includes/objectcache/SqlBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using a SQL database.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 use MediaWiki\MediaWikiServices;
  25 use Wikimedia\Rdbms\Database;
  26 use Wikimedia\Rdbms\IDatabase;
  27 use Wikimedia\Rdbms\DBError;
  28 use Wikimedia\Rdbms\DBQueryError;
  29 use Wikimedia\Rdbms\DBConnectionError;
  30 use Wikimedia\Rdbms\LoadBalancer;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\WaitConditionLoop;
  33
  34 /**
  35  * Class to store objects in the database
  36  *
  37  * @ingroup Cache
  38  */
  39 class SqlBagOStuff extends BagOStuff {
  40         /** @var array[] (server index => server config) */
  41         protected $serverInfos;
  42         /** @var string[] (server index => tag/host name) */
  43         protected $serverTags;
  44         /** @var int */
  45         protected $numServers;
  46         /** @var int */
  47         protected $lastExpireAll = 0;
  48         /** @var int */
  49         protected $purgePeriod = 100;
  50         /** @var int */
  51         protected $shards = 1;
  52         /** @var string */
  53         protected $tableName = 'objectcache';
  54         /** @var bool */
  55         protected $replicaOnly = false;
  56         /** @var int */
  57         protected $syncTimeout = 3;
  58
  59         /** @var LoadBalancer|null */
  60         protected $separateMainLB;
  61         /** @var array */
  62         protected $conns;
  63         /** @var array UNIX timestamps */
  64         protected $connFailureTimes = [];
  65         /** @var array Exceptions */
  66         protected $connFailureErrors = [];
  67
  68         /**
  69          * Constructor. Parameters are:
  70          *   - server:      A server info structure in the format required by each
  71          *                  element in $wgDBServers.
  72          *
  73          *   - servers:     An array of server info structures describing a set of database servers
  74          *                  to distribute keys to. If this is specified, the "server" option will be
  75          *                  ignored. If string keys are used, then they will be used for consistent
  76          *                  hashing *instead* of the host name (from the server config). This is useful
  77          *                  when a cluster is replicated to another site (with different host names)
  78          *                  but each server has a corresponding replica in the other cluster.
  79          *
  80          *   - purgePeriod: The average number of object cache requests in between
  81          *                  garbage collection operations, where expired entries
  82          *                  are removed from the database. Or in other words, the
  83          *                  reciprocal of the probability of purging on any given
  84          *                  request. If this is set to zero, purging will never be
  85          *                  done.
  86          *
  87          *   - tableName:   The table name to use, default is "objectcache".
  88          *
  89          *   - shards:      The number of tables to use for data storage on each server.
  90          *                  If this is more than 1, table names will be formed in the style
  91          *                  objectcacheNNN where NNN is the shard index, between 0 and
  92          *                  shards-1. The number of digits will be the minimum number
  93          *                  required to hold the largest shard index. Data will be
  94          *                  distributed across all tables by key hash. This is for
  95          *                  MySQL bugs 61735 <https://bugs.mysql.com/bug.php?id=61735>
  96          *                  and 61736 <https://bugs.mysql.com/bug.php?id=61736>.
  97          *
  98          *   - slaveOnly:   Whether to only use replica DBs and avoid triggering
  99          *                  garbage collection logic of expired items. This only
 100          *                  makes sense if the primary DB is used and only if get()
 101          *                  calls will be used. This is used by ReplicatedBagOStuff.
