includes/objectcache/SqlBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using a SQL database.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 use MediaWiki\MediaWikiServices;
  25 use Wikimedia\Rdbms\Database;
  26 use Wikimedia\Rdbms\IDatabase;
  27 use Wikimedia\Rdbms\DBError;
  28 use Wikimedia\Rdbms\DBQueryError;
  29 use Wikimedia\Rdbms\DBConnectionError;
  30 use Wikimedia\Rdbms\LoadBalancer;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\WaitConditionLoop;
  33
  34 /**
  35  * Class to store objects in the database
  36  *
  37  * @ingroup Cache
  38  */
  39 class SqlBagOStuff extends BagOStuff {
  40         /** @var array[] (server index => server config) */
  41         protected $serverInfos;
  42         /** @var string[] (server index => tag/host name) */
  43         protected $serverTags;
  44         /** @var int */
  45         protected $numServers;
  46         /** @var int */
  47         protected $lastExpireAll = 0;
  48         /** @var int */
  49         protected $purgePeriod = 100;
  50         /** @var int */
  51         protected $shards = 1;
  52         /** @var string */
  53         protected $tableName = 'objectcache';
  54         /** @var bool */
  55         protected $replicaOnly = false;
  56         /** @var int */
  57         protected $syncTimeout = 3;
  58
  59         /** @var LoadBalancer|null */
  60         protected $separateMainLB;
  61         /** @var array */
  62         protected $conns;
  63         /** @var array UNIX timestamps */
  64         protected $connFailureTimes = [];
  65         /** @var array Exceptions */
  66         protected $connFailureErrors = [];
  67
  68         /**
  69          * Constructor. Parameters are:
  70          *   - server:      A server info structure in the format required by each
  71          *                  element in $wgDBServers.
  72          *
  73          *   - servers:     An array of server info structures describing a set of database servers
  74          *                  to distribute keys to. If this is specified, the "server" option will be
  75          *                  ignored. If string keys are used, then they will be used for consistent
  76          *                  hashing *instead* of the host name (from the server config). This is useful
  77          *                  when a cluster is replicated to another site (with different host names)
  78          *                  but each server has a corresponding replica in the other cluster.
  79          *
  80          *   - purgePeriod: The average number of object cache requests in between
  81          *                  garbage collection operations, where expired entries
  82          *                  are removed from the database. Or in other words, the
  83          *                  reciprocal of the probability of purging on any given
  84          *                  request. If this is set to zero, purging will never be
  85          *                  done.
  86          *
  87          *   - tableName:   The table name to use, default is "objectcache".
  88          *
  89          *   - shards:      The number of tables to use for data storage on each server.
  90          *                  If this is more than 1, table names will be formed in the style
  91          *                  objectcacheNNN where NNN is the shard index, between 0 and
  92          *                  shards-1. The number of digits will be the minimum number
  93          *                  required to hold the largest shard index. Data will be
  94          *                  distributed across all tables by key hash. This is for
  95          *                  MySQL bugs 61735 and 61736.
  96          *   - slaveOnly:   Whether to only use replica DBs and avoid triggering
  97          *                  garbage collection logic of expired items. This only
  98          *                  makes sense if the primary DB is used and only if get()
  99          *                  calls will be used. This is used by ReplicatedBagOStuff.
 100          *   - syncTimeout: Max seconds to wait for replica DBs to catch up for WRITE_SYNC.
