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 use Wikimedia\Rdbms\Database;
  25 use Wikimedia\Rdbms\IDatabase;
  26
  27 /**
  28  * Version of LockManager based on using named/row DB locks.
  29  *
  30  * This is meant for multi-wiki systems that may share files.
  31  *
  32  * All lock requests for a resource, identified by a hash string, will map to one bucket.
  33  * Each bucket maps to one or several peer DBs, each on their own server.
  34  * A majority of peer DBs must agree for a lock to be acquired.
  35  *
  36  * Caching is used to avoid hitting servers that are down.
  37  *
  38  * @ingroup LockManager
  39  * @since 1.19
  40  */
  41 abstract class DBLockManager extends QuorumLockManager {
  42         /** @var array[]|IDatabase[] Map of (DB names => server config or IDatabase) */
  43         protected $dbServers; // (DB name => server config array)
  44         /** @var BagOStuff */
  45         protected $statusCache;
  46
  47         protected $lockExpiry; // integer number of seconds
  48         protected $safeDelay; // integer number of seconds
  49         /** @var IDatabase[] Map Database connections (DB name => Database) */
  50         protected $conns = [];
  51
  52         /**
  53          * Construct a new instance from configuration.
  54          *
  55          * @param array $config Parameters 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; bitfield of IDatabase::DBO_* constants
  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          *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  68          *                   This tells the DB server how long to wait before assuming
  69          *                   connection failure and releasing all the locks for a session.
  70          *   - srvCache    : A BagOStuff instance using APC or the like.
  71          */
  72         public function __construct( array $config ) {
  73                 parent::__construct( $config );
  74
  75                 $this->dbServers = $config['dbServers'];
  76                 // Sanitize srvsByBucket config to prevent PHP errors
  77                 $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  78                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  79
  80                 if ( isset( $config['lockExpiry'] ) ) {
  81                         $this->lockExpiry = $config['lockExpiry'];
  82                 } else {
  83                         $met = ini_get( 'max_execution_time' );
  84                         $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  85                 }
  86                 $this->safeDelay = ( $this->lockExpiry <= 0 )
  87                         ? 60 // pick a safe-ish number to match DB timeout default
  88                         : $this->lockExpiry; // cover worst case
  89
  90                 // Tracks peers that couldn't be queried recently to avoid lengthy
  91                 // connection timeouts. This is useless if each bucket has one peer.
  92                 $this->statusCache = isset( $config['srvCache'] )
  93                         ? $config['srvCache']
  94                         : new HashBagOStuff();
  95         }
  96
  97         /**
  98          * @TODO change this code to work in one batch
  99          * @param string $lockSrv
 100          * @param array $pathsByType
 101          * @return StatusValue
 102          */
 103         protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 104                 $status = StatusValue::newGood();
 105                 foreach ( $pathsByType as $type => $paths ) {
 106                         $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 107                 }
 108
 109                 return $status;
 110         }
 111
 112         abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
 113
 114         protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 115                 return StatusValue::newGood();
 116         }
 117
 118         /**
 119          * @see QuorumLockManager::isServerUp()
 120          * @param string $lockSrv
 121          * @return bool
 122          */
 123         protected function isServerUp( $lockSrv ) {
 124                 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 125                         return false; // recent failure to connect
 126                 }
 127                 try {
 128                         $this->getConnection( $lockSrv );
 129                 } catch ( DBError $e ) {
 130                         $this->cacheRecordFailure( $lockSrv );
 131
 132                         return false; // failed to connect
 133                 }
 134
 135                 return true;
 136         }
 137
 138         /**
 139          * Get (or reuse) a connection to a lock DB
 140          *
 141          * @param string $lockDb
 142          * @return IDatabase
 143          * @throws DBError
 144          * @throws UnexpectedValueException
 145          */
 146         protected function getConnection( $lockDb ) {
 147                 if ( !isset( $this->conns[$lockDb] ) ) {
 148                         if ( $this->dbServers[$lockDb] instanceof IDatabase ) {
 149                                 // Direct injected connection hande for $lockDB
 150                                 $db = $this->dbServers[$lockDb];
 151                         } elseif ( is_array( $this->dbServers[$lockDb] ) ) {
 152                                 // Parameters to construct a new database connection
 153                                 $config = $this->dbServers[$lockDb];
 154                                 $db = Database::factory( $config['type'], $config );
 155                         } else {
 156                                 throw new UnexpectedValueException( "No server called '$lockDb'." );
 157                         }
 158
 159                         $db->clearFlag( DBO_TRX );
 160                         # If the connection drops, try to avoid letting the DB rollback
 161                         # and release the locks before the file operations are finished.
 162                         # This won't handle the case of DB server restarts however.
 163                         $options = [];
 164                         if ( $this->lockExpiry > 0 ) {
 165                                 $options['connTimeout'] = $this->lockExpiry;
 166                         }
 167                         $db->setSessionOptions( $options );
 168                         $this->initConnection( $lockDb, $db );
 169
 170                         $this->conns[$lockDb] = $db;
 171                 }
 172
 173                 return $this->conns[$lockDb];
 174         }
 175
 176         /**
 177          * Do additional initialization for new lock DB connection
 178          *
 179          * @param string $lockDb
 180          * @param IDatabase $db
 181          * @throws DBError
 182          */
 183         protected function initConnection( $lockDb, IDatabase $db ) {
 184         }
 185
 186         /**
 187          * Checks if the DB has not recently had connection/query errors.
 188          * This just avoids wasting time on doomed connection attempts.
 189          *
 190          * @param string $lockDb
 191          * @return bool
 192          */
 193         protected function cacheCheckFailures( $lockDb ) {
 194                 return ( $this->safeDelay > 0 )
 195                         ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 196                         : true;
 197         }
 198
 199         /**
 200          * Log a lock request failure to the cache
 201          *
 202          * @param string $lockDb
 203          * @return bool Success
 204          */
 205         protected function cacheRecordFailure( $lockDb ) {
 206                 return ( $this->safeDelay > 0 )
 207                         ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 208                         : true;
 209         }
 210
 211         /**
 212          * Get a cache key for recent query misses for a DB
 213          *
 214          * @param string $lockDb
 215          * @return string
 216          */
 217         protected function getMissKey( $lockDb ) {
 218                 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 219         }
 220
 221         /**
 222          * Make sure remaining locks get cleared for sanity
 223          */
 224         function __destruct() {
 225                 $this->releaseAllLocks();
 226                 foreach ( $this->conns as $db ) {
 227                         $db->close();
 228                 }
 229         }
 230 }