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 $replicaOnly = 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 replica 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 replica DBs 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                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 101
 102                 if ( isset( $params['servers'] ) ) {
 103                         $this->serverInfos = [];
 104                         $this->serverTags = [];
 105                         $this->numServers = count( $params['servers'] );
 106                         $index = 0;
 107                         foreach ( $params['servers'] as $tag => $info ) {
 108                                 $this->serverInfos[$index] = $info;
 109                                 if ( is_string( $tag ) ) {
 110                                         $this->serverTags[$index] = $tag;
 111                                 } else {
 112                                         $this->serverTags[$index] = isset( $info['host'] ) ? $info['host'] : "#$index";
 113                                 }
 114                                 ++$index;
 115                         }
 116                 } elseif ( isset( $params['server'] ) ) {
 117                         $this->serverInfos = [ $params['server'] ];
 118                         $this->numServers = count( $this->serverInfos );
 119                 } else {
 120                         // Default to using the main wiki's database servers
 121                         $this->serverInfos = false;
 122                         $this->numServers = 1;
 123                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 124                 }
 125                 if ( isset( $params['purgePeriod'] ) ) {
 126                         $this->purgePeriod = intval( $params['purgePeriod'] );
 127                 }
 128                 if ( isset( $params['tableName'] ) ) {
 129                         $this->tableName = $params['tableName'];
 130                 }
 131                 if ( isset( $params['shards'] ) ) {
 132                         $this->shards = intval( $params['shards'] );
 133                 }
 134                 if ( isset( $params['syncTimeout'] ) ) {
 135                         $this->syncTimeout = $params['syncTimeout'];
 136                 }
 137                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 138         }
 139
 140         protected function getSeparateMainLB() {
 141                 global $wgDBtype;
 142
 143                 if ( $wgDBtype === 'mysql' && $this->usesMainDB() ) {
 144                         if ( !$this->separateMainLB ) {
 145                                 // We must keep a separate connection to MySQL in order to avoid deadlocks
 146                                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 147                                 $this->separateMainLB = $lbFactory->newMainLB();
 148                         }
 149                         return $this->separateMainLB;
 150                 } else {
 151                         // However, SQLite has an opposite behavior. And PostgreSQL needs to know
 152                         // if we are in transaction or not (@TODO: find some PostgreSQL work-around).
 153                         return null;
 154                 }
 155         }
 156
 157         /**
 158          * Get a connection to the specified database
 159          *
 160          * @param int $serverIndex
 161          * @return IDatabase
 162          * @throws MWException
 163          */
 164         protected function getDB( $serverIndex ) {
 165                 if ( !isset( $this->conns[$serverIndex] ) ) {
 166                         if ( $serverIndex >= $this->numServers ) {
 167                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 168                         }
 169
 170                         # Don't keep timing out trying to connect for each call if the DB is down
 171                         if ( isset( $this->connFailureErrors[$serverIndex] )
 172                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 173                         ) {
 174                                 throw $this->connFailureErrors[$serverIndex];
 175                         }
 176
 177                         # If server connection info was given, use that
 178                         if ( $this->serverInfos ) {
 179                                 $info = $this->serverInfos[$serverIndex];
 180                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 181                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 182                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 183                                 // Use a blank trx profiler to ignore expections as this is a cache
 184                                 $info['trxProfiler'] = new TransactionProfiler();
 185                                 $db = Database::factory( $type, $info );
 186                                 $db->clearFlag( DBO_TRX );
 187                         } else {
 188                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 189                                 if ( $this->getSeparateMainLB() ) {
 190                                         $db = $this->getSeparateMainLB()->getConnection( $index );
 191                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 192                                 } else {
 193                                         $db = wfGetDB( $index );
 194                                         // Can't mess with transaction rounds (DBO_TRX) :(
 195                                 }
 196                         }
 197                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 198                         $this->conns[$serverIndex] = $db;
 199                 }
 200
 201                 return $this->conns[$serverIndex];
 202         }
 203
 204         /**
 205          * Get the server index and table name for a given key
 206          * @param string $key
 207          * @return array Server index and table name
 208          */
 209         protected function getTableByKey( $key ) {
 210                 if ( $this->shards > 1 ) {
 211                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 212                         $tableIndex = $hash % $this->shards;
 213                 } else {
 214                         $tableIndex = 0;
 215                 }
 216                 if ( $this->numServers > 1 ) {
 217                         $sortedServers = $this->serverTags;
 218                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 219                         reset( $sortedServers );
 220                         $serverIndex = key( $sortedServers );
 221                 } else {
 222                         $serverIndex = 0;
 223                 }
 224                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 225         }
 226
 227         /**
 228          * Get the table name for a given shard index
 229          * @param int $index
 230          * @return string
 231          */
 232         protected function getTableNameByShard( $index ) {
 233                 if ( $this->shards > 1 ) {
 234                         $decimals = strlen( $this->shards - 1 );
 235                         return $this->tableName .
