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 use Wikimedia\Rdbms\Database;
  26 use Wikimedia\Rdbms\IDatabase;
  27 use Wikimedia\Rdbms\DBError;
  28 use Wikimedia\Rdbms\DBQueryError;
  29 use Wikimedia\Rdbms\DBConnectionError;
  30 use Wikimedia\Rdbms\LoadBalancer;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\WaitConditionLoop;
  33
  34 /**
  35  * Class to store objects in the database
  36  *
  37  * @ingroup Cache
  38  */
  39 class SqlBagOStuff extends BagOStuff {
  40         /** @var array[] (server index => server config) */
  41         protected $serverInfos;
  42         /** @var string[] (server index => tag/host name) */
  43         protected $serverTags;
  44         /** @var int */
  45         protected $numServers;
  46         /** @var int */
  47         protected $lastExpireAll = 0;
  48         /** @var int */
  49         protected $purgePeriod = 100;
  50         /** @var int */
  51         protected $shards = 1;
  52         /** @var string */
  53         protected $tableName = 'objectcache';
  54         /** @var bool */
  55         protected $replicaOnly = false;
  56         /** @var int */
  57         protected $syncTimeout = 3;
  58
  59         /** @var LoadBalancer|null */
  60         protected $separateMainLB;
  61         /** @var array */
  62         protected $conns;
  63         /** @var array UNIX timestamps */
  64         protected $connFailureTimes = [];
  65         /** @var array Exceptions */
  66         protected $connFailureErrors = [];
  67
  68         /**
  69          * Constructor. Parameters are:
  70          *   - server:      A server info structure in the format required by each
  71          *                  element in $wgDBServers.
  72          *
  73          *   - servers:     An array of server info structures describing a set of database servers
  74          *                  to distribute keys to. If this is specified, the "server" option will be
  75          *                  ignored. If string keys are used, then they will be used for consistent
  76          *                  hashing *instead* of the host name (from the server config). This is useful
  77          *                  when a cluster is replicated to another site (with different host names)
  78          *                  but each server has a corresponding replica in the other cluster.
  79          *
  80          *   - purgePeriod: The average number of object cache requests in between
  81          *                  garbage collection operations, where expired entries
  82          *                  are removed from the database. Or in other words, the
  83          *                  reciprocal of the probability of purging on any given
  84          *                  request. If this is set to zero, purging will never be
  85          *                  done.
  86          *
  87          *   - tableName:   The table name to use, default is "objectcache".
  88          *
  89          *   - shards:      The number of tables to use for data storage on each server.
  90          *                  If this is more than 1, table names will be formed in the style
  91          *                  objectcacheNNN where NNN is the shard index, between 0 and
  92          *                  shards-1. The number of digits will be the minimum number
  93          *                  required to hold the largest shard index. Data will be
  94          *                  distributed across all tables by key hash. This is for
  95          *                  MySQL bugs 61735 <https://bugs.mysql.com/bug.php?id=61735>
  96          *                  and 61736 <https://bugs.mysql.com/bug.php?id=61736>.
  97          *
  98          *   - slaveOnly:   Whether to only use replica DBs and avoid triggering
  99          *                  garbage collection logic of expired items. This only
 100          *                  makes sense if the primary DB is used and only if get()
 101          *                  calls will be used. This is used by ReplicatedBagOStuff.
