includes/cache/CacheDependency.php

   1 <?php
   2 /**
   3  * This class stores an arbitrary value along with its dependencies.
   4  * Users should typically only use DependencyWrapper::getValueFromCache(),
   5  * rather than instantiating one of these objects directly.
   6  * @ingroup Cache
   7  */
   8
   9 class DependencyWrapper {
  10         var $value;
  11         var $deps;
  12
  13         /**
  14          * Create an instance.
  15          * @param $value Mixed: the user-supplied value
  16          * @param $deps Mixed: a dependency or dependency array. All dependencies
  17          *        must be objects implementing CacheDependency.
  18          */
  19         function __construct( $value = false, $deps = array() ) {
  20                 $this->value = $value;
  21
  22                 if ( !is_array( $deps ) ) {
  23                         $deps = array( $deps );
  24                 }
  25
  26                 $this->deps = $deps;
  27         }
  28
  29         /**
  30          * Returns true if any of the dependencies have expired
  31          */
  32         function isExpired() {
  33                 foreach ( $this->deps as $dep ) {
  34                         if ( $dep->isExpired() ) {
  35                                 return true;
  36                         }
  37                 }
  38
  39                 return false;
  40         }
  41
  42         /**
  43          * Initialise dependency values in preparation for storing. This must be
  44          * called before serialization.
  45          */
  46         function initialiseDeps() {
  47                 foreach ( $this->deps as $dep ) {
  48                         $dep->loadDependencyValues();
  49                 }
  50         }
  51
  52         /**
  53          * Get the user-defined value
  54          */
  55         function getValue() {
  56                 return $this->value;
  57         }
  58
  59         /**
  60          * Store the wrapper to a cache
  61          *
  62          * @param $cache BagOStuff
  63          * @param $key
  64          * @param $expiry
  65          */
  66         function storeToCache( $cache, $key, $expiry = 0 ) {
  67                 $this->initialiseDeps();
  68                 $cache->set( $key, $this, $expiry );
  69         }
  70
  71         /**
  72          * Attempt to get a value from the cache. If the value is expired or missing,
  73          * it will be generated with the callback function (if present), and the newly
  74          * calculated value will be stored to the cache in a wrapper.
  75          *
  76          * @param $cache BagOStuff a cache object such as $wgMemc
  77          * @param $key String: the cache key
  78          * @param $expiry Integer: the expiry timestamp or interval in seconds
  79          * @param $callback Mixed: the callback for generating the value, or false
  80          * @param $callbackParams Array: the function parameters for the callback
  81          * @param $deps Array: the dependencies to store on a cache miss. Note: these
  82          *    are not the dependencies used on a cache hit! Cache hits use the stored
  83          *    dependency array.
  84          *
  85          * @return mixed The value, or null if it was not present in the cache and no
  86          *    callback was defined.
  87          */
  88         static function getValueFromCache( $cache, $key, $expiry = 0, $callback = false,
  89                 $callbackParams = array(), $deps = array() )
  90         {
  91                 $obj = $cache->get( $key );
  92
  93                 if ( is_object( $obj ) && $obj instanceof DependencyWrapper && !$obj->isExpired() ) {
  94                         $value = $obj->value;
  95                 } elseif ( $callback ) {
  96                         $value = call_user_func_array( $callback, $callbackParams );
  97                         # Cache the newly-generated value
  98                         $wrapper = new DependencyWrapper( $value, $deps );
  99                         $wrapper->storeToCache( $cache, $key, $expiry );
 100                 } else {
 101                         $value = null;
 102                 }
 103
 104                 return $value;
 105         }
 106 }
 107
 108 /**
 109  * @ingroup Cache
 110  */
 111 abstract class CacheDependency {
 112         /**
 113          * Returns true if the dependency is expired, false otherwise
 114          */
 115         abstract function isExpired();
 116
 117         /**
 118          * Hook to perform any expensive pre-serialize loading of dependency values.
