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 MediumSpecificBagOStuff {
  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 UNIX timestamp */
  47         protected $lastGarbageCollect = 0;
  48         /** @var int */
  49         protected $purgePeriod = 10;
  50         /** @var int */
  51         protected $purgeLimit = 100;
  52         /** @var int */
  53         protected $shards = 1;
  54         /** @var string */
  55         protected $tableName = 'objectcache';
  56         /** @var bool */
  57         protected $replicaOnly = false;
  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         /** @var int */
  69         private static $GARBAGE_COLLECT_DELAY_SEC = 1;
  70
  71         /** @var string */
  72         private static $OP_SET = 'set';
  73         /** @var string */
  74         private static $OP_ADD = 'add';
  75         /** @var string */
  76         private static $OP_TOUCH = 'touch';
  77         /** @var string */
  78         private static $OP_DELETE = 'delete';
  79
  80         /**
  81          * Constructor. Parameters are:
  82          *   - server:      A server info structure in the format required by each
  83          *                  element in $wgDBServers.
  84          *
  85          *   - servers:     An array of server info structures describing a set of database servers
  86          *                  to distribute keys to. If this is specified, the "server" option will be
  87          *                  ignored. If string keys are used, then they will be used for consistent
  88          *                  hashing *instead* of the host name (from the server config). This is useful
  89          *                  when a cluster is replicated to another site (with different host names)
  90          *                  but each server has a corresponding replica in the other cluster.
  91          *
  92          *   - purgePeriod: The average number of object cache writes in between
  93          *                  garbage collection operations, where expired entries
  94          *                  are removed from the database. Or in other words, the
  95          *                  reciprocal of the probability of purging on any given
  96          *                  write. If this is set to zero, purging will never be done.
  97          *
  98          *   - purgeLimit:  Maximum number of rows to purge at once.
  99          *
 100          *   - tableName:   The table name to use, default is "objectcache".
 101          *
 102          *   - shards:      The number of tables to use for data storage on each server.
 103          *                  If this is more than 1, table names will be formed in the style
 104          *                  objectcacheNNN where NNN is the shard index, between 0 and
 105          *                  shards-1. The number of digits will be the minimum number
 106          *                  required to hold the largest shard index. Data will be
 107          *                  distributed across all tables by key hash. This is for
 108          *                  MySQL bugs 61735 <https://bugs.mysql.com/bug.php?id=61735>
 109          *                  and 61736 <https://bugs.mysql.com/bug.php?id=61736>.
 110          *
 111          *   - replicaOnly: Whether to only use replica DBs and avoid triggering
 112          *                  garbage collection logic of expired items. This only
 113          *                  makes sense if the primary DB is used and only if get()
 114          *                  calls will be used. This is used by ReplicatedBagOStuff.
 115          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 116          *
 117          * @param array $params
 118          */
 119         public function __construct( $params ) {
 120                 parent::__construct( $params );
 121
 122                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 123                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 124
 125                 if ( isset( $params['servers'] ) ) {
 126                         $this->serverInfos = [];
 127                         $this->serverTags = [];
 128                         $this->numServers = count( $params['servers'] );
 129                         $index = 0;
 130                         foreach ( $params['servers'] as $tag => $info ) {
 131                                 $this->serverInfos[$index] = $info;
 132                                 if ( is_string( $tag ) ) {
 133                                         $this->serverTags[$index] = $tag;
 134                                 } else {
 135                                         $this->serverTags[$index] = $info['host'] ?? "#$index";
 136                                 }
 137                                 ++$index;
 138                         }
 139                 } elseif ( isset( $params['server'] ) ) {
 140                         $this->serverInfos = [ $params['server'] ];
 141                         $this->numServers = count( $this->serverInfos );
 142                 } else {
 143                         // Default to using the main wiki's database servers
 144                         $this->serverInfos = false;
 145                         $this->numServers = 1;
 146                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 147                 }
 148                 if ( isset( $params['purgePeriod'] ) ) {
 149                         $this->purgePeriod = intval( $params['purgePeriod'] );
 150                 }
 151                 if ( isset( $params['purgeLimit'] ) ) {
 152                         $this->purgeLimit = intval( $params['purgeLimit'] );
 153                 }
 154                 if ( isset( $params['tableName'] ) ) {
 155                         $this->tableName = $params['tableName'];
 156                 }
 157                 if ( isset( $params['shards'] ) ) {
 158                         $this->shards = intval( $params['shards'] );
 159                 }
 160                 // Backwards-compatibility for < 1.34
 161                 $this->replicaOnly = $params['replicaOnly'] ?? ( $params['slaveOnly'] ?? false );
 162         }
 163
 164         /**
 165          * Get a connection to the specified database
 166          *
 167          * @param int $serverIndex
 168          * @return Database
 169          * @throws MWException
 170          */
