includes/objectcache/SqlBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using a SQL database.
   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 Cache
  22  */
  23
  24 /**
  25  * Class to store objects in the database
  26  *
  27  * @ingroup Cache
  28  */
  29 class SqlBagOStuff extends BagOStuff {
  30         /** @var LoadBalancer */
  31         protected $lb;
  32
  33         /** @var array */
  34         protected $serverInfos;
  35
  36         /** @var array */
  37         protected $serverNames;
  38
  39         /** @var int */
  40         protected $numServers;
  41
  42         /** @var array */
  43         protected $conns;
  44
  45         /** @var int */
  46         protected $lastExpireAll = 0;
  47
  48         /** @var int */
  49         protected $purgePeriod = 100;
  50
  51         /** @var int */
  52         protected $shards = 1;
  53
  54         /** @var string */
  55         protected $tableName = 'objectcache';
  56
  57         /** @var bool */
  58         protected $slaveOnly = false;
  59
  60         /** @var array UNIX timestamps */
  61         protected $connFailureTimes = array();
  62
  63         /** @var array Exceptions */
  64         protected $connFailureErrors = array();
  65
  66         /**
  67          * Constructor. Parameters are:
  68          *   - server:      A server info structure in the format required by each
  69          *                  element in $wgDBServers.
  70          *
  71          *   - servers:     An array of server info structures describing a set of
  72          *                  database servers to distribute keys to. If this is
  73          *                  specified, the "server" option will be ignored.
  74          *
  75          *   - purgePeriod: The average number of object cache requests in between
  76          *                  garbage collection operations, where expired entries
  77          *                  are removed from the database. Or in other words, the
  78          *                  reciprocal of the probability of purging on any given
  79          *                  request. If this is set to zero, purging will never be
  80          *                  done.
  81          *
  82          *   - tableName:   The table name to use, default is "objectcache".
  83          *
  84          *   - shards:      The number of tables to use for data storage on each server.
  85          *                  If this is more than 1, table names will be formed in the style
  86          *                  objectcacheNNN where NNN is the shard index, between 0 and
  87          *                  shards-1. The number of digits will be the minimum number
  88          *                  required to hold the largest shard index. Data will be
  89          *                  distributed across all tables by key hash. This is for
  90          *                  MySQL bugs 61735 and 61736.
  91          *   - slaveOnly:   Whether to only use slave DBs and avoid triggering
  92          *                  garbage collection logic of expired items. This only
  93          *                  makes sense if the primary DB is used and only if get()
  94          *                  calls will be used. This is used by ReplicatedBagOStuff.
  95          *
  96          * @param array $params
  97          */
  98         public function __construct( $params ) {
  99                 parent::__construct( $params );
 100                 if ( isset( $params['servers'] ) ) {
 101                         $this->serverInfos = $params['servers'];
 102                         $this->numServers = count( $this->serverInfos );
 103                         $this->serverNames = array();
 104                         foreach ( $this->serverInfos as $i => $info ) {
 105                                 $this->serverNames[$i] = isset( $info['host'] ) ? $info['host'] : "#$i";
 106                         }
 107                 } elseif ( isset( $params['server'] ) ) {
 108                         $this->serverInfos = array( $params['server'] );
 109                         $this->numServers = count( $this->serverInfos );
 110                 } else {
 111                         $this->serverInfos = false;
 112                         $this->numServers = 1;
 113                 }
 114                 if ( isset( $params['purgePeriod'] ) ) {
 115                         $this->purgePeriod = intval( $params['purgePeriod'] );
 116                 }
 117                 if ( isset( $params['tableName'] ) ) {
 118                         $this->tableName = $params['tableName'];
 119                 }
 120                 if ( isset( $params['shards'] ) ) {
 121                         $this->shards = intval( $params['shards'] );
 122                 }
 123                 $this->slaveOnly = !empty( $params['slaveOnly'] );