 236                                 sprintf( "%0{$decimals}d", $index );
 237                 } else {
 238                         return $this->tableName;
 239                 }
 240         }
 241
 242         protected function doGet( $key, $flags = 0 ) {
 243                 $casToken = null;
 244
 245                 return $this->getWithToken( $key, $casToken, $flags );
 246         }
 247
 248         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 249                 $values = $this->getMulti( [ $key ] );
 250                 if ( array_key_exists( $key, $values ) ) {
 251                         $casToken = $values[$key];
 252                         return $values[$key];
 253                 }
 254                 return false;
 255         }
 256
 257         public function getMulti( array $keys, $flags = 0 ) {
 258                 $values = []; // array of (key => value)
 259
 260                 $keysByTable = [];
 261                 foreach ( $keys as $key ) {
 262                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 263                         $keysByTable[$serverIndex][$tableName][] = $key;
 264                 }
 265
 266                 $this->garbageCollect(); // expire old entries if any
 267
 268                 $dataRows = [];
 269                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 270                         try {
 271                                 $db = $this->getDB( $serverIndex );
 272                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 273                                         $res = $db->select( $tableName,
 274                                                 [ 'keyname', 'value', 'exptime' ],
 275                                                 [ 'keyname' => $tableKeys ],
 276                                                 __METHOD__,
 277                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 278                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 279                                                 // We do not want to flush the TRX as that can break callers.
 280                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 281                                         );
 282                                         if ( $res === false ) {
 283                                                 continue;
 284                                         }
 285                                         foreach ( $res as $row ) {
 286                                                 $row->serverIndex = $serverIndex;
 287                                                 $row->tableName = $tableName;
 288                                                 $dataRows[$row->keyname] = $row;
 289                                         }
 290                                 }
 291                         } catch ( DBError $e ) {
 292                                 $this->handleReadError( $e, $serverIndex );
 293                         }
 294                 }
 295
 296                 foreach ( $keys as $key ) {
 297                         if ( isset( $dataRows[$key] ) ) { // HIT?
 298                                 $row = $dataRows[$key];
 299                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 300                                 $db = null;
 301                                 try {
 302                                         $db = $this->getDB( $row->serverIndex );
 303                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 304                                                 $this->debug( "get: key has expired" );
 305                                         } else { // HIT
 306                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 307                                         }
 308                                 } catch ( DBQueryError $e ) {
 309                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 310                                 }
 311                         } else { // MISS
 312                                 $this->debug( 'get: no matching rows' );
 313                         }
 314                 }
 315
 316                 return $values;
 317         }
 318
 319         public function setMulti( array $data, $expiry = 0 ) {
 320                 $keysByTable = [];
 321                 foreach ( $data as $key => $value ) {
 322                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 323                         $keysByTable[$serverIndex][$tableName][] = $key;
 324                 }
 325
 326                 $this->garbageCollect(); // expire old entries if any
 327
 328                 $result = true;
 329                 $exptime = (int)$expiry;
 330                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 331                         $db = null;
 332                         try {
 333                                 $db = $this->getDB( $serverIndex );
 334                         } catch ( DBError $e ) {
 335                                 $this->handleWriteError( $e, $db, $serverIndex );
 336                                 $result = false;
 337                                 continue;
 338                         }
 339
 340                         if ( $exptime < 0 ) {
 341                                 $exptime = 0;
 342                         }
 343
 344                         if ( $exptime == 0 ) {
 345                                 $encExpiry = $this->getMaxDateTime( $db );
 346                         } else {
 347                                 $exptime = $this->convertExpiry( $exptime );
 348                                 $encExpiry = $db->timestamp( $exptime );
 349                         }
 350                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 351                                 $rows = [];
 352                                 foreach ( $tableKeys as $key ) {
 353                                         $rows[] = [
 354                                                 'keyname' => $key,
 355                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 356                                                 'exptime' => $encExpiry,
 357                                         ];
 358                                 }
 359
 360                                 try {
 361                                         $db->replace(
 362                                                 $tableName,
 363                                                 [ 'keyname' ],
 364                                                 $rows,
 365                                                 __METHOD__
 366                                         );
 367                                 } catch ( DBError $e ) {
 368                                         $this->handleWriteError( $e, $db, $serverIndex );
 369                                         $result = false;
 370                                 }
 371
 372                         }
 373
 374                 }
 375
 376                 return $result;
 377         }
 378
 379         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 380                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 381                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 382                         $ok = $this->waitForReplication() && $ok;
