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\AtEase\AtEase;
  26 use Wikimedia\Rdbms\Database;
  27 use Wikimedia\Rdbms\IDatabase;
  28 use Wikimedia\Rdbms\DBError;
  29 use Wikimedia\Rdbms\DBQueryError;
  30 use Wikimedia\Rdbms\DBConnectionError;
  31 use Wikimedia\Rdbms\IMaintainableDatabase;
  32 use Wikimedia\Rdbms\LoadBalancer;
  33 use Wikimedia\ScopedCallback;
  34 use Wikimedia\Timestamp\ConvertibleTimestamp;
  35 use Wikimedia\WaitConditionLoop;
  36
  37 /**
  38  * Class to store objects in the database
  39  *
  40  * @ingroup Cache
  41  */
  42 class SqlBagOStuff extends MediumSpecificBagOStuff {
  43         /** @var array[] (server index => server config) */
  44         protected $serverInfos;
  45         /** @var string[] (server index => tag/host name) */
  46         protected $serverTags;
  47         /** @var int */
  48         protected $numServerShards;
  49         /** @var int UNIX timestamp */
  50         protected $lastGarbageCollect = 0;
  51         /** @var int */
  52         protected $purgePeriod = 10;
  53         /** @var int */
  54         protected $purgeLimit = 100;
  55         /** @var int */
  56         protected $numTableShards = 1;
  57         /** @var string */
  58         protected $tableName = 'objectcache';
  59         /** @var bool */
  60         protected $replicaOnly = false;
  61
  62         /** @var LoadBalancer|null */
  63         protected $separateMainLB;
  64         /** @var array */
  65         protected $conns;
  66         /** @var array UNIX timestamps */
  67         protected $connFailureTimes = [];
  68         /** @var array Exceptions */
  69         protected $connFailureErrors = [];
  70
  71         /** @var int */
  72         private static $GC_DELAY_SEC = 1;
  73
  74         /** @var string */
  75         private static $OP_SET = 'set';
  76         /** @var string */
  77         private static $OP_ADD = 'add';
  78         /** @var string */
  79         private static $OP_TOUCH = 'touch';
  80         /** @var string */
  81         private static $OP_DELETE = 'delete';
  82
  83         /**
  84          * Constructor. Parameters are:
  85          *   - server:      A server info structure in the format required by each
  86          *                  element in $wgDBServers.
  87          *
  88          *   - servers:     An array of server info structures describing a set of database servers
  89          *                  to distribute keys to. If this is specified, the "server" option will be
  90          *                  ignored. If string keys are used, then they will be used for consistent
  91          *                  hashing *instead* of the host name (from the server config). This is useful
  92          *                  when a cluster is replicated to another site (with different host names)
  93          *                  but each server has a corresponding replica in the other cluster.
  94          *
  95          *   - purgePeriod: The average number of object cache writes in between
  96          *                  garbage collection operations, where expired entries
  97          *                  are removed from the database. Or in other words, the
  98          *                  reciprocal of the probability of purging on any given
  99          *                  write. If this is set to zero, purging will never be done.
 100          *
 101          *   - purgeLimit:  Maximum number of rows to purge at once.
 102          *
 103          *   - tableName:   The table name to use, default is "objectcache".
 104          *
 105          *   - shards:      The number of tables to use for data storage on each server.
 106          *                  If this is more than 1, table names will be formed in the style
 107          *                  objectcacheNNN where NNN is the shard index, between 0 and
 108          *                  shards-1. The number of digits will be the minimum number
 109          *                  required to hold the largest shard index. Data will be
 110          *                  distributed across all tables by key hash. This is for
 111          *                  MySQL bugs 61735 <https://bugs.mysql.com/bug.php?id=61735>
 112          *                  and 61736 <https://bugs.mysql.com/bug.php?id=61736>.
 113          *
 114          *   - replicaOnly: Whether to only use replica DBs and avoid triggering
 115          *                  garbage collection logic of expired items. This only
 116          *                  makes sense if the primary DB is used and only if get()
 117          *                  calls will be used. This is used by ReplicatedBagOStuff.
