includes/objectcache/SqlBagOStuff.php

   1 <?php
   2
   3 /**
   4  * Class to store objects in the database
   5  *
   6  * @ingroup Cache
   7  */
   8 class SqlBagOStuff extends BagOStuff {
   9
  10         /**
  11          * @var LoadBalancer
  12          */
  13         var $lb;
  14
  15         /**
  16          * @var DatabaseBase
  17          */
  18         var $db;
  19         var $serverInfo;
  20         var $lastExpireAll = 0;
  21         var $purgePeriod = 100;
  22         var $shards = 1;
  23         var $tableName = 'objectcache';
  24
  25         /**
  26          * Constructor. Parameters are:
  27          *   - server:   A server info structure in the format required by each
  28          *               element in $wgDBServers.
  29          *
  30          *   - purgePeriod: The average number of object cache requests in between
  31          *                  garbage collection operations, where expired entries
  32          *                  are removed from the database. Or in other words, the
  33          *                  reciprocal of the probability of purging on any given
  34          *                  request. If this is set to zero, purging will never be
  35          *                  done.
  36          *
  37          *   - tableName:   The table name to use, default is "objectcache".
  38          *
  39          *   - shards:      The number of tables to use for data storage. If this is
  40          *                  more than 1, table names will be formed in the style
  41          *                  objectcacheNNN where NNN is the shard index, between 0 and
  42          *                  shards-1. The number of digits will be the minimum number
  43          *                  required to hold the largest shard index. Data will be
  44          *                  distributed across all tables by key hash. This is for
  45          *                  MySQL bugs 61735 and 61736.
  46          *
  47          * @param $params array
  48          */
  49         public function __construct( $params ) {
  50                 if ( isset( $params['server'] ) ) {
  51                         $this->serverInfo = $params['server'];
  52                         $this->serverInfo['load'] = 1;
  53                 }
  54                 if ( isset( $params['purgePeriod'] ) ) {
  55                         $this->purgePeriod = intval( $params['purgePeriod'] );
  56                 }
  57                 if ( isset( $params['tableName'] ) ) {
  58                         $this->tableName = $params['tableName'];
  59                 }
  60                 if ( isset( $params['shards'] ) ) {
  61                         $this->shards = intval( $params['shards'] );
  62                 }
  63         }
  64
  65         /**
  66          * @return DatabaseBase
  67          */
  68         protected function getDB() {
  69                 if ( !isset( $this->db ) ) {
  70                         # If server connection info was given, use that
  71                         if ( $this->serverInfo ) {
  72                                 $this->lb = new LoadBalancer( array(
  73                                         'servers' => array( $this->serverInfo ) ) );
  74                                 $this->db = $this->lb->getConnection( DB_MASTER );
  75                                 $this->db->clearFlag( DBO_TRX );
  76                         } else {
  77                                 # We must keep a separate connection to MySQL in order to avoid deadlocks
  78                                 # However, SQLite has an opposite behaviour.
  79                                 # @todo Investigate behaviour for other databases
  80                                 if ( wfGetDB( DB_MASTER )->getType() == 'sqlite' ) {
  81                                         $this->db = wfGetDB( DB_MASTER );
  82                                 } else {
  83                                         $this->lb = wfGetLBFactory()->newMainLB();
  84                                         $this->db = $this->lb->getConnection( DB_MASTER );
  85                                         $this->db->clearFlag( DBO_TRX );
  86                                 }
  87                         }
  88                 }
  89
  90                 return $this->db;
  91         }
  92
  93         /**
  94          * Get the table name for a given key
  95          * @return string
  96          */
  97         protected function getTableByKey( $key ) {
  98                 if ( $this->shards > 1 ) {
  99                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 100                         return $this->getTableByShard( $hash % $this->shards );
 101                 } else {
 102                         return $this->tableName;
 103                 }
 104         }
 105
 106         /**
 107          * Get the table name for a given shard index
 108          * @return string
 109          */
 110         protected function getTableByShard( $index ) {
 111                 if ( $this->shards > 1 ) {
 112                         $decimals = strlen( $this->shards - 1 );
 113                         return $this->tableName .