 102          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 103          *
 104          * @param array $params
 105          */
 106         public function __construct( $params ) {
 107                 parent::__construct( $params );
 108
 109                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 110                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 111
 112                 if ( isset( $params['servers'] ) ) {
 113                         $this->serverInfos = [];
 114                         $this->serverTags = [];
 115                         $this->numServers = count( $params['servers'] );
 116                         $index = 0;
 117                         foreach ( $params['servers'] as $tag => $info ) {
 118                                 $this->serverInfos[$index] = $info;
 119                                 if ( is_string( $tag ) ) {
 120                                         $this->serverTags[$index] = $tag;
 121                                 } else {
 122                                         $this->serverTags[$index] = $info['host'] ?? "#$index";
 123                                 }
 124                                 ++$index;
 125                         }
 126                 } elseif ( isset( $params['server'] ) ) {
 127                         $this->serverInfos = [ $params['server'] ];
 128                         $this->numServers = count( $this->serverInfos );
 129                 } else {
 130                         // Default to using the main wiki's database servers
 131                         $this->serverInfos = false;
 132                         $this->numServers = 1;
 133                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 134                 }
 135                 if ( isset( $params['purgePeriod'] ) ) {
 136                         $this->purgePeriod = intval( $params['purgePeriod'] );
 137                 }
 138                 if ( isset( $params['tableName'] ) ) {
 139                         $this->tableName = $params['tableName'];
 140                 }
 141                 if ( isset( $params['shards'] ) ) {
 142                         $this->shards = intval( $params['shards'] );
 143                 }
 144                 if ( isset( $params['syncTimeout'] ) ) {
 145                         $this->syncTimeout = $params['syncTimeout'];
 146                 }
 147                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 148         }
 149
 150         /**
 151          * Get a connection to the specified database
 152          *
 153          * @param int $serverIndex
 154          * @return Database
 155          * @throws MWException
 156          */
 157         protected function getDB( $serverIndex ) {
 158                 if ( !isset( $this->conns[$serverIndex] ) ) {
 159                         if ( $serverIndex >= $this->numServers ) {
 160                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 161                         }
 162
 163                         # Don't keep timing out trying to connect for each call if the DB is down
 164                         if ( isset( $this->connFailureErrors[$serverIndex] )
 165                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 166                         ) {
 167                                 throw $this->connFailureErrors[$serverIndex];
 168                         }
 169
 170                         if ( $this->serverInfos ) {
 171                                 // Use custom database defined by server connection info
 172                                 $info = $this->serverInfos[$serverIndex];
 173                                 $type = $info['type'] ?? 'mysql';
 174                                 $host = $info['host'] ?? '[unknown]';
 175                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 176                                 $db = Database::factory( $type, $info );
 177                                 $db->clearFlag( DBO_TRX ); // auto-commit mode
 178                         } else {
 179                                 // Use the main LB database
 180                                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 181                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 182                                 if ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' ) {
 183                                         // Keep a separate connection to avoid contention and deadlocks
 184                                         $db = $lb->getConnection( $index, [], false, $lb::CONN_TRX_AUTOCOMMIT );
 185                                 } else {
 186                                         // However, SQLite has the opposite behavior due to DB-level locking.
 187                                         // Stock sqlite MediaWiki installs use a separate sqlite cache DB instead.
 188                                         $db = $lb->getConnection( $index );
 189                                 }
 190                         }
 191
 192                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 193                         $this->conns[$serverIndex] = $db;
 194                 }
 195
 196                 return $this->conns[$serverIndex];
 197         }
 198
 199         /**
 200          * Get the server index and table name for a given key
 201          * @param string $key
 202          * @return array Server index and table name
 203          */
 204         protected function getTableByKey( $key ) {
 205                 if ( $this->shards > 1 ) {
 206                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 207                         $tableIndex = $hash % $this->shards;
 208                 } else {
 209                         $tableIndex = 0;
 210                 }
 211                 if ( $this->numServers > 1 ) {
 212                         $sortedServers = $this->serverTags;
 213                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 214                         reset( $sortedServers );
 215                         $serverIndex = key( $sortedServers );
 216                 } else {
 217                         $serverIndex = 0;
 218                 }
 219                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 220         }
 221
 222         /**
 223          * Get the table name for a given shard index
 224          * @param int $index
 225          * @return string
 226          */
 227         protected function getTableNameByShard( $index ) {
 228                 if ( $this->shards > 1 ) {
 229                         $decimals = strlen( $this->shards - 1 );
 230                         return $this->tableName .