 124         }
 125
 126         /**
 127          * Get a connection to the specified database
 128          *
 129          * @param int $serverIndex
 130          * @return DatabaseBase
 131          * @throws MWException
 132          */
 133         protected function getDB( $serverIndex ) {
 134                 global $wgDebugDBTransactions;
 135
 136                 if ( !isset( $this->conns[$serverIndex] ) ) {
 137                         if ( $serverIndex >= $this->numServers ) {
 138                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 139                         }
 140
 141                         # Don't keep timing out trying to connect for each call if the DB is down
 142                         if ( isset( $this->connFailureErrors[$serverIndex] )
 143                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 144                         ) {
 145                                 throw $this->connFailureErrors[$serverIndex];
 146                         }
 147
 148                         # If server connection info was given, use that
 149                         if ( $this->serverInfos ) {
 150                                 if ( $wgDebugDBTransactions ) {
 151                                         $this->logger->debug( "Using provided serverInfo for SqlBagOStuff" );
 152                                 }
 153                                 $info = $this->serverInfos[$serverIndex];
 154                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 155                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 156                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 157                                 // Use a blank trx profiler to ignore expections as this is a cache
 158                                 $info['trxProfiler'] = new TransactionProfiler();
 159                                 $db = DatabaseBase::factory( $type, $info );
 160                                 $db->clearFlag( DBO_TRX );
 161                         } else {
 162                                 /*
 163                                  * We must keep a separate connection to MySQL in order to avoid deadlocks
 164                                  * However, SQLite has an opposite behavior. And PostgreSQL needs to know
 165                                  * if we are in transaction or no
 166                                  */
 167                                 $index = $this->slaveOnly ? DB_SLAVE : DB_MASTER;
 168                                 if ( wfGetDB( $index )->getType() == 'mysql' ) {
 169                                         $this->lb = wfGetLBFactory()->newMainLB();
 170                                         $db = $this->lb->getConnection( $index );
 171                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 172                                 } else {
 173                                         $db = wfGetDB( $index );
 174                                 }
 175                         }
 176                         if ( $wgDebugDBTransactions ) {
 177                                 $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 178                         }
 179                         $this->conns[$serverIndex] = $db;
 180                 }
 181
 182                 return $this->conns[$serverIndex];
 183         }
 184
 185         /**
 186          * Get the server index and table name for a given key
 187          * @param string $key
 188          * @return array Server index and table name
 189          */
 190         protected function getTableByKey( $key ) {
 191                 if ( $this->shards > 1 ) {
 192                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 193                         $tableIndex = $hash % $this->shards;
 194                 } else {
 195                         $tableIndex = 0;
 196                 }
 197                 if ( $this->numServers > 1 ) {
 198                         $sortedServers = $this->serverNames;
 199                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 200                         reset( $sortedServers );
 201                         $serverIndex = key( $sortedServers );
 202                 } else {
 203                         $serverIndex = 0;
 204                 }
 205                 return array( $serverIndex, $this->getTableNameByShard( $tableIndex ) );
 206         }
 207
 208         /**
 209          * Get the table name for a given shard index
 210          * @param int $index
 211          * @return string
 212          */
 213         protected function getTableNameByShard( $index ) {
 214                 if ( $this->shards > 1 ) {
 215                         $decimals = strlen( $this->shards - 1 );
 216                         return $this->tableName .
