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         protected $serverInfos;
  34
  35         /** @var array */
  36         protected $serverNames;
  37
  38         /** @var int */
  39         protected $numServers;
  40
  41         /** @var array */
  42         protected $conns;
  43
  44         /** @var int */
  45         protected $lastExpireAll = 0;
  46
  47         /** @var int */
  48         protected $purgePeriod = 100;
  49
  50         /** @var int */
  51         protected $shards = 1;
  52
  53         /** @var string */
  54         protected $tableName = 'objectcache';
  55
  56         /** @var array UNIX timestamps */
  57         protected $connFailureTimes = array();
  58
  59         /** @var array Exceptions */
  60         protected $connFailureErrors = array();
  61
  62         /**
  63          * Constructor. Parameters are:
  64          *   - server:      A server info structure in the format required by each
  65          *                  element in $wgDBServers.
  66          *
  67          *   - servers:     An array of server info structures describing a set of
  68          *                  database servers to distribute keys to. If this is
  69          *                  specified, the "server" option will be ignored.
  70          *
  71          *   - purgePeriod: The average number of object cache requests in between
  72          *                  garbage collection operations, where expired entries
  73          *                  are removed from the database. Or in other words, the
  74          *                  reciprocal of the probability of purging on any given
  75          *                  request. If this is set to zero, purging will never be
  76          *                  done.
  77          *
  78          *   - tableName:   The table name to use, default is "objectcache".
  79          *
  80          *   - shards:      The number of tables to use for data storage on each server.
  81          *                  If this is more than 1, table names will be formed in the style
  82          *                  objectcacheNNN where NNN is the shard index, between 0 and
  83          *                  shards-1. The number of digits will be the minimum number
  84          *                  required to hold the largest shard index. Data will be
  85          *                  distributed across all tables by key hash. This is for
  86          *                  MySQL bugs 61735 and 61736.
  87          *
  88          * @param array $params
  89          */
  90         public function __construct( $params ) {
  91                 if ( isset( $params['servers'] ) ) {
  92                         $this->serverInfos = $params['servers'];
  93                         $this->numServers = count( $this->serverInfos );
  94                         $this->serverNames = array();
  95                         foreach ( $this->serverInfos as $i => $info ) {
  96                                 $this->serverNames[$i] = isset( $info['host'] ) ? $info['host'] : "#$i";
  97                         }
  98                 } elseif ( isset( $params['server'] ) ) {
  99                         $this->serverInfos = array( $params['server'] );
 100                         $this->numServers = count( $this->serverInfos );
 101                 } else {
 102                         $this->serverInfos = false;
 103                         $this->numServers = 1;
 104                 }
 105                 if ( isset( $params['purgePeriod'] ) ) {
 106                         $this->purgePeriod = intval( $params['purgePeriod'] );
 107                 }
 108                 if ( isset( $params['tableName'] ) ) {
 109                         $this->tableName = $params['tableName'];
 110                 }
 111                 if ( isset( $params['shards'] ) ) {
 112                         $this->shards = intval( $params['shards'] );
 113                 }
 114         }
 115
 116         /**
 117          * Get a connection to the specified database
 118          *
 119          * @param int $serverIndex
 120          * @return DatabaseBase
 121          */
 122         protected function getDB( $serverIndex ) {
 123                 global $wgDebugDBTransactions;
 124
 125                 if ( !isset( $this->conns[$serverIndex] ) ) {
 126                         if ( $serverIndex >= $this->numServers ) {
 127                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 128                         }
 129
 130                         # Don't keep timing out trying to connect for each call if the DB is down
 131                         if ( isset( $this->connFailureErrors[$serverIndex] )
 132                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 133                         ) {
 134                                 throw $this->connFailureErrors[$serverIndex];
 135                         }
 136
 137                         # If server connection info was given, use that
 138                         if ( $this->serverInfos ) {
 139                                 if ( $wgDebugDBTransactions ) {
 140                                         wfDebug( "Using provided serverInfo for SqlBagOStuff\n" );
 141                                 }
 142                                 $info = $this->serverInfos[$serverIndex];
 143                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 144                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 145                                 wfDebug( __CLASS__ . ": connecting to $host\n" );
 146                                 $db = DatabaseBase::factory( $type, $info );
 147                                 $db->clearFlag( DBO_TRX );
 148                         } else {
 149                                 /*