 119          */
 120         function loadDependencyValues() { }
 121 }
 122
 123 /**
 124  * @ingroup Cache
 125  */
 126 class FileDependency extends CacheDependency {
 127         var $filename, $timestamp;
 128
 129         /**
 130          * Create a file dependency
 131          *
 132          * @param $filename String: the name of the file, preferably fully qualified
 133          * @param $timestamp Mixed: the unix last modified timestamp, or false if the
 134          *        file does not exist. If omitted, the timestamp will be loaded from
 135          *        the file.
 136          *
 137          * A dependency on a nonexistent file will be triggered when the file is
 138          * created. A dependency on an existing file will be triggered when the
 139          * file is changed.
 140          */
 141         function __construct( $filename, $timestamp = null ) {
 142                 $this->filename = $filename;
 143                 $this->timestamp = $timestamp;
 144         }
 145
 146         function __sleep() {
 147                 $this->loadDependencyValues();
 148                 return array( 'filename', 'timestamp' );
 149         }
 150
 151         function loadDependencyValues() {
 152                 if ( is_null( $this->timestamp ) ) {
 153                         if ( !file_exists( $this->filename ) ) {
 154                                 # Dependency on a non-existent file
 155                                 # This is a valid concept!
 156                                 $this->timestamp = false;
 157                         } else {
 158                                 $this->timestamp = filemtime( $this->filename );
 159                         }
 160                 }
 161         }
 162
 163         /**
 164          * @return bool
 165          */
 166         function isExpired() {
 167                 if ( !file_exists( $this->filename ) ) {
 168                         if ( $this->timestamp === false ) {
 169                                 # Still nonexistent
 170                                 return false;
 171                         } else {
 172                                 # Deleted
 173                                 wfDebug( "Dependency triggered: {$this->filename} deleted.\n" );
 174                                 return true;
 175                         }
 176                 } else {
 177                         $lastmod = filemtime( $this->filename );
 178                         if ( $lastmod > $this->timestamp ) {
 179                                 # Modified or created
 180                                 wfDebug( "Dependency triggered: {$this->filename} changed.\n" );
 181                                 return true;
 182                         } else {
 183                                 # Not modified
 184                                 return false;
 185                         }
 186                 }
 187         }
 188 }
 189
 190 /**
 191  * @ingroup Cache
 192  */
 193 class TitleDependency extends CacheDependency {
 194         var $titleObj;
 195         var $ns, $dbk;
 196         var $touched;
 197
 198         /**
 199          * Construct a title dependency
 200          * @param $title Title
 201          */
 202         function __construct( Title $title ) {
 203                 $this->titleObj = $title;
 204                 $this->ns = $title->getNamespace();
 205                 $this->dbk = $title->getDBkey();
 206         }
 207
 208         function loadDependencyValues() {
 209                 $this->touched = $this->getTitle()->getTouched();
 210         }
 211
 212         /**
 213          * Get rid of bulky Title object for sleep
 214          *
 215          * @return array
 216          */
 217         function __sleep() {
 218                 return array( 'ns', 'dbk', 'touched' );
 219         }
 220
 221         /**
 222          * @return Title
 223          */
 224         function getTitle() {
 225                 if ( !isset( $this->titleObj ) ) {
 226                         $this->titleObj = Title::makeTitle( $this->ns, $this->dbk );
 227                 }
 228
 229                 return $this->titleObj;
 230         }
 231
 232         /**
 233          * @return bool
 234          */
 235         function isExpired() {
 236                 $touched = $this->getTitle()->getTouched();
 237
 238                 if ( $this->touched === false ) {
 239                         if ( $touched === false ) {
 240                                 # Still missing
 241                                 return false;
 242                         } else {
 243                                 # Created
 244                                 return true;
 245                         }
 246                 } elseif ( $touched === false ) {
 247                         # Deleted
 248                         return true;
 249                 } elseif ( $touched > $this->touched ) {
 250                         # Updated
 251                         return true;
 252                 } else {