 383                 }
 384
 385                 return $ok;
 386         }
 387
 388         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 389                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 390                 $db = null;
 391                 try {
 392                         $db = $this->getDB( $serverIndex );
 393                         $exptime = intval( $exptime );
 394
 395                         if ( $exptime < 0 ) {
 396                                 $exptime = 0;
 397                         }
 398
 399                         if ( $exptime == 0 ) {
 400                                 $encExpiry = $this->getMaxDateTime( $db );
 401                         } else {
 402                                 $exptime = $this->convertExpiry( $exptime );
 403                                 $encExpiry = $db->timestamp( $exptime );
 404                         }
 405                         // (bug 24425) use a replace if the db supports it instead of
 406                         // delete/insert to avoid clashes with conflicting keynames
 407                         $db->update(
 408                                 $tableName,
 409                                 [
 410                                         'keyname' => $key,
 411                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 412                                         'exptime' => $encExpiry
 413                                 ],
 414                                 [
 415                                         'keyname' => $key,
 416                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 417                                 ],
 418                                 __METHOD__
 419                         );
 420                 } catch ( DBQueryError $e ) {
 421                         $this->handleWriteError( $e, $db, $serverIndex );
 422
 423                         return false;
 424                 }
 425
 426                 return (bool)$db->affectedRows();
 427         }
 428
 429         public function delete( $key ) {
 430                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 431                 $db = null;
 432                 try {
 433                         $db = $this->getDB( $serverIndex );
 434                         $db->delete(
 435                                 $tableName,
 436                                 [ 'keyname' => $key ],
 437                                 __METHOD__ );
 438                 } catch ( DBError $e ) {
 439                         $this->handleWriteError( $e, $db, $serverIndex );
 440                         return false;
 441                 }
 442
 443                 return true;
 444         }
 445
 446         public function incr( $key, $step = 1 ) {
 447                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 448                 $db = null;
 449                 try {
 450                         $db = $this->getDB( $serverIndex );
 451                         $step = intval( $step );
 452                         $row = $db->selectRow(
 453                                 $tableName,
 454                                 [ 'value', 'exptime' ],
 455                                 [ 'keyname' => $key ],
 456                                 __METHOD__,
 457                                 [ 'FOR UPDATE' ] );
 458                         if ( $row === false ) {
 459                                 // Missing
 460
 461                                 return null;
 462                         }
 463                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 464                         if ( $this->isExpired( $db, $row->exptime ) ) {
 465                                 // Expired, do not reinsert
 466
 467                                 return null;
 468                         }
 469
 470                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 471                         $newValue = $oldValue + $step;
 472                         $db->insert( $tableName,
 473                                 [
 474                                         'keyname' => $key,
 475                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 476                                         'exptime' => $row->exptime
 477                                 ], __METHOD__, 'IGNORE' );
 478
 479                         if ( $db->affectedRows() == 0 ) {
 480                                 // Race condition. See bug 28611
 481                                 $newValue = null;
 482                         }
 483                 } catch ( DBError $e ) {
 484                         $this->handleWriteError( $e, $db, $serverIndex );
 485                         return null;
 486                 }
 487
 488                 return $newValue;
 489         }
 490
 491         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 492                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 493                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 494                         $ok = $this->waitForReplication() && $ok;
 495                 }
 496
 497                 return $ok;
 498         }
 499
 500         public function changeTTL( $key, $expiry = 0 ) {
 501                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 502                 $db = null;
 503                 try {
 504                         $db = $this->getDB( $serverIndex );
 505                         $db->update(
 506                                 $tableName,
 507                                 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
 508                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 509                                 __METHOD__
 510                         );
 511                         if ( $db->affectedRows() == 0 ) {
 512                                 return false;
 513                         }
 514                 } catch ( DBError $e ) {
 515                         $this->handleWriteError( $e, $db, $serverIndex );
 516                         return false;
 517                 }
 518
 519                 return true;
 520         }
 521
 522         /**
 523          * @param IDatabase $db
 524          * @param string $exptime
 525          * @return bool
 526          */
 527         protected function isExpired( $db, $exptime ) {
 528                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 529         }
 530
 531         /**
 532          * @param IDatabase $db
 533          * @return string
 534          */
 535         protected function getMaxDateTime( $db ) {
 536                 if ( time() > 0x7fffffff ) {
 537                         return $db->timestamp( 1 << 62 );
 538                 } else {
 539                         return $db->timestamp( 0x7fffffff );
 540                 }
 541         }
 542
 543         protected function garbageCollect() {
 544                 if ( !$this->purgePeriod || $this->replicaOnly ) {
 545                         // Disabled
 546                         return;
 547                 }
 548                 // Only purge on one in every $this->purgePeriod requests.