 150                                  * We must keep a separate connection to MySQL in order to avoid deadlocks
 151                                  * However, SQLite has an opposite behavior. And PostgreSQL needs to know
 152                                  * if we are in transaction or no
 153                                  */
 154                                 if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
 155                                         $this->lb = wfGetLBFactory()->newMainLB();
 156                                         $db = $this->lb->getConnection( DB_MASTER );
 157                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 158                                 } else {
 159                                         $db = wfGetDB( DB_MASTER );
 160                                 }
 161                         }
 162                         if ( $wgDebugDBTransactions ) {
 163                                 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $db ) );
 164                         }
 165                         $this->conns[$serverIndex] = $db;
 166                 }
 167
 168                 return $this->conns[$serverIndex];
 169         }
 170
 171         /**
 172          * Get the server index and table name for a given key
 173          * @param string $key
 174          * @return array Server index and table name
 175          */
 176         protected function getTableByKey( $key ) {
 177                 if ( $this->shards > 1 ) {
 178                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 179                         $tableIndex = $hash % $this->shards;
 180                 } else {
 181                         $tableIndex = 0;
 182                 }
 183                 if ( $this->numServers > 1 ) {
 184                         $sortedServers = $this->serverNames;
 185                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 186                         reset( $sortedServers );
 187                         $serverIndex = key( $sortedServers );
 188                 } else {
 189                         $serverIndex = 0;
 190                 }
 191                 return array( $serverIndex, $this->getTableNameByShard( $tableIndex ) );
 192         }
 193
 194         /**
 195          * Get the table name for a given shard index
 196          * @param int $index
 197          * @return string
 198          */
 199         protected function getTableNameByShard( $index ) {
 200                 if ( $this->shards > 1 ) {
 201                         $decimals = strlen( $this->shards - 1 );
 202                         return $this->tableName .
 203                                 sprintf( "%0{$decimals}d", $index );
 204                 } else {
 205                         return $this->tableName;
 206                 }
 207         }
 208
 209         /**
 210          * @param string $key
 211          * @param mixed $casToken [optional]
 212          * @return mixed
 213          */
 214         public function get( $key, &$casToken = null ) {
 215                 $values = $this->getMulti( array( $key ) );
 216                 if ( array_key_exists( $key, $values ) ) {
 217                         $casToken = $values[$key];
 218                         return $values[$key];
 219                 }
 220                 return false;
 221         }
 222
 223         /**
 224          * @param array $keys
 225          * @return array
 226          */
 227         public function getMulti( array $keys ) {
 228                 $values = array(); // array of (key => value)
 229
 230                 $keysByTable = array();
 231                 foreach ( $keys as $key ) {
 232                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 233                         $keysByTable[$serverIndex][$tableName][] = $key;
 234                 }
 235
 236                 $this->garbageCollect(); // expire old entries if any
 237
 238                 $dataRows = array();
 239                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 240                         try {
 241                                 $db = $this->getDB( $serverIndex );
 242                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 243                                         $res = $db->select( $tableName,
 244                                                 array( 'keyname', 'value', 'exptime' ),
 245                                                 array( 'keyname' => $tableKeys ),
 246                                                 __METHOD__,
 247                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 248                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 249                                                 // We do not want to flush the TRX as that can break callers.
 250                                                 $db->trxLevel() ? array( 'LOCK IN SHARE MODE' ) : array()
 251                                         );
 252                                         if ( $res === false ) {
 253                                                 continue;
 254                                         }
 255                                         foreach ( $res as $row ) {
 256                                                 $row->serverIndex = $serverIndex;
 257                                                 $row->tableName = $tableName;
 258                                                 $dataRows[$row->keyname] = $row;
 259                                         }
 260                                 }
 261                         } catch ( DBError $e ) {
 262                                 $this->handleReadError( $e, $serverIndex );
 263                         }
 264                 }
 265
 266                 foreach ( $keys as $key ) {
 267                         if ( isset( $dataRows[$key] ) ) { // HIT?
