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         protected $serverInfos;
  31
  32         /** @var array */
  33         protected $serverNames;
  34
  35         /** @var int */
  36         protected $numServers;
  37
  38         /** @var array */
  39         protected $conns;
  40
  41         /** @var int */
  42         protected $lastExpireAll = 0;
  43
  44         /** @var int */
  45         protected $purgePeriod = 100;
  46
  47         /** @var int */
  48         protected $shards = 1;
  49
  50         /** @var string */
  51         protected $tableName = 'objectcache';
  52
  53         /** @var array UNIX timestamps */
  54         protected $connFailureTimes = array();
  55
  56         /** @var array Exceptions */
  57         protected $connFailureErrors = array();
  58
  59         /**
  60          * Constructor. Parameters are:
  61          *   - server:      A server info structure in the format required by each
  62          *                  element in $wgDBServers.
  63          *
  64          *   - servers:     An array of server info structures describing a set of
  65          *                  database servers to distribute keys to. If this is
  66          *                  specified, the "server" option will be ignored.
  67          *
  68          *   - purgePeriod: The average number of object cache requests in between
  69          *                  garbage collection operations, where expired entries
  70          *                  are removed from the database. Or in other words, the
  71          *                  reciprocal of the probability of purging on any given
  72          *                  request. If this is set to zero, purging will never be
  73          *                  done.
  74          *
  75          *   - tableName:   The table name to use, default is "objectcache".
  76          *
  77          *   - shards:      The number of tables to use for data storage on each server.
  78          *                  If this is more than 1, table names will be formed in the style
  79          *                  objectcacheNNN where NNN is the shard index, between 0 and
  80          *                  shards-1. The number of digits will be the minimum number
  81          *                  required to hold the largest shard index. Data will be
  82          *                  distributed across all tables by key hash. This is for
  83          *                  MySQL bugs 61735 and 61736.
  84          *
  85          * @param array $params
  86          */
  87         public function __construct( $params ) {
  88                 if ( isset( $params['servers'] ) ) {
  89                         $this->serverInfos = $params['servers'];
  90                         $this->numServers = count( $this->serverInfos );
  91                         $this->serverNames = array();
  92                         foreach ( $this->serverInfos as $i => $info ) {
  93                                 $this->serverNames[$i] = isset( $info['host'] ) ? $info['host'] : "#$i";
  94                         }
  95                 } elseif ( isset( $params['server'] ) ) {
  96                         $this->serverInfos = array( $params['server'] );
  97                         $this->numServers = count( $this->serverInfos );
  98                 } else {
  99                         $this->serverInfos = false;
 100                         $this->numServers = 1;
 101                 }
 102                 if ( isset( $params['purgePeriod'] ) ) {
 103                         $this->purgePeriod = intval( $params['purgePeriod'] );
 104                 }
 105                 if ( isset( $params['tableName'] ) ) {
 106                         $this->tableName = $params['tableName'];
 107                 }
 108                 if ( isset( $params['shards'] ) ) {
 109                         $this->shards = intval( $params['shards'] );
 110                 }
 111         }
 112
 113         /**
 114          * Get a connection to the specified database
 115          *
 116          * @param int $serverIndex
 117          * @return DatabaseBase
 118          */
 119         protected function getDB( $serverIndex ) {
 120                 global $wgDebugDBTransactions;
 121
 122                 if ( !isset( $this->conns[$serverIndex] ) ) {
 123                         if ( $serverIndex >= $this->numServers ) {
 124                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 125                         }
 126
 127                         # Don't keep timing out trying to connect for each call if the DB is down
 128                         if ( isset( $this->connFailureErrors[$serverIndex] )
 129                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 130                         ) {
 131                                 throw $this->connFailureErrors[$serverIndex];
 132                         }
 133
 134                         # If server connection info was given, use that
 135                         if ( $this->serverInfos ) {
 136                                 if ( $wgDebugDBTransactions ) {
 137                                         wfDebug( "Using provided serverInfo for SqlBagOStuff\n" );
 138                                 }
 139                                 $info = $this->serverInfos[$serverIndex];
 140                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 141                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 142                                 wfDebug( __CLASS__ . ": connecting to $host\n" );
 143                                 $db = DatabaseBase::factory( $type, $info );
 144                                 $db->clearFlag( DBO_TRX );
 145                         } else {
 146                                 // We must keep a separate connection to MySQL in order to avoid deadlocks
 147                                 // However, SQLite has an opposite behavior.