 102          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 103          *
 104          * @param array $params
 105          */
 106         public function __construct( $params ) {
 107                 parent::__construct( $params );
 108
 109                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 110                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 111
 112                 if ( isset( $params['servers'] ) ) {
 113                         $this->serverInfos = [];
 114                         $this->serverTags = [];
 115                         $this->numServers = count( $params['servers'] );
 116                         $index = 0;
 117                         foreach ( $params['servers'] as $tag => $info ) {
 118                                 $this->serverInfos[$index] = $info;
 119                                 if ( is_string( $tag ) ) {
 120                                         $this->serverTags[$index] = $tag;
 121                                 } else {
 122                                         $this->serverTags[$index] = $info['host'] ?? "#$index";
 123                                 }
 124                                 ++$index;
 125                         }
 126                 } elseif ( isset( $params['server'] ) ) {
 127                         $this->serverInfos = [ $params['server'] ];
 128                         $this->numServers = count( $this->serverInfos );
 129                 } else {
 130                         // Default to using the main wiki's database servers
 131                         $this->serverInfos = false;
 132                         $this->numServers = 1;
 133                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 134                 }
 135                 if ( isset( $params['purgePeriod'] ) ) {
 136                         $this->purgePeriod = intval( $params['purgePeriod'] );
 137                 }
 138                 if ( isset( $params['tableName'] ) ) {
 139                         $this->tableName = $params['tableName'];
 140                 }
 141                 if ( isset( $params['shards'] ) ) {
 142                         $this->shards = intval( $params['shards'] );
 143                 }
 144                 if ( isset( $params['syncTimeout'] ) ) {
 145                         $this->syncTimeout = $params['syncTimeout'];
 146                 }
 147                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 148         }
 149
 150         /**
 151          * Get a connection to the specified database
 152          *
 153          * @param int $serverIndex
 154          * @return Database
 155          * @throws MWException
 156          */
 157         protected function getDB( $serverIndex ) {
 158                 if ( !isset( $this->conns[$serverIndex] ) ) {
 159                         if ( $serverIndex >= $this->numServers ) {
 160                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 161                         }
 162
 163                         # Don't keep timing out trying to connect for each call if the DB is down
 164                         if ( isset( $this->connFailureErrors[$serverIndex] )
 165                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 166                         ) {
 167                                 throw $this->connFailureErrors[$serverIndex];
 168                         }
 169
 170                         if ( $this->serverInfos ) {
 171                                 // Use custom database defined by server connection info
 172                                 $info = $this->serverInfos[$serverIndex];
 173                                 $type = $info['type'] ?? 'mysql';
 174                                 $host = $info['host'] ?? '[unknown]';
 175                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 176                                 $db = Database::factory( $type, $info );
 177                                 $db->clearFlag( DBO_TRX ); // auto-commit mode
 178                         } else {
 179                                 // Use the main LB database
 180                                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 181                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 182                                 if ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' ) {
 183                                         // Keep a separate connection to avoid contention and deadlocks
 184                                         $db = $lb->getConnection( $index, [], false, $lb::CONN_TRX_AUTOCOMMIT );
 185                                 } else {
 186                                         // However, SQLite has the opposite behavior due to DB-level locking.
 187                                         // Stock sqlite MediaWiki installs use a separate sqlite cache DB instead.
 188                                         $db = $lb->getConnection( $index );
 189                                 }
 190                         }
 191
 192                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 193                         $this->conns[$serverIndex] = $db;
 194                 }
 195
 196                 return $this->conns[$serverIndex];
 197         }
 198
 199         /**
 200          * Get the server index and table name for a given key
 201          * @param string $key
 202          * @return array Server index and table name
 203          */
 204         protected function getTableByKey( $key ) {
 205                 if ( $this->shards > 1 ) {
 206                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 207                         $tableIndex = $hash % $this->shards;
 208                 } else {
 209                         $tableIndex = 0;
 210                 }
 211                 if ( $this->numServers > 1 ) {
 212                         $sortedServers = $this->serverTags;
 213                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 214                         reset( $sortedServers );
 215                         $serverIndex = key( $sortedServers );
 216                 } else {
 217                         $serverIndex = 0;
 218                 }
 219                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 220         }
 221
 222         /**
 223          * Get the table name for a given shard index
 224          * @param int $index
 225          * @return string
 226          */
 227         protected function getTableNameByShard( $index ) {
 228                 if ( $this->shards > 1 ) {
 229                         $decimals = strlen( $this->shards - 1 );
 230                         return $this->tableName .