 231                                 sprintf( "%0{$decimals}d", $index );
 232                 } else {
 233                         return $this->tableName;
 234                 }
 235         }
 236
 237         protected function doGet( $key, $flags = 0 ) {
 238                 $casToken = null;
 239
 240                 return $this->getWithToken( $key, $casToken, $flags );
 241         }
 242
 243         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 244                 $values = $this->getMulti( [ $key ] );
 245                 if ( array_key_exists( $key, $values ) ) {
 246                         $casToken = $values[$key];
 247                         return $values[$key];
 248                 }
 249                 return false;
 250         }
 251
 252         public function getMulti( array $keys, $flags = 0 ) {
 253                 $values = []; // array of (key => value)
 254
 255                 $keysByTable = [];
 256                 foreach ( $keys as $key ) {
 257                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 258                         $keysByTable[$serverIndex][$tableName][] = $key;
 259                 }
 260
 261                 $this->garbageCollect(); // expire old entries if any
 262
 263                 $dataRows = [];
 264                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 265                         try {
 266                                 $db = $this->getDB( $serverIndex );
 267                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 268                                         $res = $db->select( $tableName,
 269                                                 [ 'keyname', 'value', 'exptime' ],
 270                                                 [ 'keyname' => $tableKeys ],
 271                                                 __METHOD__,
 272                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 273                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 274                                                 // We do not want to flush the TRX as that can break callers.
 275                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 276                                         );
 277                                         if ( $res === false ) {
 278                                                 continue;
 279                                         }
 280                                         foreach ( $res as $row ) {
 281                                                 $row->serverIndex = $serverIndex;
 282                                                 $row->tableName = $tableName;
 283                                                 $dataRows[$row->keyname] = $row;
 284                                         }
 285                                 }
 286                         } catch ( DBError $e ) {
 287                                 $this->handleReadError( $e, $serverIndex );
 288                         }
 289                 }
 290
 291                 foreach ( $keys as $key ) {
 292                         if ( isset( $dataRows[$key] ) ) { // HIT?
 293                                 $row = $dataRows[$key];
 294                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 295                                 $db = null;
 296                                 try {
 297                                         $db = $this->getDB( $row->serverIndex );
 298                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 299                                                 $this->debug( "get: key has expired" );
 300                                         } else { // HIT
 301                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 302                                         }
 303                                 } catch ( DBQueryError $e ) {
 304                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 305                                 }
 306                         } else { // MISS
 307                                 $this->debug( 'get: no matching rows' );
 308                         }
 309                 }
 310
 311                 return $values;
 312         }
 313
 314         public function setMulti( array $data, $expiry = 0 ) {
 315                 $keysByTable = [];
 316                 foreach ( $data as $key => $value ) {
 317                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 318                         $keysByTable[$serverIndex][$tableName][] = $key;
 319                 }
 320
 321                 $this->garbageCollect(); // expire old entries if any
 322
 323                 $result = true;
 324                 $exptime = (int)$expiry;
 325                 $silenceScope = $this->silenceTransactionProfiler();
 326                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 327                         $db = null;
 328                         try {
 329                                 $db = $this->getDB( $serverIndex );
 330                         } catch ( DBError $e ) {
 331                                 $this->handleWriteError( $e, $db, $serverIndex );
 332                                 $result = false;
 333                                 continue;
 334                         }
 335
 336                         if ( $exptime < 0 ) {
 337                                 $exptime = 0;
 338                         }
 339
 340                         if ( $exptime == 0 ) {
 341                                 $encExpiry = $this->getMaxDateTime( $db );
 342                         } else {
 343                                 $exptime = $this->convertExpiry( $exptime );
 344                                 $encExpiry = $db->timestamp( $exptime );
 345                         }
 346                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 347                                 $rows = [];
 348                                 foreach ( $tableKeys as $key ) {
 349                                         $rows[] = [
 350                                                 'keyname' => $key,
 351                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 352                                                 'exptime' => $encExpiry,
 353                                         ];
 354                                 }
 355
 356                                 try {
 357                                         $db->replace(
 358                                                 $tableName,
 359                                                 [ 'keyname' ],
 360                                                 $rows,