 549                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 550                         return;
 551                 }
 552                 $now = time();
 553                 // Avoid repeating the delete within a few seconds
 554                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 555                         $this->lastExpireAll = $now;
 556                         $this->expireAll();
 557                 }
 558         }
 559
 560         public function expireAll() {
 561                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 562         }
 563
 564         /**
 565          * Delete objects from the database which expire before a certain date.
 566          * @param string $timestamp
 567          * @param bool|callable $progressCallback
 568          * @return bool
 569          */
 570         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 571                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 572                         $db = null;
 573                         try {
 574                                 $db = $this->getDB( $serverIndex );
 575                                 $dbTimestamp = $db->timestamp( $timestamp );
 576                                 $totalSeconds = false;
 577                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 578                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 579                                         $maxExpTime = false;
 580                                         while ( true ) {
 581                                                 $conds = $baseConds;
 582                                                 if ( $maxExpTime !== false ) {
 583                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 584                                                 }
 585                                                 $rows = $db->select(
 586                                                         $this->getTableNameByShard( $i ),
 587                                                         [ 'keyname', 'exptime' ],
 588                                                         $conds,
 589                                                         __METHOD__,
 590                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 591                                                 if ( $rows === false || !$rows->numRows() ) {
 592                                                         break;
 593                                                 }
 594                                                 $keys = [];
 595                                                 $row = $rows->current();
 596                                                 $minExpTime = $row->exptime;
 597                                                 if ( $totalSeconds === false ) {
 598                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 599                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 600                                                 }
 601                                                 foreach ( $rows as $row ) {
 602                                                         $keys[] = $row->keyname;
 603                                                         $maxExpTime = $row->exptime;
 604                                                 }
 605
 606                                                 $db->delete(
 607                                                         $this->getTableNameByShard( $i ),
 608                                                         [
 609                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 610                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 611                                                                 'keyname' => $keys
 612                                                         ],
 613                                                         __METHOD__ );
 614
 615                                                 if ( $progressCallback ) {
 616                                                         if ( intval( $totalSeconds ) === 0 ) {
 617                                                                 $percent = 0;
 618                                                         } else {
 619                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 620                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 621                                                                 if ( $remainingSeconds > $totalSeconds ) {
 622                                                                         $totalSeconds = $remainingSeconds;
 623                                                                 }
 624                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 625                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 626                                                                         / $this->shards * 100;
 627                                                         }
 628                                                         $percent = ( $percent / $this->numServers )
 629                                                                 + ( $serverIndex / $this->numServers * 100 );
 630                                                         call_user_func( $progressCallback, $percent );
 631                                                 }
 632                                         }
 633                                 }
 634                         } catch ( DBError $e ) {
 635                                 $this->handleWriteError( $e, $db, $serverIndex );
 636                                 return false;
 637                         }
 638                 }
 639                 return true;
 640         }
 641
 642         /**
 643          * Delete content of shard tables in every server.
 644          * Return true if the operation is successful, false otherwise.
 645          * @return bool
 646          */
 647         public function deleteAll() {
 648                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 649                         $db = null;
 650                         try {
 651                                 $db = $this->getDB( $serverIndex );
 652                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 653                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 654                                 }
 655                         } catch ( DBError $e ) {
 656                                 $this->handleWriteError( $e, $db, $serverIndex );
 657                                 return false;
 658                         }
 659                 }
 660                 return true;
 661         }
 662
 663         /**
 664          * Serialize an object and, if possible, compress the representation.
 665          * On typical message and page data, this can provide a 3X decrease
 666          * in storage requirements.
 667          *
 668          * @param mixed $data
 669          * @return string
 670          */
 671         protected function serialize( &$data ) {
 672                 $serial = serialize( $data );
 673
 674                 if ( function_exists( 'gzdeflate' ) ) {
 675                         return gzdeflate( $serial );
 676                 } else {
 677                         return $serial;
 678                 }
 679         }
 680
 681         /**
 682          * Unserialize and, if necessary, decompress an object.
