includes/BagOStuff.php

   1 <?php
   2 #
   3 # Copyright (C) 2003-2004 Brion Vibber <brion@pobox.com>
   4 # http://www.mediawiki.org/
   5 #
   6 # This program is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 2 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License along
  17 # with this program; if not, write to the Free Software Foundation, Inc.,
  18 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19 # http://www.gnu.org/copyleft/gpl.html
  20
  21 /**
  22  * @defgroup Cache Cache
  23  *
  24  * @file
  25  * @ingroup Cache
  26  */
  27
  28 /**
  29  * interface is intended to be more or less compatible with
  30  * the PHP memcached client.
  31  *
  32  * backends for local hash array and SQL table included:
  33  * <code>
  34  *   $bag = new HashBagOStuff();
  35  *   $bag = new SqlBagOStuff(); # connect to db first
  36  * </code>
  37  *
  38  * @ingroup Cache
  39  */
  40 abstract class BagOStuff {
  41         var $debugMode = false;
  42
  43         public function set_debug( $bool ) {
  44                 $this->debugMode = $bool;
  45         }
  46
  47         /* *** THE GUTS OF THE OPERATION *** */
  48         /* Override these with functional things in subclasses */
  49
  50         /**
  51          * Get an item with the given key. Returns false if it does not exist.
  52          * @param $key string
  53          */
  54         abstract public function get( $key );
  55
  56         /**
  57          * Set an item.
  58          * @param $key string
  59          * @param $value mixed
  60          * @param $exptime int Either an interval in seconds or a unix timestamp for expiry
  61          */
  62         abstract public function set( $key, $value, $exptime = 0 );
  63
  64         /*
  65          * Delete an item.
  66          * @param $key string
  67          * @param $time int Amount of time to delay the operation (mostly memcached-specific)
  68          */
  69         abstract public function delete( $key, $time = 0 );
  70
  71         public function lock( $key, $timeout = 0 ) {
  72                 /* stub */
  73                 return true;
  74         }
  75
  76         public function unlock( $key ) {
  77                 /* stub */
  78                 return true;
  79         }
  80
  81         public function keys() {
  82                 /* stub */
  83                 return array();
  84         }
  85
  86         /* *** Emulated functions *** */
  87         /* Better performance can likely be got with custom written versions */
  88         public function get_multi( $keys ) {
  89                 $out = array();
  90                 foreach ( $keys as $key ) {
  91                         $out[$key] = $this->get( $key );
  92                 }
  93                 return $out;
  94         }
  95
  96         public function set_multi( $hash, $exptime = 0 ) {
  97                 foreach ( $hash as $key => $value ) {
  98                         $this->set( $key, $value, $exptime );
  99                 }
 100         }
 101
 102         public function add( $key, $value, $exptime = 0 ) {
 103                 if ( $this->get( $key ) == false ) {
 104                         $this->set( $key, $value, $exptime );
 105                         return true;
 106                 }
 107         }
 108
 109         public function add_multi( $hash, $exptime = 0 ) {
 110                 foreach ( $hash as $key => $value ) {
 111                         $this->add( $key, $value, $exptime );
 112                 }
 113         }
 114
 115         public function delete_multi( $keys, $time = 0 ) {
 116                 foreach ( $keys as $key ) {
 117                         $this->delete( $key, $time );
 118                 }
 119         }
 120
 121         public function replace( $key, $value, $exptime = 0 ) {
 122                 if ( $this->get( $key ) !== false ) {
 123                         $this->set( $key, $value, $exptime );
 124                 }
 125         }
 126
 127         public function incr( $key, $value = 1 ) {
 128                 if ( !$this->lock( $key ) ) {
 129                         return false;
 130                 }
 131                 $value = intval( $value );
 132
 133                 $n = false;
 134                 if ( ( $n = $this->get( $key ) ) !== false ) {
 135                         $n += $value;
 136                         $this->set( $key, $n ); // exptime?