 361                                                 __METHOD__
 362                                         );
 363                                 } catch ( DBError $e ) {
 364                                         $this->handleWriteError( $e, $db, $serverIndex );
 365                                         $result = false;
 366                                 }
 367
 368                         }
 369
 370                 }
 371
 372                 return $result;
 373         }
 374
 375         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 376                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 377                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 378                         $ok = $this->waitForReplication() && $ok;
 379                 }
 380
 381                 return $ok;
 382         }
 383
 384         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 385                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 386                 $db = null;
 387                 $silenceScope = $this->silenceTransactionProfiler();
 388                 try {
 389                         $db = $this->getDB( $serverIndex );
 390                         $exptime = intval( $exptime );
 391
 392                         if ( $exptime < 0 ) {
 393                                 $exptime = 0;
 394                         }
 395
 396                         if ( $exptime == 0 ) {
 397                                 $encExpiry = $this->getMaxDateTime( $db );
 398                         } else {
 399                                 $exptime = $this->convertExpiry( $exptime );
 400                                 $encExpiry = $db->timestamp( $exptime );
 401                         }
 402                         // (T26425) use a replace if the db supports it instead of
 403                         // delete/insert to avoid clashes with conflicting keynames
 404                         $db->update(
 405                                 $tableName,
 406                                 [
 407                                         'keyname' => $key,
 408                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 409                                         'exptime' => $encExpiry
 410                                 ],
 411                                 [
 412                                         'keyname' => $key,
 413                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 414                                 ],
 415                                 __METHOD__
 416                         );
 417                 } catch ( DBQueryError $e ) {
 418                         $this->handleWriteError( $e, $db, $serverIndex );
 419
 420                         return false;
 421                 }
 422
 423                 return (bool)$db->affectedRows();
 424         }
 425
 426         public function delete( $key ) {
 427                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 428                 $db = null;
 429                 $silenceScope = $this->silenceTransactionProfiler();
 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                 $silenceScope = $this->silenceTransactionProfiler();
 448                 try {
 449                         $db = $this->getDB( $serverIndex );
 450                         $step = intval( $step );
 451                         $row = $db->selectRow(
 452                                 $tableName,
 453                                 [ 'value', 'exptime' ],
 454                                 [ 'keyname' => $key ],
 455                                 __METHOD__,
 456                                 [ 'FOR UPDATE' ] );
 457                         if ( $row === false ) {
 458                                 // Missing
 459
 460                                 return null;
 461                         }
 462                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 463                         if ( $this->isExpired( $db, $row->exptime ) ) {
 464                                 // Expired, do not reinsert
 465
 466                                 return null;
 467                         }
 468
 469                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 470                         $newValue = $oldValue + $step;
 471                         $db->insert( $tableName,
 472                                 [
 473                                         'keyname' => $key,
 474                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 475                                         'exptime' => $row->exptime
 476                                 ], __METHOD__, 'IGNORE' );
 477
 478                         if ( $db->affectedRows() == 0 ) {
 479                                 // Race condition. See T30611
 480                                 $newValue = null;
 481                         }
 482                 } catch ( DBError $e ) {
 483                         $this->handleWriteError( $e, $db, $serverIndex );
 484                         return null;
 485                 }
 486
 487                 return $newValue;
 488         }
 489
 490         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 491                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 492                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 493                         $ok = $this->waitForReplication() && $ok;
 494                 }
 495
 496                 return $ok;
 497         }
 498
 499         public function changeTTL( $key, $expiry = 0 ) {
 500                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 501                 $db = null;
 502                 $silenceScope = $this->silenceTransactionProfiler();
 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                 $silenceScope = $this->silenceTransactionProfiler();
 572                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 573                         $db = null;
 574                         try {
 575                                 $db = $this->getDB( $serverIndex );
 576                                 $dbTimestamp = $db->timestamp( $timestamp );
 577                                 $totalSeconds = false;
 578                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 579                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 580                                         $maxExpTime = false;
 581                                         while ( true ) {
 582                                                 $conds = $baseConds;
 583                                                 if ( $maxExpTime !== false ) {
