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