 231                                 sprintf( "%0{$decimals}d", $index );
 232                 } else {
 233                         return $this->tableName;
 234                 }
 235         }
 236
 237         protected function doGet( $key, $flags = 0, &$casToken = null ) {
 238                 $casToken = null;
 239
 240                 $blobs = $this->fetchBlobMulti( [ $key ] );
 241                 if ( array_key_exists( $key, $blobs ) ) {
 242                         $blob = $blobs[$key];
 243                         $value = $this->unserialize( $blob );
 244
 245                         $casToken = ( $value !== false ) ? $blob : null;
 246
 247                         return $value;
 248                 }
 249
 250                 return false;
 251         }
 252
 253         protected function doGetMulti( array $keys, $flags = 0 ) {
 254                 $values = [];
 255
 256                 $blobs = $this->fetchBlobMulti( $keys );
 257                 foreach ( $blobs as $key => $blob ) {
 258                         $values[$key] = $this->unserialize( $blob );
 259                 }
 260
 261                 return $values;
 262         }
 263
 264         protected function fetchBlobMulti( 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] = $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, $flags = 0 ) {
 327                 return $this->insertMulti( $data, $expiry, $flags, true );
 328         }
 329
 330         private function insertMulti( array $data, $expiry, $flags, $replace ) {
 331                 $keysByTable = [];
 332                 foreach ( $data as $key => $value ) {
 333                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 334                         $keysByTable[$serverIndex][$tableName][] = $key;
 335                 }
 336
 337                 $this->garbageCollect(); // expire old entries if any
 338
 339                 $result = true;
 340                 $exptime = (int)$expiry;
 341                 /** @noinspection PhpUnusedLocalVariableInspection */
 342                 $silenceScope = $this->silenceTransactionProfiler();
 343                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 344                         $db = null;
 345                         try {
 346                                 $db = $this->getDB( $serverIndex );
 347                         } catch ( DBError $e ) {
 348                                 $this->handleWriteError( $e, $db, $serverIndex );
 349                                 $result = false;
 350                                 continue;
 351                         }
 352
 353                         if ( $exptime < 0 ) {
 354                                 $exptime = 0;
 355                         }
 356
 357                         if ( $exptime == 0 ) {
 358                                 $encExpiry = $this->getMaxDateTime( $db );
 359                         } else {
 360                                 $exptime = $this->convertToExpiry( $exptime );
 361                                 $encExpiry = $db->timestamp( $exptime );
 362                         }
 363                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 364                                 $rows = [];
 365                                 foreach ( $tableKeys as $key ) {
 366                                         $rows[] = [
 367                                                 'keyname' => $key,
 368                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 369                                                 'exptime' => $encExpiry,
 370                                         ];
 371                                 }
 372
 373                                 try {
 374                                         if ( $replace ) {
 375                                                 $db->replace( $tableName, [ 'keyname' ], $rows, __METHOD__ );
 376                                         } else {
 377                                                 $db->insert( $tableName, $rows, __METHOD__, [ 'IGNORE' ] );
 378                                                 $result = ( $db->affectedRows() > 0 && $result );
 379                                         }
 380                                 } catch ( DBError $e ) {
 381                                         $this->handleWriteError( $e, $db, $serverIndex );
 382                                         $result = false;
 383                                 }
 384
 385                         }
 386                 }
 387
 388                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 389                         $result = $this->waitForReplication() && $result;
 390                 }
 391
 392                 return $result;
 393         }
 394
 395         protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
 396                 $ok = $this->insertMulti( [ $key => $value ], $exptime, $flags, true );
 397
 398                 return $ok;
 399         }
 400
 401         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
 402                 $added = $this->insertMulti( [ $key => $value ], $exptime, $flags, false );
 403
 404                 return $added;
 405         }
 406
 407         protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 408                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 409                 $db = null;
 410                 /** @noinspection PhpUnusedLocalVariableInspection */
 411                 $silenceScope = $this->silenceTransactionProfiler();
 412                 try {
 413                         $db = $this->getDB( $serverIndex );
 414                         $exptime = intval( $exptime );
 415
 416                         if ( $exptime < 0 ) {
 417                                 $exptime = 0;
 418                         }
 419
 420                         if ( $exptime == 0 ) {
 421                                 $encExpiry = $this->getMaxDateTime( $db );
 422                         } else {
 423                                 $exptime = $this->convertToExpiry( $exptime );
 424                                 $encExpiry = $db->timestamp( $exptime );
 425                         }
 426                         // (T26425) use a replace if the db supports it instead of
 427                         // delete/insert to avoid clashes with conflicting keynames
 428                         $db->update(
 429                                 $tableName,
 430                                 [
 431                                         'keyname' => $key,
 432                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 433                                         'exptime' => $encExpiry
 434                                 ],
 435                                 [
 436                                         'keyname' => $key,
 437                                         'value' => $db->encodeBlob( $casToken )
 438                                 ],
 439                                 __METHOD__
 440                         );