 253                         # Unmodified
 254                         return false;
 255                 }
 256         }
 257 }
 258
 259 /**
 260  * @ingroup Cache
 261  */
 262 class TitleListDependency extends CacheDependency {
 263         var $linkBatch;
 264         var $timestamps;
 265
 266         /**
 267          * Construct a dependency on a list of titles
 268          */
 269         function __construct( LinkBatch $linkBatch ) {
 270                 $this->linkBatch = $linkBatch;
 271         }
 272
 273         function calculateTimestamps() {
 274                 # Initialise values to false
 275                 $timestamps = array();
 276
 277                 foreach ( $this->getLinkBatch()->data as $ns => $dbks ) {
 278                         if ( count( $dbks ) > 0 ) {
 279                                 $timestamps[$ns] = array();
 280
 281                                 foreach ( $dbks as $dbk => $value ) {
 282                                         $timestamps[$ns][$dbk] = false;
 283                                 }
 284                         }
 285                 }
 286
 287                 # Do the query
 288                 if ( count( $timestamps ) ) {
 289                         $dbr = wfGetDB( DB_SLAVE );
 290                         $where = $this->getLinkBatch()->constructSet( 'page', $dbr );
 291                         $res = $dbr->select(
 292                                 'page',
 293                                 array( 'page_namespace', 'page_title', 'page_touched' ),
 294                                 $where,
 295                                 __METHOD__
 296                         );
 297
 298                         foreach ( $res as $row ) {
 299                                 $timestamps[$row->page_namespace][$row->page_title] = $row->page_touched;
 300                         }
 301                 }
 302
 303                 return $timestamps;
 304         }
 305
 306         function loadDependencyValues() {
 307                 $this->timestamps = $this->calculateTimestamps();
 308         }
 309
 310         /**
 311          * @return array
 312          */
 313         function __sleep() {
 314                 return array( 'timestamps' );
 315         }
 316
 317         function getLinkBatch() {
 318                 if ( !isset( $this->linkBatch ) ) {
 319                         $this->linkBatch = new LinkBatch;
 320                         $this->linkBatch->setArray( $this->timestamps );
 321                 }
 322                 return $this->linkBatch;
 323         }
 324
 325         /**
 326          * @return bool
 327          */
 328         function isExpired() {
 329                 $newTimestamps = $this->calculateTimestamps();
 330
 331                 foreach ( $this->timestamps as $ns => $dbks ) {
 332                         foreach ( $dbks as $dbk => $oldTimestamp ) {
 333                                 $newTimestamp = $newTimestamps[$ns][$dbk];
 334
 335                                 if ( $oldTimestamp === false ) {
 336                                         if ( $newTimestamp === false ) {
 337                                                 # Still missing
 338                                         } else {
 339                                                 # Created
 340                                                 return true;
 341                                         }
 342                                 } elseif ( $newTimestamp === false ) {
 343                                         # Deleted
 344                                         return true;
 345                                 } elseif ( $newTimestamp > $oldTimestamp ) {
 346                                         # Updated
 347                                         return true;
 348                                 } else {
 349                                         # Unmodified
 350                                 }
 351                         }
 352                 }
 353
 354                 return false;
 355         }
 356 }
 357
 358 /**
 359  * @ingroup Cache
 360  */
 361 class GlobalDependency extends CacheDependency {
 362         var $name, $value;
 363
 364         function __construct( $name ) {
 365                 $this->name = $name;
 366                 $this->value = $GLOBALS[$name];
 367         }
 368
 369         /**
 370          * @return bool
 371          */
 372         function isExpired() {
 373                 return $GLOBALS[$this->name] != $this->value;
 374         }
 375 }
 376
 377 /**
 378  * @ingroup Cache
 379  */
 380 class ConstantDependency extends CacheDependency {
 381         var $name, $value;
 382
 383         function __construct( $name ) {
 384                 $this->name = $name;
 385                 $this->value = constant( $name );
 386         }
 387
 388         /**
 389          * @return bool
 390          */
 391         function isExpired() {
 392                 return constant( $this->name ) != $this->value;
 393         }
 394 }