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 use \MediaWiki\MediaWikiServices;
  25
  26 /**
  27  * Class to store objects in the database
  28  *
  29  * @ingroup Cache
  30  */
  31 class SqlBagOStuff extends BagOStuff {
  32         /** @var array[] (server index => server config) */
  33         protected $serverInfos;
  34         /** @var string[] (server index => tag/host name) */
  35         protected $serverTags;
  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 LoadBalancer|null */
  52         protected $separateMainLB;
  53         /** @var array */
  54         protected $conns;
  55         /** @var array UNIX timestamps */
  56         protected $connFailureTimes = [];
  57         /** @var array Exceptions */
  58         protected $connFailureErrors = [];
  59
  60         /**
  61          * Constructor. Parameters are:
  62          *   - server:      A server info structure in the format required by each
  63          *                  element in $wgDBServers.
  64          *
  65          *   - servers:     An array of server info structures describing a set of database servers
  66          *                  to distribute keys to. If this is specified, the "server" option will be
  67          *                  ignored. If string keys are used, then they will be used for consistent
  68          *                  hashing *instead* of the host name (from the server config). This is useful
  69          *                  when a cluster is replicated to another site (with different host names)
  70          *                  but each server has a corresponding replica in the other cluster.
  71          *
  72          *   - purgePeriod: The average number of object cache requests in between
  73          *                  garbage collection operations, where expired entries
  74          *                  are removed from the database. Or in other words, the
  75          *                  reciprocal of the probability of purging on any given
  76          *                  request. If this is set to zero, purging will never be
  77          *                  done.
  78          *
  79          *   - tableName:   The table name to use, default is "objectcache".
  80          *
  81          *   - shards:      The number of tables to use for data storage on each server.
  82          *                  If this is more than 1, table names will be formed in the style
  83          *                  objectcacheNNN where NNN is the shard index, between 0 and
  84          *                  shards-1. The number of digits will be the minimum number
  85          *                  required to hold the largest shard index. Data will be
  86          *                  distributed across all tables by key hash. This is for
  87          *                  MySQL bugs 61735 and 61736.
  88          *   - slaveOnly:   Whether to only use slave DBs and avoid triggering
  89          *                  garbage collection logic of expired items. This only
  90          *                  makes sense if the primary DB is used and only if get()
  91          *                  calls will be used. This is used by ReplicatedBagOStuff.
  92          *   - syncTimeout: Max seconds to wait for slaves to catch up for WRITE_SYNC.
  93          *
  94          * @param array $params
  95          */
  96         public function __construct( $params ) {
  97                 parent::__construct( $params );
  98
  99                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 100
 101                 if ( isset( $params['servers'] ) ) {
 102                         $this->serverInfos = [];
 103                         $this->serverTags = [];
 104                         $this->numServers = count( $params['servers'] );
 105                         $index = 0;
 106                         foreach ( $params['servers'] as $tag => $info ) {
 107                                 $this->serverInfos[$index] = $info;
 108                                 if ( is_string( $tag ) ) {
 109                                         $this->serverTags[$index] = $tag;
 110                                 } else {
 111                                         $this->serverTags[$index] = isset( $info['host'] ) ? $info['host'] : "#$index";
 112                                 }
 113                                 ++$index;
 114                         }
 115                 } elseif ( isset( $params['server'] ) ) {
 116                         $this->serverInfos = [ $params['server'] ];
 117                         $this->numServers = count( $this->serverInfos );
 118                 } else {
 119                         // Default to using the main wiki's database servers
 120                         $this->serverInfos = false;
 121                         $this->numServers = 1;
 122                 }
 123                 if ( isset( $params['purgePeriod'] ) ) {
 124                         $this->purgePeriod = intval( $params['purgePeriod'] );
 125                 }
 126                 if ( isset( $params['tableName'] ) ) {
 127                         $this->tableName = $params['tableName'];
 128                 }
 129                 if ( isset( $params['shards'] ) ) {
 130                         $this->shards = intval( $params['shards'] );
 131                 }
 132                 if ( isset( $params['syncTimeout'] ) ) {
 133                         $this->syncTimeout = $params['syncTimeout'];
 134                 }
 135                 $this->slaveOnly = !empty( $params['slaveOnly'] );
 136         }
 137
 138         protected function getSeparateMainLB() {
 139                 global $wgDBtype;
 140
 141                 if ( $wgDBtype === 'mysql' && $this->usesMainDB() ) {
 142                         if ( !$this->separateMainLB ) {
 143                                 // We must keep a separate connection to MySQL in order to avoid deadlocks
 144                                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 145                                 $this->separateMainLB = $lbFactory->newMainLB();
 146                         }
 147                         return $this->separateMainLB;
 148                 } else {
 149                         // However, SQLite has an opposite behavior. And PostgreSQL needs to know
 150                         // if we are in transaction or not (@TODO: find some PostgreSQL work-around).