 171         protected function getDB( $serverIndex ) {
 172                 if ( $serverIndex >= $this->numServers ) {
 173                         throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 174                 }
 175
 176                 # Don't keep timing out trying to connect for each call if the DB is down
 177                 if (
 178                         isset( $this->connFailureErrors[$serverIndex] ) &&
 179                         ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 180                 ) {
 181                         throw $this->connFailureErrors[$serverIndex];
 182                 }
 183
 184                 if ( $this->serverInfos ) {
 185                         if ( !isset( $this->conns[$serverIndex] ) ) {
 186                                 // Use custom database defined by server connection info
 187                                 $info = $this->serverInfos[$serverIndex];
 188                                 $type = $info['type'] ?? 'mysql';
 189                                 $host = $info['host'] ?? '[unknown]';
 190                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 191                                 $db = Database::factory( $type, $info );
 192                                 $db->clearFlag( DBO_TRX ); // auto-commit mode
 193                                 $this->conns[$serverIndex] = $db;
 194                         }
 195                         $db = $this->conns[$serverIndex];
 196                 } else {
 197                         // Use the main LB database
 198                         $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 199                         $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 200                         if ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' ) {
 201                                 // Keep a separate connection to avoid contention and deadlocks
 202                                 $db = $lb->getConnection( $index, [], false, $lb::CONN_TRX_AUTOCOMMIT );
 203                         } else {
 204                                 // However, SQLite has the opposite behavior due to DB-level locking.
 205                                 // Stock sqlite MediaWiki installs use a separate sqlite cache DB instead.
 206                                 $db = $lb->getConnection( $index );
 207                         }
 208                 }
 209
 210                 $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 211
 212                 return $db;
 213         }
 214
 215         /**
 216          * Get the server index and table name for a given key
 217          * @param string $key
 218          * @return array Server index and table name
 219          */
 220         protected function getTableByKey( $key ) {
 221                 if ( $this->shards > 1 ) {
 222                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 223                         $tableIndex = $hash % $this->shards;
 224                 } else {
 225                         $tableIndex = 0;
 226                 }
 227                 if ( $this->numServers > 1 ) {
 228                         $sortedServers = $this->serverTags;
 229                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 230                         reset( $sortedServers );
 231                         $serverIndex = key( $sortedServers );
 232                 } else {
 233                         $serverIndex = 0;
 234                 }
 235                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 236         }
 237
 238         /**
 239          * Get the table name for a given shard index
 240          * @param int $index
 241          * @return string
 242          */
 243         protected function getTableNameByShard( $index ) {
 244                 if ( $this->shards > 1 ) {
 245                         $decimals = strlen( $this->shards - 1 );
 246                         return $this->tableName .
 247                                 sprintf( "%0{$decimals}d", $index );
 248                 } else {
 249                         return $this->tableName;
 250                 }
 251         }
 252
 253         protected function doGet( $key, $flags = 0, &$casToken = null ) {
 254                 $casToken = null;
 255
 256                 $blobs = $this->fetchBlobMulti( [ $key ] );
 257                 if ( array_key_exists( $key, $blobs ) ) {
 258                         $blob = $blobs[$key];
 259                         $value = $this->unserialize( $blob );
 260
 261                         $casToken = ( $value !== false ) ? $blob : null;
 262
 263                         return $value;
 264                 }
 265
 266                 return false;
 267         }
 268
 269         protected function doGetMulti( array $keys, $flags = 0 ) {
 270                 $values = [];
 271
 272                 $blobs = $this->fetchBlobMulti( $keys );
 273                 foreach ( $blobs as $key => $blob ) {
 274                         $values[$key] = $this->unserialize( $blob );
 275                 }
 276
 277                 return $values;
 278         }
 279
 280         protected function fetchBlobMulti( array $keys, $flags = 0 ) {
 281                 $values = []; // array of (key => value)
 282
 283                 $keysByTable = [];
 284                 foreach ( $keys as $key ) {
 285                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 286                         $keysByTable[$serverIndex][$tableName][] = $key;
 287                 }
 288
 289                 $dataRows = [];
 290                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 291                         try {
 292                                 $db = $this->getDB( $serverIndex );
 293                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 294                                         $res = $db->select( $tableName,
 295                                                 [ 'keyname', 'value', 'exptime' ],
 296                                                 [ 'keyname' => $tableKeys ],
 297                                                 __METHOD__,
 298                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 299                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 300                                                 // We do not want to flush the TRX as that can break callers.