 441                 } catch ( DBQueryError $e ) {
 442                         $this->handleWriteError( $e, $db, $serverIndex );
 443
 444                         return false;
 445                 }
 446
 447                 return (bool)$db->affectedRows();
 448         }
 449
 450         public function deleteMulti( array $keys, $flags = 0 ) {
 451                 return $this->purgeMulti( $keys, $flags );
 452         }
 453
 454         public function purgeMulti( array $keys, $flags = 0 ) {
 455                 $keysByTable = [];
 456                 foreach ( $keys as $key ) {
 457                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 458                         $keysByTable[$serverIndex][$tableName][] = $key;
 459                 }
 460
 461                 $result = true;
 462                 /** @noinspection PhpUnusedLocalVariableInspection */
 463                 $silenceScope = $this->silenceTransactionProfiler();
 464                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 465                         $db = null;
 466                         try {
 467                                 $db = $this->getDB( $serverIndex );
 468                         } catch ( DBError $e ) {
 469                                 $this->handleWriteError( $e, $db, $serverIndex );
 470                                 $result = false;
 471                                 continue;
 472                         }
 473
 474                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 475                                 try {
 476                                         $db->delete( $tableName, [ 'keyname' => $tableKeys ], __METHOD__ );
 477                                 } catch ( DBError $e ) {
 478                                         $this->handleWriteError( $e, $db, $serverIndex );
 479                                         $result = false;
 480                                 }
 481
 482                         }
 483                 }
 484
 485                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 486                         $result = $this->waitForReplication() && $result;
 487                 }
 488
 489                 return $result;
 490         }
 491
 492         protected function doDelete( $key, $flags = 0 ) {
 493                 $ok = $this->purgeMulti( [ $key ], $flags );
 494
 495                 return $ok;
 496         }
 497
 498         public function incr( $key, $step = 1 ) {
 499                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 500                 $db = null;
 501                 /** @noinspection PhpUnusedLocalVariableInspection */
 502                 $silenceScope = $this->silenceTransactionProfiler();
 503                 try {
 504                         $db = $this->getDB( $serverIndex );
 505                         $step = intval( $step );
 506                         $row = $db->selectRow(
 507                                 $tableName,
 508                                 [ 'value', 'exptime' ],
 509                                 [ 'keyname' => $key ],
 510                                 __METHOD__,
 511                                 [ 'FOR UPDATE' ]
 512                         );
 513                         if ( $row === false ) {
 514                                 // Missing
 515                                 return false;
 516                         }
 517                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 518                         if ( $this->isExpired( $db, $row->exptime ) ) {
 519                                 // Expired, do not reinsert
 520                                 return false;
 521                         }
 522
 523                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 524                         $newValue = $oldValue + $step;
 525                         $db->insert(
 526                                 $tableName,
 527                                 [
 528                                         'keyname' => $key,
 529                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 530                                         'exptime' => $row->exptime
 531                                 ],
 532                                 __METHOD__,
 533                                 [ 'IGNORE' ]
 534                         );
 535
 536                         if ( $db->affectedRows() == 0 ) {
 537                                 // Race condition. See T30611
 538                                 $newValue = false;
 539                         }
 540                 } catch ( DBError $e ) {
 541                         $this->handleWriteError( $e, $db, $serverIndex );
 542                         return false;
 543                 }
 544
 545                 return $newValue;
 546         }
 547
 548         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 549                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
 550                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 551                         $ok = $this->waitForReplication() && $ok;
 552                 }
 553
 554                 return $ok;
 555         }
 556
 557         public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
 558                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 559                 $db = null;
 560                 /** @noinspection PhpUnusedLocalVariableInspection */
 561                 $silenceScope = $this->silenceTransactionProfiler();
 562                 try {
 563                         $db = $this->getDB( $serverIndex );
 564                         if ( $exptime == 0 ) {
 565                                 $timestamp = $this->getMaxDateTime( $db );
 566                         } else {
 567                                 $timestamp = $db->timestamp( $this->convertToExpiry( $exptime ) );
 568                         }
 569                         $db->update(
 570                                 $tableName,
 571                                 [ 'exptime' => $timestamp ],
 572                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 573                                 __METHOD__
 574                         );
 575                         if ( $db->affectedRows() == 0 ) {
 576                                 $exists = (bool)$db->selectField(
 577                                         $tableName,
 578                                         1,
 579                                         [ 'keyname' => $key, 'exptime' => $timestamp ],
 580                                         __METHOD__,
 581                                         [ 'FOR UPDATE' ]
 582                                 );
 583
 584                                 return $exists;
 585                         }
 586                 } catch ( DBError $e ) {
 587                         $this->handleWriteError( $e, $db, $serverIndex );
 588                         return false;
 589                 }
 590
 591                 return true;
 592         }
 593