 101          *
 102          * @param array $params
 103          */
 104         public function __construct( $params ) {
 105                 parent::__construct( $params );
 106
 107                 $this->attrMap[self::ATTR_EMULATION] = self::QOS_EMULATION_SQL;
 108                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
 109
 110                 if ( isset( $params['servers'] ) ) {
 111                         $this->serverInfos = [];
 112                         $this->serverTags = [];
 113                         $this->numServers = count( $params['servers'] );
 114                         $index = 0;
 115                         foreach ( $params['servers'] as $tag => $info ) {
 116                                 $this->serverInfos[$index] = $info;
 117                                 if ( is_string( $tag ) ) {
 118                                         $this->serverTags[$index] = $tag;
 119                                 } else {
 120                                         $this->serverTags[$index] = $info['host'] ?? "#$index";
 121                                 }
 122                                 ++$index;
 123                         }
 124                 } elseif ( isset( $params['server'] ) ) {
 125                         $this->serverInfos = [ $params['server'] ];
 126                         $this->numServers = count( $this->serverInfos );
 127                 } else {
 128                         // Default to using the main wiki's database servers
 129                         $this->serverInfos = false;
 130                         $this->numServers = 1;
 131                         $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE;
 132                 }
 133                 if ( isset( $params['purgePeriod'] ) ) {
 134                         $this->purgePeriod = intval( $params['purgePeriod'] );
 135                 }
 136                 if ( isset( $params['tableName'] ) ) {
 137                         $this->tableName = $params['tableName'];
 138                 }
 139                 if ( isset( $params['shards'] ) ) {
 140                         $this->shards = intval( $params['shards'] );
 141                 }
 142                 if ( isset( $params['syncTimeout'] ) ) {
 143                         $this->syncTimeout = $params['syncTimeout'];
 144                 }
 145                 $this->replicaOnly = !empty( $params['slaveOnly'] );
 146         }
 147
 148         /**
 149          * Get a connection to the specified database
 150          *
 151          * @param int $serverIndex
 152          * @return Database
 153          * @throws MWException
 154          */
 155         protected function getDB( $serverIndex ) {
 156                 if ( !isset( $this->conns[$serverIndex] ) ) {
 157                         if ( $serverIndex >= $this->numServers ) {
 158                                 throw new MWException( __METHOD__ . ": Invalid server index \"$serverIndex\"" );
 159                         }
 160
 161                         # Don't keep timing out trying to connect for each call if the DB is down
 162                         if ( isset( $this->connFailureErrors[$serverIndex] )
 163                                 && ( time() - $this->connFailureTimes[$serverIndex] ) < 60
 164                         ) {
 165                                 throw $this->connFailureErrors[$serverIndex];
 166                         }
 167
 168                         if ( $this->serverInfos ) {
 169                                 // Use custom database defined by server connection info
 170                                 $info = $this->serverInfos[$serverIndex];
 171                                 $type = $info['type'] ?? 'mysql';
 172                                 $host = $info['host'] ?? '[unknown]';
 173                                 $this->logger->debug( __CLASS__ . ": connecting to $host" );
 174                                 $db = Database::factory( $type, $info );
 175                                 $db->clearFlag( DBO_TRX ); // auto-commit mode
 176                         } else {
 177                                 // Use the main LB database
 178                                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 179                                 $index = $this->replicaOnly ? DB_REPLICA : DB_MASTER;
 180                                 if ( $lb->getServerType( $lb->getWriterIndex() ) !== 'sqlite' ) {
 181                                         // Keep a separate connection to avoid contention and deadlocks
 182                                         $db = $lb->getConnection( $index, [], false, $lb::CONN_TRX_AUTOCOMMIT );
 183                                 } else {
 184                                         // However, SQLite has the opposite behavior due to DB-level locking.
 185                                         // Stock sqlite MediaWiki installs use a separate sqlite cache DB instead.
 186                                         $db = $lb->getConnection( $index );
 187                                 }
 188                         }
 189
 190                         $this->logger->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
 191                         $this->conns[$serverIndex] = $db;
 192                 }
 193
 194                 return $this->conns[$serverIndex];
 195         }
 196
 197         /**
 198          * Get the server index and table name for a given key
 199          * @param string $key
 200          * @return array Server index and table name
 201          */
 202         protected function getTableByKey( $key ) {
 203                 if ( $this->shards > 1 ) {
 204                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 205                         $tableIndex = $hash % $this->shards;
 206                 } else {
 207                         $tableIndex = 0;
 208                 }
 209                 if ( $this->numServers > 1 ) {
 210                         $sortedServers = $this->serverTags;
 211                         ArrayUtils::consistentHashSort( $sortedServers, $key );
 212                         reset( $sortedServers );
 213                         $serverIndex = key( $sortedServers );
 214                 } else {
 215                         $serverIndex = 0;
 216                 }
 217                 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
 218         }
 219
 220         /**
 221          * Get the table name for a given shard index
 222          * @param int $index
 223          * @return string
 224          */
 225         protected function getTableNameByShard( $index ) {
 226                 if ( $this->shards > 1 ) {
 227                         $decimals = strlen( $this->shards - 1 );
 228                         return $this->tableName .