 114                                 sprintf( "%0{$decimals}d", $index );
 115                 } else {
 116                         return $this->tableName;
 117                 }
 118         }
 119
 120         public function get( $key ) {
 121                 # expire old entries if any
 122                 $this->garbageCollect();
 123                 $db = $this->getDB();
 124                 $tableName = $this->getTableByKey( $key );
 125                 $row = $db->selectRow( $tableName, array( 'value', 'exptime' ),
 126                         array( 'keyname' => $key ), __METHOD__ );
 127
 128                 if ( !$row ) {
 129                         $this->debug( 'get: no matching rows' );
 130                         return false;
 131                 }
 132
 133                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 134
 135                 if ( $this->isExpired( $row->exptime ) ) {
 136                         $this->debug( "get: key has expired, deleting" );
 137                         try {
 138                                 $db->begin( __METHOD__ );
 139                                 # Put the expiry time in the WHERE condition to avoid deleting a
 140                                 # newly-inserted value
 141                                 $db->delete( $tableName,
 142                                         array(
 143                                                 'keyname' => $key,
 144                                                 'exptime' => $row->exptime
 145                                         ), __METHOD__ );
 146                                 $db->commit( __METHOD__ );
 147                         } catch ( DBQueryError $e ) {
 148                                 $this->handleWriteError( $e );
 149                         }
 150
 151                         return false;
 152                 }
 153
 154                 return $this->unserialize( $db->decodeBlob( $row->value ) );
 155         }
 156
 157         public function set( $key, $value, $exptime = 0 ) {
 158                 $db = $this->getDB();
 159                 $exptime = intval( $exptime );
 160
 161                 if ( $exptime < 0 ) {
 162                         $exptime = 0;
 163                 }
 164
 165                 if ( $exptime == 0 ) {
 166                         $encExpiry = $this->getMaxDateTime();
 167                 } else {
 168                         if ( $exptime < 3.16e8 ) { # ~10 years
 169                                 $exptime += time();
 170                         }
 171
 172                         $encExpiry = $db->timestamp( $exptime );
 173                 }
 174                 try {
 175                         $db->begin( __METHOD__ );
 176                         // (bug 24425) use a replace if the db supports it instead of
 177                         // delete/insert to avoid clashes with conflicting keynames
 178                         $db->replace(
 179                                 $this->getTableByKey( $key ),
 180                                 array( 'keyname' ),
 181                                 array(
 182                                         'keyname' => $key,
 183                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 184                                         'exptime' => $encExpiry
 185                                 ), __METHOD__ );
 186                         $db->commit( __METHOD__ );
 187                 } catch ( DBQueryError $e ) {
 188                         $this->handleWriteError( $e );
 189
 190                         return false;
 191                 }
 192
 193                 return true;
 194         }
 195
 196         public function delete( $key, $time = 0 ) {
 197                 $db = $this->getDB();
 198
 199                 try {
 200                         $db->begin( __METHOD__ );
 201                         $db->delete(
 202                                 $this->getTableByKey( $key ),
 203                                 array( 'keyname' => $key ),
 204                                 __METHOD__ );
 205                         $db->commit( __METHOD__ );
 206                 } catch ( DBQueryError $e ) {
 207                         $this->handleWriteError( $e );
 208
 209                         return false;
 210                 }
 211
 212                 return true;
 213         }
 214
 215         public function incr( $key, $step = 1 ) {
 216                 $db = $this->getDB();
 217                 $tableName = $this->getTableByKey( $key );
 218                 $step = intval( $step );
 219
 220                 try {
 221                         $db->begin( __METHOD__ );
 222                         $row = $db->selectRow(
 223                                 $tableName,
 224                                 array( 'value', 'exptime' ),
 225                                 array( 'keyname' => $key ),
 226                                 __METHOD__,
 227                                 array( 'FOR UPDATE' ) );
 228                         if ( $row === false ) {
 229                                 // Missing
 230                                 $db->commit( __METHOD__ );
 231
 232                                 return null;
 233                         }
 234                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 235                         if ( $this->isExpired( $row->exptime ) ) {
 236                                 // Expired, do not reinsert
 237                                 $db->commit( __METHOD__ );