 148                                 // @TODO: get this trick to work on PostgreSQL too
 149                                 if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
 150                                         $lb = wfGetLBFactory()->newMainLB();
 151                                         $db = $lb->getConnection( DB_MASTER );
 152                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 153                                 } else {
 154                                         $db = wfGetDB( DB_MASTER );
 155                                 }
 156                         }
 157                         if ( $wgDebugDBTransactions ) {
 158                                 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $db ) );
 159                         }
 160                         $this->conns[$serverIndex] = $db;
 161                 }
 162
 163                 return $this->conns[$serverIndex];
 164         }
 165
 166         /**
 167          * Get the server index and table name for a given key
 168          * @param string $key
 169          * @return array Server index and table name
 170          */
 171         protected function getTableByKey( $key ) {
 172                 if ( $this->shards > 1 ) {
 173                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 174                         $tableIndex = $hash % $this->shards;
 175                 } else {
 176                         $tableIndex = 0;
 177                 }
 178                 if ( $this->numServers > 1 ) {
 179                         $sortedServers = $this->serverNames;
 180                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 181                         reset( $sortedServers );
 182                         $serverIndex = key( $sortedServers );
 183                 } else {
 184                         $serverIndex = 0;
 185                 }
 186                 return array( $serverIndex, $this->getTableNameByShard( $tableIndex ) );
 187         }
 188
 189         /**
 190          * Get the table name for a given shard index
 191          * @param int $index
 192          * @return string
 193          */
 194         protected function getTableNameByShard( $index ) {
 195                 if ( $this->shards > 1 ) {
 196                         $decimals = strlen( $this->shards - 1 );
 197                         return $this->tableName .
 198                                 sprintf( "%0{$decimals}d", $index );
 199                 } else {
 200                         return $this->tableName;
 201                 }
 202         }
 203
 204         /**
 205          * @param string $key
 206          * @param mixed $casToken [optional]
 207          * @return mixed
 208          */
 209         public function get( $key, &$casToken = null ) {
 210                 $values = $this->getMulti( array( $key ) );
 211                 if ( array_key_exists( $key, $values ) ) {
 212                         $casToken = $values[$key];
 213                         return $values[$key];
 214                 }
 215                 return false;
 216         }
 217
 218         /**
 219          * @param array $keys
 220          * @return array
 221          */
 222         public function getMulti( array $keys ) {
 223                 $values = array(); // array of (key => value)
 224
 225                 $keysByTable = array();
 226                 foreach ( $keys as $key ) {
 227                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 228                         $keysByTable[$serverIndex][$tableName][] = $key;
 229                 }
 230
 231                 $this->garbageCollect(); // expire old entries if any
 232
 233                 $dataRows = array();
 234                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 235                         try {
 236                                 $db = $this->getDB( $serverIndex );
 237                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 238                                         $res = $db->select( $tableName,
 239                                                 array( 'keyname', 'value', 'exptime' ),
 240                                                 array( 'keyname' => $tableKeys ),
 241                                                 __METHOD__ );
 242                                         foreach ( $res as $row ) {
 243                                                 $row->serverIndex = $serverIndex;
 244                                                 $row->tableName = $tableName;
 245                                                 $dataRows[$row->keyname] = $row;
 246                                         }
 247                                 }
 248                         } catch ( DBError $e ) {
 249                                 $this->handleReadError( $e, $serverIndex );
 250                         }
 251                 }
 252
 253                 foreach ( $keys as $key ) {
 254                         if ( isset( $dataRows[$key] ) ) { // HIT?