 118          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 119          *
 120          * @param array $params
 121          */
 122         public function __construct( $params ) {
 123                 parent::__construct( $params );
 124
 125                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 126                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 127
 128                 if ( isset( $params['servers'] ) ) {
 129                         $this->serverInfos = [];
 130                         $this->serverTags = [];
 131                         $this->numServerShards = count( $params['servers'] );
 132                         $index = 0;
 133                         foreach ( $params['servers'] as $tag => $info ) {
 134                                 $this->serverInfos[$index] = $info;
 135                                 if ( is_string( $tag ) ) {
 136                                         $this->serverTags[$index] = $tag;
 137                                 } else {
 138                                         $this->serverTags[$index] = $info['host'] ?? "#$index";
 139                                 }
 140                                 ++$index;
 141                         }
 142                 } elseif ( isset( $params['server'] ) ) {
 143                         $this->serverInfos = [ $params['server'] ];
 144                         $this->numServerShards = count( $this->serverInfos );
 145                 } else {
 146                         // Default to using the main wiki's database servers
 147                         $this->serverInfos = [];
 148                         $this->numServerShards = 1;
 149                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 150                 }
 151                 if ( isset( $params['purgePeriod'] ) ) {
 152                         $this->purgePeriod = intval( $params['purgePeriod'] );
 153                 }
 154                 if ( isset( $params['purgeLimit'] ) ) {
 155                         $this->purgeLimit = intval( $params['purgeLimit'] );
 156                 }
 157                 if ( isset( $params['tableName'] ) ) {
 158                         $this->tableName = $params['tableName'];
 159                 }
 160                 if ( isset( $params['shards'] ) ) {
 161                         $this->numTableShards = intval( $params['shards'] );
 162                 }
 163                 // Backwards-compatibility for < 1.34
 164                 $this->replicaOnly = $params['replicaOnly'] ?? ( $params['slaveOnly'] ?? false );
 165         }
 166
 167         /**
 168          * Get a connection to the specified database
 169          *
 170          * @param int $shardIndex
 171          * @return IMaintainableDatabase
 172          * @throws MWException
 173          */
 174         private function getConnection( $shardIndex ) {
 175                 if ( $shardIndex >= $this->numServerShards ) {
 176                         throw new MWException( __METHOD__ . ": Invalid server index \"$shardIndex\"" );
 177                 }
 178
 179                 # Don't keep timing out trying to connect for each call if the DB is down
 180                 if (
 181                         isset( $this->connFailureErrors[$shardIndex] ) &&
 182                         ( $this->getCurrentTime() - $this->connFailureTimes[$shardIndex] ) < 60
 183                 ) {
 184                         throw $this->connFailureErrors[$shardIndex];
 185                 }
 186
 187                 if ( $this->serverInfos ) {
 188                         if ( !isset( $this->conns[$shardIndex] ) ) {
 189                                 // Use custom database defined by server connection info
 190                                 $info = $this->serverInfos[$shardIndex];
 191                                 $type = $info['type'] ?? 'mysql';
 192                                 $host = $info['host'] ?? '[unknown]';
 193                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 194                                 $conn = Database::factory( $type, $info );
 195                                 $conn->clearFlag( DBO_TRX ); // auto-commit mode
 196                                 $this->conns[$shardIndex] = $conn;
 197                                 // Automatically create the objectcache table for sqlite as needed
 198                                 if ( $conn->getType() === 'sqlite' ) {
 199                                         $this->initSqliteDatabase( $conn );
 200                                 }
 201                         }
 202                         $conn = $this->conns[$shardIndex];
 203                 } else {
 204                         // Use the main LB database
 205                         $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 206                         $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 207                         // If the RDBMS has row-level locking, use the autocommit connection to avoid
 208                         // contention and deadlocks. Do not do this if it only has DB-level locking since
 209                         // that would just cause deadlocks.
 210                         $attribs = $lb->getServerAttributes( $lb->getWriterIndex() );
 211                         $flags = $attribs[Database::ATTR_DB_LEVEL_LOCKING] ? 0 : $lb::CONN_TRX_AUTOCOMMIT;
 212                         $conn = $lb->getMaintenanceConnectionRef( $index, [], false, $flags );
 213                 }
 214
 215                 $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $conn ) );
 216
 217                 return $conn;
 218         }
 219
 220         /**
 221          * Get the server index and table name for a given key
 222          * @param string $key
 223          * @return array Server index and table name
 224          */
 225         private function getTableByKey( $key ) {
 226                 if ( $this->numTableShards > 1 ) {
 227                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 228                         $tableIndex = $hash % $this->numTableShards;
 229                 } else {
 230                         $tableIndex = 0;
 231                 }
 232                 if ( $this->numServerShards > 1 ) {
 233                         $sortedServers = $this->serverTags;
 234                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 235                         reset( $sortedServers );
 236                         $shardIndex = key( $sortedServers );
 237                 } else {
 238                         $shardIndex = 0;
 239                 }
 240                 return [ $shardIndex, $this->getTableNameByShard( $tableIndex ) ];
 241         }
 242
 243         /**
 244          * Get the table name for a given shard index
 245          * @param int $index
 246          * @return string
 247          */
 248         private function getTableNameByShard( $index ) {
 249                 if ( $this->numTableShards > 1 ) {
 250                         $decimals = strlen( $this->numTableShards - 1 );
 251                         return $this->tableName .