 683          * @param string $serial
 684          * @return mixed
 685          */
 686         protected function unserialize( $serial ) {
 687                 if ( function_exists( 'gzinflate' ) ) {
 688                         MediaWiki\suppressWarnings();
 689                         $decomp = gzinflate( $serial );
 690                         MediaWiki\restoreWarnings();
 691
 692                         if ( false !== $decomp ) {
 693                                 $serial = $decomp;
 694                         }
 695                 }
 696
 697                 $ret = unserialize( $serial );
 698
 699                 return $ret;
 700         }
 701
 702         /**
 703          * Handle a DBError which occurred during a read operation.
 704          *
 705          * @param DBError $exception
 706          * @param int $serverIndex
 707          */
 708         protected function handleReadError( DBError $exception, $serverIndex ) {
 709                 if ( $exception instanceof DBConnectionError ) {
 710                         $this->markServerDown( $exception, $serverIndex );
 711                 }
 712                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 713                 if ( $exception instanceof DBConnectionError ) {
 714                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 715                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 716                 } else {
 717                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 718                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 719                 }
 720         }
 721
 722         /**
 723          * Handle a DBQueryError which occurred during a write operation.
 724          *
 725          * @param DBError $exception
 726          * @param IDatabase|null $db DB handle or null if connection failed
 727          * @param int $serverIndex
 728          * @throws Exception
 729          */
 730         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 731                 if ( !$db ) {
 732                         $this->markServerDown( $exception, $serverIndex );
 733                 } elseif ( $db->wasReadOnlyError() ) {
 734                         if ( $db->trxLevel() && $this->usesMainDB() ) {
 735                                 // Errors like deadlocks and connection drops already cause rollback.
 736                                 // For consistency, we have no choice but to throw an error and trigger
 737                                 // complete rollback if the main DB is also being used as the cache DB.
 738                                 throw $exception;
 739                         }
 740                 }
 741
 742                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 743                 if ( $exception instanceof DBConnectionError ) {
 744                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 745                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 746                 } else {
 747                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 748                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 749                 }
 750         }
 751
 752         /**
 753          * Mark a server down due to a DBConnectionError exception
 754          *
 755          * @param DBError $exception
 756          * @param int $serverIndex
 757          */
 758         protected function markServerDown( DBError $exception, $serverIndex ) {
 759                 unset( $this->conns[$serverIndex] ); // bug T103435
 760
 761                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 762                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 763                                 unset( $this->connFailureTimes[$serverIndex] );
 764                                 unset( $this->connFailureErrors[$serverIndex] );
 765                         } else {
 766                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 767                                 return;
 768                         }
 769                 }
 770                 $now = time();
 771                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 772                 $this->connFailureTimes[$serverIndex] = $now;
 773                 $this->connFailureErrors[$serverIndex] = $exception;
 774         }
 775
 776         /**
 777          * Create shard tables. For use from eval.php.
 778          */
 779         public function createTables() {
 780                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 781                         $db = $this->getDB( $serverIndex );
 782                         if ( $db->getType() !== 'mysql' ) {
 783                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 784                         }
 785
 786                         for ( $i = 0; $i < $this->shards; $i++ ) {
 787                                 $db->query(
 788                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 789                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 790                                         __METHOD__ );
 791                         }
 792                 }
 793         }
 794
 795         /**
 796          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 797          */
 798         protected function usesMainDB() {
 799                 return !$this->serverInfos;
 800         }
 801
 802         protected function waitForReplication() {
 803                 if ( !$this->usesMainDB() ) {
 804                         // Custom DB server list; probably doesn't use replication
 805                         return true;
 806                 }
 807
 808                 $lb = $this->getSeparateMainLB()
 809                         ?: MediaWikiServices::getInstance()->getDBLoadBalancer();
 810
 811                 if ( $lb->getServerCount() <= 1 ) {
 812                         return true; // no replica DBs
 813                 }
 814
 815                 // Main LB is used; wait for any replica DBs to catch up
 816                 $masterPos = $lb->getMasterPos();
 817
 818                 $loop = new WaitConditionLoop(
 819                         function () use ( $lb, $masterPos ) {
 820                                 return $lb->waitForAll( $masterPos, 1 );
 821                         },
 822                         $this->syncTimeout,
 823                         $this->busyCallbacks
 824                 );
 825
 826                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
 827         }
 828 }