 151                         return null;
 152                 }
 153         }
 154
 155         /**
 156          * Get a connection to the specified database
 157          *
 158          * @param int $serverIndex
 159          * @return IDatabase
 160          * @throws MWException
 161          */
 162         protected function getDB( $serverIndex ) {
 163                 if ( !isset( $this->conns[$serverIndex] ) ) {
 164                         if ( $serverIndex >= $this->numServers ) {
 165                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 166                         }
 167
 168                         # Don't keep timing out trying to connect for each call if the DB is down
 169                         if ( isset( $this->connFailureErrors[$serverIndex] )
 170                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 171                         ) {
 172                                 throw $this->connFailureErrors[$serverIndex];
 173                         }
 174
 175                         # If server connection info was given, use that
 176                         if ( $this->serverInfos ) {
 177                                 $info = $this->serverInfos[$serverIndex];
 178                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 179                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 180                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 181                                 // Use a blank trx profiler to ignore expections as this is a cache
 182                                 $info['trxProfiler'] = new TransactionProfiler();
 183                                 $db = DatabaseBase::factory( $type, $info );
 184                                 $db->clearFlag( DBO_TRX );
 185                         } else {
 186                                 $index = $this->slaveOnly ? DB_SLAVE : DB_MASTER;
 187                                 if ( $this->getSeparateMainLB() ) {
 188                                         $db = $this->getSeparateMainLB()->getConnection( $index );
 189                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 190                                 } else {
 191                                         $db = wfGetDB( $index );
 192                                         // Can't mess with transaction rounds (DBO_TRX) :(
 193                                 }
 194                         }
 195                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 196                         $this->conns[$serverIndex] = $db;
 197                 }
 198
 199                 return $this->conns[$serverIndex];
 200         }
 201
 202         /**
 203          * Get the server index and table name for a given key
 204          * @param string $key
 205          * @return array Server index and table name
 206          */
 207         protected function getTableByKey( $key ) {
 208                 if ( $this->shards > 1 ) {
 209                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 210                         $tableIndex = $hash % $this->shards;
 211                 } else {
 212                         $tableIndex = 0;
 213                 }
 214                 if ( $this->numServers > 1 ) {
 215                         $sortedServers = $this->serverTags;
 216                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 217                         reset( $sortedServers );
 218                         $serverIndex = key( $sortedServers );
 219                 } else {
 220                         $serverIndex = 0;
 221                 }
 222                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 223         }
 224
 225         /**
 226          * Get the table name for a given shard index
 227          * @param int $index
 228          * @return string
 229          */
 230         protected function getTableNameByShard( $index ) {
 231                 if ( $this->shards > 1 ) {
 232                         $decimals = strlen( $this->shards - 1 );
 233                         return $this->tableName .
 234                                 sprintf( "%0{$decimals}d", $index );
 235                 } else {
 236                         return $this->tableName;
 237                 }
 238         }
 239
 240         protected function doGet( $key, $flags = 0 ) {
 241                 $casToken = null;
 242
 243                 return $this->getWithToken( $key, $casToken, $flags );
 244         }
 245
 246         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 247                 $values = $this->getMulti( [ $key ] );
 248                 if ( array_key_exists( $key, $values ) ) {
 249                         $casToken = $values[$key];
 250                         return $values[$key];
 251                 }
 252                 return false;
 253         }
 254
 255         public function getMulti( array $keys, $flags = 0 ) {
 256                 $values = []; // array of (key => value)
 257
 258                 $keysByTable = [];
 259                 foreach ( $keys as $key ) {
 260                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 261                         $keysByTable[$serverIndex][$tableName][] = $key;
 262                 }
 263
 264                 $this->garbageCollect(); // expire old entries if any
 265
 266                 $dataRows = [];
 267                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 268                         try {
 269                                 $db = $this->getDB( $serverIndex );
 270                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 271                                         $res = $db->select( $tableName,
 272                                                 [ 'keyname', 'value', 'exptime' ],
 273                                                 [ 'keyname' => $tableKeys ],
 274                                                 __METHOD__,
 275                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 276                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 277                                                 // We do not want to flush the TRX as that can break callers.