 255                                 $row = $dataRows[$key];
 256                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 257                                 try {
 258                                         $db = $this->getDB( $row->serverIndex );
 259                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 260                                                 $this->debug( "get: key has expired, deleting" );
 261                                                 $db->commit( __METHOD__, 'flush' );
 262                                                 # Put the expiry time in the WHERE condition to avoid deleting a
 263                                                 # newly-inserted value
 264                                                 $db->delete( $row->tableName,
 265                                                         array( 'keyname' => $key, 'exptime' => $row->exptime ),
 266                                                         __METHOD__ );
 267                                                 $db->commit( __METHOD__, 'flush' );
 268                                         } else { // HIT
 269                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 270                                         }
 271                                 } catch ( DBQueryError $e ) {
 272                                         $this->handleWriteError( $e, $row->serverIndex );
 273                                 }
 274                         } else { // MISS
 275                                 $this->debug( 'get: no matching rows' );
 276                         }
 277                 }
 278
 279                 return $values;
 280         }
 281
 282         /**
 283          * @param array $data
 284          * @param int $expiry
 285          * @return bool
 286          */
 287         public function setMulti( array $data, $expiry = 0 ) {
 288                 $keysByTable = array();
 289                 foreach ( $data as $key => $value ) {
 290                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 291                         $keysByTable[$serverIndex][$tableName][] = $key;
 292                 }
 293
 294                 $this->garbageCollect(); // expire old entries if any
 295
 296                 $result = true;
 297                 $exptime = (int)$expiry;
 298                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 299                         try {
 300                                 $db = $this->getDB( $serverIndex );
 301                         } catch ( DBError $e ) {
 302                                 $this->handleWriteError( $e, $serverIndex );
 303                                 $result = false;
 304                                 continue;
 305                         }
 306
 307                         if ( $exptime < 0 ) {
 308                                 $exptime = 0;
 309                         }
 310
 311                         if ( $exptime == 0 ) {
 312                                 $encExpiry = $this->getMaxDateTime( $db );
 313                         } else {
 314                                 if ( $exptime < 3.16e8 ) { # ~10 years
 315                                         $exptime += time();
 316                                 }
 317                                 $encExpiry = $db->timestamp( $exptime );
 318                         }
 319                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 320                                 $rows = array();
 321                                 foreach ( $tableKeys as $key ) {
 322                                         $rows[] = array(
 323                                                 'keyname' => $key,
 324                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 325                                                 'exptime' => $encExpiry,
 326                                         );
 327                                 }
 328
 329                                 try {
 330                                         $db->commit( __METHOD__, 'flush' );
 331                                         $db->replace(
 332                                                 $tableName,
 333                                                 array( 'keyname' ),
 334                                                 $rows,
 335                                                 __METHOD__
 336                                         );
 337                                         $db->commit( __METHOD__, 'flush' );
 338                                 } catch ( DBError $e ) {
 339                                         $this->handleWriteError( $e, $serverIndex );
 340                                         $result = false;
 341                                 }
 342
 343                         }
 344
 345                 }
 346
 347                 return $result;
 348         }
 349
 350
 351
 352         /**
 353          * @param string $key
 354          * @param mixed $value
 355          * @param int $exptime
 356          * @return bool
 357          */
 358         public function set( $key, $value, $exptime = 0 ) {
 359                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 360                 try {
 361                         $db = $this->getDB( $serverIndex );
 362                         $exptime = intval( $exptime );
 363
 364                         if ( $exptime < 0 ) {
 365                                 $exptime = 0;
 366                         }
 367
 368                         if ( $exptime == 0 ) {
 369                                 $encExpiry = $this->getMaxDateTime( $db );
 370                         } else {
 371                                 if ( $exptime < 3.16e8 ) { # ~10 years
 372                                         $exptime += time();
 373                                 }
 374
 375                                 $encExpiry = $db->timestamp( $exptime );
 376                         }
 377                         $db->commit( __METHOD__, 'flush' );
 378                         // (bug 24425) use a replace if the db supports it instead of
 379                         // delete/insert to avoid clashes with conflicting keynames
 380                         $db->replace(
 381                                 $tableName,
 382                                 array( 'keyname' ),
 383                                 array(
 384                                         'keyname' => $key,
 385                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 386                                         'exptime' => $encExpiry
 387                                 ), __METHOD__ );
 388                         $db->commit( __METHOD__, 'flush' );
 389                 } catch ( DBError $e ) {
 390                         $this->handleWriteError( $e, $serverIndex );
