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 use Wikimedia\Rdbms\DBError;
  27
  28 /**
  29  * Version of LockManager based on using named/row DB locks.
  30  *
  31  * This is meant for multi-wiki systems that may share files.
  32  *
  33  * All lock requests for a resource, identified by a hash string, will map to one bucket.
  34  * Each bucket maps to one or several peer DBs, each on their own server.
  35  * A majority of peer DBs must agree for a lock to be acquired.
  36  *
  37  * Caching is used to avoid hitting servers that are down.
  38  *
  39  * @ingroup LockManager
  40  * @since 1.19
  41  */
  42 abstract class DBLockManager extends QuorumLockManager {
  43         /** @var array[]|IDatabase[] Map of (DB names => server config or IDatabase) */
  44         protected $dbServers; // (DB name => server config array)
  45         /** @var BagOStuff */
  46         protected $statusCache;
  47
  48         protected $lockExpiry; // integer number of seconds
  49         protected $safeDelay; // integer number of seconds
  50         /** @var IDatabase[] Map Database connections (DB name => Database) */
  51         protected $conns = [];
  52
  53         /**
  54          * Construct a new instance from configuration.
  55          *
  56          * @param array $config Parameters include:
  57          *   - dbServers   : Associative array of DB names to server configuration.
  58          *                   Configuration is an associative array that includes:
  59          *                     - host        : DB server name
  60          *                     - dbname      : DB name
  61          *                     - type        : DB type (mysql,postgres,...)
  62          *                     - user        : DB user
  63          *                     - password    : DB user password
  64          *                     - tablePrefix : DB table prefix
  65          *                     - flags       : DB flags; bitfield of IDatabase::DBO_* constants
  66          *   - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
  67          *                   each having an odd-numbered list of DB names (peers) as values.
  68          *   - lockExpiry  : Lock timeout (seconds) for dropped connections. [optional]
  69          *                   This tells the DB server how long to wait before assuming
  70          *                   connection failure and releasing all the locks for a session.
  71          *   - srvCache    : A BagOStuff instance using APC or the like.
  72          */
  73         public function __construct( array $config ) {
  74                 parent::__construct( $config );
  75
  76                 $this->dbServers = $config['dbServers'];
  77                 // Sanitize srvsByBucket config to prevent PHP errors
  78                 $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
  79                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  80
  81                 if ( isset( $config['lockExpiry'] ) ) {
  82                         $this->lockExpiry = $config['lockExpiry'];
  83                 } else {
  84                         $met = ini_get( 'max_execution_time' );
  85                         $this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
  86                 }
  87                 $this->safeDelay = ( $this->lockExpiry <= 0 )
  88                         ? 60 // pick a safe-ish number to match DB timeout default
  89                         : $this->lockExpiry; // cover worst case
  90
  91                 // Tracks peers that couldn't be queried recently to avoid lengthy
  92                 // connection timeouts. This is useless if each bucket has one peer.
  93                 $this->statusCache = isset( $config['srvCache'] )
  94                         ? $config['srvCache']
  95                         : new HashBagOStuff();
  96         }
  97
  98         /**
  99          * @TODO change this code to work in one batch
 100          * @param string $lockSrv
 101          * @param array $pathsByType
 102          * @return StatusValue
 103          */
 104         protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
 105                 $status = StatusValue::newGood();
 106                 foreach ( $pathsByType as $type => $paths ) {
 107                         $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
 108                 }
 109
 110                 return $status;
 111         }
 112
 113         abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
 114
 115         protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
 116                 return StatusValue::newGood();
 117         }
 118
 119         /**
 120          * @see QuorumLockManager::isServerUp()
 121          * @param string $lockSrv
 122          * @return bool
 123          */
 124         protected function isServerUp( $lockSrv ) {
 125                 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
 126                         return false; // recent failure to connect
 127                 }
 128                 try {
 129                         $this->getConnection( $lockSrv );
 130                 } catch ( DBError $e ) {
 131                         $this->cacheRecordFailure( $lockSrv );
 132
 133                         return false; // failed to connect
 134                 }
 135
 136                 return true;
 137         }
 138
 139         /**
 140          * Get (or reuse) a connection to a lock DB
 141          *
 142          * @param string $lockDb
 143          * @return IDatabase
 144          * @throws DBError
 145          * @throws UnexpectedValueException
 146          */
 147         protected function getConnection( $lockDb ) {
 148                 if ( !isset( $this->conns[$lockDb] ) ) {
 149                         if ( $this->dbServers[$lockDb] instanceof IDatabase ) {
 150                                 // Direct injected connection hande for $lockDB
 151                                 $db = $this->dbServers[$lockDb];
 152                         } elseif ( is_array( $this->dbServers[$lockDb] ) ) {
 153                                 // Parameters to construct a new database connection
 154                                 $config = $this->dbServers[$lockDb];
 155                                 $db = Database::factory( $config['type'], $config );
 156                         } else {
 157                                 throw new UnexpectedValueException( "No server called '$lockDb'." );
 158                         }
 159
 160                         $db->clearFlag( DBO_TRX );
 161                         # If the connection drops, try to avoid letting the DB rollback
 162                         # and release the locks before the file operations are finished.
 163                         # This won't handle the case of DB server restarts however.
 164                         $options = [];
 165                         if ( $this->lockExpiry > 0 ) {
 166                                 $options['connTimeout'] = $this->lockExpiry;
 167                         }
 168                         $db->setSessionOptions( $options );
 169                         $this->initConnection( $lockDb, $db );
 170
 171                         $this->conns[$lockDb] = $db;
 172                 }
 173
 174                 return $this->conns[$lockDb];
 175         }
 176
 177         /**
 178          * Do additional initialization for new lock DB connection
 179          *
 180          * @param string $lockDb
 181          * @param IDatabase $db
 182          * @throws DBError
 183          */
 184         protected function initConnection( $lockDb, IDatabase $db ) {
 185         }
 186
 187         /**
 188          * Checks if the DB has not recently had connection/query errors.
 189          * This just avoids wasting time on doomed connection attempts.
 190          *
 191          * @param string $lockDb
 192          * @return bool
 193          */
 194         protected function cacheCheckFailures( $lockDb ) {
 195                 return ( $this->safeDelay > 0 )
 196                         ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
 197                         : true;
 198         }
 199
 200         /**
 201          * Log a lock request failure to the cache
 202          *
 203          * @param string $lockDb
 204          * @return bool Success
 205          */
 206         protected function cacheRecordFailure( $lockDb ) {
 207                 return ( $this->safeDelay > 0 )
 208                         ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
 209                         : true;
 210         }
 211
 212         /**
 213          * Get a cache key for recent query misses for a DB
 214          *
 215          * @param string $lockDb
 216          * @return string
 217          */
 218         protected function getMissKey( $lockDb ) {
 219                 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
 220         }
 221
 222         /**
 223          * Make sure remaining locks get cleared for sanity
 224          */
 225         function __destruct() {
 226                 $this->releaseAllLocks();
 227                 foreach ( $this->conns as $db ) {
 228                         $db->close();
 229                 }
 230         }
 231 }