 268                                 $row = $dataRows[$key];
 269                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 270                                 try {
 271                                         $db = $this->getDB( $row->serverIndex );
 272                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 273                                                 $this->debug( "get: key has expired, deleting" );
 274                                                 # Put the expiry time in the WHERE condition to avoid deleting a
 275                                                 # newly-inserted value
 276                                                 $db->delete( $row->tableName,
 277                                                         array( 'keyname' => $key, 'exptime' => $row->exptime ),
 278                                                         __METHOD__ );
 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
 359         /**
 360          * @param string $key
 361          * @param mixed $value
 362          * @param int $exptime
 363          * @return bool
 364          */
 365         public function set( $key, $value, $exptime = 0 ) {
 366                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 367                 try {
 368                         $db = $this->getDB( $serverIndex );
 369                         $exptime = intval( $exptime );
 370
 371                         if ( $exptime < 0 ) {
 372                                 $exptime = 0;
 373                         }
 374
 375                         if ( $exptime == 0 ) {
 376                                 $encExpiry = $this->getMaxDateTime( $db );
 377                         } else {
 378                                 $exptime = $this->convertExpiry( $exptime );
 379                                 $encExpiry = $db->timestamp( $exptime );
 380                         }
 381                         // (bug 24425) use a replace if the db supports it instead of
 382                         // delete/insert to avoid clashes with conflicting keynames
 383                         $db->replace(
 384                                 $tableName,
 385                                 array( 'keyname' ),
 386                                 array(
 387                                         'keyname' => $key,
 388                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 389                                         'exptime' => $encExpiry
 390                                 ), __METHOD__ );
 391                 } catch ( DBError $e ) {
 392                         $this->handleWriteError( $e, $serverIndex );
 393                         return false;
 394                 }
 395
 396                 return true;
 397         }
 398
 399         /**
 400          * @param mixed $casToken
 401          * @param string $key
 402          * @param mixed $value
 403          * @param int $exptime
 404          * @return bool
 405          */
 406         public function cas( $casToken, $key, $value, $exptime = 0 ) {
 407                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 408                 try {
 409                         $db = $this->getDB( $serverIndex );
 410                         $exptime = intval( $exptime );
 411
 412                         if ( $exptime < 0 ) {
 413                                 $exptime = 0;
 414                         }
 415
 416                         if ( $exptime == 0 ) {
 417                                 $encExpiry = $this->getMaxDateTime( $db );
 418                         } else {
 419                                 $exptime = $this->convertExpiry( $exptime );
 420                                 $encExpiry = $db->timestamp( $exptime );
 421                         }
 422                         // (bug 24425) use a replace if the db supports it instead of
 423                         // delete/insert to avoid clashes with conflicting keynames
 424                         $db->update(
 425                                 $tableName,
 426                                 array(
 427                                         'keyname' => $key,
 428                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 429                                         'exptime' => $encExpiry
 430                                 ),
 431                                 array(
 432                                         'keyname' => $key,
 433                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 434                                 ),
 435                                 __METHOD__
 436                         );
 437                 } catch ( DBQueryError $e ) {
 438                         $this->handleWriteError( $e, $serverIndex );
 439
 440                         return false;
 441                 }
 442
 443                 return (bool)$db->affectedRows();
 444         }
 445
 446         /**
 447          * @param string $key
 448          * @param int $time
 449          * @return bool
 450          */
 451         public function delete( $key, $time = 0 ) {
 452                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 453                 try {
 454                         $db = $this->getDB( $serverIndex );
 455                         $db->delete(
 456                                 $tableName,
 457                                 array( 'keyname' => $key ),
 458                                 __METHOD__ );
 459                 } catch ( DBError $e ) {
 460                         $this->handleWriteError( $e, $serverIndex );
 461                         return false;
 462                 }
 463
 464                 return true;
 465         }
 466
 467         /**
 468          * @param string $key
 469          * @param int $step
 470          * @return int|null
 471          */
 472         public function incr( $key, $step = 1 ) {
 473                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 474                 try {
 475                         $db = $this->getDB( $serverIndex );
 476                         $step = intval( $step );
 477                         $row = $db->selectRow(
 478                                 $tableName,
 479                                 array( 'value', 'exptime' ),
 480                                 array( 'keyname' => $key ),
 481                                 __METHOD__,
 482                                 array( 'FOR UPDATE' ) );
 483                         if ( $row === false ) {
 484                                 // Missing
 485
 486                                 return null;
 487                         }
 488                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 489                         if ( $this->isExpired( $db, $row->exptime ) ) {
 490                                 // Expired, do not reinsert
 491
 492                                 return null;
 493                         }
 494
 495                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 496                         $newValue = $oldValue + $step;
 497                         $db->insert( $tableName,
 498                                 array(
 499                                         'keyname' => $key,
 500                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 501                                         'exptime' => $row->exptime
