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\Database;
  25 use Wikimedia\Rdbms\IDatabase;
  26 use Wikimedia\Rdbms\DBError;
  27 use Wikimedia\Rdbms\DBQueryError;
  28 use Wikimedia\Rdbms\DBConnectionError;
  29 use \MediaWiki\MediaWikiServices;
  30 use \Wikimedia\WaitConditionLoop;
  31 use \Wikimedia\Rdbms\TransactionProfiler;
  32 use Wikimedia\Rdbms\LoadBalancer;
  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 and 61736.
  96          *   - slaveOnly:   Whether to only use replica DBs and avoid triggering
  97          *                  garbage collection logic of expired items. This only
  98          *                  makes sense if the primary DB is used and only if get()
  99          *                  calls will be used. This is used by ReplicatedBagOStuff.
 100          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 101          *
 102          * @param array $params
 103          */
 104         public function __construct( $params ) {
 105                 parent::__construct( $params );
 106
 107                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 108                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 109
 110                 if ( isset( $params['servers'] ) ) {
 111                         $this->serverInfos = [];
 112                         $this->serverTags = [];
 113                         $this->numServers = count( $params['servers'] );
 114                         $index = 0;
 115                         foreach ( $params['servers'] as $tag => $info ) {
 116                                 $this->serverInfos[$index] = $info;
 117                                 if ( is_string( $tag ) ) {
 118                                         $this->serverTags[$index] = $tag;
 119                                 } else {
 120                                         $this->serverTags[$index] = isset( $info['host'] ) ? $info['host'] : "#$index";
 121                                 }
 122                                 ++$index;
 123                         }
 124                 } elseif ( isset( $params['server'] ) ) {
 125                         $this->serverInfos = [ $params['server'] ];
 126                         $this->numServers = count( $this->serverInfos );
 127                 } else {
 128                         // Default to using the main wiki's database servers
 129                         $this->serverInfos = false;
 130                         $this->numServers = 1;
 131                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 132                 }
 133                 if ( isset( $params['purgePeriod'] ) ) {
 134                         $this->purgePeriod = intval( $params['purgePeriod'] );
 135                 }
 136                 if ( isset( $params['tableName'] ) ) {
 137                         $this->tableName = $params['tableName'];
 138                 }
 139                 if ( isset( $params['shards'] ) ) {
 140                         $this->shards = intval( $params['shards'] );
 141                 }
 142                 if ( isset( $params['syncTimeout'] ) ) {
 143                         $this->syncTimeout = $params['syncTimeout'];
 144                 }
 145                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 146         }
 147
 148         protected function getSeparateMainLB() {
 149                 global $wgDBtype;
 150
 151                 if ( $this->usesMainDB() && $wgDBtype !== 'sqlite' ) {
 152                         if ( !$this->separateMainLB ) {
 153                                 // We must keep a separate connection to MySQL in order to avoid deadlocks
 154                                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 155                                 $this->separateMainLB = $lbFactory->newMainLB();
 156                         }
 157                         return $this->separateMainLB;
 158                 } else {
 159                         // However, SQLite has an opposite behavior due to DB-level locking
 160                         return null;
 161                 }
 162         }
 163
 164         /**
 165          * Get a connection to the specified database
 166          *
 167          * @param int $serverIndex
 168          * @return IDatabase
 169          * @throws MWException
 170          */
 171         protected function getDB( $serverIndex ) {
 172                 if ( !isset( $this->conns[$serverIndex] ) ) {
 173                         if ( $serverIndex >= $this->numServers ) {
 174                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 175                         }
 176
 177                         # Don't keep timing out trying to connect for each call if the DB is down
 178                         if ( isset( $this->connFailureErrors[$serverIndex] )
 179                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 180                         ) {
 181                                 throw $this->connFailureErrors[$serverIndex];
 182                         }
 183
 184                         # If server connection info was given, use that
 185                         if ( $this->serverInfos ) {
 186                                 $info = $this->serverInfos[$serverIndex];
 187                                 $type = isset( $info['type'] ) ? $info['type'] : 'mysql';
 188                                 $host = isset( $info['host'] ) ? $info['host'] : '[unknown]';
 189                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 190                                 // Use a blank trx profiler to ignore expections as this is a cache