 594         /**
 595          * @param IDatabase $db
 596          * @param string $exptime
 597          * @return bool
 598          */
 599         protected function isExpired( $db, $exptime ) {
 600                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 601         }
 602
 603         /**
 604          * @param IDatabase $db
 605          * @return string
 606          */
 607         protected function getMaxDateTime( $db ) {
 608                 if ( time() > 0x7fffffff ) {
 609                         return $db->timestamp( 1 << 62 );
 610                 } else {
 611                         return $db->timestamp( 0x7fffffff );
 612                 }
 613         }
 614
 615         protected function garbageCollect() {
 616                 if ( !$this->purgePeriod || $this->replicaOnly ) {
 617                         // Disabled
 618                         return;
 619                 }
 620                 // Only purge on one in every $this->purgePeriod requests.
 621                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 622                         return;
 623                 }
 624                 $now = time();
 625                 // Avoid repeating the delete within a few seconds
 626                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 627                         $this->lastExpireAll = $now;
 628                         $this->expireAll();
 629                 }
 630         }
 631
 632         public function expireAll() {
 633                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 634         }
 635
 636         /**
 637          * Delete objects from the database which expire before a certain date.
 638          * @param string $timestamp
 639          * @param bool|callable $progressCallback
 640          * @return bool
 641          */
 642         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 643                 /** @noinspection PhpUnusedLocalVariableInspection */
 644                 $silenceScope = $this->silenceTransactionProfiler();
 645                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 646                         $db = null;
 647                         try {
 648                                 $db = $this->getDB( $serverIndex );
 649                                 $dbTimestamp = $db->timestamp( $timestamp );
 650                                 $totalSeconds = false;
 651                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 652                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 653                                         $maxExpTime = false;
 654                                         while ( true ) {
 655                                                 $conds = $baseConds;
 656                                                 if ( $maxExpTime !== false ) {
 657                                                         $conds[] = 'exptime >= ' . $db->addQuotes( $maxExpTime );
 658                                                 }
 659                                                 $rows = $db->select(
 660                                                         $this->getTableNameByShard( $i ),
 661                                                         [ 'keyname', 'exptime' ],
 662                                                         $conds,
 663                                                         __METHOD__,
 664                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 665                                                 if ( $rows === false || !$rows->numRows() ) {
 666                                                         break;
 667                                                 }
 668                                                 $keys = [];
 669                                                 $row = $rows->current();
 670                                                 $minExpTime = $row->exptime;
 671                                                 if ( $totalSeconds === false ) {
 672                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 673                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 674                                                 }
 675                                                 foreach ( $rows as $row ) {
 676                                                         $keys[] = $row->keyname;
 677                                                         $maxExpTime = $row->exptime;
 678                                                 }
 679
 680                                                 $db->delete(
 681                                                         $this->getTableNameByShard( $i ),
 682                                                         [
 683                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 684                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 685                                                                 'keyname' => $keys
 686                                                         ],
 687                                                         __METHOD__ );
 688
 689                                                 if ( $progressCallback ) {
 690                                                         if ( intval( $totalSeconds ) === 0 ) {
 691                                                                 $percent = 0;
 692                                                         } else {
 693                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 694                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 695                                                                 if ( $remainingSeconds > $totalSeconds ) {
 696                                                                         $totalSeconds = $remainingSeconds;
 697                                                                 }
 698                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 699                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 700                                                                         / $this->shards * 100;
 701                                                         }
 702                                                         $percent = ( $percent / $this->numServers )
 703                                                                 + ( $serverIndex / $this->numServers * 100 );
 704                                                         call_user_func( $progressCallback, $percent );
 705                                                 }
 706                                         }
 707                                 }
 708                         } catch ( DBError $e ) {
 709                                 $this->handleWriteError( $e, $db, $serverIndex );
 710                                 return false;
 711                         }
 712                 }
 713                 return true;
 714         }
 715
 716         /**
 717          * Delete content of shard tables in every server.