 584                                                         $conds[] = 'exptime >= ' . $db->addQuotes( $maxExpTime );
 585                                                 }
 586                                                 $rows = $db->select(
 587                                                         $this->getTableNameByShard( $i ),
 588                                                         [ 'keyname', 'exptime' ],
 589                                                         $conds,
 590                                                         __METHOD__,
 591                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 592                                                 if ( $rows === false || !$rows->numRows() ) {
 593                                                         break;
 594                                                 }
 595                                                 $keys = [];
 596                                                 $row = $rows->current();
 597                                                 $minExpTime = $row->exptime;
 598                                                 if ( $totalSeconds === false ) {
 599                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 600                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 601                                                 }
 602                                                 foreach ( $rows as $row ) {
 603                                                         $keys[] = $row->keyname;
 604                                                         $maxExpTime = $row->exptime;
 605                                                 }
 606
 607                                                 $db->delete(
 608                                                         $this->getTableNameByShard( $i ),
 609                                                         [
 610                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 611                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 612                                                                 'keyname' => $keys
 613                                                         ],
 614                                                         __METHOD__ );
 615
 616                                                 if ( $progressCallback ) {
 617                                                         if ( intval( $totalSeconds ) === 0 ) {
 618                                                                 $percent = 0;
 619                                                         } else {
 620                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 621                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 622                                                                 if ( $remainingSeconds > $totalSeconds ) {
 623                                                                         $totalSeconds = $remainingSeconds;
 624                                                                 }
 625                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 626                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 627                                                                         / $this->shards * 100;
 628                                                         }
 629                                                         $percent = ( $percent / $this->numServers )
 630                                                                 + ( $serverIndex / $this->numServers * 100 );
 631                                                         call_user_func( $progressCallback, $percent );
 632                                                 }
 633                                         }
 634                                 }
 635                         } catch ( DBError $e ) {
 636                                 $this->handleWriteError( $e, $db, $serverIndex );
 637                                 return false;
 638                         }
 639                 }
 640                 return true;
 641         }
 642
 643         /**
 644          * Delete content of shard tables in every server.
 645          * Return true if the operation is successful, false otherwise.
 646          * @return bool
 647          */
 648         public function deleteAll() {
 649                 $silenceScope = $this->silenceTransactionProfiler();
 650                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 651                         $db = null;
 652                         try {
 653                                 $db = $this->getDB( $serverIndex );
 654                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 655                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 656                                 }
 657                         } catch ( DBError $e ) {
 658                                 $this->handleWriteError( $e, $db, $serverIndex );
 659                                 return false;
 660                         }
 661                 }
 662                 return true;
 663         }
 664
 665         /**
 666          * Serialize an object and, if possible, compress the representation.
 667          * On typical message and page data, this can provide a 3X decrease
 668          * in storage requirements.
 669          *
 670          * @param mixed &$data
 671          * @return string
 672          */
 673         protected function serialize( &$data ) {
 674                 $serial = serialize( $data );
 675
 676                 if ( function_exists( 'gzdeflate' ) ) {
 677                         return gzdeflate( $serial );
 678                 } else {
 679                         return $serial;
 680                 }
 681         }
 682
 683         /**
 684          * Unserialize and, if necessary, decompress an object.
 685          * @param string $serial
 686          * @return mixed
 687          */
 688         protected function unserialize( $serial ) {
 689                 if ( function_exists( 'gzinflate' ) ) {
 690                         Wikimedia\suppressWarnings();
 691                         $decomp = gzinflate( $serial );
 692                         Wikimedia\restoreWarnings();
 693
 694                         if ( $decomp !== false ) {
 695                                 $serial = $decomp;
 696                         }
 697                 }
 698
 699                 $ret = unserialize( $serial );
 700
 701                 return $ret;
 702         }
 703
 704         /**
 705          * Handle a DBError which occurred during a read operation.
