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