC or the like.
  70          */
  71         public function __construct( array $config ) {
  72                 parent::__construct( $config );
  73
  74                 $this->dbServers = $config['dbServers'];
  75                 // Sanitize srvsByBucket config to prevent PHP errors
  76                 $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  77                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  78
  79                 if ( isset( $config['lockExpiry'] ) ) {
  80                         $this->lockExpiry = $config['lockExpiry'];
  81                 } else {
  82                         $met = ini_get( 'max_execution_time' );
  83                         $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  84                 }
  85                 $this->safeDelay = ( $this->lockExpiry <= 0 )
  86                         ? 60 // pick a safe-ish number to match DB timeout default
  87                         : $this->lockExpiry; // cover worst case
  88
  89                 // Tracks peers that couldn't be queried recently to avoid lengthy
  90                 // connection timeouts. This is useless if each bucket has one peer.
  91                 $this->statusCache = isset( $config['srvCache'] )
  92                         ? $config['srvCache']
  93                         : new HashBagOStuff();
  94
  95                 $random = [];
  96                 for ( $i = 1; $i <= 5; ++$i ) {
  97                         $random[] = mt_rand( 0, 0xFFFFFFF );
  98                 }
  99                 $this->session = substr( md5( implode( '-', $random ) ), 0, 31 );
 100         }
 101
 102         /**
 103          * @TODO change this code to work in one batch
 104          * @param string $lockSrv
 105          * @param array $pathsByType
 106          * @return StatusValue
 107          */
 108         protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 109                 $status = StatusValue::newGood();
 110                 foreach ( $pathsByType as $type => $paths ) {
 111                         $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 112                 }
 113
 114                 return $status;
 115         }
 116
 117         abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
 118
 119         protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 120                 return StatusValue::newGood();
 121         }
 122
 123         /**
 124          * @see QuorumLockManager::isServerUp()
 125          * @param string $lockSrv
 126          * @return bool
 127          */
 128         protected function isServerUp( $lockSrv ) {
 129                 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 130                         return false; // recent failure to connect
 131                 }
 132                 try {
 133                         $this->getConnection( $lockSrv );
 134                 } catch ( DBError $e ) {
 135                         $this->cacheRecordFailure( $lockSrv );
 136
 137                         return false; // failed to connect
 138                 }
 139
 140                 return true;
 141         }
 142
 143         /**
 144          * Get (or reuse) a connection to a lock DB
 145          *
 146          * @param string $lockDb
 147          * @return IDatabase
 148          * @throws DBError
 149          * @throws UnexpectedValueException
 150          */
 151         protected function getConnection( $lockDb ) {
 152                 if ( !isset( $this->conns[$lockDb] ) ) {
 153                         if ( $this->dbServers[$lockDb] instanceof IDatabase ) {
 154                                 // Direct injected connection hande for $lockDB
 155                                 $db = $this->dbServers[$lockDb];
 156                         } elseif ( is_array( $this->dbServers[$lockDb] ) ) {
 157                                 // Parameters to construct a new database connection
 158                                 $config = $this->dbServers[$lockDb];
 159                                 $db = DatabaseBase::factory( $config['type'], $config );
 160                         } else {
 161                                 throw new UnexpectedValueException( "No server called '$lockDb'." );
 162                         }
 163
 164                         $db->clearFlag( DBO_TRX );
 165                         # If the connection drops, try to avoid letting the DB rollback
 166                         # and release the locks before the file operations are finished.
 167                         # This won't handle the case of DB server restarts however.
 168                         $options = [];
 169                         if ( $this->lockExpiry > 0 ) {
 170                                 $options['connTimeout'] = $this->lockExpiry;
 171                         }
 172                         $db->setSessionOptions( $options );
 173                         $this->initConnection( $lockDb, $db );
 174
 175                         $this->conns[$lockDb] = $db;
 176                 }
 177
 178                 return $this->conns[$lockDb];
 179         }
 180
 181         /**
 182          * Do additional initialization for new lock DB connection
 183          *
 184          * @param string $lockDb
 185          * @param IDatabase $db
 186          * @throws DBError
 187          */
 188         protected function initConnection( $lockDb, IDatabase $db ) {
 189         }
 190
 191         /**
 192          * Checks if the DB has not recently had connection/query errors.
 193          * This just avoids wasting time on doomed connection attempts.
 194          *
 195          * @param string $lockDb
 196          * @return bool
 197          */
 198         protected function cacheCheckFailures( $lockDb ) {
 199                 return ( $this->safeDelay > 0 )
 200                         ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 201                         : true;
 202         }
 203
 204         /**
 205          * Log a lock request failure to the cache
 206          *
 207          * @param string $lockDb
 208          * @return bool Success
 209          */
 210         protected function cacheRecordFailure( $lockDb ) {
 211                 return ( $this->safeDelay > 0 )
 212                         ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 213                         : true;
 214         }
 215
 216         /**
 217          * Get a cache key for recent query misses for a DB
 218          *
 219          * @param string $lockDb
 220          * @return string
 221          */
 222         protected function getMissKey( $lockDb ) {
 223                 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 224         }
 225
 226         /**
 227          * Make sure remaining locks get cleared for sanity
 228          */
 229         function __destruct() {
 230                 $this->releaseAllLocks();
 231                 foreach ( $this->conns as $db ) {
 232                         $db->close();
 233                 }
 234         }
 235 }