includes/filebackend/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[] Map of DB names to server config */
  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          *                   Any DB named 'localDBMaster' will automatically use the DB master
  67          *                   settings for this wiki (without the need for a dbServers entry).
  68          *                   Only use 'localDBMaster' if the domain is a valid wiki ID.
  69          *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  70          *                   This tells the DB server how long to wait before assuming
  71          *                   connection failure and releasing all the locks for a session.
  72          */
  73         public function __construct( array $config ) {
  74                 parent::__construct( $config );
  75
  76                 $this->dbServers = isset( $config['dbServers'] )
  77                         ? $config['dbServers']
  78                         : []; // likely just using 'localDBMaster'
  79                 // Sanitize srvsByBucket config to prevent PHP errors
  80                 $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  81                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  82
  83                 if ( isset( $config['lockExpiry'] ) ) {
  84                         $this->lockExpiry = $config['lockExpiry'];
  85                 } else {
  86                         $met = ini_get( 'max_execution_time' );
  87                         $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  88                 }
  89                 $this->safeDelay = ( $this->lockExpiry <= 0 )
  90                         ? 60 // pick a safe-ish number to match DB timeout default
  91                         : $this->lockExpiry; // cover worst case
  92
  93                 foreach ( $this->srvsByBucket as $bucket ) {
  94                         if ( count( $bucket ) > 1 ) { // multiple peers
  95                                 // Tracks peers that couldn't be queried recently to avoid lengthy
  96                                 // connection timeouts. This is useless if each bucket has one peer.
  97                                 $this->statusCache = ObjectCache::getLocalServerInstance();
  98                                 break;
  99                         }
 100                 }
 101
 102                 $this->session = wfRandomString( 31 );
 103         }
 104
 105         // @todo change this code to work in one batch
 106         protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 107                 $status = Status::newGood();
 108                 foreach ( $pathsByType as $type => $paths ) {
 109                         $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 110                 }
 111
 112                 return $status;
 113         }
 114
 115         abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
 116
 117         protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 118                 return Status::newGood();
 119         }
 120
 121         /**
 122          * @see QuorumLockManager::isServerUp()
 123          * @param string $lockSrv
 124          * @return bool
 125          */
 126         protected function isServerUp( $lockSrv ) {
 127                 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 128                         return false; // recent failure to connect
 129                 }
 130                 try {
 131                         $this->getConnection( $lockSrv );
 132                 } catch ( DBError $e ) {
 133                         $this->cacheRecordFailure( $lockSrv );
 134
 135                         return false; // failed to connect
 136                 }
 137
 138                 return true;
 139         }
 140
 141         /**
 142          * Get (or reuse) a connection to a lock DB
 143          *
 144          * @param string $lockDb
 145          * @return IDatabase
 146          * @throws DBError
 147          * @throws UnexpectedValueException
 148          */
 149         protected function getConnection( $lockDb ) {
 150                 if ( !isset( $this->conns[$lockDb] ) ) {
 151                         if ( $lockDb === 'localDBMaster' ) {
 152                                 $lb = $this->getLocalLB();
 153                                 $db = $lb->getConnection( DB_MASTER, [], $this->domain );
 154                                 # Do not mess with settings if the LoadBalancer is the main singleton
 155                                 # to avoid clobbering the settings of handles from wfGetDB( DB_MASTER ).
 156                                 $init = ( wfGetLB() !== $lb );
 157                         } elseif ( isset( $this->dbServers[$lockDb] ) ) {
 158                                 $config = $this->dbServers[$lockDb];
 159                                 $db = DatabaseBase::factory( $config['type'], $config );
 160                                 $init = true;
 161                         } else {
 162                                 throw new UnexpectedValueException( "No server called '$lockDb'." );
 163                         }
 164
 165                         if ( $init ) {
 166                                 $db->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 = [];
 171                                 if ( $this->lockExpiry > 0 ) {
 172                                         $options['connTimeout'] = $this->lockExpiry;
 173                                 }
 174                                 $db->setSessionOptions( $options );
 175                                 $this->initConnection( $lockDb, $db );
 176                         }
 177
 178                         $this->conns[$lockDb] = $db;
 179                 }
 180
 181                 return $this->conns[$lockDb];
 182         }
 183
 184         /**
 185          * @return LoadBalancer
 186          */
 187         protected function getLocalLB() {
 188                 return wfGetLBFactory()->getMainLB( $this->domain );
 189         }
 190
 191         /**
 192          * Do additional initialization for new lock DB connection
 193          *
 194          * @param string $lockDb
 195          * @param IDatabase $db
 196          * @throws DBError
 197          */
 198         protected function initConnection( $lockDb, IDatabase $db ) {
 199         }
 200
 201         /**
 202          * Checks if the DB has not recently had connection/query errors.
 203          * This just avoids wasting time on doomed connection attempts.
 204          *
 205          * @param string $lockDb
 206          * @return bool
 207          */
 208         protected function cacheCheckFailures( $lockDb ) {
 209                 return ( $this->statusCache && $this->safeDelay > 0 )
 210                         ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 211                         : true;
 212         }
 213
 214         /**
 215          * Log a lock request failure to the cache
 216          *
 217          * @param string $lockDb
 218          * @return bool Success
 219          */
 220         protected function cacheRecordFailure( $lockDb ) {
 221                 return ( $this->statusCache && $this->safeDelay > 0 )
 222                         ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 223                         : true;
 224         }
 225
 226         /**
 227          * Get a cache key for recent query misses for a DB
 228          *
 229          * @param string $lockDb
 230          * @return string
 231          */
 232         protected function getMissKey( $lockDb ) {
 233                 $lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
 234                 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 235         }
 236
 237         /**
 238          * Make sure remaining locks get cleared for sanity
 239          */
 240         function __destruct() {
 241                 $this->releaseAllLocks();
 242                 foreach ( $this->conns as $db ) {
 243                         $db->close();
 244                 }
 245         }
 246 }