 238
 239                                 return null;
 240                         }
 241
 242                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 243                         $newValue = $oldValue + $step;
 244                         $db->insert( $tableName,
 245                                 array(
 246                                         'keyname' => $key,
 247                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 248                                         'exptime' => $row->exptime
 249                                 ), __METHOD__, 'IGNORE' );
 250
 251                         if ( $db->affectedRows() == 0 ) {
 252                                 // Race condition. See bug 28611
 253                                 $newValue = null;
 254                         }
 255                         $db->commit( __METHOD__ );
 256                 } catch ( DBQueryError $e ) {
 257                         $this->handleWriteError( $e );
 258
 259                         return null;
 260                 }
 261
 262                 return $newValue;
 263         }
 264
 265         public function keys() {
 266                 $db = $this->getDB();
 267                 $result = array();
 268
 269                 for ( $i = 0; $i < $this->shards; $i++ ) {
 270                         $res = $db->select( $this->getTableByShard( $i ),
 271                                 array( 'keyname' ), false, __METHOD__ );
 272                         foreach ( $res as $row ) {
 273                                 $result[] = $row->keyname;
 274                         }
 275                 }
 276
 277                 return $result;
 278         }
 279
 280         protected function isExpired( $exptime ) {
 281                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 282         }
 283
 284         protected function getMaxDateTime() {
 285                 if ( time() > 0x7fffffff ) {
 286                         return $this->getDB()->timestamp( 1 << 62 );
 287                 } else {
 288                         return $this->getDB()->timestamp( 0x7fffffff );
 289                 }
 290         }
 291
 292         protected function garbageCollect() {
 293                 if ( !$this->purgePeriod ) {
 294                         // Disabled
 295                         return;
 296                 }
 297                 // Only purge on one in every $this->purgePeriod requests.
 298                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 299                         return;
 300                 }
 301                 $now = time();
 302                 // Avoid repeating the delete within a few seconds
 303                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 304                         $this->lastExpireAll = $now;
 305                         $this->expireAll();
 306                 }
 307         }
 308
 309         public function expireAll() {
 310                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 311         }
 312
 313         /**
 314          * Delete objects from the database which expire before a certain date.
 315          * @return bool
 316          */
 317         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 318                 $db = $this->getDB();
 319                 $dbTimestamp = $db->timestamp( $timestamp );
 320                 $totalSeconds = false;
 321                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 322
 323                 try {
 324                         for ( $i = 0; $i < $this->shards; $i++ ) {
 325                                 $maxExpTime = false;
 326                                 while ( true ) {
 327                                         $conds = $baseConds;
 328                                         if ( $maxExpTime !== false ) {
 329                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 330                                         }
 331                                         $rows = $db->select(
 332                                                 $this->getTableByShard( $i ),
 333                                                 array( 'keyname', 'exptime' ),
 334                                                 $conds,
 335                                                 __METHOD__,
 336                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 337                                         if ( !$rows->numRows() ) {
 338                                                 break;
 339                                         }
 340                                         $keys = array();
 341                                         $row = $rows->current();
 342                                         $minExpTime = $row->exptime;
 343                                         if ( $totalSeconds === false ) {
 344                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 345                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 346                                         }
 347                                         foreach ( $rows as $row ) {
 348                                                 $keys[] = $row->keyname;
 349                                                 $maxExpTime = $row->exptime;
 350                                         }
 351
 352                                         $db->begin( __METHOD__ );
 353                                         $db->delete(
 354                                                 $this->getTableByShard( $i ),