 278                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 279                                         );
 280                                         if ( $res === false ) {
 281                                                 continue;
 282                                         }
 283                                         foreach ( $res as $row ) {
 284                                                 $row->serverIndex = $serverIndex;
 285                                                 $row->tableName = $tableName;
 286                                                 $dataRows[$row->keyname] = $row;
 287                                         }
 288                                 }
 289                         } catch ( DBError $e ) {
 290                                 $this->handleReadError( $e, $serverIndex );
 291                         }
 292                 }
 293
 294                 foreach ( $keys as $key ) {
 295                         if ( isset( $dataRows[$key] ) ) { // HIT?
 296                                 $row = $dataRows[$key];
 297                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 298                                 $db = null;
 299                                 try {
 300                                         $db = $this->getDB( $row->serverIndex );
 301                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 302                                                 $this->debug( "get: key has expired" );
 303                                         } else { // HIT
 304                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 305                                         }
 306                                 } catch ( DBQueryError $e ) {
 307                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 308                                 }
 309                         } else { // MISS
 310                                 $this->debug( 'get: no matching rows' );
 311                         }
 312                 }
 313
 314                 return $values;
 315         }
 316
 317         public function setMulti( array $data, $expiry = 0 ) {
 318                 $keysByTable = [];
 319                 foreach ( $data as $key => $value ) {
 320                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 321                         $keysByTable[$serverIndex][$tableName][] = $key;
 322                 }
 323
 324                 $this->garbageCollect(); // expire old entries if any
 325
 326                 $result = true;
 327                 $exptime = (int)$expiry;
 328                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 329                         $db = null;
 330                         try {
 331                                 $db = $this->getDB( $serverIndex );
 332                         } catch ( DBError $e ) {
 333                                 $this->handleWriteError( $e, $db, $serverIndex );
 334                                 $result = false;
 335                                 continue;
 336                         }
 337
 338                         if ( $exptime < 0 ) {
 339                                 $exptime = 0;
 340                         }
 341
 342                         if ( $exptime == 0 ) {
 343                                 $encExpiry = $this->getMaxDateTime( $db );
 344                         } else {
 345                                 $exptime = $this->convertExpiry( $exptime );
 346                                 $encExpiry = $db->timestamp( $exptime );
 347                         }
 348                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 349                                 $rows = [];
 350                                 foreach ( $tableKeys as $key ) {
 351                                         $rows[] = [
 352                                                 'keyname' => $key,
 353                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 354                                                 'exptime' => $encExpiry,
 355                                         ];
 356                                 }
 357
 358                                 try {
 359                                         $db->replace(
 360                                                 $tableName,
 361                                                 [ 'keyname' ],
 362                                                 $rows,
 363                                                 __METHOD__
 364                                         );
 365                                 } catch ( DBError $e ) {
 366                                         $this->handleWriteError( $e, $db, $serverIndex );
 367                                         $result = false;
 368                                 }
 369
 370                         }
 371
 372                 }
 373
 374                 return $result;
 375         }
 376
 377         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 378                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 379                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 380                         $ok = $ok && $this->waitForSlaves();
 381                 }
 382
 383                 return $ok;
 384         }
 385
 386         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 387                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 388                 $db = null;
 389                 try {
 390                         $db = $this->getDB( $serverIndex );
 391                         $exptime = intval( $exptime );
 392
 393                         if ( $exptime < 0 ) {
 394                                 $exptime = 0;
 395                         }
 396
 397                         if ( $exptime == 0 ) {
 398                                 $encExpiry = $this->getMaxDateTime( $db );
 399                         } else {
 400                                 $exptime = $this->convertExpiry( $exptime );
 401                                 $encExpiry = $db->timestamp( $exptime );
 402                         }
 403                         // (bug 24425) use a replace if the db supports it instead of