 217                                 sprintf( "%0{$decimals}d", $index );
 218                 } else {
 219                         return $this->tableName;
 220                 }
 221         }
 222
 223         public function get( $key, &$casToken = null, $flags = 0 ) {
 224                 $values = $this->getMulti( array( $key ) );
 225                 if ( array_key_exists( $key, $values ) ) {
 226                         $casToken = $values[$key];
 227                         return $values[$key];
 228                 }
 229                 return false;
 230         }
 231
 232         public function getMulti( array $keys, $flags = 0 ) {
 233                 $values = array(); // array of (key => value)
 234
 235                 $keysByTable = array();
 236                 foreach ( $keys as $key ) {
 237                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 238                         $keysByTable[$serverIndex][$tableName][] = $key;
 239                 }
 240
 241                 $this->garbageCollect(); // expire old entries if any
 242
 243                 $dataRows = array();
 244                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 245                         try {
 246                                 $db = $this->getDB( $serverIndex );
 247                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 248                                         $res = $db->select( $tableName,
 249                                                 array( 'keyname', 'value', 'exptime' ),
 250                                                 array( 'keyname' => $tableKeys ),
 251                                                 __METHOD__,
 252                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 253                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 254                                                 // We do not want to flush the TRX as that can break callers.
 255                                                 $db->trxLevel() ? array( 'LOCK IN SHARE MODE' ) : array()
 256                                         );
 257                                         if ( $res === false ) {
 258                                                 continue;
 259                                         }
 260                                         foreach ( $res as $row ) {
 261                                                 $row->serverIndex = $serverIndex;
 262                                                 $row->tableName = $tableName;
 263                                                 $dataRows[$row->keyname] = $row;
 264                                         }
 265                                 }
 266                         } catch ( DBError $e ) {
 267                                 $this->handleReadError( $e, $serverIndex );
 268                         }
 269                 }
 270
 271                 foreach ( $keys as $key ) {
 272                         if ( isset( $dataRows[$key] ) ) { // HIT?
 273                                 $row = $dataRows[$key];
 274                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 275                                 try {
 276                                         $db = $this->getDB( $row->serverIndex );
 277                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 278                                                 $this->debug( "get: key has expired" );
 279                                         } else { // HIT
 280                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 281                                         }
 282                                 } catch ( DBQueryError $e ) {
 283                                         $this->handleWriteError( $e, $row->serverIndex );
 284                                 }
 285                         } else { // MISS
 286                                 $this->debug( 'get: no matching rows' );
 287                         }
 288                 }
 289
 290                 return $values;
 291         }
 292
 293         /**
 294          * @param array $data
 295          * @param int $expiry
 296          * @return bool
 297          */
 298         public function setMulti( array $data, $expiry = 0 ) {
 299                 $keysByTable = array();
 300                 foreach ( $data as $key => $value ) {
 301                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 302                         $keysByTable[$serverIndex][$tableName][] = $key;
 303                 }
 304
 305                 $this->garbageCollect(); // expire old entries if any
 306
 307                 $result = true;
 308                 $exptime = (int)$expiry;
 309                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 310                         try {
 311                                 $db = $this->getDB( $serverIndex );
 312                         } catch ( DBError $e ) {
 313                                 $this->handleWriteError( $e, $serverIndex );
 314                                 $result = false;
 315                                 continue;
 316                         }
 317
 318                         if ( $exptime < 0 ) {
 319                                 $exptime = 0;
 320                         }
 321
 322                         if ( $exptime == 0 ) {
 323                                 $encExpiry = $this->getMaxDateTime( $db );
 324                         } else {
 325                                 $exptime = $this->convertExpiry( $exptime );
 326                                 $encExpiry = $db->timestamp( $exptime );
 327                         }
 328                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 329                                 $rows = array();
 330                                 foreach ( $tableKeys as $key ) {
 331                                         $rows[] = array(
 332                                                 'keyname' => $key,
 333                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 334                                                 'exptime' => $encExpiry,
 335                                         );
 336                                 }
 337
 338                                 try {
 339                                         $db->replace(
 340                                                 $tableName,
 341                                                 array( 'keyname' ),
 342                                                 $rows,
 343                                                 __METHOD__
 344                                         );
 345                                 } catch ( DBError $e ) {
 346                                         $this->handleWriteError( $e, $serverIndex );
 347                                         $result = false;
 348                                 }