 301                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 302                                         );
 303                                         if ( $res === false ) {
 304                                                 continue;
 305                                         }
 306                                         foreach ( $res as $row ) {
 307                                                 $row->serverIndex = $serverIndex;
 308                                                 $row->tableName = $tableName;
 309                                                 $dataRows[$row->keyname] = $row;
 310                                         }
 311                                 }
 312                         } catch ( DBError $e ) {
 313                                 $this->handleReadError( $e, $serverIndex );
 314                         }
 315                 }
 316
 317                 foreach ( $keys as $key ) {
 318                         if ( isset( $dataRows[$key] ) ) { // HIT?
 319                                 $row = $dataRows[$key];
 320                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 321                                 $db = null; // in case of connection failure
 322                                 try {
 323                                         $db = $this->getDB( $row->serverIndex );
 324                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 325                                                 $this->debug( "get: key has expired" );
 326                                         } else { // HIT
 327                                                 $values[$key] = $db->decodeBlob( $row->value );
 328                                         }
 329                                 } catch ( DBQueryError $e ) {
 330                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 331                                 }
 332                         } else { // MISS
 333                                 $this->debug( 'get: no matching rows' );
 334                         }
 335                 }
 336
 337                 return $values;
 338         }
 339
 340         protected function doSetMulti( array $data, $exptime = 0, $flags = 0 ) {
 341                 return $this->modifyMulti( $data, $exptime, $flags, self::$OP_SET );
 342         }
 343
 344         /**
 345          * @param mixed[]|null[] $data Map of (key => new value or null)
 346          * @param int $exptime UNIX timestamp, TTL in seconds, or 0 (no expiration)
 347          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 348          * @param string $op Cache operation
 349          * @return bool
 350          */
 351         private function modifyMulti( array $data, $exptime, $flags, $op ) {
 352                 $keysByTable = [];
 353                 foreach ( $data as $key => $value ) {
 354                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 355                         $keysByTable[$serverIndex][$tableName][] = $key;
 356                 }
 357
 358                 $exptime = $this->convertToExpiry( $exptime );
 359
 360                 $result = true;
 361                 /** @noinspection PhpUnusedLocalVariableInspection */
 362                 $silenceScope = $this->silenceTransactionProfiler();
 363                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 364                         $db = null; // in case of connection failure
 365                         try {
 366                                 $db = $this->getDB( $serverIndex );
 367                                 $this->occasionallyGarbageCollect( $db ); // expire old entries if any
 368                                 $dbExpiry = $exptime ? $db->timestamp( $exptime ) : $this->getMaxDateTime( $db );
 369                         } catch ( DBError $e ) {
 370                                 $this->handleWriteError( $e, $db, $serverIndex );
 371                                 $result = false;
 372                                 continue;
 373                         }
 374
 375                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 376                                 try {
 377                                         $result = $this->updateTableKeys(
 378                                                 $op,
 379                                                 $db,
 380                                                 $tableName,
 381                                                 $tableKeys,
 382                                                 $data,
 383                                                 $dbExpiry
 384                                         ) && $result;
 385                                 } catch ( DBError $e ) {
 386                                         $this->handleWriteError( $e, $db, $serverIndex );
 387                                         $result = false;
 388                                 }
 389
 390                         }
 391                 }
 392
 393                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 394                         $result = $this->waitForReplication() && $result;
 395                 }
 396
 397                 return $result;
 398         }
 399
 400         /**
 401          * @param string $op
 402          * @param IDatabase $db
 403          * @param string $table
 404          * @param string[] $tableKeys Keys in $data to update
 405          * @param mixed[]|null[] $data Map of (key => new value or null)
 406          * @param string $dbExpiry DB-encoded expiry