 137                 }
 138                 $this->unlock( $key );
 139                 return $n;
 140         }
 141
 142         public function decr( $key, $value = 1 ) {
 143                 return $this->incr( $key, -$value );
 144         }
 145
 146         public function debug( $text ) {
 147                 if ( $this->debugMode )
 148                         wfDebug( "BagOStuff debug: $text\n" );
 149         }
 150
 151         /**
 152          * Convert an optionally relative time to an absolute time
 153          */
 154         protected function convertExpiry( $exptime ) {
 155                 if ( ( $exptime != 0 ) && ( $exptime < 3600 * 24 * 30 ) ) {
 156                         return time() + $exptime;
 157                 } else {
 158                         return $exptime;
 159                 }
 160         }
 161 }
 162
 163
 164 /**
 165  * Functional versions!
 166  * This is a test of the interface, mainly. It stores things in an associative
 167  * array, which is not going to persist between program runs.
 168  *
 169  * @ingroup Cache
 170  */
 171 class HashBagOStuff extends BagOStuff {
 172         var $bag;
 173
 174         function __construct() {
 175                 $this->bag = array();
 176         }
 177
 178         protected function expire( $key ) {
 179                 $et = $this->bag[$key][1];
 180                 if ( ( $et == 0 ) || ( $et > time() ) ) {
 181                         return false;
 182                 }
 183                 $this->delete( $key );
 184                 return true;
 185         }
 186
 187         function get( $key ) {
 188                 if ( !isset( $this->bag[$key] ) ) {
 189                         return false;
 190                 }
 191                 if ( $this->expire( $key ) ) {
 192                         return false;
 193                 }
 194                 return $this->bag[$key][0];
 195         }
 196
 197         function set( $key, $value, $exptime = 0 ) {
 198                 $this->bag[$key] = array( $value, $this->convertExpiry( $exptime ) );
 199         }
 200
 201         function delete( $key, $time = 0 ) {
 202                 if ( !isset( $this->bag[$key] ) ) {
 203                         return false;
 204                 }
 205                 unset( $this->bag[$key] );
 206                 return true;
 207         }
 208
 209         function keys() {
 210                 return array_keys( $this->bag );
 211         }
 212 }
 213
 214 /**
 215  * Class to store objects in the database
 216  *
 217  * @ingroup Cache
 218  */
 219 class SqlBagOStuff extends BagOStuff {
 220         var $lb, $db;
 221         var $lastExpireAll = 0;
 222
 223         protected function getDB() {
 224                 global $wgDBtype;
 225                 if ( !isset( $this->db ) ) {
 226                         /* We must keep a separate connection to MySQL in order to avoid deadlocks
 227                          * However, SQLite has an opposite behaviour.
 228                          * @todo Investigate behaviour for other databases
 229                          */
 230                         if ( $wgDBtype == 'sqlite' ) {
 231                                 $this->db = wfGetDB( DB_MASTER );
 232                         } else {
 233                                 $this->lb = wfGetLBFactory()->newMainLB();
 234                                 $this->db = $this->lb->getConnection( DB_MASTER );
 235                                 $this->db->clearFlag( DBO_TRX );
 236                         }
 237                 }
 238                 return $this->db;
 239         }
 240
 241         public function get( $key ) {
 242                 # expire old entries if any
 243                 $this->garbageCollect();
 244                 $db = $this->getDB();
 245                 $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
 246                         array( 'keyname' => $key ), __METHOD__ );
 247                 if ( !$row ) {
 248                         $this->debug( 'get: no matching rows' );
 249                         return false;
 250                 }
 251
 252                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 253                 if ( $this->isExpired( $row->exptime ) ) {
 254                         $this->debug( "get: key has expired, deleting" );
 255                         try {
 256                                 $db->begin();
 257                                 # Put the expiry time in the WHERE condition to avoid deleting a
 258                                 # newly-inserted value
 259                                 $db->delete( 'objectcache',
 260                                         array(
 261                                                 'keyname' => $key,
 262                                                 'exptime' => $row->exptime
 263                                         ), __METHOD__ );
 264                                 $db->commit();
 265                         } catch ( DBQueryError $e ) {
 266                                 $this->handleWriteError( $e );
 267                         }
 268                         return false;
 269                 }
 270                 return $this->unserialize( $db->decodeBlob( $row->value ) );
 271         }
 272
 273         public function set( $key, $value, $exptime = 0 ) {
 274                 $db = $this->getDB();
 275                 $exptime = intval( $exptime );
 276                 if ( $exptime < 0 ) $exptime = 0;
 277                 if ( $exptime == 0 ) {
 278                         $encExpiry = $this->getMaxDateTime();
 279                 } else {
 280                         if ( $exptime < 3.16e8 ) # ~10 years