 349
 350                         }
 351
 352                 }
 353
 354                 return $result;
 355         }
 356
 357         /**
 358          * @param string $key
 359          * @param mixed $value
 360          * @param int $exptime
 361          * @return bool
 362          */
 363         public function set( $key, $value, $exptime = 0 ) {
 364                 return $this->setMulti( array( $key => $value ), $exptime );
 365         }
 366
 367         /**
 368          * @param mixed $casToken
 369          * @param string $key
 370          * @param mixed $value
 371          * @param int $exptime
 372          * @return bool
 373          */
 374         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 375                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 376                 try {
 377                         $db = $this->getDB( $serverIndex );
 378                         $exptime = intval( $exptime );
 379
 380                         if ( $exptime < 0 ) {
 381                                 $exptime = 0;
 382                         }
 383
 384                         if ( $exptime == 0 ) {
 385                                 $encExpiry = $this->getMaxDateTime( $db );
 386                         } else {
 387                                 $exptime = $this->convertExpiry( $exptime );
 388                                 $encExpiry = $db->timestamp( $exptime );
 389                         }
 390                         // (bug 24425) use a replace if the db supports it instead of
 391                         // delete/insert to avoid clashes with conflicting keynames
 392                         $db->update(
 393                                 $tableName,
 394                                 array(
 395                                         'keyname' => $key,
 396                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 397                                         'exptime' => $encExpiry
 398                                 ),
 399                                 array(
 400                                         'keyname' => $key,
 401                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 402                                 ),
 403                                 __METHOD__
 404                         );
 405                 } catch ( DBQueryError $e ) {
 406                         $this->handleWriteError( $e, $serverIndex );
 407
 408                         return false;
 409                 }
 410
 411                 return (bool)$db->affectedRows();
 412         }
 413
 414         /**
 415          * @param string $key
 416          * @return bool
 417          */
 418         public function delete( $key ) {
 419                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 420                 try {
 421                         $db = $this->getDB( $serverIndex );
 422                         $db->delete(
 423                                 $tableName,
 424                                 array( 'keyname' => $key ),
 425                                 __METHOD__ );
 426                 } catch ( DBError $e ) {
 427                         $this->handleWriteError( $e, $serverIndex );
 428                         return false;
 429                 }
 430
 431                 return true;
 432         }
 433
 434         /**
 435          * @param string $key
 436          * @param int $step
 437          * @return int|null
 438          */
 439         public function incr( $key, $step = 1 ) {
 440                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 441                 try {
 442                         $db = $this->getDB( $serverIndex );
 443                         $step = intval( $step );
 444                         $row = $db->selectRow(
 445                                 $tableName,
 446                                 array( 'value', 'exptime' ),
 447                                 array( 'keyname' => $key ),
 448                                 __METHOD__,
 449                                 array( 'FOR UPDATE' ) );
 450                         if ( $row === false ) {
 451                                 // Missing
 452
 453                                 return null;
 454                         }
 455                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 456                         if ( $this->isExpired( $db, $row->exptime ) ) {
 457                                 // Expired, do not reinsert
 458
 459                                 return null;
 460                         }
 461
 462                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 463                         $newValue = $oldValue + $step;
 464                         $db->insert( $tableName,
 465                                 array(
 466                                         'keyname' => $key,
 467                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 468                                         'exptime' => $row->exptime
 469                                 ), __METHOD__, 'IGNORE' );
 470
 471                         if ( $db->affectedRows() == 0 ) {
 472                                 // Race condition. See bug 28611
 473                                 $newValue = null;
 474                         }
 475                 } catch ( DBError $e ) {
 476                         $this->handleWriteError( $e, $serverIndex );
 477                         return null;
 478                 }
 479
 480                 return $newValue;
 481         }
 482
 483         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 484                 if ( !is_callable( $callback ) ) {
 485                         throw new Exception( "Got invalid callback." );
 486                 }
 487
 488                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 489         }
 490
 491         /**
 492          * @param DatabaseBase $db
 493          * @param string $exptime
 494          * @return bool
 495          */
 496         protected function isExpired( $db, $exptime ) {
 497                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 498         }
 499
 500         /**
 501          * @param DatabaseBase $db
 502          * @return string
 503          */
 504         protected function getMaxDateTime( $db ) {
 505                 if ( time() > 0x7fffffff ) {
 506                         return $db->timestamp( 1 << 62 );
 507                 } else {
 508                         return $db->timestamp( 0x7fffffff );
 509                 }
 510         }
 511
 512         protected function garbageCollect() {
 513                 if ( !$this->purgePeriod || $this->slaveOnly ) {
 514                         // Disabled
 515                         return;
 516                 }
 517                 // Only purge on one in every $this->purgePeriod requests.