 391                         return false;
 392                 }
 393
 394                 return true;
 395         }
 396
 397         /**
 398          * @param mixed $casToken
 399          * @param string $key
 400          * @param mixed $value
 401          * @param int $exptime
 402          * @return bool
 403          */
 404         public function cas( $casToken, $key, $value, $exptime = 0 ) {
 405                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 406                 try {
 407                         $db = $this->getDB( $serverIndex );
 408                         $exptime = intval( $exptime );
 409
 410                         if ( $exptime < 0 ) {
 411                                 $exptime = 0;
 412                         }
 413
 414                         if ( $exptime == 0 ) {
 415                                 $encExpiry = $this->getMaxDateTime( $db );
 416                         } else {
 417                                 if ( $exptime < 3.16e8 ) { # ~10 years
 418                                         $exptime += time();
 419                                 }
 420                                 $encExpiry = $db->timestamp( $exptime );
 421                         }
 422                         $db->commit( __METHOD__, 'flush' );
 423                         // (bug 24425) use a replace if the db supports it instead of
 424                         // delete/insert to avoid clashes with conflicting keynames
 425                         $db->update(
 426                                 $tableName,
 427                                 array(
 428                                         'keyname' => $key,
 429                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 430                                         'exptime' => $encExpiry
 431                                 ),
 432                                 array(
 433                                         'keyname' => $key,
 434                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 435                                 ),
 436                                 __METHOD__
 437                         );
 438                         $db->commit( __METHOD__, 'flush' );
 439                 } catch ( DBQueryError $e ) {
 440                         $this->handleWriteError( $e, $serverIndex );
 441
 442                         return false;
 443                 }
 444
 445                 return (bool)$db->affectedRows();
 446         }
 447
 448         /**
 449          * @param string $key
 450          * @param int $time
 451          * @return bool
 452          */
 453         public function delete( $key, $time = 0 ) {
 454                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 455                 try {
 456                         $db = $this->getDB( $serverIndex );
 457                         $db->commit( __METHOD__, 'flush' );
 458                         $db->delete(
 459                                 $tableName,
 460                                 array( 'keyname' => $key ),
 461                                 __METHOD__ );
 462                         $db->commit( __METHOD__, 'flush' );
 463                 } catch ( DBError $e ) {
 464                         $this->handleWriteError( $e, $serverIndex );
 465                         return false;
 466                 }
 467
 468                 return true;
 469         }
 470
 471         /**
 472          * @param string $key
 473          * @param int $step
 474          * @return int|null
 475          */
 476         public function incr( $key, $step = 1 ) {
 477                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 478                 try {
 479                         $db = $this->getDB( $serverIndex );
 480                         $step = intval( $step );
 481                         $db->commit( __METHOD__, 'flush' );
 482                         $row = $db->selectRow(
 483                                 $tableName,
 484                                 array( 'value', 'exptime' ),
 485                                 array( 'keyname' => $key ),
 486                                 __METHOD__,
 487                                 array( 'FOR UPDATE' ) );
 488                         if ( $row === false ) {
 489                                 // Missing
 490                                 $db->commit( __METHOD__, 'flush' );
 491
 492                                 return null;
 493                         }
 494                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 495                         if ( $this->isExpired( $db, $row->exptime ) ) {
 496                                 // Expired, do not reinsert
 497                                 $db->commit( __METHOD__, 'flush' );
 498
 499                                 return null;
 500                         }
 501
 502                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 503                         $newValue = $oldValue + $step;
 504                         $db->insert( $tableName,
 505                                 array(
 506                                         'keyname' => $key,
 507                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 508                                         'exptime' => $row->exptime
 509                                 ), __METHOD__, 'IGNORE' );
 510
 511                         if ( $db->affectedRows() == 0 ) {
 512                                 // Race condition. See bug 28611
 513                                 $newValue = null;
 514                         }
 515                         $db->commit( __METHOD__, 'flush' );
 516                 } catch ( DBError $e ) {
 517                         $this->handleWriteError( $e, $serverIndex );
 518                         return null;
 519                 }
 520
 521                 return $newValue;
 522         }
 523
 524         /**
 525          * @param string $exptime
 526          * @return bool
 527          */
 528         protected function isExpired( $db, $exptime ) {
 529                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 530         }
 531
 532         /**
 533          * @param DatabaseBase $db
 534          * @return string
 535          */
 536         protected function getMaxDateTime( $db ) {
 537                 if ( time() > 0x7fffffff ) {
 538                         return $db->timestamp( 1 << 62 );
 539                 } else {
 540                         return $db->timestamp( 0x7fffffff );
 541                 }
 542         }
 543
 544         protected function garbageCollect() {
 545                 if ( !$this->purgePeriod ) {
 546                         // Disabled
 547                         return;
 548                 }
 549                 // Only purge on one in every $this->purgePeriod requests.