 281                                 $exptime += time();
 282                         $encExpiry = $db->timestamp( $exptime );
 283                 }
 284                 try {
 285                         $db->begin();
 286                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 287                         $db->insert( 'objectcache',
 288                                 array(
 289                                         'keyname' => $key,
 290                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 291                                         'exptime' => $encExpiry
 292                                 ), __METHOD__ );
 293                         $db->commit();
 294                 } catch ( DBQueryError $e ) {
 295                         $this->handleWriteError( $e );
 296                         return false;
 297                 }
 298                 return true;
 299         }
 300
 301         public function delete( $key, $time = 0 ) {
 302                 $db = $this->getDB();
 303                 try {
 304                         $db->begin();
 305                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 306                         $db->commit();
 307                 } catch ( DBQueryError $e ) {
 308                         $this->handleWriteError( $e );
 309                         return false;
 310                 }
 311                 return true;
 312         }
 313
 314         public function incr( $key, $step = 1 ) {
 315                 $db = $this->getDB();
 316                 $step = intval( $step );
 317
 318                 try {
 319                         $db->begin();
 320                         $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
 321                                 array( 'keyname' => $key ), __METHOD__, array( 'FOR UPDATE' ) );
 322                         if ( $row === false ) {
 323                                 // Missing
 324                                 $db->commit();
 325                                 return false;
 326                         }
 327                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 328                         if ( $this->isExpired( $row->exptime ) ) {
 329                                 // Expired, do not reinsert
 330                                 $db->commit();
 331                                 return false;
 332                         }
 333
 334                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 335                         $newValue = $oldValue + $step;
 336                         $db->insert( 'objectcache',
 337                                 array(
 338                                         'keyname' => $key,
 339                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 340                                         'exptime' => $row->exptime
 341                                 ), __METHOD__ );
 342                         $db->commit();
 343                 } catch ( DBQueryError $e ) {
 344                         $this->handleWriteError( $e );
 345                         return false;
 346                 }
 347                 return $newValue;
 348         }
 349
 350         public function keys() {
 351                 $db = $this->getDB();
 352                 $res = $db->select( 'objectcache', array( 'keyname' ), false, __METHOD__ );
 353                 $result = array();
 354                 foreach ( $res as $row ) {
 355                         $result[] = $row->keyname;
 356                 }
 357                 return $result;
 358         }
 359
 360         protected function isExpired( $exptime ) {
 361                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 362         }
 363
 364         protected function getMaxDateTime() {
 365                 if ( time() > 0x7fffffff ) {
 366                         return $this->getDB()->timestamp( 1 << 62 );
 367                 } else {
 368                         return $this->getDB()->timestamp( 0x7fffffff );
 369                 }
 370         }
 371
 372         protected function garbageCollect() {
 373                 /* Ignore 99% of requests */
 374                 if ( !mt_rand( 0, 100 ) ) {
 375                         $now = time();
 376                         /* Avoid repeating the delete within a few seconds */
 377                         if ( $now > ( $this->lastExpireAll + 1 ) ) {
 378                                 $this->lastExpireAll = $now;
 379                                 $this->expireAll();
 380                         }
 381                 }
 382         }
 383
 384         public function expireAll() {
 385                 $db = $this->getDB();
 386                 $now = $db->timestamp();
 387                 try {
 388                         $db->begin();
 389                         $db->delete( 'objectcache', array( 'exptime < ' . $db->addQuotes( $now ) ), __METHOD__ );
 390                         $db->commit();
 391                 } catch ( DBQueryError $e ) {
 392                         $this->handleWriteError( $e );
 393                 }
 394         }
 395
 396         public function deleteAll() {
 397                 $db = $this->getDB();
 398                 try {
 399                         $db->begin();
 400                         $db->delete( 'objectcache', '*', __METHOD__ );
 401                         $db->commit();
 402                 } catch ( DBQueryError $e ) {
 403                         $this->handleWriteError( $e );
 404                 }
 405         }
 406
 407         /**
 408          * Serialize an object and, if possible, compress the representation.