 407          * @return bool
 408          * @throws DBError
 409          * @throws InvalidArgumentException
 410          */
 411         private function updateTableKeys( $op, $db, $table, $tableKeys, $data, $dbExpiry ) {
 412                 $success = true;
 413
 414                 if ( $op === self::$OP_ADD ) {
 415                         $rows = [];
 416                         foreach ( $tableKeys as $key ) {
 417                                 $rows[] = [
 418                                         'keyname' => $key,
 419                                         'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 420                                         'exptime' => $dbExpiry
 421                                 ];
 422                         }
 423                         $db->delete(
 424                                 $table,
 425                                 [
 426                                         'keyname' => $tableKeys,
 427                                         'exptime <= ' . $db->addQuotes( $db->timestamp() )
 428                                 ],
 429                                 __METHOD__
 430                         );
 431                         $db->insert( $table, $rows, __METHOD__, [ 'IGNORE' ] );
 432
 433                         $success = ( $db->affectedRows() == count( $rows ) );
 434                 } elseif ( $op === self::$OP_SET ) {
 435                         $rows = [];
 436                         foreach ( $tableKeys as $key ) {
 437                                 $rows[] = [
 438                                         'keyname' => $key,
 439                                         'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 440                                         'exptime' => $dbExpiry
 441                                 ];
 442                         }
 443                         $db->replace( $table, [ 'keyname' ], $rows, __METHOD__ );
 444                 } elseif ( $op === self::$OP_DELETE ) {
 445                         $db->delete( $table, [ 'keyname' => $tableKeys ], __METHOD__ );
 446                 } elseif ( $op === self::$OP_TOUCH ) {
 447                         $db->update(
 448                                 $table,
 449                                 [ 'exptime' => $dbExpiry ],
 450                                 [
 451                                         'keyname' => $tableKeys,
 452                                         'exptime > ' . $db->addQuotes( $db->timestamp() )
 453                                 ],
 454                                 __METHOD__
 455                         );
 456
 457                         $success = ( $db->affectedRows() == count( $tableKeys ) );
 458                 } else {
 459                         throw new InvalidArgumentException( "Invalid operation '$op'" );
 460                 }
 461
 462                 return $success;
 463         }
 464
 465         protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
 466                 return $this->modifyMulti( [ $key => $value ], $exptime, $flags, self::$OP_SET );
 467         }
 468
 469         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
 470                 return $this->modifyMulti( [ $key => $value ], $exptime, $flags, self::$OP_ADD );
 471         }
 472
 473         protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 474                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 475                 $exptime = $this->convertToExpiry( $exptime );
 476
 477                 /** @noinspection PhpUnusedLocalVariableInspection */
 478                 $silenceScope = $this->silenceTransactionProfiler();
 479                 $db = null; // in case of connection failure
 480                 try {
 481                         $db = $this->getDB( $serverIndex );
 482                         // (T26425) use a replace if the db supports it instead of
 483                         // delete/insert to avoid clashes with conflicting keynames
 484                         $db->update(
 485                                 $tableName,
 486                                 [
 487                                         'keyname' => $key,
 488                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 489                                         'exptime' => $exptime
 490                                                 ? $db->timestamp( $exptime )
 491                                                 : $this->getMaxDateTime( $db )
 492                                 ],
 493                                 [
 494                                         'keyname' => $key,
 495                                         'value' => $db->encodeBlob( $casToken ),
 496                                         'exptime > ' . $db->addQuotes( $db->timestamp() )
 497                                 ],
 498                                 __METHOD__
 499                         );
 500                 } catch ( DBQueryError $e ) {
 501                         $this->handleWriteError( $e, $db, $serverIndex );
 502
 503                         return false;
 504                 }
 505
 506                 return (bool)$db->affectedRows();
 507         }
 508
 509         protected function doDeleteMulti( array $keys, $flags = 0 ) {
 510                 return $this->modifyMulti(
 511                         array_fill_keys( $keys, null ),
 512                         0,
 513                         $flags,
 514                         self::$OP_DELETE
 515                 );
 516         }
 517