 229                                 sprintf( "%0{$decimals}d", $index );
 230                 } else {
 231                         return $this->tableName;
 232                 }
 233         }
 234
 235         protected function doGet( $key, $flags = 0 ) {
 236                 $casToken = null;
 237
 238                 return $this->getWithToken( $key, $casToken, $flags );
 239         }
 240
 241         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 242                 $values = $this->getMulti( [ $key ] );
 243                 if ( array_key_exists( $key, $values ) ) {
 244                         $casToken = $values[$key];
 245                         return $values[$key];
 246                 }
 247                 return false;
 248         }
 249
 250         public function getMulti( array $keys, $flags = 0 ) {
 251                 $values = []; // array of (key => value)
 252
 253                 $keysByTable = [];
 254                 foreach ( $keys as $key ) {
 255                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 256                         $keysByTable[$serverIndex][$tableName][] = $key;
 257                 }
 258
 259                 $this->garbageCollect(); // expire old entries if any
 260
 261                 $dataRows = [];
 262                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 263                         try {
 264                                 $db = $this->getDB( $serverIndex );
 265                                 foreach ( $serverKeys as $tableName => $tableKeys ) {
 266                                         $res = $db->select( $tableName,
 267                                                 [ 'keyname', 'value', 'exptime' ],
 268                                                 [ 'keyname' => $tableKeys ],
 269                                                 __METHOD__,
 270                                                 // Approximate write-on-the-fly BagOStuff API via blocking.
 271                                                 // This approximation fails if a ROLLBACK happens (which is rare).
 272                                                 // We do not want to flush the TRX as that can break callers.
 273                                                 $db->trxLevel() ? [ 'LOCK IN SHARE MODE' ] : []
 274                                         );
 275                                         if ( $res === false ) {
 276                                                 continue;
 277                                         }
 278                                         foreach ( $res as $row ) {
 279                                                 $row->serverIndex = $serverIndex;
 280                                                 $row->tableName = $tableName;
 281                                                 $dataRows[$row->keyname] = $row;
 282                                         }
 283                                 }
 284                         } catch ( DBError $e ) {
 285                                 $this->handleReadError( $e, $serverIndex );
 286                         }
 287                 }
 288
 289                 foreach ( $keys as $key ) {
 290                         if ( isset( $dataRows[$key] ) ) { // HIT?
 291                                 $row = $dataRows[$key];
 292                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 293                                 $db = null;
 294                                 try {
 295                                         $db = $this->getDB( $row->serverIndex );
 296                                         if ( $this->isExpired( $db, $row->exptime ) ) { // MISS
 297                                                 $this->debug( "get: key has expired" );
 298                                         } else { // HIT
 299                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 300                                         }
 301                                 } catch ( DBQueryError $e ) {
 302                                         $this->handleWriteError( $e, $db, $row->serverIndex );
 303                                 }
 304                         } else { // MISS
 305                                 $this->debug( 'get: no matching rows' );
 306                         }
 307                 }
 308
 309                 return $values;
 310         }
 311
 312         public function setMulti( array $data, $expiry = 0 ) {
 313                 $keysByTable = [];
 314                 foreach ( $data as $key => $value ) {
 315                         list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 316                         $keysByTable[$serverIndex][$tableName][] = $key;
 317                 }
 318
 319                 $this->garbageCollect(); // expire old entries if any
 320
 321                 $result = true;
 322                 $exptime = (int)$expiry;
 323                 $silenceScope = $this->silenceTransactionProfiler();
 324                 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
 325                         $db = null;
 326                         try {
 327                                 $db = $this->getDB( $serverIndex );
 328                         } catch ( DBError $e ) {
 329                                 $this->handleWriteError( $e, $db, $serverIndex );
 330                                 $result = false;
 331                                 continue;
 332                         }
 333
 334                         if ( $exptime < 0 ) {
 335                                 $exptime = 0;
 336                         }
 337
 338                         if ( $exptime == 0 ) {
 339                                 $encExpiry = $this->getMaxDateTime( $db );
 340                         } else {
 341                                 $exptime = $this->convertExpiry( $exptime );
 342                                 $encExpiry = $db->timestamp( $exptime );
 343                         }
 344                         foreach ( $serverKeys as $tableName => $tableKeys ) {
 345                                 $rows = [];
 346                                 foreach ( $tableKeys as $key ) {
 347                                         $rows[] = [
 348                                                 'keyname' => $key,
 349                                                 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