 252                                 sprintf( "%0{$decimals}d", $index );
 253                 } else {
 254                         return $this->tableName;
 255                 }
 256         }
 257
 258         protected function doGet( $key, $flags = 0, &$casToken = null ) {
 259                 $casToken = null;
 260
 261                 $blobs = $this->fetchBlobMulti( [ $key ] );
 262                 if ( array_key_exists( $key, $blobs ) ) {
 263                         $blob = $blobs[$key];
 264                         $value = $this->unserialize( $blob );
 265
 266                         $casToken = ( $value !== false ) ? $blob : null;
 267
 268                         return $value;
 269                 }
 270
 271                 return false;
 272         }
 273
 274         protected function doGetMulti( array $keys, $flags = 0 ) {
 275                 $values = [];
 276
 277                 $blobs = $this->fetchBlobMulti( $keys );
 278                 foreach ( $blobs as $key => $blob ) {
 279                         $values[$key] = $this->unserialize( $blob );
 280                 }
 281
 282                 return $values;
 283         }
 284
 285         private function fetchBlobMulti( array $keys, $flags = 0 ) {
 286                 $values = []; // array of (key => value)
 287
 288                 $keysByTable = [];
 289                 foreach ( $keys as $key ) {
 290                         list( $shardIndex, $tableName ) = $this->getTableByKey( $key );
 291                         $keysByTable[$shardIndex][$tableName][] = $key;
 292                 }
 293
 294                 $dataRows = [];
 295                 foreach ( $keysByTable as $shardIndex => $serverKeys ) {
 296                         try {
 297                                 $db = $this->getConnection( $shardIndex );
 298                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 299                                         $res = $db->select( $tableName,
 300                                                 [ 'keyname', 'value', 'exptime' ],
 301                                                 [ 'keyname' => $tableKeys ],
 302                                                 __METHOD__,
 303                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 304                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 305                                                 // We do not want to flush the TRX as that can break callers.
 306                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 307                                         );
 308                                         if ( $res === false ) {
 309                                                 continue;
 310                                         }
 311                                         foreach ( $res as $row ) {
 312                                                 $row->shardIndex = $shardIndex;
 313                                                 $row->tableName = $tableName;
 314                                                 $dataRows[$row->keyname] = $row;
 315                                         }
 316                                 }
 317                         } catch ( DBError $e ) {
 318                                 $this->handleReadError( $e, $shardIndex );
 319                         }
 320                 }
 321
 322                 foreach ( $keys as $key ) {
 323                         if ( isset( $dataRows[$key] ) ) { // HIT?
 324                                 $row = $dataRows[$key];
 325                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 326                                 $db = null; // in case of connection failure
 327                                 try {
 328                                         $db = $this->getConnection( $row->shardIndex );
 329                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 330                                                 $this->debug( "get: key has expired" );
 331                                         } else { // HIT
 332                                                 $values[$key] = $db->decodeBlob( $row->value );
 333                                         }
 334                                 } catch ( DBQueryError $e ) {
 335                                         $this->handleWriteError( $e, $db, $row->shardIndex );
 336                                 }
 337                         } else { // MISS
 338                                 $this->debug( 'get: no matching rows' );
 339                         }
 340                 }
 341
 342                 return $values;
 343         }
 344
 345         protected function doSetMulti( array $data, $exptime = 0, $flags = 0 ) {
 346                 return $this->modifyMulti( $data, $exptime, $flags, self::$OP_SET );
 347         }
 348
 349         /**
 350          * @param mixed[]|null[] $data Map of (key => new value or null)
 351          * @param int $exptime UNIX timestamp, TTL in seconds, or 0 (no expiration)
 352          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 353          * @param string $op Cache operation
 354          * @return bool
 355          */
 356         private function modifyMulti( array $data, $exptime, $flags, $op ) {
 357                 $keysByTable = [];
 358                 foreach ( $data as $key => $value ) {
 359                         list( $shardIndex, $tableName ) = $this->getTableByKey( $key );
 360                         $keysByTable[$shardIndex][$tableName][] = $key;
 361                 }
 362
 363                 $exptime = $this->getExpirationAsTimestamp( $exptime );
 364
 365                 $result = true;
 366                 /** @noinspection PhpUnusedLocalVariableInspection */
 367                 $silenceScope = $this->silenceTransactionProfiler();
 368                 foreach ( $keysByTable as $shardIndex => $serverKeys ) {
 369                         $db = null; // in case of connection failure
 370                         try {
 371                                 $db = $this->getConnection( $shardIndex );
 372                                 $this->occasionallyGarbageCollect( $db ); // expire old entries if any
 373                                 $dbExpiry = $exptime ? $db->timestamp( $exptime ) : $this->getMaxDateTime( $db );
 374                         } catch ( DBError $e ) {