 404                         // delete/insert to avoid clashes with conflicting keynames
 405                         $db->update(
 406                                 $tableName,
 407                                 [
 408                                         'keyname' => $key,
 409                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 410                                         'exptime' => $encExpiry
 411                                 ],
 412                                 [
 413                                         'keyname' => $key,
 414                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 415                                 ],
 416                                 __METHOD__
 417                         );
 418                 } catch ( DBQueryError $e ) {
 419                         $this->handleWriteError( $e, $db, $serverIndex );
 420
 421                         return false;
 422                 }
 423
 424                 return (bool)$db->affectedRows();
 425         }
 426
 427         public function delete( $key ) {
 428                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 429                 $db = null;
 430                 try {
 431                         $db = $this->getDB( $serverIndex );
 432                         $db->delete(
 433                                 $tableName,
 434                                 [ 'keyname' => $key ],
 435                                 __METHOD__ );
 436                 } catch ( DBError $e ) {
 437                         $this->handleWriteError( $e, $db, $serverIndex );
 438                         return false;
 439                 }
 440
 441                 return true;
 442         }
 443
 444         public function incr( $key, $step = 1 ) {
 445                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 446                 $db = null;
 447                 try {
 448                         $db = $this->getDB( $serverIndex );
 449                         $step = intval( $step );
 450                         $row = $db->selectRow(
 451                                 $tableName,
 452                                 [ 'value', 'exptime' ],
 453                                 [ 'keyname' => $key ],
 454                                 __METHOD__,
 455                                 [ 'FOR UPDATE' ] );
 456                         if ( $row === false ) {
 457                                 // Missing
 458
 459                                 return null;
 460                         }
 461                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 462                         if ( $this->isExpired( $db, $row->exptime ) ) {
 463                                 // Expired, do not reinsert
 464
 465                                 return null;
 466                         }
 467
 468                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 469                         $newValue = $oldValue + $step;
 470                         $db->insert( $tableName,
 471                                 [
 472                                         'keyname' => $key,
 473                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 474                                         'exptime' => $row->exptime
 475                                 ], __METHOD__, 'IGNORE' );
 476
 477                         if ( $db->affectedRows() == 0 ) {
 478                                 // Race condition. See bug 28611
 479                                 $newValue = null;
 480                         }
 481                 } catch ( DBError $e ) {
 482                         $this->handleWriteError( $e, $db, $serverIndex );
 483                         return null;
 484                 }
 485
 486                 return $newValue;
 487         }
 488
 489         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 490                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 491                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 492                         $ok = $ok && $this->waitForSlaves();
 493                 }
 494
 495                 return $ok;
 496         }
 497
 498         public function changeTTL( $key, $expiry = 0 ) {
 499                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 500                 $db = null;
 501                 try {
 502                         $db = $this->getDB( $serverIndex );
 503                         $db->update(
 504                                 $tableName,
 505                                 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
 506                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 507                                 __METHOD__
 508                         );
 509                         if ( $db->affectedRows() == 0 ) {
 510                                 return false;
 511                         }
 512                 } catch ( DBError $e ) {
 513                         $this->handleWriteError( $e, $db, $serverIndex );
 514                         return false;
 515                 }
 516
 517                 return true;
 518         }
 519
 520         /**
 521          * @param IDatabase $db
 522          * @param string $exptime
 523          * @return bool
 524          */
 525         protected function isExpired( $db, $exptime ) {
 526                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 527         }
 528
 529         /**
 530          * @param IDatabase $db
 531          * @return string
 532          */
 533         protected function getMaxDateTime( $db ) {
 534                 if ( time() > 0x7fffffff ) {
 535                         return $db->timestamp( 1 << 62 );
 536                 } else {
 537                         return $db->timestamp( 0x7fffffff );
 538                 }
 539         }
 540
 541         protected function garbageCollect() {
 542                 if ( !$this->purgePeriod || $this->slaveOnly ) {
 543                         // Disabled
 544                         return;
 545                 }
 546                 // Only purge on one in every $this->purgePeriod requests.