 350                                                 'exptime' => $encExpiry,
 351                                         ];
 352                                 }
 353
 354                                 try {
 355                                         $db->replace(
 356                                                 $tableName,
 357                                                 [ 'keyname' ],
 358                                                 $rows,
 359                                                 __METHOD__
 360                                         );
 361                                 } catch ( DBError $e ) {
 362                                         $this->handleWriteError( $e, $db, $serverIndex );
 363                                         $result = false;
 364                                 }
 365
 366                         }
 367
 368                 }
 369
 370                 return $result;
 371         }
 372
 373         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 374                 $ok = $this->setMulti( [ $key => $value ], $exptime );
 375                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 376                         $ok = $this->waitForReplication() && $ok;
 377                 }
 378
 379                 return $ok;
 380         }
 381
 382         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 383                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 384                 $db = null;
 385                 $silenceScope = $this->silenceTransactionProfiler();
 386                 try {
 387                         $db = $this->getDB( $serverIndex );
 388                         $exptime = intval( $exptime );
 389
 390                         if ( $exptime < 0 ) {
 391                                 $exptime = 0;
 392                         }
 393
 394                         if ( $exptime == 0 ) {
 395                                 $encExpiry = $this->getMaxDateTime( $db );
 396                         } else {
 397                                 $exptime = $this->convertExpiry( $exptime );
 398                                 $encExpiry = $db->timestamp( $exptime );
 399                         }
 400                         // (T26425) use a replace if the db supports it instead of
 401                         // delete/insert to avoid clashes with conflicting keynames
 402                         $db->update(
 403                                 $tableName,
 404                                 [
 405                                         'keyname' => $key,
 406                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 407                                         'exptime' => $encExpiry
 408                                 ],
 409                                 [
 410                                         'keyname' => $key,
 411                                         'value' => $db->encodeBlob( $this->serialize( $casToken ) )
 412                                 ],
 413                                 __METHOD__
 414                         );
 415                 } catch ( DBQueryError $e ) {
 416                         $this->handleWriteError( $e, $db, $serverIndex );
 417
 418                         return false;
 419                 }
 420
 421                 return (bool)$db->affectedRows();
 422         }
 423
 424         public function delete( $key ) {
 425                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 426                 $db = null;
 427                 $silenceScope = $this->silenceTransactionProfiler();
 428                 try {
 429                         $db = $this->getDB( $serverIndex );
 430                         $db->delete(
 431                                 $tableName,
 432                                 [ 'keyname' => $key ],
 433                                 __METHOD__ );
 434                 } catch ( DBError $e ) {
 435                         $this->handleWriteError( $e, $db, $serverIndex );
 436                         return false;
 437                 }
 438
 439                 return true;
 440         }
 441
 442         public function incr( $key, $step = 1 ) {
 443                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 444                 $db = null;
 445                 $silenceScope = $this->silenceTransactionProfiler();
 446                 try {
 447                         $db = $this->getDB( $serverIndex );
 448                         $step = intval( $step );
 449                         $row = $db->selectRow(
 450                                 $tableName,
 451                                 [ 'value', 'exptime' ],
 452                                 [ 'keyname' => $key ],
 453                                 __METHOD__,
 454                                 [ 'FOR UPDATE' ] );
 455                         if ( $row === false ) {
 456                                 // Missing
 457
 458                                 return null;
 459                         }
 460                         $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__ );
 461                         if ( $this->isExpired( $db, $row->exptime ) ) {
 462                                 // Expired, do not reinsert
 463
 464                                 return null;
 465                         }
 466
 467                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 468                         $newValue = $oldValue + $step;
 469                         $db->insert( $tableName,
 470                                 [
 471                                         'keyname' => $key,
 472                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 473                                         'exptime' => $row->exptime
 474                                 ], __METHOD__, 'IGNORE' );
 475
 476                         if ( $db->affectedRows() == 0 ) {
 477                                 // Race condition. See T30611
 478                                 $newValue = null;
 479                         }
 480                 } catch ( DBError $e ) {
 481                         $this->handleWriteError( $e, $db, $serverIndex );
 482                         return null;
 483                 }
 484
 485                 return $newValue;
 486         }
 487
 488         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 489                 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 490                 if ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC ) {