 191                                 $info['trxProfiler'] = new TransactionProfiler();
 192                                 $db = Database::factory( $type, $info );
 193                                 $db->clearFlag( DBO_TRX );
 194                         } else {
 195                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 196                                 if ( $this->getSeparateMainLB() ) {
 197                                         $db = $this->getSeparateMainLB()->getConnection( $index );
 198                                         $db->clearFlag( DBO_TRX ); // auto-commit mode
 199                                 } else {
 200                                         $db = wfGetDB( $index );
 201                                         // Can't mess with transaction rounds (DBO_TRX) :(
 202                                 }
 203                         }
 204                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 205                         $this->conns[$serverIndex] = $db;
 206                 }
 207
 208                 return $this->conns[$serverIndex];
 209         }
 210
 211         /**
 212          * Get the server index and table name for a given key
 213          * @param string $key
 214          * @return array Server index and table name
 215          */
 216         protected function getTableByKey( $key ) {
 217                 if ( $this->shards > 1 ) {
 218                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 219                         $tableIndex = $hash % $this->shards;
 220                 } else {
 221                         $tableIndex = 0;
 222                 }
 223                 if ( $this->numServers > 1 ) {
 224                         $sortedServers = $this->serverTags;
 225                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 226                         reset( $sortedServers );
 227                         $serverIndex = key( $sortedServers );
 228                 } else {
 229                         $serverIndex = 0;
 230                 }
 231                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 232         }
 233
 234         /**
 235          * Get the table name for a given shard index
 236          * @param int $index
 237          * @return string
 238          */
 239         protected function getTableNameByShard( $index ) {
 240                 if ( $this->shards > 1 ) {
 241                         $decimals = strlen( $this->shards - 1 );
 242                         return $this->tableName .
 243                                 sprintf( "%0{$decimals}d", $index );
 244                 } else {
 245                         return $this->tableName;
 246                 }
 247         }
 248
 249         protected function doGet( $key, $flags = 0 ) {
 250                 $casToken = null;
 251
 252                 return $this->getWithToken( $key, $casToken, $flags );
 253         }
 254
 255         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 256                 $values = $this->getMulti( [ $key ] );
 257                 if ( array_key_exists( $key, $values ) ) {
 258                         $casToken = $values[$key];
 259                         return $values[$key];
 260                 }
 261                 return false;
 262         }
 263
 264         public function getMulti( array $keys, $flags = 0 ) {
 265                 $values = []; // array of (key => value)
 266
 267                 $keysByTable = [];
 268                 foreach ( $keys as $key ) {
 269                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 270                         $keysByTable[$serverIndex][$tableName][] = $key;
 271                 }
 272
 273                 $this->garbageCollect(); // expire old entries if any
 274
 275                 $dataRows = [];
 276                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 277                         try {
 278                                 $db = $this->getDB( $serverIndex );
 279                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 280                                         $res = $db->select( $tableName,
 281                                                 [ 'keyname', 'value', 'exptime' ],
 282                                                 [ 'keyname' => $tableKeys ],
 283                                                 __METHOD__,
 284                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 285                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 286                                                 // We do not want to flush the TRX as that can break callers.
 287                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 288                                         );
 289                                         if ( $res === false ) {
 290                                                 continue;
 291                                         }
 292                                         foreach ( $res as $row ) {
 293                                                 $row->serverIndex = $serverIndex;
 294                                                 $row->tableName = $tableName;
 295                                                 $dataRows[$row->keyname] = $row;
 296                                         }
 297                                 }
 298                         } catch ( DBError $e ) {
 299                                 $this->handleReadError( $e, $serverIndex );
 300                         }
 301                 }
 302
 303                 foreach ( $keys as $key ) {
 304                         if ( isset( $dataRows[$key] ) ) { // HIT?