 547                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 548                         return;
 549                 }
 550                 $now = time();
 551                 // Avoid repeating the delete within a few seconds
 552                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 553                         $this->lastExpireAll = $now;
 554                         $this->expireAll();
 555                 }
 556         }
 557
 558         public function expireAll() {
 559                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 560         }
 561
 562         /**
 563          * Delete objects from the database which expire before a certain date.
 564          * @param string $timestamp
 565          * @param bool|callable $progressCallback
 566          * @return bool
 567          */
 568         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 569                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 570                         $db = null;
 571                         try {
 572                                 $db = $this->getDB( $serverIndex );
 573                                 $dbTimestamp = $db->timestamp( $timestamp );
 574                                 $totalSeconds = false;
 575                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 576                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 577                                         $maxExpTime = false;
 578                                         while ( true ) {
 579                                                 $conds = $baseConds;
 580                                                 if ( $maxExpTime !== false ) {
 581                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 582                                                 }
 583                                                 $rows = $db->select(
 584                                                         $this->getTableNameByShard( $i ),
 585                                                         [ 'keyname', 'exptime' ],
 586                                                         $conds,
 587                                                         __METHOD__,
 588                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 589                                                 if ( $rows === false || !$rows->numRows() ) {
 590                                                         break;
 591                                                 }
 592                                                 $keys = [];
 593                                                 $row = $rows->current();
 594                                                 $minExpTime = $row->exptime;
 595                                                 if ( $totalSeconds === false ) {
 596                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 597                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 598                                                 }
 599                                                 foreach ( $rows as $row ) {
 600                                                         $keys[] = $row->keyname;
 601                                                         $maxExpTime = $row->exptime;
 602                                                 }
 603
 604                                                 $db->delete(
 605                                                         $this->getTableNameByShard( $i ),
 606                                                         [
 607                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 608                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 609                                                                 'keyname' => $keys
 610                                                         ],
 611                                                         __METHOD__ );
 612
 613                                                 if ( $progressCallback ) {
 614                                                         if ( intval( $totalSeconds ) === 0 ) {
 615                                                                 $percent = 0;
 616                                                         } else {
 617                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 618                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 619                                                                 if ( $remainingSeconds > $totalSeconds ) {
 620                                                                         $totalSeconds = $remainingSeconds;
 621                                                                 }
 622                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 623                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 624                                                                         / $this->shards * 100;
 625                                                         }
 626                                                         $percent = ( $percent / $this->numServers )
 627                                                                 + ( $serverIndex / $this->numServers * 100 );
 628                                                         call_user_func( $progressCallback, $percent );
 629                                                 }
 630                                         }
 631                                 }
 632                         } catch ( DBError $e ) {
 633                                 $this->handleWriteError( $e, $db, $serverIndex );
 634                                 return false;
 635                         }
 636                 }
 637                 return true;
 638         }
 639
 640         /**
 641          * Delete content of shard tables in every server.
 642          * Return true if the operation is successful, false otherwise.
 643          * @return bool
 644          */
 645         public function deleteAll() {
 646                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 647                         $db = null;
 648                         try {
 649                                 $db = $this->getDB( $serverIndex );
 650                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 651                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 652                                 }
 653                         } catch ( DBError $e ) {
 654                                 $this->handleWriteError( $e, $db, $serverIndex );
 655                                 return false;
 656                         }
 657                 }
 658                 return true;
 659         }
 660
 661         /**
 662          * Serialize an object and, if possible, compress the representation.
 663          * On typical message and page data, this can provide a 3X decrease
 664          * in storage requirements.
 665          *
 666          * @param mixed $data
 667          * @return string
 668          */
 669         protected function serialize( &$data ) {
 670                 $serial = serialize( $data );
 671
 672                 if ( function_exists( 'gzdeflate' ) ) {
 673                         return gzdeflate( $serial );
 674                 } else {
 675                         return $serial;
 676                 }
 677         }
 678
 679         /**
 680          * Unserialize and, if necessary, decompress an object.