 491                         $ok = $this->waitForReplication() && $ok;
 492                 }
 493
 494                 return $ok;
 495         }
 496
 497         public function changeTTL( $key, $expiry = 0 ) {
 498                 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
 499                 $db = null;
 500                 $silenceScope = $this->silenceTransactionProfiler();
 501                 try {
 502                         $db = $this->getDB( $serverIndex );
 503                         $db->update(
 504                                 $tableName,
 505                                 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
 506                                 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
 507                                 __METHOD__
 508                         );
 509                         if ( $db->affectedRows() == 0 ) {
 510                                 return false;
 511                         }
 512                 } catch ( DBError $e ) {
 513                         $this->handleWriteError( $e, $db, $serverIndex );
 514                         return false;
 515                 }
 516
 517                 return true;
 518         }
 519
 520         /**
 521          * @param IDatabase $db
 522          * @param string $exptime
 523          * @return bool
 524          */
 525         protected function isExpired( $db, $exptime ) {
 526                 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX, $exptime ) < time();
 527         }
 528
 529         /**
 530          * @param IDatabase $db
 531          * @return string
 532          */
 533         protected function getMaxDateTime( $db ) {
 534                 if ( time() > 0x7fffffff ) {
 535                         return $db->timestamp( 1 << 62 );
 536                 } else {
 537                         return $db->timestamp( 0x7fffffff );
 538                 }
 539         }
 540
 541         protected function garbageCollect() {
 542                 if ( !$this->purgePeriod || $this->replicaOnly ) {
 543                         // Disabled
 544                         return;
 545                 }
 546                 // Only purge on one in every $this->purgePeriod requests.
 547                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 548                         return;
 549                 }
 550                 $now = time();
 551                 // Avoid repeating the delete within a few seconds
 552                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 553                         $this->lastExpireAll = $now;
 554                         $this->expireAll();
 555                 }
 556         }
 557
 558         public function expireAll() {
 559                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 560         }
 561
 562         /**
 563          * Delete objects from the database which expire before a certain date.
 564          * @param string $timestamp
 565          * @param bool|callable $progressCallback
 566          * @return bool
 567          */
 568         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 569                 $silenceScope = $this->silenceTransactionProfiler();
 570                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 571                         $db = null;
 572                         try {
 573                                 $db = $this->getDB( $serverIndex );
 574                                 $dbTimestamp = $db->timestamp( $timestamp );
 575                                 $totalSeconds = false;
 576                                 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
 577                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 578                                         $maxExpTime = false;
 579                                         while ( true ) {
 580                                                 $conds = $baseConds;
 581                                                 if ( $maxExpTime !== false ) {
 582                                                         $conds[] = 'exptime >= ' . $db->addQuotes( $maxExpTime );
 583                                                 }
 584                                                 $rows = $db->select(
 585                                                         $this->getTableNameByShard( $i ),
 586                                                         [ 'keyname', 'exptime' ],
 587                                                         $conds,
 588                                                         __METHOD__,
 589                                                         [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
 590                                                 if ( $rows === false || !$rows->numRows() ) {
 591                                                         break;
 592                                                 }
 593                                                 $keys = [];
 594                                                 $row = $rows->current();
 595                                                 $minExpTime = $row->exptime;
 596                                                 if ( $totalSeconds === false ) {
 597                                                         $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 598                                                                 - wfTimestamp( TS_UNIX, $minExpTime );
 599                                                 }
 600                                                 foreach ( $rows as $row ) {
 601                                                         $keys[] = $row->keyname;
 602                                                         $maxExpTime = $row->exptime;
 603                                                 }
 604
 605                                                 $db->delete(
 606                                                         $this->getTableNameByShard( $i ),
 607                                                         [
 608                                                                 'exptime >= ' . $db->addQuotes( $minExpTime ),
 609                                                                 'exptime < ' . $db->addQuotes( $dbTimestamp ),
 610                                                                 'keyname' => $keys