 502                                 ), __METHOD__, 'IGNORE' );
 503
 504                         if ( $db->affectedRows() == 0 ) {
 505                                 // Race condition. See bug 28611
 506                                 $newValue = null;
 507                         }
 508                 } catch ( DBError $e ) {
 509                         $this->handleWriteError( $e, $serverIndex );
 510                         return null;
 511                 }
 512
 513                 return $newValue;
 514         }
 515
 516         /**
 517          * @param DatabaseBase $db
 518          * @param string $exptime
 519          * @return bool
 520          */
 521         protected function isExpired( $db, $exptime ) {
 522                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 523         }
 524
 525         /**
 526          * @param DatabaseBase $db
 527          * @return string
 528          */
 529         protected function getMaxDateTime( $db ) {
 530                 if ( time() > 0x7fffffff ) {
 531                         return $db->timestamp( 1 << 62 );
 532                 } else {
 533                         return $db->timestamp( 0x7fffffff );
 534                 }
 535         }
 536
 537         protected function garbageCollect() {
 538                 if ( !$this->purgePeriod ) {
 539                         // Disabled
 540                         return;
 541                 }
 542                 // Only purge on one in every $this->purgePeriod requests.
 543                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 544                         return;
 545                 }
 546                 $now = time();
 547                 // Avoid repeating the delete within a few seconds
 548                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 549                         $this->lastExpireAll = $now;
 550                         $this->expireAll();
 551                 }
 552         }
 553
 554         public function expireAll() {
 555                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 556         }
 557
 558         /**
 559          * Delete objects from the database which expire before a certain date.
 560          * @param string $timestamp
 561          * @param bool|callable $progressCallback
 562          * @return bool
 563          */
 564         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 565                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 566                         try {
 567                                 $db = $this->getDB( $serverIndex );
 568                                 $dbTimestamp = $db->timestamp( $timestamp );
 569                                 $totalSeconds = false;
 570                                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 571                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 572                                         $maxExpTime = false;
 573                                         while ( true ) {
 574                                                 $conds = $baseConds;
 575                                                 if ( $maxExpTime !== false ) {
 576                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 577                                                 }
 578                                                 $rows = $db->select(
 579                                                         $this->getTableNameByShard( $i ),
 580                                                         array( 'keyname', 'exptime' ),
 581                                                         $conds,
 582                                                         __METHOD__,
 583                                                         array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 584                                                 if ( $rows === false || !$rows->numRows() ) {
 585                                                         break;
 586                                                 }
 587                                                 $keys = array();
 588                                                 $row = $rows->current();
 589                                                 $minExpTime = $row->exptime;
 590                                                 if ( $totalSeconds === false ) {
 591                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 592                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 593                                                 }
 594                                                 foreach ( $rows as $row ) {
 595                                                         $keys[] = $row->keyname;
 596                                                         $maxExpTime = $row->exptime;
 597                                                 }
 598
 599                                                 $db->delete(
 600                                                         $this->getTableNameByShard( $i ),
 601                                                         array(
 602                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 603                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 604                                                                 'keyname' => $keys
 605                                                         ),
 606                                                         __METHOD__ );
 607
 608                                                 if ( $progressCallback ) {
 609                                                         if ( intval( $totalSeconds ) === 0 ) {
 610                                                                 $percent = 0;
 611                                                         } else {
 612                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 613                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 614                                                                 if ( $remainingSeconds > $totalSeconds ) {
 615                                                                         $totalSeconds = $remainingSeconds;
 616                                                                 }
 617                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 618                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 619                                                                         / $this->shards * 100;
 620                                                         }
 621                                                         $percent = ( $percent / $this->numServers )
 622                                                                 + ( $serverIndex / $this->numServers * 100 );
 623                                                         call_user_func( $progressCallback, $percent );
 624                                                 }
 625                                         }
 626                                 }
 627                         } catch ( DBError $e ) {
 628                                 $this->handleWriteError( $e, $serverIndex );
 629                                 return false;
 630                         }
 631                 }
 632                 return true;
 633         }
 634
 635         /**
 636          * Delete content of shard tables in every server.