 518         protected function doDelete( $key, $flags = 0 ) {
 519                 return $this->modifyMulti( [ $key => null ], 0, $flags, self::$OP_DELETE );
 520         }
 521
 522         public function incr( $key, $step = 1 ) {
 523                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 524
 525                 $newCount = false;
 526                 /** @noinspection PhpUnusedLocalVariableInspection */
 527                 $silenceScope = $this->silenceTransactionProfiler();
 528                 $db = null; // in case of connection failure
 529                 try {
 530                         $db = $this->getDB( $serverIndex );
 531                         $encTimestamp = $db->addQuotes( $db->timestamp() );
 532                         $db->update(
 533                                 $tableName,
 534                                 [ 'value = value + ' . (int)$step ],
 535                                 [ 'keyname' => $key, "exptime > $encTimestamp" ],
 536                                 __METHOD__
 537                         );
 538                         if ( $db->affectedRows() > 0 ) {
 539                                 $newValue = $db->selectField(
 540                                         $tableName,
 541                                         'value',
 542                                         [ 'keyname' => $key, "exptime > $encTimestamp" ],
 543                                         __METHOD__
 544                                 );
 545                                 if ( $this->isInteger( $newValue ) ) {
 546                                         $newCount = (int)$newValue;
 547                                 }
 548                         }
 549                 } catch ( DBError $e ) {
 550                         $this->handleWriteError( $e, $db, $serverIndex );
 551                 }
 552
 553                 return $newCount;
 554         }
 555
 556         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 557                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
 558                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 559                         $ok = $this->waitForReplication() && $ok;
 560                 }
 561
 562                 return $ok;
 563         }
 564
 565         protected function doChangeTTLMulti( array $keys, $exptime, $flags = 0 ) {
 566                 return $this->modifyMulti(
 567                         array_fill_keys( $keys, null ),
 568                         $exptime,
 569                         $flags,
 570                         self::$OP_TOUCH
 571                 );
 572         }
 573
 574         protected function doChangeTTL( $key, $exptime, $flags ) {
 575                 return $this->modifyMulti( [ $key => null ], $exptime, $flags, self::$OP_TOUCH );
 576         }
 577
 578         /**
 579          * @param IDatabase $db
 580          * @param string $exptime
 581          * @return bool
 582          */
 583         protected function isExpired( $db, $exptime ) {
 584                 return (
 585                         $exptime != $this->getMaxDateTime( $db ) &&
 586                         wfTimestamp( TS_UNIX, $exptime ) < time()
 587                 );
 588         }
 589
 590         /**
 591          * @param IDatabase $db
 592          * @return string
 593          */
 594         protected function getMaxDateTime( $db ) {
 595                 if ( time() > 0x7fffffff ) {
 596                         return $db->timestamp( 1 << 62 );
 597                 } else {
 598                         return $db->timestamp( 0x7fffffff );
 599                 }
 600         }
 601
 602         /**
 603          * @param IDatabase $db
 604          * @throws DBError
 605          */
 606         protected function occasionallyGarbageCollect( IDatabase $db ) {
 607                 if (
 608                         // Random purging is enabled
 609                         $this->purgePeriod &&
 610                         // Only purge on one in every $this->purgePeriod writes
 611                         mt_rand( 0, $this->purgePeriod - 1 ) == 0 &&
 612                         // Avoid repeating the delete within a few seconds
 613                         ( time() - $this->lastGarbageCollect ) > self::$GARBAGE_COLLECT_DELAY_SEC
 614                 ) {
 615                         $garbageCollector = function () use ( $db ) {
 616                                 $this->deleteServerObjectsExpiringBefore( $db, time(), null, $this->purgeLimit );
 617                                 $this->lastGarbageCollect = time();
 618                         };
 619                         if ( $this->asyncHandler ) {
 620                                 $this->lastGarbageCollect = time(); // avoid duplicate enqueues
 621                                 ( $this->asyncHandler )( $garbageCollector );
 622                         } else {
 623                                 $garbageCollector();
 624                         }
 625                 }
 626         }
 627
 628         public function expireAll() {
 629                 $this->deleteObjectsExpiringBefore( time() );
 630         }
 631
 632         public function deleteObjectsExpiringBefore(
 633                 $timestamp,
 634                 callable $progress = null,
 635                 $limit = INF
 636         ) {
 637                 /** @noinspection PhpUnusedLocalVariableInspection */
 638                 $silenceScope = $this->silenceTransactionProfiler();
 639
 640                 $serverIndexes = range( 0, $this->numServers - 1 );