 375                                 $this->handleWriteError( $e, $db, $shardIndex );
 376                                 $result = false;
 377                                 continue;
 378                         }
 379
 380                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 381                                 try {
 382                                         $result = $this->updateTableKeys(
 383                                                 $op,
 384                                                 $db,
 385                                                 $tableName,
 386                                                 $tableKeys,
 387                                                 $data,
 388                                                 $dbExpiry
 389                                         ) && $result;
 390                                 } catch ( DBError $e ) {
 391                                         $this->handleWriteError( $e, $db, $shardIndex );
 392                                         $result = false;
 393                                 }
 394
 395                         }
 396                 }
 397
 398                 if ( $this->fieldHasFlags( $flags, self::WRITE_SYNC ) ) {
 399                         $result = $this->waitForReplication() && $result;
 400                 }
 401
 402                 return $result;
 403         }
 404
 405         /**
 406          * @param string $op
 407          * @param IDatabase $db
 408          * @param string $table
 409          * @param string[] $tableKeys Keys in $data to update
 410          * @param mixed[]|null[] $data Map of (key => new value or null)
 411          * @param string $dbExpiry DB-encoded expiry
 412          * @return bool
 413          * @throws DBError
 414          * @throws InvalidArgumentException
 415          */
 416         private function updateTableKeys( $op, $db, $table, $tableKeys, $data, $dbExpiry ) {
 417                 $success = true;
 418
 419                 if ( $op === self::$OP_ADD ) {
 420                         $rows = [];
 421                         foreach ( $tableKeys as $key ) {
 422                                 $rows[] = [
 423                                         'keyname' => $key,
 424                                         'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 425                                         'exptime' => $dbExpiry
 426                                 ];
 427                         }
 428                         $db->delete(
 429                                 $table,
 430                                 [
 431                                         'keyname' => $tableKeys,
 432                                         'exptime <= ' . $db->addQuotes( $db->timestamp() )
 433                                 ],
 434                                 __METHOD__
 435                         );
 436                         $db->insert( $table, $rows, __METHOD__, [ 'IGNORE' ] );
 437
 438                         $success = ( $db->affectedRows() == count( $rows ) );
 439                 } elseif ( $op === self::$OP_SET ) {
 440                         $rows = [];
 441                         foreach ( $tableKeys as $key ) {
 442                                 $rows[] = [
 443                                         'keyname' => $key,
 444                                         'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 445                                         'exptime' => $dbExpiry
 446                                 ];
 447                         }
 448                         $db->replace( $table, [ 'keyname' ], $rows, __METHOD__ );
 449                 } elseif ( $op === self::$OP_DELETE ) {
 450                         $db->delete( $table, [ 'keyname' => $tableKeys ], __METHOD__ );
 451                 } elseif ( $op === self::$OP_TOUCH ) {
 452                         $db->update(
 453                                 $table,
 454                                 [ 'exptime' => $dbExpiry ],
 455                                 [
 456                                         'keyname' => $tableKeys,
 457                                         'exptime > ' . $db->addQuotes( $db->timestamp() )
 458                                 ],
 459                                 __METHOD__
 460                         );
 461
 462                         $success = ( $db->affectedRows() == count( $tableKeys ) );
 463                 } else {
 464                         throw new InvalidArgumentException( "Invalid operation '$op'" );
 465                 }
 466
 467                 return $success;
 468         }
 469
 470         protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
 471                 return $this->modifyMulti( [ $key => $value ], $exptime, $flags, self::$OP_SET );
 472         }
 473
 474         protected function doAdd( $key, $value, $exptime = 0, $flags = 0 ) {
 475                 return $this->modifyMulti( [ $key => $value ], $exptime, $flags, self::$OP_ADD );
 476         }
 477
 478         protected function doCas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 479                 list( $shardIndex, $tableName ) = $this->getTableByKey( $key );
 480                 $exptime = $this->getExpirationAsTimestamp( $exptime );
 481
 482                 /** @noinspection PhpUnusedLocalVariableInspection */
 483                 $silenceScope = $this->silenceTransactionProfiler();
 484                 $db = null; // in case of connection failure
 485                 try {
 486                         $db = $this->getConnection( $shardIndex );
 487                         // (T26425) use a replace if the db supports it instead of
 488                         // delete/insert to avoid clashes with conflicting keynames
 489                         $db->update(
 490                                 $tableName,
 491                                 [
 492                                         'keyname' => $key,
 493                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 494                                         'exptime' => $exptime
 495                                                 ? $db->timestamp( $exptime )
 496                                                 : $this->getMaxDateTime( $db )
 497                                 ],
 498                                 [