 637          * Return true if the operation is successful, false otherwise.
 638          * @return bool
 639          */
 640         public function deleteAll() {
 641                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 642                         try {
 643                                 $db = $this->getDB( $serverIndex );
 644                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 645                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 646                                 }
 647                         } catch ( DBError $e ) {
 648                                 $this->handleWriteError( $e, $serverIndex );
 649                                 return false;
 650                         }
 651                 }
 652                 return true;
 653         }
 654
 655         /**
 656          * Serialize an object and, if possible, compress the representation.
 657          * On typical message and page data, this can provide a 3X decrease
 658          * in storage requirements.
 659          *
 660          * @param mixed $data
 661          * @return string
 662          */
 663         protected function serialize( &$data ) {
 664                 $serial = serialize( $data );
 665
 666                 if ( function_exists( 'gzdeflate' ) ) {
 667                         return gzdeflate( $serial );
 668                 } else {
 669                         return $serial;
 670                 }
 671         }
 672
 673         /**
 674          * Unserialize and, if necessary, decompress an object.
 675          * @param string $serial
 676          * @return mixed
 677          */
 678         protected function unserialize( $serial ) {
 679                 if ( function_exists( 'gzinflate' ) ) {
 680                         wfSuppressWarnings();
 681                         $decomp = gzinflate( $serial );
 682                         wfRestoreWarnings();
 683
 684                         if ( false !== $decomp ) {
 685                                 $serial = $decomp;
 686                         }
 687                 }
 688
 689                 $ret = unserialize( $serial );
 690
 691                 return $ret;
 692         }
 693
 694         /**
 695          * Handle a DBError which occurred during a read operation.
 696          *
 697          * @param DBError $exception
 698          * @param int $serverIndex
 699          */
 700         protected function handleReadError( DBError $exception, $serverIndex ) {
 701                 if ( $exception instanceof DBConnectionError ) {
 702                         $this->markServerDown( $exception, $serverIndex );
 703                 }
 704                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 705                 if ( $exception instanceof DBConnectionError ) {
 706                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 707                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 708                 } else {
 709                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 710                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 711                 }
 712         }
 713
 714         /**
 715          * Handle a DBQueryError which occurred during a write operation.
 716          *
 717          * @param DBError $exception
 718          * @param int $serverIndex
 719          */
 720         protected function handleWriteError( DBError $exception, $serverIndex ) {
 721                 if ( $exception instanceof DBConnectionError ) {
 722                         $this->markServerDown( $exception, $serverIndex );
 723                 }
 724                 if ( $exception->db && $exception->db->wasReadOnlyError() ) {
 725                         try {
 726                                 $exception->db->rollback( __METHOD__ );
 727                         } catch ( DBError $e ) {
 728                         }
 729                 }
 730                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 731                 if ( $exception instanceof DBConnectionError ) {
 732                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 733                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 734                 } else {
 735                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 736                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 737                 }
 738         }
 739
 740         /**
 741          * Mark a server down due to a DBConnectionError exception
 742          *
 743          * @param DBError $exception
 744          * @param int $serverIndex
 745          */
 746         protected function markServerDown( $exception, $serverIndex ) {
 747                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 748                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 749                                 unset( $this->connFailureTimes[$serverIndex] );
 750                                 unset( $this->connFailureErrors[$serverIndex] );
 751                         } else {
 752                                 wfDebug( __METHOD__ . ": Server #$serverIndex already down\n" );
 753                                 return;
 754                         }
 755                 }
 756                 $now = time();
 757                 wfDebug( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) . "\n" );
 758                 $this->connFailureTimes[$serverIndex] = $now;
 759                 $this->connFailureErrors[$serverIndex] = $exception;
 760         }
 761
 762         /**
 763          * Create shard tables. For use from eval.php.
 764          */
 765         public function createTables() {
 766                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 767                         $db = $this->getDB( $serverIndex );
 768                         if ( $db->getType() !== 'mysql' ) {
 769                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 770                         }
 771
 772                         for ( $i = 0; $i < $this->shards; $i++ ) {
 773                                 $db->query(
 774                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 775                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 776                                         __METHOD__ );
 777                         }
 778                 }
 779         }
 780 }
 781
 782 /**
 783  * Backwards compatibility alias
 784  */
 785 class MediaWikiBagOStuff extends SqlBagOStuff {
 786 }