 681          * @param string $serial
 682          * @return mixed
 683          */
 684         protected function unserialize( $serial ) {
 685                 if ( function_exists( 'gzinflate' ) ) {
 686                         MediaWiki\suppressWarnings();
 687                         $decomp = gzinflate( $serial );
 688                         MediaWiki\restoreWarnings();
 689
 690                         if ( false !== $decomp ) {
 691                                 $serial = $decomp;
 692                         }
 693                 }
 694
 695                 $ret = unserialize( $serial );
 696
 697                 return $ret;
 698         }
 699
 700         /**
 701          * Handle a DBError which occurred during a read operation.
 702          *
 703          * @param DBError $exception
 704          * @param int $serverIndex
 705          */
 706         protected function handleReadError( DBError $exception, $serverIndex ) {
 707                 if ( $exception instanceof DBConnectionError ) {
 708                         $this->markServerDown( $exception, $serverIndex );
 709                 }
 710                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 711                 if ( $exception instanceof DBConnectionError ) {
 712                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 713                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 714                 } else {
 715                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 716                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 717                 }
 718         }
 719
 720         /**
 721          * Handle a DBQueryError which occurred during a write operation.
 722          *
 723          * @param DBError $exception
 724          * @param IDatabase|null $db DB handle or null if connection failed
 725          * @param int $serverIndex
 726          * @throws Exception
 727          */
 728         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 729                 if ( !$db ) {
 730                         $this->markServerDown( $exception, $serverIndex );
 731                 } elseif ( $db->wasReadOnlyError() ) {
 732                         if ( $db->trxLevel() && $this->usesMainDB() ) {
 733                                 // Errors like deadlocks and connection drops already cause rollback.
 734                                 // For consistency, we have no choice but to throw an error and trigger
 735                                 // complete rollback if the main DB is also being used as the cache DB.
 736                                 throw $exception;
 737                         }
 738                 }
 739
 740                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 741                 if ( $exception instanceof DBConnectionError ) {
 742                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 743                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 744                 } else {
 745                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 746                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 747                 }
 748         }
 749
 750         /**
 751          * Mark a server down due to a DBConnectionError exception
 752          *
 753          * @param DBError $exception
 754          * @param int $serverIndex
 755          */
 756         protected function markServerDown( DBError $exception, $serverIndex ) {
 757                 unset( $this->conns[$serverIndex] ); // bug T103435
 758
 759                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 760                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 761                                 unset( $this->connFailureTimes[$serverIndex] );
 762                                 unset( $this->connFailureErrors[$serverIndex] );
 763                         } else {
 764                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 765                                 return;
 766                         }
 767                 }
 768                 $now = time();
 769                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 770                 $this->connFailureTimes[$serverIndex] = $now;
 771                 $this->connFailureErrors[$serverIndex] = $exception;
 772         }
 773
 774         /**
 775          * Create shard tables. For use from eval.php.
 776          */
 777         public function createTables() {
 778                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 779                         $db = $this->getDB( $serverIndex );
 780                         if ( $db->getType() !== 'mysql' ) {
 781                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 782                         }
 783
 784                         for ( $i = 0; $i < $this->shards; $i++ ) {
 785                                 $db->query(
 786                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 787                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 788                                         __METHOD__ );
 789                         }
 790                 }
 791         }
 792
 793         /**
 794          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 795          */
 796         protected function usesMainDB() {
 797                 return !$this->serverInfos;
 798         }
 799
 800         protected function waitForSlaves() {
 801                 if ( $this->usesMainDB() ) {
 802                         $lb = $this->getSeparateMainLB()
 803                                 ?: MediaWikiServices::getInstance()->getDBLoadBalancer();
 804                         // Return if there are no slaves
 805                         if ( $lb->getServerCount() <= 1 ) {
 806                                 return true;
 807                         }
 808                         // Main LB is used; wait for any slaves to catch up
 809                         try {
 810                                 $pos = $lb->getMasterPos();
 811                                 if ( $pos ) {
 812                                         return $lb->waitForAll( $pos, 3 );
 813                                 }
 814                         } catch ( DBReplicationWaitError $e ) {
 815                                 return false;
 816                         }
 817                 }
 818
 819                 // Custom DB server list; probably doesn't use replication
 820                 return true;
 821         }
 822 }