 305                                 $row = $dataRows[$key];
 306                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 307                                 $db = null;
 308                                 try {
 309                                         $db = $this->getDB( $row->serverIndex );
 310                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 311                                                 $this->debug( "get: key has expired" );
 312                                         } else { // HIT
 313                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 314                                         }
 315                                 } catch ( DBQueryError $e ) {
 316                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 317                                 }
 318                         } else { // MISS
 319                                 $this->debug( 'get: no matching rows' );
 320                         }
 321                 }
 322
 323                 return $values;
 324         }
 325
 326         public function setMulti( array $data, $expiry = 0 ) {
 327                 $keysByTable = [];
 328                 foreach ( $data as $key => $value ) {
 329                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 330                         $keysByTable[$serverIndex][$tableName][] = $key;
 331                 }
 332
 333                 $this->garbageCollect(); // expire old entries if any
 334
 335                 $result = true;
 336                 $exptime = (int)$expiry;
 337                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 338                         $db = null;
 339                         try {
 340                                 $db = $this->getDB( $serverIndex );
 341                         } catch ( DBError $e ) {
 342                                 $this->handleWriteError( $e, $db, $serverIndex );
 343                                 $result = false;
 344                                 continue;
 345                         }
 346
 347                         if ( $exptime < 0 ) {
 348                                 $exptime = 0;
 349                         }
 350
 351                         if ( $exptime == 0 ) {
 352                                 $encExpiry = $this->getMaxDateTime( $db );
 353                         } else {
 354                                 $exptime = $this->convertExpiry( $exptime );
 355                                 $encExpiry = $db->timestamp( $exptime );
 356                         }
 357                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 358                                 $rows = [];
 359                                 foreach ( $tableKeys as $key ) {
 360                                         $rows[] = [
 361                                                 'keyname' => $key,
 362                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 363                                                 'exptime' => $encExpiry,
 364                                         ];
 365                                 }
 366
 367                                 try {
 368                                         $db->replace(
 369                                                 $tableName,
 370                                                 [ 'keyname' ],
 371                                                 $rows,
 372                                                 __METHOD__
 373                                         );
 374                                 } catch ( DBError $e ) {
 375                                         $this->handleWriteError( $e, $db, $serverIndex );
 376                                         $result = false;
 377                                 }
 378
 379                         }
 380
 381                 }
 382
 383                 return $result;
 384         }
 385
 386         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 387                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 388                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 389                         $ok = $this->waitForReplication() && $ok;
 390                 }
 391
 392                 return $ok;
 393         }
 394
 395         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 396                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 397                 $db = null;
 398                 try {
 399                         $db = $this->getDB( $serverIndex );
 400                         $exptime = intval( $exptime );
 401
 402                         if ( $exptime < 0 ) {
 403                                 $exptime = 0;
 404                         }
 405
 406                         if ( $exptime == 0 ) {
 407                                 $encExpiry = $this->getMaxDateTime( $db );
 408                         } else {
 409                                 $exptime = $this->convertExpiry( $exptime );
 410                                 $encExpiry = $db->timestamp( $exptime );
 411                         }
 412                         // (T26425) use a replace if the db supports it instead of
 413                         // delete/insert to avoid clashes with conflicting keynames
 414                         $db->update(
 415                                 $tableName,
 416                                 [
 417                                         'keyname' => $key,
 418                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 419                                         'exptime' => $encExpiry
 420                                 ],
 421                                 [
 422                                         'keyname' => $key,
 423                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 424                                 ],
 425                                 __METHOD__
 426                         );
 427                 } catch ( DBQueryError $e ) {
