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 Wikimedia\Rdbms\IDatabase;
  25 use \MediaWiki\MediaWikiServices;
  26 use \Wikimedia\WaitConditionLoop;
  27 use \Wikimedia\Rdbms\TransactionProfiler;
  28 use Wikimedia\Rdbms\LoadBalancer;
  29
  30 /**
  31  * Class to store objects in the database
  32  *
  33  * @ingroup Cache
  34  */
  35 class SqlBagOStuff extends BagOStuff {
  36         /** @var array[] (server index => server config) */
  37         protected $serverInfos;
  38         /** @var string[] (server index => tag/host name) */
  39         protected $serverTags;
  40         /** @var int */
  41         protected $numServers;
  42         /** @var int */
  43         protected $lastExpireAll = 0;
  44         /** @var int */
  45         protected $purgePeriod = 100;
  46         /** @var int */
  47         protected $shards = 1;
  48         /** @var string */
  49         protected $tableName = 'objectcache';
  50         /** @var bool */
  51         protected $replicaOnly = false;
  52         /** @var int */
  53         protected $syncTimeout = 3;
  54
  55         /** @var LoadBalancer|null */
  56         protected $separateMainLB;
  57         /** @var array */
  58         protected $conns;
  59         /** @var array UNIX timestamps */
  60         protected $connFailureTimes = [];
  61         /** @var array Exceptions */
  62         protected $connFailureErrors = [];
  63
  64         /**
  65          * Constructor. Parameters are:
  66          *   - server:      A server info structure in the format required by each
  67          *                  element in $wgDBServers.
  68          *
  69          *   - servers:     An array of server info structures describing a set of database servers
  70          *                  to distribute keys to. If this is specified, the "server" option will be
  71          *                  ignored. If string keys are used, then they will be used for consistent
  72          *                  hashing *instead* of the host name (from the server config). This is useful
  73          *                  when a cluster is replicated to another site (with different host names)
  74          *                  but each server has a corresponding replica in the other cluster.
  75          *
  76          *   - purgePeriod: The average number of object cache requests in between
  77          *                  garbage collection operations, where expired entries
  78          *                  are removed from the database. Or in other words, the
  79          *                  reciprocal of the probability of purging on any given
  80          *                  request. If this is set to zero, purging will never be
  81          *                  done.
  82          *
  83          *   - tableName:   The table name to use, default is "objectcache".
  84          *
  85          *   - shards:      The number of tables to use for data storage on each server.
  86          *                  If this is more than 1, table names will be formed in the style
  87          *                  objectcacheNNN where NNN is the shard index, between 0 and
  88          *                  shards-1. The number of digits will be the minimum number
  89          *                  required to hold the largest shard index. Data will be
  90          *                  distributed across all tables by key hash. This is for
  91          *                  MySQL bugs 61735 and 61736.
  92          *   - slaveOnly:   Whether to only use replica DBs and avoid triggering
  93          *                  garbage collection logic of expired items. This only
  94          *                  makes sense if the primary DB is used and only if get()
  95          *                  calls will be used. This is used by ReplicatedBagOStuff.