 409          * On typical message and page data, this can provide a 3X decrease
 410          * in storage requirements.
 411          *
 412          * @param $data mixed
 413          * @return string
 414          */
 415         protected function serialize( &$data ) {
 416                 $serial = serialize( $data );
 417                 if ( function_exists( 'gzdeflate' ) ) {
 418                         return gzdeflate( $serial );
 419                 } else {
 420                         return $serial;
 421                 }
 422         }
 423
 424         /**
 425          * Unserialize and, if necessary, decompress an object.
 426          * @param $serial string
 427          * @return mixed
 428          */
 429         protected function unserialize( $serial ) {
 430                 if ( function_exists( 'gzinflate' ) ) {
 431                         $decomp = @gzinflate( $serial );
 432                         if ( false !== $decomp ) {
 433                                 $serial = $decomp;
 434                         }
 435                 }
 436                 $ret = unserialize( $serial );
 437                 return $ret;
 438         }
 439
 440         /**
 441          * Handle a DBQueryError which occurred during a write operation.
 442          * Ignore errors which are due to a read-only database, rethrow others.
 443          */
 444         protected function handleWriteError( $exception ) {
 445                 $db = $this->getDB();
 446                 if ( !$db->wasReadOnlyError() ) {
 447                         throw $exception;
 448                 }
 449                 try {
 450                         $db->rollback();
 451                 } catch ( DBQueryError $e ) {
 452                 }
 453                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 454                 $db->ignoreErrors( false );
 455         }
 456 }
 457
 458 /**
 459  * Backwards compatibility alias
 460  */
 461 class MediaWikiBagOStuff extends SqlBagOStuff {}
 462
 463 /**
 464  * This is a wrapper for Turck MMCache's shared memory functions.
 465  *
 466  * You can store objects with mmcache_put() and mmcache_get(), but Turck seems
 467  * to use a weird custom serializer that randomly segfaults. So we wrap calls
 468  * with serialize()/unserialize().
 469  *
 470  * The thing I noticed about the Turck serialized data was that unlike ordinary
 471  * serialize(), it contained the names of methods, and judging by the amount of
 472  * binary data, perhaps even the bytecode of the methods themselves. It may be
 473  * that Turck's serializer is faster, so a possible future extension would be
 474  * to use it for arrays but not for objects.
 475  *
 476  * @ingroup Cache
 477  */
 478 class TurckBagOStuff extends BagOStuff {
 479         public function get( $key ) {
 480                 $val = mmcache_get( $key );
 481                 if ( is_string( $val ) ) {
 482                         $val = unserialize( $val );
 483                 }
 484                 return $val;
 485         }
 486
 487         public function set( $key, $value, $exptime = 0 ) {
 488                 mmcache_put( $key, serialize( $value ), $exptime );
 489                 return true;
 490         }
 491
 492         public function delete( $key, $time = 0 ) {
 493                 mmcache_rm( $key );
 494                 return true;
 495         }
 496
 497         public function lock( $key, $waitTimeout = 0 ) {
 498                 mmcache_lock( $key );
 499                 return true;
 500         }
 501
 502         public function unlock( $key ) {
 503                 mmcache_unlock( $key );
 504                 return true;
 505         }
 506 }
 507
 508 /**
 509  * This is a wrapper for APC's shared memory functions
 510  *
 511  * @ingroup Cache
 512  */
 513 class APCBagOStuff extends BagOStuff {
 514         public function get( $key ) {
 515                 $val = apc_fetch( $key );
 516                 if ( is_string( $val ) ) {
 517                         $val = unserialize( $val );
 518                 }
 519                 return $val;
 520         }
 521
 522         public function set( $key, $value, $exptime = 0 ) {
 523                 apc_store( $key, serialize( $value ), $exptime );
 524                 return true;
 525         }
 526
 527         public function delete( $key, $time = 0 ) {
 528                 apc_delete( $key );
 529                 return true;
 530         }
 531
 532         public function keys() {
 533                 $info = apc_cache_info( 'user' );
 534                 $list = $info['cache_list'];
 535                 $keys = array();
 536                 foreach( $list as $entry ) {
 537                         $keys[] = $entry['info'];
 538                 }
 539                 return $keys;
 540         }
 541 }
 542
 543
 544 /**
 545  * This is a wrapper for eAccelerator's shared memory functions.