 355                                                 array(
 356                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 357                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 358                                                         'keyname' => $keys
 359                                                 ),
 360                                                 __METHOD__ );
 361                                         $db->commit( __METHOD__ );
 362
 363                                         if ( $progressCallback ) {
 364                                                 if ( intval( $totalSeconds ) === 0 ) {
 365                                                         $percent = 0;
 366                                                 } else {
 367                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 368                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 369                                                         if ( $remainingSeconds > $totalSeconds ) {
 370                                                                 $totalSeconds = $remainingSeconds;
 371                                                         }
 372                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 373                                                                 / $this->shards * 100;
 374                                                 }
 375                                                 call_user_func( $progressCallback, $percent );
 376                                         }
 377                                 }
 378                         }
 379                 } catch ( DBQueryError $e ) {
 380                         $this->handleWriteError( $e );
 381                 }
 382                 return true;
 383         }
 384
 385         public function deleteAll() {
 386                 $db = $this->getDB();
 387
 388                 try {
 389                         for ( $i = 0; $i < $this->shards; $i++ ) {
 390                                 $db->begin( __METHOD__ );
 391                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 392                                 $db->commit( __METHOD__ );
 393                         }
 394                 } catch ( DBQueryError $e ) {
 395                         $this->handleWriteError( $e );
 396                 }
 397         }
 398
 399         /**
 400          * Serialize an object and, if possible, compress the representation.
 401          * On typical message and page data, this can provide a 3X decrease
 402          * in storage requirements.
 403          *
 404          * @param $data mixed
 405          * @return string
 406          */
 407         protected function serialize( &$data ) {
 408                 $serial = serialize( $data );
 409
 410                 if ( function_exists( 'gzdeflate' ) ) {
 411                         return gzdeflate( $serial );
 412                 } else {
 413                         return $serial;
 414                 }
 415         }
 416
 417         /**
 418          * Unserialize and, if necessary, decompress an object.
 419          * @param $serial string
 420          * @return mixed
 421          */
 422         protected function unserialize( $serial ) {
 423                 if ( function_exists( 'gzinflate' ) ) {
 424                         wfSuppressWarnings();
 425                         $decomp = gzinflate( $serial );
 426                         wfRestoreWarnings();
 427
 428                         if ( false !== $decomp ) {
 429                                 $serial = $decomp;
 430                         }
 431                 }
 432
 433                 $ret = unserialize( $serial );
 434
 435                 return $ret;
 436         }
 437
 438         /**
 439          * Handle a DBQueryError which occurred during a write operation.
 440          * Ignore errors which are due to a read-only database, rethrow others.
 441          */
 442         protected function handleWriteError( $exception ) {
 443                 $db = $this->getDB();
 444
 445                 if ( !$db->wasReadOnlyError() ) {
 446                         throw $exception;
 447                 }
 448
 449                 try {
 450                         $db->rollback( __METHOD__ );
 451                 } catch ( DBQueryError $e ) {
 452                 }
 453
 454                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 455                 $db->ignoreErrors( false );
 456         }
 457
 458         /**
 459          * Create shard tables. For use from eval.php.
 460          */
 461         public function createTables() {
 462                 $db = $this->getDB();
 463                 if ( $db->getType() !== 'mysql'
 464                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 465                 {
 466                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 467                 }
 468
 469                 for ( $i = 0; $i < $this->shards; $i++ ) {
 470                         $db->begin( __METHOD__ );
 471                         $db->query(
 472                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 473                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 474                                 __METHOD__ );
 475                         $db->commit( __METHOD__ );
 476                 }
 477         }
 478 }
 479
 480 /**
 481  * Backwards compatibility alias
 482  */
 483 class MediaWikiBagOStuff extends SqlBagOStuff { }
 484