  96          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
  97          *
  98          * @param array $params
  99          */
 100         public function __construct( $params ) {
 101                 parent::__construct( $params );
 102
 103                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 104                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 105
 106                 if ( isset( $params['servers'] ) ) {
 107                         $this->serverInfos = [];
 108                         $this->serverTags = [];
 109                         $this->numServers = count( $params['servers'] );
 110                         $index = 0;
 111                         foreach ( $params['servers'] as $tag => $info ) {
 112                                 $this->serverInfos[$index] = $info;
 113                                 if ( is_string( $tag ) ) {
 114                                         $this->serverTags[$index] = $tag;
 115                                 } else {
 116                                         $this->serverTags[$index] = isset( $info['host'] ) ? $info['host'] : "#$index";
 117                                 }
 118                                 ++$index;
 119                         }
 120                 } elseif ( isset( $params['server'] ) ) {
 121                         $this->serverInfos = [ $params['server'] ];
 122                         $this->numServers = count( $this->serverInfos );
 123                 } else {
 124                         // Default to using the main wiki's database servers
 125                         $this->serverInfos = false;
 126                         $this->numServers = 1;
 127                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 128                 }
 129                 if ( isset( $params['purgePeriod'] ) ) {
 130                         $this->purgePeriod = intval( $params['purgePeriod'] );
 131                 }
 132                 if ( isset( $params['tableName'] ) ) {
 133                         $this->tableName = $params['tableName'];
 134                 }
 135                 if ( isset( $params['shards'] ) ) {
 136                         $this->shards = intval( $params['shards'] );
 137                 }
 138                 if ( isset( $params['syncTimeout'] ) ) {
 139                         $this->syncTimeout = $params['syncTimeout'];
 140                 }
 141                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 142         }
 143
 144         protected function getSeparateMainLB() {
 145                 global $wgDBtype;
 146
 147                 if ( $wgDBtype === 'mysql' && $this->usesMainDB() ) {
 148                         if ( !$this->separateMainLB ) {
 149                                 // We must keep a separate connection to MySQL in order to avoid deadlocks
 150                                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 151                                 $this->separateMainLB = $lbFactory->newMainLB();
 152                         }
 153                         return $this->separateMainLB;
 154                 } else {
 155                         // However, SQLite has an opposite behavior. And PostgreSQL needs to know
 156                         // if we are in transaction or not (@TODO: find some PostgreSQL work-around).
 157                         return null;
 158                 }
 159         }
 160
 161         /**
 162          * Get a connection to the specified database
 163          *
 164          * @param int $serverIndex
 165          * @return IDatabase
 166          * @throws MWException
 167          */
 168         protected function getDB( $serverIndex ) {
 169                 if ( !isset( $this->conns[$serverIndex] ) ) {
 170                         if ( $serverIndex >= $this->numServers ) {
 171                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 172                         }
 173
 174                         # Don't keep timing out trying to connect for each call if the DB is down
 175                         if ( isset( $this->connFailureErrors[$serverIndex] )
 176                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 177                         ) {
 178                                 throw $this->connFailureErrors[$serverIndex];
 179                         }
 180
 181                         # If server connection info was given, use that
 182                         if ( $this->serverInfos ) {
 183                                 $info = $this->serverInfos[$serverIndex];
 184                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 185                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 186                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 187                                 // Use a blank trx profiler to ignore expections as this is a cache
 188                                 $info['trxProfiler'] = new TransactionProfiler();
 189                                 $db = Database::factory( $type, $info );
 190                                 $db->clearFlag( DBO_TRX );
 191                         } else {
 192                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 193                                 if ( $this->getSeparateMainLB() ) {
 194                                         $db = $this->getSeparateMainLB()->getConnection( $index );
 195                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 196                                 } else {
 197                                         $db = wfGetDB( $index );
 198                                         // Can't mess with transaction rounds (DBO_TRX) :(
 199                                 }
 200                         }
 201                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 202                         $this->conns[$serverIndex] = $db;
 203                 }
 204
 205                 return $this->conns[$serverIndex];
 206         }
 207
 208         /**
 209          * Get the server index and table name for a given key
 210          * @param string $key
 211          * @return array Server index and table name
 212          */
 213         protected function getTableByKey( $key ) {
 214                 if ( $this->shards > 1 ) {
 215                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 216                         $tableIndex = $hash % $this->shards;
 217                 } else {
 218                         $tableIndex = 0;
 219                 }
 220                 if ( $this->numServers > 1 ) {
 221                         $sortedServers = $this->serverTags;
 222                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 223                         reset( $sortedServers );
 224                         $serverIndex = key( $sortedServers );
 225                 } else {
 226                         $serverIndex = 0;
 227                 }
 228                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 229         }
 230
 231         /**
 232          * Get the table name for a given shard index
 233          * @param int $index
 234          * @return string
 235          */
 236         protected function getTableNameByShard( $index ) {
 237                 if ( $this->shards > 1 ) {
 238                         $decimals = strlen( $this->shards - 1 );
 239                         return $this->tableName .