 546  *
 547  * This is basically identical to the Turck MMCache version,
 548  * mostly because eAccelerator is based on Turck MMCache.
 549  *
 550  * @ingroup Cache
 551  */
 552 class eAccelBagOStuff extends BagOStuff {
 553         public function get( $key ) {
 554                 $val = eaccelerator_get( $key );
 555                 if ( is_string( $val ) ) {
 556                         $val = unserialize( $val );
 557                 }
 558                 return $val;
 559         }
 560
 561         public function set( $key, $value, $exptime = 0 ) {
 562                 eaccelerator_put( $key, serialize( $value ), $exptime );
 563                 return true;
 564         }
 565
 566         public function delete( $key, $time = 0 ) {
 567                 eaccelerator_rm( $key );
 568                 return true;
 569         }
 570
 571         public function lock( $key, $waitTimeout = 0 ) {
 572                 eaccelerator_lock( $key );
 573                 return true;
 574         }
 575
 576         public function unlock( $key ) {
 577                 eaccelerator_unlock( $key );
 578                 return true;
 579         }
 580 }
 581
 582 /**
 583  * Wrapper for XCache object caching functions; identical interface
 584  * to the APC wrapper
 585  *
 586  * @ingroup Cache
 587  */
 588 class XCacheBagOStuff extends BagOStuff {
 589
 590         /**
 591          * Get a value from the XCache object cache
 592          *
 593          * @param $key String: cache key
 594          * @return mixed
 595          */
 596         public function get( $key ) {
 597                 $val = xcache_get( $key );
 598                 if ( is_string( $val ) )
 599                         $val = unserialize( $val );
 600                 return $val;
 601         }
 602
 603         /**
 604          * Store a value in the XCache object cache
 605          *
 606          * @param $key String: cache key
 607          * @param $value Mixed: object to store
 608          * @param $expire Int: expiration time
 609          * @return bool
 610          */
 611         public function set( $key, $value, $expire = 0 ) {
 612                 xcache_set( $key, serialize( $value ), $expire );
 613                 return true;
 614         }
 615
 616         /**
 617          * Remove a value from the XCache object cache
 618          *
 619          * @param $key String: cache key
 620          * @param $time Int: not used in this implementation
 621          * @return bool
 622          */
 623         public function delete( $key, $time = 0 ) {
 624                 xcache_unset( $key );
 625                 return true;
 626         }
 627
 628 }
 629
 630 /**
 631  * Cache that uses DBA as a backend.
 632  * Slow due to the need to constantly open and close the file to avoid holding
 633  * writer locks. Intended for development use only,  as a memcached workalike
 634  * for systems that don't have it.