 641                 shuffle( $serverIndexes );
 642
 643                 $ok = true;
 644
 645                 $keysDeletedCount = 0;
 646                 foreach ( $serverIndexes as $numServersDone => $serverIndex ) {
 647                         $db = null; // in case of connection failure
 648                         try {
 649                                 $db = $this->getDB( $serverIndex );
 650                                 $this->deleteServerObjectsExpiringBefore(
 651                                         $db,
 652                                         $timestamp,
 653                                         $progress,
 654                                         $limit,
 655                                         $numServersDone,
 656                                         $keysDeletedCount
 657                                 );
 658                         } catch ( DBError $e ) {
 659                                 $this->handleWriteError( $e, $db, $serverIndex );
 660                                 $ok = false;
 661                         }
 662                 }
 663
 664                 return $ok;
 665         }
 666
 667         /**
 668          * @param IDatabase $db
 669          * @param string|int $timestamp
 670          * @param callable|null $progressCallback
 671          * @param int $limit
 672          * @param int $serversDoneCount
 673          * @param int &$keysDeletedCount
 674          * @throws DBError
 675          */
 676         private function deleteServerObjectsExpiringBefore(
 677                 IDatabase $db,
 678                 $timestamp,
 679                 $progressCallback,
 680                 $limit,
 681                 $serversDoneCount = 0,
 682                 &$keysDeletedCount = 0
 683         ) {
 684                 $cutoffUnix = wfTimestamp( TS_UNIX, $timestamp );
 685                 $shardIndexes = range( 0, $this->shards - 1 );
 686                 shuffle( $shardIndexes );
 687
 688                 foreach ( $shardIndexes as $numShardsDone => $shardIndex ) {
 689                         $continue = null; // last exptime
 690                         $lag = null; // purge lag
 691                         do {
 692                                 $res = $db->select(
 693                                         $this->getTableNameByShard( $shardIndex ),
 694                                         [ 'keyname', 'exptime' ],
 695                                         array_merge(
 696                                                 [ 'exptime < ' . $db->addQuotes( $db->timestamp( $cutoffUnix ) ) ],
 697                                                 $continue ? [ 'exptime >= ' . $db->addQuotes( $continue ) ] : []
 698                                         ),
 699                                         __METHOD__,
 700                                         [ 'LIMIT' => min( $limit, 100 ), 'ORDER BY' => 'exptime' ]
 701                                 );
 702
 703                                 if ( $res->numRows() ) {
 704                                         $row = $res->current();
 705                                         if ( $lag === null ) {
 706                                                 $lag = max( $cutoffUnix - wfTimestamp( TS_UNIX, $row->exptime ), 1 );
 707                                         }
 708
 709                                         $keys = [];
 710                                         foreach ( $res as $row ) {
 711                                                 $keys[] = $row->keyname;
 712                                                 $continue = $row->exptime;
 713                                         }
 714
 715                                         $db->delete(
 716                                                 $this->getTableNameByShard( $shardIndex ),
 717                                                 [
 718                                                         'exptime < ' . $db->addQuotes( $db->timestamp( $cutoffUnix ) ),
 719                                                         'keyname' => $keys
 720                                                 ],
 721                                                 __METHOD__
 722                                         );
 723                                         $keysDeletedCount += $db->affectedRows();
 724                                 }
 725
 726                                 if ( is_callable( $progressCallback ) ) {
 727                                         if ( $lag ) {
 728                                                 $remainingLag = $cutoffUnix - wfTimestamp( TS_UNIX, $continue );
 729                                                 $processedLag = max( $lag - $remainingLag, 0 );
 730                                                 $doneRatio = ( $numShardsDone + $processedLag / $lag ) / $this->shards;
 731                                         } else {
 732                                                 $doneRatio = 1;
 733                                         }
 734
 735                                         $overallRatio = ( $doneRatio / $this->numServers )
 736                                                 + ( $serversDoneCount / $this->numServers );
 737                                         call_user_func( $progressCallback, $overallRatio * 100 );
 738                                 }
 739                         } while ( $res->numRows() && $keysDeletedCount < $limit );
 740                 }
 741         }
 742
 743         /**
 744          * Delete content of shard tables in every server.