 240                                 sprintf( "%0{$decimals}d", $index );
 241                 } else {
 242                         return $this->tableName;
 243                 }
 244         }
 245
 246         protected function doGet( $key, $flags = 0 ) {
 247                 $casToken = null;
 248
 249                 return $this->getWithToken( $key, $casToken, $flags );
 250         }
 251
 252         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 253                 $values = $this->getMulti( [ $key ] );
 254                 if ( array_key_exists( $key, $values ) ) {
 255                         $casToken = $values[$key];
 256                         return $values[$key];
 257                 }
 258                 return false;
 259         }
 260
 261         public function getMulti( array $keys, $flags = 0 ) {
 262                 $values = []; // array of (key => value)
 263
 264                 $keysByTable = [];
 265                 foreach ( $keys as $key ) {
 266                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 267                         $keysByTable[$serverIndex][$tableName][] = $key;
 268                 }
 269
 270                 $this->garbageCollect(); // expire old entries if any
 271
 272                 $dataRows = [];
 273                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 274                         try {
 275                                 $db = $this->getDB( $serverIndex );
 276                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 277                                         $res = $db->select( $tableName,
 278                                                 [ 'keyname', 'value', 'exptime' ],
 279                                                 [ 'keyname' => $tableKeys ],
 280                                                 __METHOD__,
 281                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 282                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 283                                                 // We do not want to flush the TRX as that can break callers.
 284                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 285                                         );
 286                                         if ( $res === false ) {
 287                                                 continue;
 288                                         }
 289                                         foreach ( $res as $row ) {
 290                                                 $row->serverIndex = $serverIndex;
 291                                                 $row->tableName = $tableName;
 292                                                 $dataRows[$row->keyname] = $row;
 293                                         }
 294                                 }
 295                         } catch ( DBError $e ) {
 296                                 $this->handleReadError( $e, $serverIndex );
 297                         }
 298                 }
 299
 300                 foreach ( $keys as $key ) {
 301                         if ( isset( $dataRows[$key] ) ) { // HIT?
 302                                 $row = $dataRows[$key];
 303                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 304                                 $db = null;
 305                                 try {
 306                                         $db = $this->getDB( $row->serverIndex );
 307                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 308                                                 $this->debug( "get: key has expired" );
 309                                         } else { // HIT
 310                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 311                                         }
 312                                 } catch ( DBQueryError $e ) {
 313                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 314                                 }
 315                         } else { // MISS
 316                                 $this->debug( 'get: no matching rows' );
 317                         }
 318                 }
 319
 320                 return $values;
 321         }
 322
 323         public function setMulti( array $data, $expiry = 0 ) {
 324                 $keysByTable = [];
 325                 foreach ( $data as $key => $value ) {
 326                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 327                         $keysByTable[$serverIndex][$tableName][] = $key;
 328                 }
 329
 330                 $this->garbageCollect(); // expire old entries if any
 331
 332                 $result = true;
 333                 $exptime = (int)$expiry;
 334                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 335                         $db = null;
 336                         try {
 337                                 $db = $this->getDB( $serverIndex );
 338                         } catch ( DBError $e ) {
 339                                 $this->handleWriteError( $e, $db, $serverIndex );
 340                                 $result = false;
 341                                 continue;
 342                         }
 343
 344                         if ( $exptime < 0 ) {
 345                                 $exptime = 0;
 346                         }
 347
 348                         if ( $exptime == 0 ) {
 349                                 $encExpiry = $this->getMaxDateTime( $db );
 350                         } else {
 351                                 $exptime = $this->convertExpiry( $exptime );
 352                                 $encExpiry = $db->timestamp( $exptime );
 353                         }
 354                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 355                                 $rows = [];
 356                                 foreach ( $tableKeys as $key ) {
 357                                         $rows[] = [
 358                                                 'keyname' => $key,
 359                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 360                                                 'exptime' => $encExpiry,
 361                                         ];
 362                                 }
 363
 364                                 try {
 365                                         $db->replace(
 366                                                 $tableName,
 367                                                 [ 'keyname' ],
 368                                                 $rows,
 369                                                 __METHOD__
 370                                         );
 371                                 } catch ( DBError $e ) {
 372                                         $this->handleWriteError( $e, $db, $serverIndex );
 373                                         $result = false;
 374                                 }
 375
 376                         }
 377
 378                 }
 379
 380                 return $result;
 381         }
 382
 383         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 384                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 385                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 386                         $ok = $this->waitForReplication() && $ok;