 499                                         'keyname' => $key,
 500                                         'value' => $db->encodeBlob( $casToken ),
 501                                         'exptime > ' . $db->addQuotes( $db->timestamp() )
 502                                 ],
 503                                 __METHOD__
 504                         );
 505                 } catch ( DBQueryError $e ) {
 506                         $this->handleWriteError( $e, $db, $shardIndex );
 507
 508                         return false;
 509                 }
 510
 511                 $success = (bool)$db->affectedRows();
 512                 if ( $this->fieldHasFlags( $flags, self::WRITE_SYNC ) ) {
 513                         $success = $this->waitForReplication() && $success;
 514                 }
 515
 516                 return $success;
 517         }
 518
 519         protected function doDeleteMulti( array $keys, $flags = 0 ) {
 520                 return $this->modifyMulti(
 521                         array_fill_keys( $keys, null ),
 522                         0,
 523                         $flags,
 524                         self::$OP_DELETE
 525                 );
 526         }
 527
 528         protected function doDelete( $key, $flags = 0 ) {
 529                 return $this->modifyMulti( [ $key => null ], 0, $flags, self::$OP_DELETE );
 530         }
 531
 532         public function incr( $key, $step = 1, $flags = 0 ) {
 533                 list( $shardIndex, $tableName ) = $this->getTableByKey( $key );
 534
 535                 $newCount = false;
 536                 /** @noinspection PhpUnusedLocalVariableInspection */
 537                 $silenceScope = $this->silenceTransactionProfiler();
 538                 $db = null; // in case of connection failure
 539                 try {
 540                         $db = $this->getConnection( $shardIndex );
 541                         $encTimestamp = $db->addQuotes( $db->timestamp() );
 542                         $db->update(
 543                                 $tableName,
 544                                 [ 'value = value + ' . (int)$step ],
 545                                 [ 'keyname' => $key, "exptime > $encTimestamp" ],
 546                                 __METHOD__
 547                         );
 548                         if ( $db->affectedRows() > 0 ) {
 549                                 $newValue = $db->selectField(
 550                                         $tableName,
 551                                         'value',
 552                                         [ 'keyname' => $key, "exptime > $encTimestamp" ],
 553                                         __METHOD__
 554                                 );
 555                                 if ( $this->isInteger( $newValue ) ) {
 556                                         $newCount = (int)$newValue;
 557                                 }
 558                         }
 559                 } catch ( DBError $e ) {
 560                         $this->handleWriteError( $e, $db, $shardIndex );
 561                 }
 562
 563                 return $newCount;
 564         }
 565
 566         public function decr( $key, $value = 1, $flags = 0 ) {
 567                 return $this->incr( $key, -$value, $flags );
 568         }
 569
 570         public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
 571                 return $this->modifyMulti(
 572                         array_fill_keys( $keys, null ),
 573                         $exptime,
 574                         $flags,
 575                         self::$OP_TOUCH
 576                 );
 577         }
 578
 579         protected function doChangeTTL( $key, $exptime, $flags ) {
 580                 return $this->modifyMulti( [ $key => null ], $exptime, $flags, self::$OP_TOUCH );
 581         }
 582
 583         /**
 584          * @param IDatabase $db
 585          * @param string $exptime
 586          * @return bool
 587          */
 588         private function isExpired( IDatabase $db, $exptime ) {
 589                 return (
 590                         $exptime != $this->getMaxDateTime( $db ) &&
 591                         ConvertibleTimestamp::convert( TS_UNIX, $exptime ) < $this->getCurrentTime()
 592                 );
 593         }
 594
 595         /**
 596          * @param IDatabase $db
 597          * @return string
 598          */
 599         private function getMaxDateTime( $db ) {
 600                 if ( (int)$this->getCurrentTime() > 0x7fffffff ) {
 601                         return $db->timestamp( 1 << 62 );
 602                 } else {
 603                         return $db->timestamp( 0x7fffffff );
 604                 }
 605         }
 606
 607         /**
 608          * @param IDatabase $db
 609          * @throws DBError
 610          */
 611         private function occasionallyGarbageCollect( IDatabase $db ) {
 612                 if (
 613                         // Random purging is enabled
 614                         $this->purgePeriod &&
 615                         // Only purge on one in every $this->purgePeriod writes
 616                         mt_rand( 0, $this->purgePeriod - 1 ) == 0 &&
 617                         // Avoid repeating the delete within a few seconds
 618                         ( $this->getCurrentTime() - $this->lastGarbageCollect ) > self::$GC_DELAY_SEC
 619                 ) {
 620                         $garbageCollector = function () use ( $db ) {
 621                                 $this->deleteServerObjectsExpiringBefore(
 622                                         $db, $this->getCurrentTime(),
 623                                         null,
 624                                         $this->purgeLimit
 625                                 );
 626                                 $this->lastGarbageCollect = time();
 627                         };
 628                         if ( $this->asyncHandler ) {
 629                                 $this->lastGarbageCollect = $this->getCurrentTime(); // avoid duplicate enqueues
 630                                 ( $this->asyncHandler )( $garbageCollector );
 631                         } else {
 632                                 $garbageCollector();
 633                         }
 634                 }
 635         }
 636
 637         public function expireAll() {
 638                 $this->deleteObjectsExpiringBefore( $this->getCurrentTime() );