 518                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 519                         return;
 520                 }
 521                 $now = time();
 522                 // Avoid repeating the delete within a few seconds
 523                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 524                         $this->lastExpireAll = $now;
 525                         $this->expireAll();
 526                 }
 527         }
 528
 529         public function expireAll() {
 530                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 531         }
 532
 533         /**
 534          * Delete objects from the database which expire before a certain date.
 535          * @param string $timestamp
 536          * @param bool|callable $progressCallback
 537          * @return bool
 538          */
 539         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 540                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 541                         try {
 542                                 $db = $this->getDB( $serverIndex );
 543                                 $dbTimestamp = $db->timestamp( $timestamp );
 544                                 $totalSeconds = false;
 545                                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 546                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 547                                         $maxExpTime = false;
 548                                         while ( true ) {
 549                                                 $conds = $baseConds;
 550                                                 if ( $maxExpTime !== false ) {
 551                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 552                                                 }
 553                                                 $rows = $db->select(
 554                                                         $this->getTableNameByShard( $i ),
 555                                                         array( 'keyname', 'exptime' ),
 556                                                         $conds,
 557                                                         __METHOD__,
 558                                                         array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 559                                                 if ( $rows === false || !$rows->numRows() ) {
 560                                                         break;
 561                                                 }
 562                                                 $keys = array();
 563                                                 $row = $rows->current();
 564                                                 $minExpTime = $row->exptime;
 565                                                 if ( $totalSeconds === false ) {
 566                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 567                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 568                                                 }
 569                                                 foreach ( $rows as $row ) {
 570                                                         $keys[] = $row->keyname;
 571                                                         $maxExpTime = $row->exptime;
 572                                                 }
 573
 574                                                 $db->delete(
 575                                                         $this->getTableNameByShard( $i ),
 576                                                         array(
 577                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 578                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 579                                                                 'keyname' => $keys
 580                                                         ),
 581                                                         __METHOD__ );
 582
 583                                                 if ( $progressCallback ) {
 584                                                         if ( intval( $totalSeconds ) === 0 ) {
 585                                                                 $percent = 0;
 586                                                         } else {
 587                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 588                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 589                                                                 if ( $remainingSeconds > $totalSeconds ) {
 590                                                                         $totalSeconds = $remainingSeconds;
 591                                                                 }
 592                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 593                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 594                                                                         / $this->shards * 100;
 595                                                         }
 596                                                         $percent = ( $percent / $this->numServers )
 597                                                                 + ( $serverIndex / $this->numServers * 100 );
 598                                                         call_user_func( $progressCallback, $percent );
 599                                                 }
 600                                         }
 601                                 }
 602                         } catch ( DBError $e ) {
 603                                 $this->handleWriteError( $e, $serverIndex );
 604                                 return false;
 605                         }
 606                 }
 607                 return true;
 608         }
 609
 610         /**
 611          * Delete content of shard tables in every server.
 612          * Return true if the operation is successful, false otherwise.
 613          * @return bool
 614          */
 615         public function deleteAll() {
 616                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 617                         try {
 618                                 $db = $this->getDB( $serverIndex );
 619                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 620                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 621                                 }
 622                         } catch ( DBError $e ) {
 623                                 $this->handleWriteError( $e, $serverIndex );
 624                                 return false;
 625                         }
 626                 }
 627                 return true;
 628         }
 629
 630         /**
 631          * Serialize an object and, if possible, compress the representation.
