includes/CacheDependency.php

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