 745          * Return true if the operation is successful, false otherwise.
 746          * @return bool
 747          */
 748         public function deleteAll() {
 749                 /** @noinspection PhpUnusedLocalVariableInspection */
 750                 $silenceScope = $this->silenceTransactionProfiler();
 751                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 752                         $db = null; // in case of connection failure
 753                         try {
 754                                 $db = $this->getDB( $serverIndex );
 755                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 756                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 757                                 }
 758                         } catch ( DBError $e ) {
 759                                 $this->handleWriteError( $e, $db, $serverIndex );
 760                                 return false;
 761                         }
 762                 }
 763                 return true;
 764         }
 765
 766         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 767                 // Avoid deadlocks and allow lock reentry if specified
 768                 if ( isset( $this->locks[$key] ) ) {
 769                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 770                                 ++$this->locks[$key]['depth'];
 771                                 return true;
 772                         } else {
 773                                 return false;
 774                         }
 775                 }
 776
 777                 list( $serverIndex ) = $this->getTableByKey( $key );
 778
 779                 $db = null; // in case of connection failure
 780                 try {
 781                         $db = $this->getDB( $serverIndex );
 782                         $ok = $db->lock( $key, __METHOD__, $timeout );
 783                         if ( $ok ) {
 784                                 $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 785                         }
 786
 787                         $this->logger->warning(
 788                                 __METHOD__ . " failed due to timeout for {key}.",
 789                                 [ 'key' => $key, 'timeout' => $timeout ]
 790                         );
 791
 792                         return $ok;
 793                 } catch ( DBError $e ) {
 794                         $this->handleWriteError( $e, $db, $serverIndex );
 795                         $ok = false;
 796                 }
 797
 798                 return $ok;
 799         }
 800
 801         public function unlock( $key ) {
 802                 if ( !isset( $this->locks[$key] ) ) {
 803                         return false;
 804                 }
 805
 806                 if ( --$this->locks[$key]['depth'] <= 0 ) {
 807                         unset( $this->locks[$key] );
 808
 809                         list( $serverIndex ) = $this->getTableByKey( $key );
 810
 811                         $db = null; // in case of connection failure
 812                         try {
 813                                 $db = $this->getDB( $serverIndex );
 814                                 $ok = $db->unlock( $key, __METHOD__ );
 815                                 if ( !$ok ) {
 816                                         $this->logger->warning(
 817                                                 __METHOD__ . ' failed to release lock for {key}.',
 818                                                 [ 'key' => $key ]
 819                                         );
 820                                 }
 821                         } catch ( DBError $e ) {
 822                                 $this->handleWriteError( $e, $db, $serverIndex );
 823                                 $ok = false;
 824                         }
 825
 826                         return $ok;
 827                 }
 828
 829                 return true;
 830         }
 831
 832         /**
 833          * Serialize an object and, if possible, compress the representation.
 834          * On typical message and page data, this can provide a 3X decrease
 835          * in storage requirements.
 836          *
 837          * @param mixed $data
 838          * @return string|int
 839          */
 840         protected function serialize( $data ) {
 841                 if ( is_int( $data ) ) {
 842                         return $data;
 843                 }
 844
 845                 $serial = serialize( $data );
 846                 if ( function_exists( 'gzdeflate' ) ) {
 847                         $serial = gzdeflate( $serial );
 848                 }
 849
 850                 return $serial;
 851         }
 852
 853         /**
 854          * Unserialize and, if necessary, decompress an object.
 855          * @param string $serial
 856          * @return mixed
 857          */
 858         protected function unserialize( $serial ) {
 859                 if ( $this->isInteger( $serial ) ) {
 860                         return (int)$serial;
 861                 }
 862
 863                 if ( function_exists( 'gzinflate' ) ) {
 864                         Wikimedia\suppressWarnings();
 865                         $decomp = gzinflate( $serial );
 866                         Wikimedia\restoreWarnings();
 867
 868                         if ( $decomp !== false ) {
 869                                 $serial = $decomp;
 870                         }
 871                 }
 872
 873                 return unserialize( $serial );
 874         }
 875
 876         /**
 877          * Handle a DBError which occurred during a read operation.