 387                 }
 388
 389                 return $ok;
 390         }
 391
 392         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 393                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 394                 $db = null;
 395                 try {
 396                         $db = $this->getDB( $serverIndex );
 397                         $exptime = intval( $exptime );
 398
 399                         if ( $exptime < 0 ) {
 400                                 $exptime = 0;
 401                         }
 402
 403                         if ( $exptime == 0 ) {
 404                                 $encExpiry = $this->getMaxDateTime( $db );
 405                         } else {
 406                                 $exptime = $this->convertExpiry( $exptime );
 407                                 $encExpiry = $db->timestamp( $exptime );
 408                         }
 409                         // (T26425) use a replace if the db supports it instead of
 410                         // delete/insert to avoid clashes with conflicting keynames
 411                         $db->update(
 412                                 $tableName,
 413                                 [
 414                                         'keyname' => $key,
 415                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 416                                         'exptime' => $encExpiry
 417                                 ],
 418                                 [
 419                                         'keyname' => $key,
 420                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 421                                 ],
 422                                 __METHOD__
 423                         );
 424                 } catch ( DBQueryError $e ) {
 425                         $this->handleWriteError( $e, $db, $serverIndex );
 426
 427                         return false;
 428                 }
 429
 430                 return (bool)$db->affectedRows();
 431         }
 432
 433         public function delete( $key ) {
 434                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 435                 $db = null;
 436                 try {
 437                         $db = $this->getDB( $serverIndex );
 438                         $db->delete(
 439                                 $tableName,
 440                                 [ 'keyname' => $key ],
 441                                 __METHOD__ );
 442                 } catch ( DBError $e ) {
 443                         $this->handleWriteError( $e, $db, $serverIndex );
 444                         return false;
 445                 }
 446
 447                 return true;
 448         }
 449
 450         public function incr( $key, $step = 1 ) {
 451                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 452                 $db = null;
 453                 try {
 454                         $db = $this->getDB( $serverIndex );
 455                         $step = intval( $step );
 456                         $row = $db->selectRow(
 457                                 $tableName,
 458                                 [ 'value', 'exptime' ],
 459                                 [ 'keyname' => $key ],
 460                                 __METHOD__,
 461                                 [ 'FOR UPDATE' ] );
 462                         if ( $row === false ) {
 463                                 // Missing
 464
 465                                 return null;
 466                         }
 467                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 468                         if ( $this->isExpired( $db, $row->exptime ) ) {
 469                                 // Expired, do not reinsert
 470
 471                                 return null;
 472                         }
 473
 474                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 475                         $newValue = $oldValue + $step;
 476                         $db->insert( $tableName,
 477                                 [
 478                                         'keyname' => $key,
 479                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 480                                         'exptime' => $row->exptime
 481                                 ], __METHOD__, 'IGNORE' );
 482
 483                         if ( $db->affectedRows() == 0 ) {
 484                                 // Race condition. See T30611
 485                                 $newValue = null;
 486                         }
 487                 } catch ( DBError $e ) {
 488                         $this->handleWriteError( $e, $db, $serverIndex );
 489                         return null;
 490                 }
 491
 492                 return $newValue;
 493         }
 494
 495         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 496                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 497                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 498                         $ok = $this->waitForReplication() && $ok;
 499                 }
 500
 501                 return $ok;
 502         }
 503
 504         public function changeTTL( $key, $expiry = 0 ) {
 505                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 506                 $db = null;
 507                 try {
 508                         $db = $this->getDB( $serverIndex );
 509                         $db->update(
 510                                 $tableName,
 511                                 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
 512                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 513                                 __METHOD__
 514                         );
 515                         if ( $db->affectedRows() == 0 ) {
 516                                 return false;
 517                         }
 518                 } catch ( DBError $e ) {
 519                         $this->handleWriteError( $e, $db, $serverIndex );
 520                         return false;
 521                 }
 522
 523                 return true;
 524         }
 525
 526         /**
 527          * @param IDatabase $db
 528          * @param string $exptime
 529          * @return bool
 530          */
 531         protected function isExpired( $db, $exptime ) {
 532                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 533         }
 534
 535         /**
 536          * @param IDatabase $db
 537          * @return string
 538          */
 539         protected function getMaxDateTime( $db ) {
 540                 if ( time() > 0x7fffffff ) {
 541                         return $db->timestamp( 1 << 62 );
 542                 } else {
 543                         return $db->timestamp( 0x7fffffff );
 544                 }
 545         }
 546
 547         protected function garbageCollect() {
 548                 if ( !$this->purgePeriod || $this->replicaOnly ) {
 549                         // Disabled
 550                         return;
 551                 }
 552                 // Only purge on one in every $this->purgePeriod requests.