 632          * On typical message and page data, this can provide a 3X decrease
 633          * in storage requirements.
 634          *
 635          * @param mixed $data
 636          * @return string
 637          */
 638         protected function serialize( &$data ) {
 639                 $serial = serialize( $data );
 640
 641                 if ( function_exists( 'gzdeflate' ) ) {
 642                         return gzdeflate( $serial );
 643                 } else {
 644                         return $serial;
 645                 }
 646         }
 647
 648         /**
 649          * Unserialize and, if necessary, decompress an object.
 650          * @param string $serial
 651          * @return mixed
 652          */
 653         protected function unserialize( $serial ) {
 654                 if ( function_exists( 'gzinflate' ) ) {
 655                         MediaWiki\suppressWarnings();
 656                         $decomp = gzinflate( $serial );
 657                         MediaWiki\restoreWarnings();
 658
 659                         if ( false !== $decomp ) {
 660                                 $serial = $decomp;
 661                         }
 662                 }
 663
 664                 $ret = unserialize( $serial );
 665
 666                 return $ret;
 667         }
 668
 669         /**
 670          * Handle a DBError which occurred during a read operation.
 671          *
 672          * @param DBError $exception
 673          * @param int $serverIndex
 674          */
 675         protected function handleReadError( DBError $exception, $serverIndex ) {
 676                 if ( $exception instanceof DBConnectionError ) {
 677                         $this->markServerDown( $exception, $serverIndex );
 678                 }
 679                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 680                 if ( $exception instanceof DBConnectionError ) {
 681                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 682                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 683                 } else {
 684                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 685                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 686                 }
 687         }
 688
 689         /**
 690          * Handle a DBQueryError which occurred during a write operation.
 691          *
 692          * @param DBError $exception
 693          * @param int $serverIndex
 694          */
 695         protected function handleWriteError( DBError $exception, $serverIndex ) {
 696                 if ( $exception instanceof DBConnectionError ) {
 697                         $this->markServerDown( $exception, $serverIndex );
 698                 }
 699                 if ( $exception->db && $exception->db->wasReadOnlyError() ) {
 700                         if ( $exception->db->trxLevel() ) {
 701                                 try {
 702                                         $exception->db->rollback( __METHOD__ );
 703                                 } catch ( DBError $e ) {
 704                                 }
 705                         }
 706                 }
 707
 708                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 709                 if ( $exception instanceof DBConnectionError ) {
 710                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 711                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 712                 } else {
 713                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 714                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 715                 }
 716         }
 717
 718         /**
 719          * Mark a server down due to a DBConnectionError exception
 720          *
 721          * @param DBError $exception
 722          * @param int $serverIndex
 723          */
 724         protected function markServerDown( $exception, $serverIndex ) {
 725                 unset( $this->conns[$serverIndex] ); // bug T103435
 726
 727                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 728                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 729                                 unset( $this->connFailureTimes[$serverIndex] );
 730                                 unset( $this->connFailureErrors[$serverIndex] );
 731                         } else {
 732                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 733                                 return;
 734                         }
 735                 }
 736                 $now = time();
 737                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 738                 $this->connFailureTimes[$serverIndex] = $now;
 739                 $this->connFailureErrors[$serverIndex] = $exception;
 740         }
 741
 742         /**
 743          * Create shard tables. For use from eval.php.
 744          */
 745         public function createTables() {
 746                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 747                         $db = $this->getDB( $serverIndex );
 748                         if ( $db->getType() !== 'mysql' ) {
 749                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 750                         }
 751
 752                         for ( $i = 0; $i < $this->shards; $i++ ) {
 753                                 $db->query(
 754                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 755                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 756                                         __METHOD__ );
 757                         }
 758                 }
 759         }
 760 }