 878          *
 879          * @param DBError $exception
 880          * @param int $serverIndex
 881          */
 882         protected function handleReadError( DBError $exception, $serverIndex ) {
 883                 if ( $exception instanceof DBConnectionError ) {
 884                         $this->markServerDown( $exception, $serverIndex );
 885                 }
 886
 887                 $this->setAndLogDBError( $exception );
 888         }
 889
 890         /**
 891          * Handle a DBQueryError which occurred during a write operation.
 892          *
 893          * @param DBError $exception
 894          * @param IDatabase|null $db DB handle or null if connection failed
 895          * @param int $serverIndex
 896          * @throws Exception
 897          */
 898         protected function handleWriteError( DBError $exception, $db, $serverIndex ) {
 899                 if ( !( $db instanceof IDatabase ) ) {
 900                         $this->markServerDown( $exception, $serverIndex );
 901                 }
 902
 903                 $this->setAndLogDBError( $exception );
 904         }
 905
 906         /**
 907          * @param DBError $exception
 908          */
 909         private function setAndLogDBError( DBError $exception ) {
 910                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 911                 if ( $exception instanceof DBConnectionError ) {
 912                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 913                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 914                 } else {
 915                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 916                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 917                 }
 918         }
 919
 920         /**
 921          * Mark a server down due to a DBConnectionError exception
 922          *
 923          * @param DBError $exception
 924          * @param int $serverIndex
 925          */
 926         protected function markServerDown( DBError $exception, $serverIndex ) {
 927                 unset( $this->conns[$serverIndex] ); // bug T103435
 928
 929                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 930                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 931                                 unset( $this->connFailureTimes[$serverIndex] );
 932                                 unset( $this->connFailureErrors[$serverIndex] );
 933                         } else {
 934                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 935                                 return;
 936                         }
 937                 }
 938                 $now = time();
 939                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 940                 $this->connFailureTimes[$serverIndex] = $now;
 941                 $this->connFailureErrors[$serverIndex] = $exception;
 942         }
 943
 944         /**
 945          * Create shard tables. For use from eval.php.
 946          */
 947         public function createTables() {
 948                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 949                         $db = $this->getDB( $serverIndex );
 950                         if ( $db->getType() !== 'mysql' ) {
 951                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 952                         }
 953
 954                         for ( $i = 0; $i < $this->shards; $i++ ) {
 955                                 $db->query(
 956                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 957                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 958                                         __METHOD__ );
 959                         }
 960                 }
 961         }
 962
 963         /**
 964          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 965          */
 966         protected function usesMainDB() {
 967                 return !$this->serverInfos;
 968         }
 969
 970         protected function waitForReplication() {
 971                 if ( !$this->usesMainDB() ) {
 972                         // Custom DB server list; probably doesn't use replication
 973                         return true;
 974                 }
 975
 976                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 977                 if ( $lb->getServerCount() <= 1 ) {
 978                         return true; // no replica DBs
 979                 }
 980
 981                 // Main LB is used; wait for any replica DBs to catch up
 982                 try {
 983                         $masterPos = $lb->getMasterPos();
 984                         if ( !$masterPos ) {
 985                                 return true; // not applicable
 986                         }
 987
 988                         $loop = new WaitConditionLoop(
 989                                 function () use ( $lb, $masterPos ) {
 990                                         return $lb->waitForAll( $masterPos, 1 );
 991                                 },
 992                                 $this->syncTimeout,
 993                                 $this->busyCallbacks
 994                         );
 995
 996                         return ( $loop->invoke() === $loop::CONDITION_REACHED );
 997                 } catch ( DBError $e ) {
 998                         $this->setAndLogDBError( $e );
 999
1000                         return false;
1001                 }
1002         }
1003
1004         /**
1005          * Returns a ScopedCallback which resets the silence flag in the transaction profiler when it is
1006          * destroyed on the end of a scope, for example on return or throw
1007          * @return ScopedCallback
1008          * @since 1.32
1009          */
1010         protected function silenceTransactionProfiler() {
1011                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
1012                 $oldSilenced = $trxProfiler->setSilenced( true );
1013                 return new ScopedCallback( function () use ( $trxProfiler, $oldSilenced ) {
1014                         $trxProfiler->setSilenced( $oldSilenced );
1015                 } );
1016         }
1017 }