 428                         $this->handleWriteError( $e, $db, $serverIndex );
 429
 430                         return false;
 431                 }
 432
 433                 return (bool)$db->affectedRows();
 434         }
 435
 436         public function delete( $key ) {
 437                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 438                 $db = null;
 439                 try {
 440                         $db = $this->getDB( $serverIndex );
 441                         $db->delete(
 442                                 $tableName,
 443                                 [ 'keyname' => $key ],
 444                                 __METHOD__ );
 445                 } catch ( DBError $e ) {
 446                         $this->handleWriteError( $e, $db, $serverIndex );
 447                         return false;
 448                 }
 449
 450                 return true;
 451         }
 452
 453         public function incr( $key, $step = 1 ) {
 454                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 455                 $db = null;
 456                 try {
 457                         $db = $this->getDB( $serverIndex );
 458                         $step = intval( $step );
 459                         $row = $db->selectRow(
 460                                 $tableName,
 461                                 [ 'value', 'exptime' ],
 462                                 [ 'keyname' => $key ],
 463                                 __METHOD__,
 464                                 [ 'FOR UPDATE' ] );
 465                         if ( $row === false ) {
 466                                 // Missing
 467
 468                                 return null;
 469                         }
 470                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 471                         if ( $this->isExpired( $db, $row->exptime ) ) {
 472                                 // Expired, do not reinsert
 473
 474                                 return null;
 475                         }
 476
 477                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 478                         $newValue = $oldValue + $step;
 479                         $db->insert( $tableName,
 480                                 [
 481                                         'keyname' => $key,
 482                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 483                                         'exptime' => $row->exptime
 484                                 ], __METHOD__, 'IGNORE' );
 485
 486                         if ( $db->affectedRows() == 0 ) {
 487                                 // Race condition. See T30611
 488                                 $newValue = null;
 489                         }
 490                 } catch ( DBError $e ) {
 491                         $this->handleWriteError( $e, $db, $serverIndex );
 492                         return null;
 493                 }
 494
 495                 return $newValue;
 496         }
 497
 498         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 499                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 500                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 501                         $ok = $this->waitForReplication() && $ok;
 502                 }
 503
 504                 return $ok;
 505         }
 506
 507         public function changeTTL( $key, $expiry = 0 ) {
 508                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 509                 $db = null;
 510                 try {
 511                         $db = $this->getDB( $serverIndex );
 512                         $db->update(
 513                                 $tableName,
 514                                 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
 515                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 516                                 __METHOD__
 517                         );
 518                         if ( $db->affectedRows() == 0 ) {
 519                                 return false;
 520                         }
 521                 } catch ( DBError $e ) {
 522                         $this->handleWriteError( $e, $db, $serverIndex );
 523                         return false;
 524                 }
 525
 526                 return true;
 527         }
 528
 529         /**
 530          * @param IDatabase $db
 531          * @param string $exptime
 532          * @return bool
 533          */
 534         protected function isExpired( $db, $exptime ) {
 535                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 536         }
 537
 538         /**
 539          * @param IDatabase $db
 540          * @return string
 541          */
 542         protected function getMaxDateTime( $db ) {
 543                 if ( time() > 0x7fffffff ) {
 544                         return $db->timestamp( 1 << 62 );
 545                 } else {
 546                         return $db->timestamp( 0x7fffffff );
 547                 }
 548         }
 549
 550         protected function garbageCollect() {
 551                 if ( !$this->purgePeriod || $this->replicaOnly ) {
 552                         // Disabled
 553                         return;
 554                 }
 555                 // Only purge on one in every $this->purgePeriod requests.
 556                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 557                         return;
 558                 }
 559                 $now = time();
 560                 // Avoid repeating the delete within a few seconds
 561                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 562                         $this->lastExpireAll = $now;
 563                         $this->expireAll();
 564                 }
 565         }
 566
 567         public function expireAll() {
 568                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 569         }
 570
 571         /**
 572          * Delete objects from the database which expire before a certain date.