 639         }
 640
 641         public function deleteObjectsExpiringBefore(
 642                 $timestamp,
 643                 callable $progress = null,
 644                 $limit = INF
 645         ) {
 646                 /** @noinspection PhpUnusedLocalVariableInspection */
 647                 $silenceScope = $this->silenceTransactionProfiler();
 648
 649                 $shardIndexes = range( 0, $this->numServerShards - 1 );
 650                 shuffle( $shardIndexes );
 651
 652                 $ok = true;
 653
 654                 $keysDeletedCount = 0;
 655                 foreach ( $shardIndexes as $numServersDone => $shardIndex ) {
 656                         $db = null; // in case of connection failure
 657                         try {
 658                                 $db = $this->getConnection( $shardIndex );
 659                                 $this->deleteServerObjectsExpiringBefore(
 660                                         $db,
 661                                         $timestamp,
 662                                         $progress,
 663                                         $limit,
 664                                         $numServersDone,
 665                                         $keysDeletedCount
 666                                 );
 667                         } catch ( DBError $e ) {
 668                                 $this->handleWriteError( $e, $db, $shardIndex );
 669                                 $ok = false;
 670                         }
 671                 }
 672
 673                 return $ok;
 674         }
 675
 676         /**
 677          * @param IDatabase $db
 678          * @param string|int $timestamp
 679          * @param callable|null $progressCallback
 680          * @param int $limit
 681          * @param int $serversDoneCount
 682          * @param int &$keysDeletedCount
 683          * @throws DBError
 684          */
 685         private function deleteServerObjectsExpiringBefore(
 686                 IDatabase $db,
 687                 $timestamp,
 688                 $progressCallback,
 689                 $limit,
 690                 $serversDoneCount = 0,
 691                 &$keysDeletedCount = 0
 692         ) {
 693                 $cutoffUnix = ConvertibleTimestamp::convert( TS_UNIX, $timestamp );
 694                 $shardIndexes = range( 0, $this->numTableShards - 1 );
 695                 shuffle( $shardIndexes );
 696
 697                 foreach ( $shardIndexes as $numShardsDone => $shardIndex ) {
 698                         $continue = null; // last exptime
 699                         $lag = null; // purge lag
 700                         do {
 701                                 $res = $db->select(
 702                                         $this->getTableNameByShard( $shardIndex ),
 703                                         [ 'keyname', 'exptime' ],
 704                                         array_merge(
 705                                                 [ 'exptime < ' . $db->addQuotes( $db->timestamp( $cutoffUnix ) ) ],
 706                                                 $continue ? [ 'exptime >= ' . $db->addQuotes( $continue ) ] : []
 707                                         ),
 708                                         __METHOD__,
 709                                         [ 'LIMIT' => min( $limit, 100 ), 'ORDER BY' => 'exptime' ]
 710                                 );
 711
 712                                 if ( $res->numRows() ) {
 713                                         $row = $res->current();
 714                                         if ( $lag === null ) {
 715                                                 $rowExpUnix = ConvertibleTimestamp::convert( TS_UNIX, $row->exptime );
 716                                                 $lag = max( $cutoffUnix - $rowExpUnix, 1 );
 717                                         }
 718
 719                                         $keys = [];
 720                                         foreach ( $res as $row ) {
 721                                                 $keys[] = $row->keyname;
 722                                                 $continue = $row->exptime;
 723                                         }
 724
 725                                         $db->delete(
 726                                                 $this->getTableNameByShard( $shardIndex ),
 727                                                 [
 728                                                         'exptime < ' . $db->addQuotes( $db->timestamp( $cutoffUnix ) ),
 729                                                         'keyname' => $keys
 730                                                 ],
 731                                                 __METHOD__
 732                                         );
 733                                         $keysDeletedCount += $db->affectedRows();
 734                                 }
 735
 736                                 if ( is_callable( $progressCallback ) ) {
 737                                         if ( $lag ) {
 738                                                 $continueUnix = ConvertibleTimestamp::convert( TS_UNIX, $continue );
 739                                                 $remainingLag = $cutoffUnix - $continueUnix;
 740                                                 $processedLag = max( $lag - $remainingLag, 0 );
 741                                                 $doneRatio = ( $numShardsDone + $processedLag / $lag ) / $this->numTableShards;
 742                                         } else {
 743                                                 $doneRatio = 1;
 744                                         }
 745
 746                                         $overallRatio = ( $doneRatio / $this->numServerShards )
 747                                                 + ( $serversDoneCount / $this->numServerShards );
 748                                         call_user_func( $progressCallback, $overallRatio * 100 );
 749                                 }
 750                         } while ( $res->numRows() && $keysDeletedCount < $limit );
 751                 }
 752         }
 753
 754         /**
 755          * Delete content of shard tables in every server.
 756          * Return true if the operation is successful, false otherwise.