 550                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 551                         return;
 552                 }
 553                 $now = time();
 554                 // Avoid repeating the delete within a few seconds
 555                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 556                         $this->lastExpireAll = $now;
 557                         $this->expireAll();
 558                 }
 559         }
 560
 561         public function expireAll() {
 562                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 563         }
 564
 565         /**
 566          * Delete objects from the database which expire before a certain date.
 567          * @param string $timestamp
 568          * @param bool|callable $progressCallback
 569          * @return bool
 570          */
 571         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 572                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 573                         try {
 574                                 $db = $this->getDB( $serverIndex );
 575                                 $dbTimestamp = $db->timestamp( $timestamp );
 576                                 $totalSeconds = false;
 577                                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 578                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 579                                         $maxExpTime = false;
 580                                         while ( true ) {
 581                                                 $conds = $baseConds;
 582                                                 if ( $maxExpTime !== false ) {
 583                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 584                                                 }
 585                                                 $rows = $db->select(
 586                                                         $this->getTableNameByShard( $i ),
 587                                                         array( 'keyname', 'exptime' ),
 588                                                         $conds,
 589                                                         __METHOD__,
 590                                                         array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 591                                                 if ( !$rows->numRows() ) {
 592                                                         break;
 593                                                 }
 594                                                 $keys = array();
 595                                                 $row = $rows->current();
 596                                                 $minExpTime = $row->exptime;
 597                                                 if ( $totalSeconds === false ) {
 598                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 599                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 600                                                 }
 601                                                 foreach ( $rows as $row ) {
 602                                                         $keys[] = $row->keyname;
 603                                                         $maxExpTime = $row->exptime;
 604                                                 }
 605
 606                                                 $db->commit( __METHOD__, 'flush' );
 607                                                 $db->delete(
 608                                                         $this->getTableNameByShard( $i ),
 609                                                         array(
 610                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 611                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 612                                                                 'keyname' => $keys
 613                                                         ),
 614                                                         __METHOD__ );
 615                                                 $db->commit( __METHOD__, 'flush' );
 616
 617                                                 if ( $progressCallback ) {
 618                                                         if ( intval( $totalSeconds ) === 0 ) {
 619                                                                 $percent = 0;
 620                                                         } else {
 621                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 622                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 623                                                                 if ( $remainingSeconds > $totalSeconds ) {
 624                                                                         $totalSeconds = $remainingSeconds;
 625                                                                 }
 626                                                                 $percent = ( $i + $remainingSeconds / $totalSeconds )
 627                                                                         / $this->shards * 100;
 628                                                         }
 629                                                         $percent = ( $percent / $this->numServers )
 630                                                                 + ( $serverIndex / $this->numServers * 100 );
 631                                                         call_user_func( $progressCallback, $percent );
 632                                                 }
 633                                         }
 634                                 }
 635                         } catch ( DBError $e ) {
 636                                 $this->handleWriteError( $e, $serverIndex );
 637                                 return false;
 638                         }
 639                 }
 640                 return true;
 641         }
 642
 643         public function deleteAll() {
 644                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 645                         try {
 646                                 $db = $this->getDB( $serverIndex );
 647                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 648                                         $db->commit( __METHOD__, 'flush' );
 649                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 650                                         $db->commit( __METHOD__, 'flush' );
 651                                 }
 652                         } catch ( DBError $e ) {
 653                                 $this->handleWriteError( $e, $serverIndex );
 654                                 return false;
 655                         }
 656                 }
 657                 return true;
 658         }
 659
 660         /**
 661          * Serialize an object and, if possible, compress the representation.
