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