 757          * @return bool
 758          */
 759         public function deleteAll() {
 760                 /** @noinspection PhpUnusedLocalVariableInspection */
 761                 $silenceScope = $this->silenceTransactionProfiler();
 762                 for ( $shardIndex = 0; $shardIndex < $this->numServerShards; $shardIndex++ ) {
 763                         $db = null; // in case of connection failure
 764                         try {
 765                                 $db = $this->getConnection( $shardIndex );
 766                                 for ( $i = 0; $i < $this->numTableShards; $i++ ) {
 767                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 768                                 }
 769                         } catch ( DBError $e ) {
 770                                 $this->handleWriteError( $e, $db, $shardIndex );
 771                                 return false;
 772                         }
 773                 }
 774                 return true;
 775         }
 776
 777         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 778                 // Avoid deadlocks and allow lock reentry if specified
 779                 if ( isset( $this->locks[$key] ) ) {
 780                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 781                                 ++$this->locks[$key]['depth'];
 782                                 return true;
 783                         } else {
 784                                 return false;
 785                         }
 786                 }
 787
 788                 list( $shardIndex ) = $this->getTableByKey( $key );
 789
 790                 $db = null; // in case of connection failure
 791                 try {
 792                         $db = $this->getConnection( $shardIndex );
 793                         $ok = $db->lock( $key, __METHOD__, $timeout );
 794                         if ( $ok ) {
 795                                 $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 796                         }
 797
 798                         $this->logger->warning(
 799                                 __METHOD__ . " failed due to timeout for {key}.",
 800                                 [ 'key' => $key, 'timeout' => $timeout ]
 801                         );
 802
 803                         return $ok;
 804                 } catch ( DBError $e ) {
 805                         $this->handleWriteError( $e, $db, $shardIndex );
 806                         $ok = false;
 807                 }
 808
 809                 return $ok;
 810         }
 811
 812         public function unlock( $key ) {
 813                 if ( !isset( $this->locks[$key] ) ) {
 814                         return false;
 815                 }
 816
 817                 if ( --$this->locks[$key]['depth'] <= 0 ) {
 818                         unset( $this->locks[$key] );
 819
 820                         list( $shardIndex ) = $this->getTableByKey( $key );
 821
 822                         $db = null; // in case of connection failure
 823                         try {
 824                                 $db = $this->getConnection( $shardIndex );
 825                                 $ok = $db->unlock( $key, __METHOD__ );
 826                                 if ( !$ok ) {
 827                                         $this->logger->warning(
 828                                                 __METHOD__ . ' failed to release lock for {key}.',
 829                                                 [ 'key' => $key ]
 830                                         );
 831                                 }
 832                         } catch ( DBError $e ) {
 833                                 $this->handleWriteError( $e, $db, $shardIndex );
 834                                 $ok = false;
 835                         }
 836
 837                         return $ok;
 838                 }
 839
 840                 return true;
 841         }
 842
 843         /**
 844          * Serialize an object and, if possible, compress the representation.
 845          * On typical message and page data, this can provide a 3X decrease
 846          * in storage requirements.
 847          *
 848          * @param mixed $data
 849          * @return string|int
 850          */
 851         protected function serialize( $data ) {
 852                 if ( is_int( $data ) ) {
 853                         return $data;
 854                 }
 855
 856                 $serial = serialize( $data );
 857                 if ( function_exists( 'gzdeflate' ) ) {
 858                         $serial = gzdeflate( $serial );
 859                 }
 860
 861                 return $serial;
 862         }
 863
 864         /**
 865          * Unserialize and, if necessary, decompress an object.
 866          * @param string $serial
 867          * @return mixed
 868          */
 869         protected function unserialize( $serial ) {
 870                 if ( $this->isInteger( $serial ) ) {
 871                         return (int)$serial;
 872                 }
 873
 874                 if ( function_exists( 'gzinflate' ) ) {
 875                         AtEase::suppressWarnings();
 876                         $decomp = gzinflate( $serial );
 877                         AtEase::restoreWarnings();
 878
 879                         if ( $decomp !== false ) {
 880                                 $serial = $decomp;
 881                         }
 882                 }
 883
 884                 return unserialize( $serial );
 885         }
 886
 887         /**
 888          * Handle a DBError which occurred during a read operation.
 889          *
 890          * @param DBError $exception
 891          * @param int $shardIndex
 892          */
 893         private function handleReadError( DBError $exception, $shardIndex ) {
 894                 if ( $exception instanceof DBConnectionError ) {
 895                         $this->markServerDown( $exception, $shardIndex );
 896                 }
 897
 898                 $this->setAndLogDBError( $exception );
 899         }
 900
 901         /**
 902          * Handle a DBQueryError which occurred during a write operation.