 553                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 554                         return;
 555                 }
 556                 $now = time();
 557                 // Avoid repeating the delete within a few seconds
 558                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 559                         $this->lastExpireAll = $now;
 560                         $this->expireAll();
 561                 }
 562         }
 563
 564         public function expireAll() {
 565                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 566         }
 567
 568         /**
 569          * Delete objects from the database which expire before a certain date.
 570          * @param string $timestamp
 571          * @param bool|callable $progressCallback
 572          * @return bool
 573          */
 574         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 575                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 576                         $db = null;
 577                         try {
 578                                 $db = $this->getDB( $serverIndex );
 579                                 $dbTimestamp = $db->timestamp( $timestamp );
 580                                 $totalSeconds = false;
 581                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 582                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 583                                         $maxExpTime = false;
 584                                         while ( true ) {
 585                                                 $conds = $baseConds;
 586                                                 if ( $maxExpTime !== false ) {
 587                                                         $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 588                                                 }
 589                                                 $rows = $db->select(
 590                                                         $this->getTableNameByShard( $i ),
 591                                                         [ 'keyname', 'exptime' ],
 592                                                         $conds,
 593                                                         __METHOD__,
 594                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 595                                                 if ( $rows === false || !$rows->numRows() ) {
 596                                                         break;
 597                                                 }
 598                                                 $keys = [];
 599                                                 $row = $rows->current();
 600                                                 $minExpTime = $row->exptime;
 601                                                 if ( $totalSeconds === false ) {
 602                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 603                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 604                                                 }
 605                                                 foreach ( $rows as $row ) {
 606                                                         $keys[] = $row->keyname;
 607                                                         $maxExpTime = $row->exptime;
 608                                                 }
 609
 610                                                 $db->delete(
 611                                                         $this->getTableNameByShard( $i ),
 612                                                         [
 613                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 614                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 615                                                                 'keyname' => $keys
 616                                                         ],
 617                                                         __METHOD__ );
 618
 619                                                 if ( $progressCallback ) {
 620                                                         if ( intval( $totalSeconds ) === 0 ) {
 621                                                                 $percent = 0;
 622                                                         } else {
 623                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 624                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 625                                                                 if ( $remainingSeconds > $totalSeconds ) {
 626                                                                         $totalSeconds = $remainingSeconds;
 627                                                                 }
 628                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 629                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 630                                                                         / $this->shards * 100;
 631                                                         }
 632                                                         $percent = ( $percent / $this->numServers )
 633                                                                 + ( $serverIndex / $this->numServers * 100 );
 634                                                         call_user_func( $progressCallback, $percent );
 635                                                 }
 636                                         }
 637                                 }
 638                         } catch ( DBError $e ) {
 639                                 $this->handleWriteError( $e, $db, $serverIndex );
 640                                 return false;
 641                         }
 642                 }
 643                 return true;
 644         }
 645
 646         /**
 647          * Delete content of shard tables in every server.
 648          * Return true if the operation is successful, false otherwise.
 649          * @return bool
 650          */
 651         public function deleteAll() {
 652                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 653                         $db = null;
 654                         try {
 655                                 $db = $this->getDB( $serverIndex );
 656                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 657                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 658                                 }
 659                         } catch ( DBError $e ) {
 660                                 $this->handleWriteError( $e, $db, $serverIndex );
 661                                 return false;
 662                         }
 663                 }
 664                 return true;
 665         }
 666
 667         /**
 668          * Serialize an object and, if possible, compress the representation.
 669          * On typical message and page data, this can provide a 3X decrease
 670          * in storage requirements.
 671          *
 672          * @param mixed $data
 673          * @return string
 674          */
 675         protected function serialize( &$data ) {
 676                 $serial = serialize( $data );
 677
 678                 if ( function_exists( 'gzdeflate' ) ) {
 679                         return gzdeflate( $serial );
 680                 } else {
 681                         return $serial;
 682                 }
 683         }
 684
 685         /**
 686          * Unserialize and, if necessary, decompress an object.