 611                                                         ],
 612                                                         __METHOD__ );
 613
 614                                                 if ( $progressCallback ) {
 615                                                         if ( intval( $totalSeconds ) === 0 ) {
 616                                                                 $percent = 0;
 617                                                         } else {
 618                                                                 $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 619                                                                         - wfTimestamp( TS_UNIX, $maxExpTime );
 620                                                                 if ( $remainingSeconds > $totalSeconds ) {
 621                                                                         $totalSeconds = $remainingSeconds;
 622                                                                 }
 623                                                                 $processedSeconds = $totalSeconds - $remainingSeconds;
 624                                                                 $percent = ( $i + $processedSeconds / $totalSeconds )
 625                                                                         / $this->shards * 100;
 626                                                         }
 627                                                         $percent = ( $percent / $this->numServers )
 628                                                                 + ( $serverIndex / $this->numServers * 100 );
 629                                                         call_user_func( $progressCallback, $percent );
 630                                                 }
 631                                         }
 632                                 }
 633                         } catch ( DBError $e ) {
 634                                 $this->handleWriteError( $e, $db, $serverIndex );
 635                                 return false;
 636                         }
 637                 }
 638                 return true;
 639         }
 640
 641         /**
 642          * Delete content of shard tables in every server.
 643          * Return true if the operation is successful, false otherwise.
 644          * @return bool
 645          */
 646         public function deleteAll() {
 647                 $silenceScope = $this->silenceTransactionProfiler();
 648                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 649                         $db = null;
 650                         try {
 651                                 $db = $this->getDB( $serverIndex );
 652                                 for ( $i = 0; $i < $this->shards; $i++ ) {
 653                                         $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__ );
 654                                 }
 655                         } catch ( DBError $e ) {
 656                                 $this->handleWriteError( $e, $db, $serverIndex );
 657                                 return false;
 658                         }
 659                 }
 660                 return true;
 661         }
 662
 663         /**
 664          * Serialize an object and, if possible, compress the representation.
 665          * On typical message and page data, this can provide a 3X decrease
 666          * in storage requirements.
 667          *
 668          * @param mixed &$data
 669          * @return string
 670          */
 671         protected function serialize( &$data ) {
 672                 $serial = serialize( $data );
 673
 674                 if ( function_exists( 'gzdeflate' ) ) {
 675                         return gzdeflate( $serial );
 676                 } else {
 677                         return $serial;
 678                 }
 679         }
 680
 681         /**
 682          * Unserialize and, if necessary, decompress an object.
 683          * @param string $serial
 684          * @return mixed
 685          */
 686         protected function unserialize( $serial ) {
 687                 if ( function_exists( 'gzinflate' ) ) {
 688                         Wikimedia\suppressWarnings();
 689                         $decomp = gzinflate( $serial );
 690                         Wikimedia\restoreWarnings();
 691
 692                         if ( false !== $decomp ) {
 693                                 $serial = $decomp;
 694                         }
 695                 }
 696
 697                 $ret = unserialize( $serial );
 698
 699                 return $ret;
 700         }
 701
 702         /**
 703          * Handle a DBError which occurred during a read operation.
 704          *
 705          * @param DBError $exception
 706          * @param int $serverIndex
 707          */
 708         protected function handleReadError( DBError $exception, $serverIndex ) {
 709                 if ( $exception instanceof DBConnectionError ) {
 710                         $this->markServerDown( $exception, $serverIndex );
 711                 }
 712                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 713                 if ( $exception instanceof DBConnectionError ) {
 714                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 715                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 716                 } else {
 717                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 718                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 719                 }
 720         }
 721
 722         /**
 723          * Handle a DBQueryError which occurred during a write operation.
 724          *
 725          * @param DBError $exception
 726          * @param IDatabase|null $db DB handle or null if connection failed
 727          * @param int $serverIndex
 728          * @throws Exception
 729          */
 730         protected function handleWriteError( DBError $exception, IDatabase $db = null, $serverIndex ) {
 731                 if ( !$db ) {
 732                         $this->markServerDown( $exception, $serverIndex );
 733                 } elseif ( $db->wasReadOnlyError() ) {
 734                         if ( $db->trxLevel() && $this->usesMainDB() ) {
 735                                 // Errors like deadlocks and connection drops already cause rollback.