 662          * On typical message and page data, this can provide a 3X decrease
 663          * in storage requirements.
 664          *
 665          * @param mixed $data
 666          * @return string
 667          */
 668         protected function serialize( &$data ) {
 669                 $serial = serialize( $data );
 670
 671                 if ( function_exists( 'gzdeflate' ) ) {
 672                         return gzdeflate( $serial );
 673                 } else {
 674                         return $serial;
 675                 }
 676         }
 677
 678         /**
 679          * Unserialize and, if necessary, decompress an object.
 680          * @param string $serial
 681          * @return mixed
 682          */
 683         protected function unserialize( $serial ) {
 684                 if ( function_exists( 'gzinflate' ) ) {
 685                         wfSuppressWarnings();
 686                         $decomp = gzinflate( $serial );
 687                         wfRestoreWarnings();
 688
 689                         if ( false !== $decomp ) {
 690                                 $serial = $decomp;
 691                         }
 692                 }
 693
 694                 $ret = unserialize( $serial );
 695
 696                 return $ret;
 697         }
 698
 699         /**
 700          * Handle a DBError which occurred during a read operation.
 701          *
 702          * @param DBError $exception
 703          * @param int $serverIndex
 704          */
 705         protected function handleReadError( DBError $exception, $serverIndex ) {
 706                 if ( $exception instanceof DBConnectionError ) {
 707                         $this->markServerDown( $exception, $serverIndex );
 708                 }
 709                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 710                 if ( $exception instanceof DBConnectionError ) {
 711                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 712                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 713                 } else {
 714                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 715                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 716                 }
 717         }
 718
 719         /**
 720          * Handle a DBQueryError which occurred during a write operation.
 721          *
 722          * @param DBError $exception
 723          * @param int $serverIndex
 724          */
 725         protected function handleWriteError( DBError $exception, $serverIndex ) {
 726                 if ( $exception instanceof DBConnectionError ) {
 727                         $this->markServerDown( $exception, $serverIndex );
 728                 }
 729                 if ( $exception->db && $exception->db->wasReadOnlyError() ) {
 730                         try {
 731                                 $exception->db->rollback( __METHOD__ );
 732                         } catch ( DBError $e ) {
 733                         }
 734                 }
 735                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 736                 if ( $exception instanceof DBConnectionError ) {
 737                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 738                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 739                 } else {
 740                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 741                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 742                 }
 743         }
 744
 745         /**
 746          * Mark a server down due to a DBConnectionError exception
 747          *
 748          * @param DBError $exception
 749          * @param int $serverIndex
 750          */
 751         protected function markServerDown( $exception, $serverIndex ) {
 752                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 753                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 754                                 unset( $this->connFailureTimes[$serverIndex] );
 755                                 unset( $this->connFailureErrors[$serverIndex] );
 756                         } else {
 757                                 wfDebug( __METHOD__ . ": Server #$serverIndex already down\n" );
 758                                 return;
 759                         }
 760                 }
 761                 $now = time();
 762                 wfDebug( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) . "\n" );
 763                 $this->connFailureTimes[$serverIndex] = $now;
 764                 $this->connFailureErrors[$serverIndex] = $exception;
 765         }
 766
 767         /**
 768          * Create shard tables. For use from eval.php.
 769          */
 770         public function createTables() {
 771                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 772                         $db = $this->getDB( $serverIndex );
 773                         if ( $db->getType() !== 'mysql' ) {
 774                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 775                         }
 776
 777                         for ( $i = 0; $i < $this->shards; $i++ ) {
 778                                 $db->commit( __METHOD__, 'flush' );
 779                                 $db->query(
 780                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 781                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 782                                         __METHOD__ );
 783                                 $db->commit( __METHOD__, 'flush' );
 784                         }
 785                 }
 786         }
 787 }
 788
 789 /**
 790  * Backwards compatibility alias
 791  */
 792 class MediaWikiBagOStuff extends SqlBagOStuff {
 793 }