 718          * Return true if the operation is successful, false otherwise.
 719          * @return bool
 720          */
 721         public function deleteAll() {
 722                 /** @noinspection PhpUnusedLocalVariableInspection */
 723                 $silenceScope = $this->silenceTransactionProfiler();
 724                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 725                         $db = null;
 726                         try {
 727                                 $db = $this->getDB( $serverIndex );
 728                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 729                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 730                                 }
 731                         } catch ( DBError $e ) {
 732                                 $this->handleWriteError( $e, $db, $serverIndex );
 733                                 return false;
 734                         }
 735                 }
 736                 return true;
 737         }
 738
 739         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 740                 // Avoid deadlocks and allow lock reentry if specified
 741                 if ( isset( $this->locks[$key] ) ) {
 742                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 743                                 ++$this->locks[$key]['depth'];
 744                                 return true;
 745                         } else {
 746                                 return false;
 747                         }
 748                 }
 749
 750                 list( $serverIndex ) = $this->getTableByKey( $key );
 751                 try {
 752                         $db = $this->getDB( $serverIndex );
 753                         $ok = $db->lock( $key, __METHOD__, $timeout );
 754                         if ( $ok ) {
 755                                 $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 756                         }
 757
 758                         $this->logger->warning(
 759                                 __METHOD__ . " failed due to timeout for {key}.",
 760                                 [ 'key' => $key, 'timeout' => $timeout ]
 761                         );
 762
 763                         return $ok;
 764                 } catch ( DBError $e ) {
 765                         $this->handleWriteError( $e, $db, $serverIndex );
 766                         $ok = false;
 767                 }
 768
 769                 return $ok;
 770         }
 771
 772         public function unlock( $key ) {
 773                 if ( !isset( $this->locks[$key] ) ) {
 774                         return false;
 775                 }
 776
 777                 if ( --$this->locks[$key]['depth'] <= 0 ) {
 778                         unset( $this->locks[$key] );
 779
 780                         list( $serverIndex ) = $this->getTableByKey( $key );
 781                         try {
 782                                 $db = $this->getDB( $serverIndex );
 783                                 $ok = $db->unlock( $key, __METHOD__ );
 784                                 if ( !$ok ) {
 785                                         $this->logger->warning(
 786                                                 __METHOD__ . ' failed to release lock for {key}.',
 787                                                 [ 'key' => $key ]
 788                                         );
 789                                 }
 790                         } catch ( DBError $e ) {
 791                                 $this->handleWriteError( $e, $db, $serverIndex );
 792                                 $ok = false;
 793                         }
 794                 } else {
 795                         $ok = false;
 796                 }
 797
 798                 return $ok;
 799         }
 800
 801         /**
 802          * Serialize an object and, if possible, compress the representation.
 803          * On typical message and page data, this can provide a 3X decrease
 804          * in storage requirements.
 805          *
 806          * @param mixed $data
 807          * @return string
 808          */
 809         protected function serialize( $data ) {
 810                 $serial = serialize( $data );
 811
 812                 if ( function_exists( 'gzdeflate' ) ) {
 813                         return gzdeflate( $serial );
 814                 } else {
 815                         return $serial;
 816                 }
 817         }
 818
 819         /**
 820          * Unserialize and, if necessary, decompress an object.
 821          * @param string $serial
 822          * @return mixed
 823          */
 824         protected function unserialize( $serial ) {
 825                 if ( function_exists( 'gzinflate' ) ) {
 826                         Wikimedia\suppressWarnings();
 827                         $decomp = gzinflate( $serial );
 828                         Wikimedia\restoreWarnings();
 829
 830                         if ( $decomp !== false ) {
 831                                 $serial = $decomp;
 832                         }
 833                 }
 834
 835                 $ret = unserialize( $serial );
 836
 837                 return $ret;
 838         }
 839
 840         /**
 841          * Handle a DBError which occurred during a read operation.
