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