 706          *
 707          * @param DBError $exception
 708          * @param int $serverIndex
 709          */
 710         protected function handleReadError( DBError $exception, $serverIndex ) {
 711                 if ( $exception instanceof DBConnectionError ) {
 712                         $this->markServerDown( $exception, $serverIndex );
 713                 }
 714                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 715                 if ( $exception instanceof DBConnectionError ) {
 716                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 717                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 718                 } else {
 719                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 720                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 721                 }
 722         }
 723
 724         /**
 725          * Handle a DBQueryError which occurred during a write operation.
 726          *
 727          * @param DBError $exception
 728          * @param IDatabase|null $db DB handle or null if connection failed
 729          * @param int $serverIndex
 730          * @throws Exception
 731          */
 732         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 733                 if ( !$db ) {
 734                         $this->markServerDown( $exception, $serverIndex );
 735                 }
 736
 737                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 738                 if ( $exception instanceof DBConnectionError ) {
 739                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 740                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 741                 } else {
 742                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 743                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 744                 }
 745         }
 746
 747         /**
 748          * Mark a server down due to a DBConnectionError exception
 749          *
 750          * @param DBError $exception
 751          * @param int $serverIndex
 752          */
 753         protected function markServerDown( DBError $exception, $serverIndex ) {
 754                 unset( $this->conns[$serverIndex] ); // bug T103435
 755
 756                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 757                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 758                                 unset( $this->connFailureTimes[$serverIndex] );
 759                                 unset( $this->connFailureErrors[$serverIndex] );
 760                         } else {
 761                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 762                                 return;
 763                         }
 764                 }
 765                 $now = time();
 766                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 767                 $this->connFailureTimes[$serverIndex] = $now;
 768                 $this->connFailureErrors[$serverIndex] = $exception;
 769         }
 770
 771         /**
 772          * Create shard tables. For use from eval.php.
 773          */
 774         public function createTables() {
 775                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 776                         $db = $this->getDB( $serverIndex );
 777                         if ( $db->getType() !== 'mysql' ) {
 778                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 779                         }
 780
 781                         for ( $i = 0; $i < $this->shards; $i++ ) {
 782                                 $db->query(
 783                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 784                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 785                                         __METHOD__ );
 786                         }
 787                 }
 788         }
 789
 790         /**
 791          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 792          */
 793         protected function usesMainDB() {
 794                 return !$this->serverInfos;
 795         }
 796
 797         protected function waitForReplication() {
 798                 if ( !$this->usesMainDB() ) {
 799                         // Custom DB server list; probably doesn't use replication
 800                         return true;
 801                 }
 802
 803                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 804                 if ( $lb->getServerCount() <= 1 ) {
 805                         return true; // no replica DBs
 806                 }
 807
 808                 // Main LB is used; wait for any replica DBs to catch up
 809                 $masterPos = $lb->getMasterPos();
 810                 if ( !$masterPos ) {
 811                         return true; // not applicable
 812                 }
 813
 814                 $loop = new WaitConditionLoop(
 815                         function () use ( $lb, $masterPos ) {
 816                                 return $lb->waitForAll( $masterPos, 1 );
 817                         },
 818                         $this->syncTimeout,
 819                         $this->busyCallbacks
 820                 );
 821
 822                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
 823         }
 824
 825         /**
 826          * Returns a ScopedCallback which resets the silence flag in the transaction profiler when it is
 827          * destroyed on the end of a scope, for example on return or throw
 828          * @return ScopedCallback
 829          * @since 1.32
 830          */
 831         protected function silenceTransactionProfiler() {
 832                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
 833                 $oldSilenced = $trxProfiler->setSilenced( true );
 834                 return new ScopedCallback( function () use ( $trxProfiler, $oldSilenced ) {
 835                         $trxProfiler->setSilenced( $oldSilenced );
 836                 } );
 837         }
 838 }