 736                                 // For consistency, we have no choice but to throw an error and trigger
 737                                 // complete rollback if the main DB is also being used as the cache DB.
 738                                 throw $exception;
 739                         }
 740                 }
 741
 742                 $this->logger->error( "DBError: {$exception->getMessage()}" );
 743                 if ( $exception instanceof DBConnectionError ) {
 744                         $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 745                         $this->logger->debug( __METHOD__ . ": ignoring connection error" );
 746                 } else {
 747                         $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 748                         $this->logger->debug( __METHOD__ . ": ignoring query error" );
 749                 }
 750         }
 751
 752         /**
 753          * Mark a server down due to a DBConnectionError exception
 754          *
 755          * @param DBError $exception
 756          * @param int $serverIndex
 757          */
 758         protected function markServerDown( DBError $exception, $serverIndex ) {
 759                 unset( $this->conns[$serverIndex] ); // bug T103435
 760
 761                 if ( isset( $this->connFailureTimes[$serverIndex] ) ) {
 762                         if ( time() - $this->connFailureTimes[$serverIndex] >= 60 ) {
 763                                 unset( $this->connFailureTimes[$serverIndex] );
 764                                 unset( $this->connFailureErrors[$serverIndex] );
 765                         } else {
 766                                 $this->logger->debug( __METHOD__ . ": Server #$serverIndex already down" );
 767                                 return;
 768                         }
 769                 }
 770                 $now = time();
 771                 $this->logger->info( __METHOD__ . ": Server #$serverIndex down until " . ( $now + 60 ) );
 772                 $this->connFailureTimes[$serverIndex] = $now;
 773                 $this->connFailureErrors[$serverIndex] = $exception;
 774         }
 775
 776         /**
 777          * Create shard tables. For use from eval.php.
 778          */
 779         public function createTables() {
 780                 for ( $serverIndex = 0; $serverIndex < $this->numServers; $serverIndex++ ) {
 781                         $db = $this->getDB( $serverIndex );
 782                         if ( $db->getType() !== 'mysql' ) {
 783                                 throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 784                         }
 785
 786                         for ( $i = 0; $i < $this->shards; $i++ ) {
 787                                 $db->query(
 788                                         'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
 789                                         ' LIKE ' . $db->tableName( 'objectcache' ),
 790                                         __METHOD__ );
 791                         }
 792                 }
 793         }
 794
 795         /**
 796          * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
 797          */
 798         protected function usesMainDB() {
 799                 return !$this->serverInfos;
 800         }
 801
 802         protected function waitForReplication() {
 803                 if ( !$this->usesMainDB() ) {
 804                         // Custom DB server list; probably doesn't use replication
 805                         return true;
 806                 }
 807
 808                 $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
 809                 if ( $lb->getServerCount() <= 1 ) {
 810                         return true; // no replica DBs
 811                 }
 812
 813                 // Main LB is used; wait for any replica DBs to catch up
 814                 $masterPos = $lb->getMasterPos();
 815                 if ( !$masterPos ) {
 816                         return true; // not applicable
 817                 }
 818
 819                 $loop = new WaitConditionLoop(
 820                         function () use ( $lb, $masterPos ) {
 821                                 return $lb->waitForAll( $masterPos, 1 );
 822                         },
 823                         $this->syncTimeout,
 824                         $this->busyCallbacks
 825                 );
 826
 827                 return ( $loop->invoke() === $loop::CONDITION_REACHED );
 828         }
 829
 830         /**
 831          * Returns a ScopedCallback which resets the silence flag in the transaction profiler when it is
 832          * destroyed on the end of a scope, for example on return or throw
 833          * @return ScopedCallback
 834          * @since 1.32
 835          */
 836         protected function silenceTransactionProfiler() {
 837                 $trxProfiler = Profiler::instance()->getTransactionProfiler();
 838                 $oldSilenced = $trxProfiler->setSilenced( true );
 839                 return new ScopedCallback( function () use ( $trxProfiler, $oldSilenced ) {
 840                         $trxProfiler->setSilenced( $oldSilenced );
 841                 } );
 842         }
 843 }