 842          *
 843          * @param DBError $exception
 844          * @param int $serverIndex
 845          */
 846         protected function handleReadError( DBError $exception, $serverIndex ) {
 847                 if ( $exception instanceof DBConnectionError ) {
 848                         $this->markServerDown( $exception, $serverIndex );
 849                 }
 850
 851                 $this->setAndLogDBError( $exception );
 852         }
 853
 854         /**
 855          * Handle a DBQueryError which occurred during a write operation.
 856          *
 857          * @param DBError $exception
 858          * @param IDatabase|null $db DB handle or null if connection failed
 859          * @param int $serverIndex
 860          * @throws Exception
 861          */
 862         protected function handleWriteError( DBError $exception, $db, $serverIndex ) {
 863                 if ( !( $db instanceof IDatabase ) ) {
 864                         $this->markServerDown( $exception, $serverIndex );
 865                 }
 866
 867                 $this->setAndLogDBError( $exception );
 868         }
 869
 870         /**
 871          * @param DBError $exception
 872          */
 873         private function setAndLogDBError( DBError $exception ) {
 874                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 875                 if ( $exception instanceof DBConnectionError ) {
 876                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 877                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 878                 } else {
 879                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 880                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 881                 }
 882         }
 883
 884         /**
 885          * Mark a server down due to a DBConnectionError exception
 886          *
 887          * @param DBError $exception
 888          * @param int $serverIndex
 889          */
 890         protected function markServerDown( DBError $exception, $serverIndex ) {
 891                 unset( $this->conns[$serverIndex] ); // bug T103435
 892
 893                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 894                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 895                                 unset( $this->connFailureTimes[$serverIndex] );
 896                                 unset( $this->connFailureErrors[$serverIndex] );
 897                         } else {
 898                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 899                                 return;
 900                         }
 901                 }
 902                 $now = time();
 903                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 904                 $this->connFailureTimes[$serverIndex] = $now;
 905                 $this->connFailureErrors[$serverIndex] = $exception;
 906         }
 907
 908         /**
 909          * Create shard tables. For use from eval.php.
 910          */
 911         public function createTables() {
 912                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 913                         $db = $this->getDB( $serverIndex );
 914                         if ( $db->getType() !== 'mysql' ) {
 915                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 916                         }
 917
 918                         for ( $i = 0; $i < $this->shards; $i++ ) {
 919                                 $db->query(
 920                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 921                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 922                                         __METHOD__ );
 923                         }
 924                 }
 925         }
 926
 927         /**
 928          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 929          */
 930         protected function usesMainDB() {
 931                 return !$this->serverInfos;
 932         }
 933
 934         protected function waitForReplication() {
 935                 if ( !$this->usesMainDB() ) {
 936                         // Custom DB server list; probably doesn't use replication
 937                         return true;
 938                 }
 939
 940                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 941                 if ( $lb->getServerCount() <= 1 ) {
 942                         return true; // no replica DBs
 943                 }
 944
 945                 // Main LB is used; wait for any replica DBs to catch up
 946                 try {
 947                         $masterPos = $lb->getMasterPos();
 948                         if ( !$masterPos ) {
 949                                 return true; // not applicable
 950                         }
 951
 952                         $loop = new WaitConditionLoop(
 953                                 function () use ( $lb, $masterPos ) {
 954                                         return $lb->waitForAll( $masterPos, 1 );
 955                                 },
 956                                 $this->syncTimeout,
 957                                 $this->busyCallbacks
 958                         );
 959
 960                         return ( $loop->invoke() === $loop::CONDITION_REACHED );
 961                 } catch ( DBError $e ) {
 962                         $this->setAndLogDBError( $e );
 963
 964                         return false;
 965                 }
 966         }
 967
 968         /**
 969          * Returns a ScopedCallback which resets the silence flag in the transaction profiler when it is
 970          * destroyed on the end of a scope, for example on return or throw
 971          * @return ScopedCallback
 972          * @since 1.32
 973          */
 974         protected function silenceTransactionProfiler() {
 975                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
 976                 $oldSilenced = $trxProfiler->setSilenced( true );
 977                 return new ScopedCallback( function () use ( $trxProfiler, $oldSilenced ) {
 978                         $trxProfiler->setSilenced( $oldSilenced );
 979                 } );
 980         }
 981 }