 903          *
 904          * @param DBError $exception
 905          * @param IDatabase|null $db DB handle or null if connection failed
 906          * @param int $shardIndex
 907          * @throws Exception
 908          */
 909         private function handleWriteError( DBError $exception, $db, $shardIndex ) {
 910                 if ( !( $db instanceof IDatabase ) ) {
 911                         $this->markServerDown( $exception, $shardIndex );
 912                 }
 913
 914                 $this->setAndLogDBError( $exception );
 915         }
 916
 917         /**
 918          * @param DBError $exception
 919          */
 920         private function setAndLogDBError( DBError $exception ) {
 921                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 922                 if ( $exception instanceof DBConnectionError ) {
 923                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 924                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 925                 } else {
 926                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 927                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 928                 }
 929         }
 930
 931         /**
 932          * Mark a server down due to a DBConnectionError exception
 933          *
 934          * @param DBError $exception
 935          * @param int $shardIndex
 936          */
 937         private function markServerDown( DBError $exception, $shardIndex ) {
 938                 unset( $this->conns[$shardIndex] ); // bug T103435
 939
 940                 $now = $this->getCurrentTime();
 941                 if ( isset( $this->connFailureTimes[$shardIndex] ) ) {
 942                         if ( $now - $this->connFailureTimes[$shardIndex] >= 60 ) {
 943                                 unset( $this->connFailureTimes[$shardIndex] );
 944                                 unset( $this->connFailureErrors[$shardIndex] );
 945                         } else {
 946                                 $this->logger->debug( __METHOD__ . ": Server #$shardIndex already down" );
 947                                 return;
 948                         }
 949                 }
 950                 $this->logger->info( __METHOD__ . ": Server #$shardIndex down until " . ( $now + 60 ) );
 951                 $this->connFailureTimes[$shardIndex] = $now;
 952                 $this->connFailureErrors[$shardIndex] = $exception;
 953         }
 954
 955         /**
 956          * @param IMaintainableDatabase $db
 957          * @throws DBError
 958          */
 959         private function initSqliteDatabase( IMaintainableDatabase $db ) {
 960                 if ( $db->tableExists( 'objectcache' ) ) {
 961                         return;
 962                 }
 963                 // Use one table for SQLite; sharding does not seem to have much benefit
 964                 $db->query( "PRAGMA journal_mode=WAL" ); // this is permanent
 965                 $db->startAtomic( __METHOD__ ); // atomic DDL
 966                 try {
 967                         $encTable = $db->tableName( 'objectcache' );
 968                         $encExptimeIndex = $db->addIdentifierQuotes( $db->tablePrefix() . 'exptime' );
 969                         $db->query(
 970                                 "CREATE TABLE $encTable (\n" .
 971                                 "       keyname BLOB NOT NULL default '' PRIMARY KEY,\n" .
 972                                 "       value BLOB,\n" .
 973                                 "       exptime TEXT\n" .
 974                                 ")",
 975                                 __METHOD__
 976                         );
 977                         $db->query( "CREATE INDEX $encExptimeIndex ON $encTable (exptime)" );
 978                         $db->endAtomic( __METHOD__ );
 979                 } catch ( DBError $e ) {
 980                         $db->rollback( __METHOD__ );
 981                         throw $e;
 982                 }
 983         }
 984
 985         /**
 986          * Create the shard tables on all databases (e.g. via eval.php/shell.php)
 987          */
 988         public function createTables() {
 989                 for ( $shardIndex = 0; $shardIndex < $this->numServerShards; $shardIndex++ ) {
 990                         $db = $this->getConnection( $shardIndex );
 991                         if ( in_array( $db->getType(), [ 'mysql', 'postgres' ], true ) ) {
 992                                 for ( $i = 0; $i < $this->numTableShards; $i++ ) {
 993                                         $encBaseTable = $db->tableName( 'objectcache' );
 994                                         $encShardTable = $db->tableName( $this->getTableNameByShard( $i ) );
 995                                         $db->query( "CREATE TABLE $encShardTable LIKE $encBaseTable" );
 996                                 }
 997                         }
 998                 }
 999         }
1000
1001         /**
1002          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
1003          */
1004         private function usesMainDB() {
1005                 return !$this->serverInfos;
1006         }
1007
1008         private function waitForReplication() {
1009                 if ( !$this->usesMainDB() ) {
1010                         // Custom DB server list; probably doesn't use replication
1011                         return true;
1012                 }
1013
1014                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
1015                 if ( $lb->getServerCount() <= 1 ) {
1016                         return true; // no replica DBs
1017                 }
1018
1019                 // Main LB is used; wait for any replica DBs to catch up
1020                 try {
1021                         $masterPos = $lb->getMasterPos();
1022                         if ( !$masterPos ) {
1023                                 return true; // not applicable
1024                         }
1025
1026                         $loop = new WaitConditionLoop(
1027                                 function () use ( $lb, $masterPos ) {
1028                                         return $lb->waitForAll( $masterPos, 1 );
1029                                 },
1030                                 $this->syncTimeout,
1031                                 $this->busyCallbacks
1032                         );
1033
1034                         return ( $loop->invoke() === $loop::CONDITION_REACHED );
1035                 } catch ( DBError $e ) {
1036                         $this->setAndLogDBError( $e );
1037
1038                         return false;
1039                 }
1040         }
1041
1042         /**
1043          * Silence the transaction profiler until the return value falls out of scope
1044          *
1045          * @return ScopedCallback|null
1046          */
1047         private function silenceTransactionProfiler() {
1048                 if ( !$this->usesMainDB() ) {
1049                         // Custom DB is configured which either has no TransactionProfiler injected,
1050                         // or has one specific for cache use, which we shouldn't silence
1051                         return null;
1052                 }
1053
1054                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
1055                 $oldSilenced = $trxProfiler->setSilenced( true );
1056                 return new ScopedCallback( function () use ( $trxProfiler, $oldSilenced ) {
1057                         $trxProfiler->setSilenced( $oldSilenced );
1058                 } );
1059         }
1060 }