 573          * @param string $timestamp
 574          * @param bool|callable $progressCallback
 575          * @return bool
 576          */
 577         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 578                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 579                         $db = null;
 580                         try {
 581                                 $db = $this->getDB( $serverIndex );
 582                                 $dbTimestamp = $db->timestamp( $timestamp );
 583                                 $totalSeconds = false;
 584                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 585                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 586                                         $maxExpTime = false;
 587                                         while ( true ) {
 588                                                 $conds = $baseConds;
 589                                                 if ( $maxExpTime !== false ) {
 590                                                         $conds[] = 'exptime >= ' . $db->addQuotes( $maxExpTime );
 591                                                 }
 592                                                 $rows = $db->select(
 593                                                         $this->getTableNameByShard( $i ),
 594                                                         [ 'keyname', 'exptime' ],
 595                                                         $conds,
 596                                                         __METHOD__,
 597                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 598                                                 if ( $rows === false || !$rows->numRows() ) {
 599                                                         break;
 600                                                 }
 601                                                 $keys = [];
 602                                                 $row = $rows->current();
 603                                                 $minExpTime = $row->exptime;
 604                                                 if ( $totalSeconds === false ) {
 605                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 606                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 607                                                 }
 608                                                 foreach ( $rows as $row ) {
 609                                                         $keys[] = $row->keyname;
 610                                                         $maxExpTime = $row->exptime;
 611                                                 }
 612
 613                                                 $db->delete(
 614                                                         $this->getTableNameByShard( $i ),
 615                                                         [
 616                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 617                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 618                                                                 'keyname' => $keys
 619                                                         ],
 620                                                         __METHOD__ );
 621
 622                                                 if ( $progressCallback ) {
 623                                                         if ( intval( $totalSeconds ) === 0 ) {
 624                                                                 $percent = 0;
 625                                                         } else {
 626                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 627                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 628                                                                 if ( $remainingSeconds > $totalSeconds ) {
 629                                                                         $totalSeconds = $remainingSeconds;
 630                                                                 }
 631                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 632                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 633                                                                         / $this->shards * 100;
 634                                                         }
 635                                                         $percent = ( $percent / $this->numServers )
 636                                                                 + ( $serverIndex / $this->numServers * 100 );
 637                                                         call_user_func( $progressCallback, $percent );
 638                                                 }
 639                                         }
 640                                 }
 641                         } catch ( DBError $e ) {
 642                                 $this->handleWriteError( $e, $db, $serverIndex );
 643                                 return false;
 644                         }
 645                 }
 646                 return true;
 647         }
 648
 649         /**
 650          * Delete content of shard tables in every server.
 651          * Return true if the operation is successful, false otherwise.
 652          * @return bool
 653          */
 654         public function deleteAll() {
 655                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 656                         $db = null;
 657                         try {
 658                                 $db = $this->getDB( $serverIndex );
 659                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 660                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 661                                 }
 662                         } catch ( DBError $e ) {
 663                                 $this->handleWriteError( $e, $db, $serverIndex );
 664                                 return false;
 665                         }
 666                 }
 667                 return true;
 668         }
 669
 670         /**
 671          * Serialize an object and, if possible, compress the representation.
 672          * On typical message and page data, this can provide a 3X decrease
 673          * in storage requirements.
 674          *
 675          * @param mixed $data
 676          * @return string
 677          */
 678         protected function serialize( &$data ) {
 679                 $serial = serialize( $data );
 680
 681                 if ( function_exists( 'gzdeflate' ) ) {
 682                         return gzdeflate( $serial );
 683                 } else {
 684                         return $serial;
 685                 }
 686         }
 687
 688         /**
 689          * Unserialize and, if necessary, decompress an object.
 690          * @param string $serial
 691          * @return mixed
 692          */
 693         protected function unserialize( $serial ) {
 694                 if ( function_exists( 'gzinflate' ) ) {
 695                         MediaWiki\suppressWarnings();
 696                         $decomp = gzinflate( $serial );
 697                         MediaWiki\restoreWarnings();
 698
 699                         if ( false !== $decomp ) {
 700                                 $serial = $decomp;
 701                         }
 702                 }
 703
 704                 $ret = unserialize( $serial );
 705
 706                 return $ret;
 707         }
 708
 709         /**
 710          * Handle a DBError which occurred during a read operation.