 635  *
 636  * @ingroup Cache
 637  */
 638 class DBABagOStuff extends BagOStuff {
 639         var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
 640
 641         public function __construct( $dir = false ) {
 642                 global $wgDBAhandler;
 643                 if ( $dir === false ) {
 644                         global $wgTmpDirectory;
 645                         $dir = $wgTmpDirectory;
 646                 }
 647                 $this->mFile = "$dir/mw-cache-" . wfWikiID();
 648                 $this->mFile .= '.db';
 649                 wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
 650                 $this->mHandler = $wgDBAhandler;
 651         }
 652
 653         /**
 654          * Encode value and expiry for storage
 655          */
 656         function encode( $value, $expiry ) {
 657                 # Convert to absolute time
 658                 $expiry = $this->convertExpiry( $expiry );
 659                 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
 660         }
 661
 662         /**
 663          * @return list containing value first and expiry second
 664          */
 665         function decode( $blob ) {
 666                 if ( !is_string( $blob ) ) {
 667                         return array( null, 0 );
 668                 } else {
 669                         return array(
 670                                 unserialize( substr( $blob, 11 ) ),
 671                                 intval( substr( $blob, 0, 10 ) )
 672                         );
 673                 }
 674         }
 675
 676         function getReader() {
 677                 if ( file_exists( $this->mFile ) ) {
 678                         $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
 679                 } else {
 680                         $handle = $this->getWriter();
 681                 }
 682                 if ( !$handle ) {
 683                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
 684                 }
 685                 return $handle;
 686         }
 687
 688         function getWriter() {
 689                 $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
 690                 if ( !$handle ) {
 691                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
 692                 }
 693                 return $handle;
 694         }
 695
 696         function get( $key ) {
 697                 wfProfileIn( __METHOD__ );
 698                 wfDebug( __METHOD__ . "($key)\n" );
 699                 $handle = $this->getReader();
 700                 if ( !$handle ) {
 701                         return null;
 702                 }
 703                 $val = dba_fetch( $key, $handle );
 704                 list( $val, $expiry ) = $this->decode( $val );
 705                 # Must close ASAP because locks are held
 706                 dba_close( $handle );
 707
 708                 if ( !is_null( $val ) && $expiry && $expiry < time() ) {
 709                         # Key is expired, delete it
 710                         $handle = $this->getWriter();
 711                         dba_delete( $key, $handle );
 712                         dba_close( $handle );
 713                         wfDebug( __METHOD__ . ": $key expired\n" );
 714                         $val = null;
 715                 }
 716                 wfProfileOut( __METHOD__ );
 717                 return $val;
 718         }
 719
 720         function set( $key, $value, $exptime = 0 ) {
 721                 wfProfileIn( __METHOD__ );
 722                 wfDebug( __METHOD__ . "($key)\n" );
 723                 $blob = $this->encode( $value, $exptime );
 724                 $handle = $this->getWriter();
 725                 if ( !$handle ) {
 726                         return false;
 727                 }
 728                 $ret = dba_replace( $key, $blob, $handle );
 729                 dba_close( $handle );
 730                 wfProfileOut( __METHOD__ );
 731                 return $ret;
 732         }
 733
 734         function delete( $key, $time = 0 ) {
 735                 wfProfileIn( __METHOD__ );
 736                 wfDebug( __METHOD__ . "($key)\n" );
 737                 $handle = $this->getWriter();
 738                 if ( !$handle ) {
 739                         return false;
 740                 }
 741                 $ret = dba_delete( $key, $handle );
 742                 dba_close( $handle );
 743                 wfProfileOut( __METHOD__ );
 744                 return $ret;
 745         }
 746
 747         function add( $key, $value, $exptime = 0 ) {
 748                 wfProfileIn( __METHOD__ );
 749                 $blob = $this->encode( $value, $exptime );
 750                 $handle = $this->getWriter();
 751                 if ( !$handle ) {
 752                         return false;
 753                 }
 754                 $ret = dba_insert( $key, $blob, $handle );
 755                 # Insert failed, check to see if it failed due to an expired key
 756                 if ( !$ret ) {
 757                         list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
 758                         if ( $expiry < time() ) {
 759                                 # Yes expired, delete and try again
 760                                 dba_delete( $key, $handle );
 761                                 $ret = dba_insert( $key, $blob, $handle );
 762                                 # This time if it failed then it will be handled by the caller like any other race
 763                         }
 764                 }
 765
 766                 dba_close( $handle );
 767                 wfProfileOut( __METHOD__ );
 768                 return $ret;
 769         }
 770
 771         function keys() {
 772                 $reader = $this->getReader();
 773                 $k1 = dba_firstkey( $reader );
 774                 if ( !$k1 ) {
 775                         return array();
 776                 }
 777                 $result[] = $k1;
 778                 while ( $key = dba_nextkey( $reader ) ) {
 779                         $result[] = $key;
 780                 }
 781                 return $result;
 782         }
 783 }