 687          * @param string $serial
 688          * @return mixed
 689          */
 690         protected function unserialize( $serial ) {
 691                 if ( function_exists( 'gzinflate' ) ) {
 692                         MediaWiki\suppressWarnings();
 693                         $decomp = gzinflate( $serial );
 694                         MediaWiki\restoreWarnings();
 695
 696                         if ( false !== $decomp ) {
 697                                 $serial = $decomp;
 698                         }
 699                 }
 700
 701                 $ret = unserialize( $serial );
 702
 703                 return $ret;
 704         }
 705
 706         /**
 707          * Handle a DBError which occurred during a read operation.
 708          *
 709          * @param DBError $exception
 710          * @param int $serverIndex
 711          */
 712         protected function handleReadError( DBError $exception, $serverIndex ) {
 713                 if ( $exception instanceof DBConnectionError ) {
 714                         $this->markServerDown( $exception, $serverIndex );
 715                 }
 716                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 717                 if ( $exception instanceof DBConnectionError ) {
 718                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 719                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 720                 } else {
 721                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 722                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 723                 }
 724         }
 725
 726         /**
 727          * Handle a DBQueryError which occurred during a write operation.
 728          *
 729          * @param DBError $exception
 730          * @param IDatabase|null $db DB handle or null if connection failed
 731          * @param int $serverIndex
 732          * @throws Exception
 733          */
 734         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 735                 if ( !$db ) {
 736                         $this->markServerDown( $exception, $serverIndex );
 737                 } elseif ( $db->wasReadOnlyError() ) {
 738                         if ( $db->trxLevel() && $this->usesMainDB() ) {
 739                                 // Errors like deadlocks and connection drops already cause rollback.
 740                                 // For consistency, we have no choice but to throw an error and trigger
 741                                 // complete rollback if the main DB is also being used as the cache DB.
 742                                 throw $exception;
 743                         }
 744                 }
 745
 746                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 747                 if ( $exception instanceof DBConnectionError ) {
 748                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 749                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 750                 } else {
 751                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 752                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 753                 }
 754         }
 755
 756         /**
 757          * Mark a server down due to a DBConnectionError exception
 758          *
 759          * @param DBError $exception
 760          * @param int $serverIndex
 761          */
 762         protected function markServerDown( DBError $exception, $serverIndex ) {
 763                 unset( $this->conns[$serverIndex] ); // bug T103435
 764
 765                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 766                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 767                                 unset( $this->connFailureTimes[$serverIndex] );
 768                                 unset( $this->connFailureErrors[$serverIndex] );
 769                         } else {
 770                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 771                                 return;
 772                         }
 773                 }
 774                 $now = time();
 775                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 776                 $this->connFailureTimes[$serverIndex] = $now;
 777                 $this->connFailureErrors[$serverIndex] = $exception;
 778         }
 779
 780         /**
 781          * Create shard tables. For use from eval.php.
 782          */
 783         public function createTables() {
 784                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 785                         $db = $this->getDB( $serverIndex );
 786                         if ( $db->getType() !== 'mysql' ) {
 787                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 788                         }
 789
 790                         for ( $i = 0; $i < $this->shards; $i++ ) {
 791                                 $db->query(
 792                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 793                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 794                                         __METHOD__ );
 795                         }
 796                 }
 797         }
 798
 799         /**
 800          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 801          */
 802         protected function usesMainDB() {
 803                 return !$this->serverInfos;
 804         }
 805
 806         protected function waitForReplication() {
 807                 if ( !$this->usesMainDB() ) {
 808                         // Custom DB server list; probably doesn't use replication
 809                         return true;
 810                 }
 811
 812                 $lb = $this->getSeparateMainLB()
 813                         ?: MediaWikiServices::getInstance()->getDBLoadBalancer();
 814
 815                 if ( $lb->getServerCount() <= 1 ) {
 816                         return true; // no replica DBs
 817                 }
 818
 819                 // Main LB is used; wait for any replica DBs to catch up
 820                 $masterPos = $lb->getMasterPos();
 821
 822                 $loop = new WaitConditionLoop(
 823                         function () use ( $lb, $masterPos ) {
 824                                 return $lb->waitForAll( $masterPos, 1 );
 825                         },
 826                         $this->syncTimeout,
 827                         $this->busyCallbacks
 828                 );
 829
 830                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
 831         }
 832 }