 711          *
 712          * @param DBError $exception
 713          * @param int $serverIndex
 714          */
 715         protected function handleReadError( DBError $exception, $serverIndex ) {
 716                 if ( $exception instanceof DBConnectionError ) {
 717                         $this->markServerDown( $exception, $serverIndex );
 718                 }
 719                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 720                 if ( $exception instanceof DBConnectionError ) {
 721                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 722                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 723                 } else {
 724                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 725                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 726                 }
 727         }
 728
 729         /**
 730          * Handle a DBQueryError which occurred during a write operation.
 731          *
 732          * @param DBError $exception
 733          * @param IDatabase|null $db DB handle or null if connection failed
 734          * @param int $serverIndex
 735          * @throws Exception
 736          */
 737         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 738                 if ( !$db ) {
 739                         $this->markServerDown( $exception, $serverIndex );
 740                 } elseif ( $db->wasReadOnlyError() ) {
 741                         if ( $db->trxLevel() && $this->usesMainDB() ) {
 742                                 // Errors like deadlocks and connection drops already cause rollback.
 743                                 // For consistency, we have no choice but to throw an error and trigger
 744                                 // complete rollback if the main DB is also being used as the cache DB.
 745                                 throw $exception;
 746                         }
 747                 }
 748
 749                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 750                 if ( $exception instanceof DBConnectionError ) {
 751                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 752                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 753                 } else {
 754                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 755                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 756                 }
 757         }
 758
 759         /**
 760          * Mark a server down due to a DBConnectionError exception
 761          *
 762          * @param DBError $exception
 763          * @param int $serverIndex
 764          */
 765         protected function markServerDown( DBError $exception, $serverIndex ) {
 766                 unset( $this->conns[$serverIndex] ); // bug T103435
 767
 768                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 769                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 770                                 unset( $this->connFailureTimes[$serverIndex] );
 771                                 unset( $this->connFailureErrors[$serverIndex] );
 772                         } else {
 773                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 774                                 return;
 775                         }
 776                 }
 777                 $now = time();
 778                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 779                 $this->connFailureTimes[$serverIndex] = $now;
 780                 $this->connFailureErrors[$serverIndex] = $exception;
 781         }
 782
 783         /**
 784          * Create shard tables. For use from eval.php.
 785          */
 786         public function createTables() {
 787                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 788                         $db = $this->getDB( $serverIndex );
 789                         if ( $db->getType() !== 'mysql' ) {
 790                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 791                         }
 792
 793                         for ( $i = 0; $i < $this->shards; $i++ ) {
 794                                 $db->query(
 795                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 796                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 797                                         __METHOD__ );
 798                         }
 799                 }
 800         }
 801
 802         /**
 803          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 804          */
 805         protected function usesMainDB() {
 806                 return !$this->serverInfos;
 807         }
 808
 809         protected function waitForReplication() {
 810                 if ( !$this->usesMainDB() ) {
 811                         // Custom DB server list; probably doesn't use replication
 812                         return true;
 813                 }
 814
 815                 $lb = $this->getSeparateMainLB()
 816                         ?: MediaWikiServices::getInstance()->getDBLoadBalancer();
 817
 818                 if ( $lb->getServerCount() <= 1 ) {
 819                         return true; // no replica DBs
 820                 }
 821
 822                 // Main LB is used; wait for any replica DBs to catch up
 823                 $masterPos = $lb->getMasterPos();
 824
 825                 $loop = new WaitConditionLoop(
 826                         function () use ( $lb, $masterPos ) {
 827                                 return $lb->waitForAll( $masterPos, 1 );
 828                         },
 829                         $this->syncTimeout,
 830                         $this->busyCallbacks
 831                 );
 832
 833                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
 834         }
 835 }