includes/CacheDependency.php

   1 <?php
   2
   3 /**
   4  * This class stores an arbitrary value along with its dependencies.
   5  * Users should typically only use DependencyWrapper::getFromCache(), rather
   6  * than instantiating one of these objects directly.
   7  */
   8 class DependencyWrapper {
   9         var $value;
  10         var $deps;
  11
  12         /**
  13          * Create an instance.
  14          * @param mixed $value The user-supplied value
  15          * @param mixed $deps 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 object $cache A cache object such as $wgMemc
  69          * @param string $key The cache key
  70          * @param integer $expiry The expiry timestamp or interval in seconds
  71          * @param mixed $callback The callback for generating the value, or false
  72          * @param array $callbackParams The function parameters for the callback
  73          * @param array $deps 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 abstract class CacheDependency {
  99         /**
 100          * Returns true if the dependency is expired, false otherwise
 101          */
 102         abstract function isExpired();
 103
 104         /**
 105          * Hook to perform any expensive pre-serialize loading of dependency values.
 106          */
 107         function loadDependencyValues() {}
 108 }
 109
 110 class FileDependency extends CacheDependency {
 111         var $filename, $timestamp;
 112
 113         /**
 114          * Create a file dependency
 115          *
 116          * @param string $filename The name of the file, preferably fully qualified
 117          * @param mixed $timestamp The unix last modified timestamp, or false if the
 118          *        file does not exist. If omitted, the timestamp will be loaded from
 119          *        the file.
 120          *
 121          * A dependency on a nonexistent file will be triggered when the file is
 122          * created. A dependency on an existing file will be triggered when the
 123          * file is changed.
 124          */
 125         function __construct( $filename, $timestamp = null ) {
 126                 $this->filename = $filename;
 127                 $this->timestamp = $timestamp;
 128         }
 129
 130         function loadDependencyValues() {
 131                 if ( is_null( $this->timestamp ) ) {
 132                         if ( !file_exists( $this->filename ) ) {
 133                                 # Dependency on a non-existent file
 134                                 # This is a valid concept!
 135                                 $this->timestamp = false;
 136                         } else {
 137                                 $this->timestamp = filemtime( $this->filename );
 138                         }
 139                 }
 140         }
 141
 142         function isExpired() {
 143                 if ( !file_exists( $this->filename ) ) {
 144                         if ( $this->timestamp === false ) {
 145                                 # Still nonexistent
 146                                 return false;
 147                         } else {
 148                                 # Deleted
 149                                 wfDebug( "Dependency triggered: {$this->filename} deleted.\n" );
 150                                 return true;
 151                         }
 152                 } else {
 153                         $lastmod = filemtime( $this->filename );
 154                         if ( $lastmod > $this->timestamp ) {
 155                                 # Modified or created
 156                                 wfDebug( "Dependency triggered: {$this->filename} changed.\n" );
 157                                 return true;
 158                         } else {
 159                                 # Not modified
 160                                 return false;
 161                         }
 162                 }
 163         }
 164 }
 165
 166 class TitleDependency extends CacheDependency {
 167         var $titleObj;
 168         var $ns, $dbk;
 169         var $touched;
 170
 171         /**
 172          * Construct a title dependency
 173          * @param Title $title
 174          */
 175         function __construct( Title $title ) {
 176                 $this->titleObj = $title;
 177                 $this->ns = $title->getNamespace();
 178                 $this->dbk = $title->getDBkey();
 179         }
 180
 181         function loadDependencyValues() {
 182                 $this->touched = $this->getTitle()->getTouched();
 183         }
 184
 185         /**
 186          * Get rid of bulky Title object for sleep
 187          */
 188         function __sleep() {
 189                 return array( 'ns', 'dbk', 'touched' );
 190         }
 191
 192         function getTitle() {
 193                 if ( !isset( $this->titleObj ) ) {
 194                         $this->titleObj = Title::makeTitle( $this->ns, $this->dbk );
 195                 }
 196                 return $this->titleObj;
 197         }
 198
 199         function isExpired() {
 200                 $touched = $this->getTitle()->getTouched();
 201                 if ( $this->touched === false ) {
 202                         if ( $touched === false ) {
 203                                 # Still missing
 204                                 return false;
 205                         } else {
 206                                 # Created
 207                                 return true;
 208                         }
 209                 } elseif ( $touched === false ) {
 210                         # Deleted
 211                         return true;
 212                 } elseif ( $touched > $this->touched ) {
 213                         # Updated
 214                         return true;
 215                 } else {
 216                         # Unmodified
 217                         return false;
 218                 }
 219         }
 220 }
 221
 222 class TitleListDependency extends CacheDependency {
 223         var $linkBatch;
 224         var $timestamps;
 225
 226         /**
 227          * Construct a dependency on a list of titles
 228          */
 229         function __construct( LinkBatch $linkBatch ) {
 230                 $this->linkBatch = $linkBatch;
 231         }
 232
 233         function calculateTimestamps() {
 234                 # Initialise values to false
 235                 $timestamps = array();
 236                 foreach ( $this->getLinkBatch()->data as $ns => $dbks ) {
 237                         if ( count( $dbks ) > 0 ) {
 238                                 $timestamps[$ns] = array();
 239                                 foreach ( $dbks as $dbk => $value ) {
 240                                         $timestamps[$ns][$dbk] = false;
 241                                 }
 242                         }
 243                 }
 244
 245                 # Do the query
 246                 if ( count( $timestamps ) ) {
 247                         $dbr = wfGetDB( DB_SLAVE );
 248                         $where = $this->getLinkBatch()->constructSet( 'page', $dbr );
 249                         $res = $dbr->select( 'page',
 250                                 array( 'page_namespace', 'page_title', 'page_touched' ),
 251                                 $where, __METHOD__ );
 252                         while ( $row = $dbr->fetchObject( $res ) ) {
 253                                 $timestamps[$row->page_namespace][$row->page_title] = $row->page_touched;
 254                         }
 255                 }
 256                 return $timestamps;
 257         }
 258
 259         function loadDependencyValues() {
 260                 $this->timestamps = $this->calculateTimestamps();
 261         }
 262
 263         function __sleep() {
 264                 return array( 'timestamps' );
 265         }
 266
 267         function getLinkBatch() {
 268                 if ( !isset( $this->linkBatch ) ){
 269                         $this->linkBatch = new LinkBatch;
 270                         $this->linkBatch->setArray( $this->timestamps );
 271                 }
 272                 return $this->linkBatch;
 273         }
 274
 275         function isExpired() {
 276                 $newTimestamps = $this->calculateTimestamps();
 277                 foreach ( $this->timestamps as $ns => $dbks ) {
 278                         foreach ( $dbks as $dbk => $oldTimestamp ) {
 279                                 $newTimestamp = $newTimestamps[$ns][$dbk];
 280                                 if ( $oldTimestamp === false ) {
 281                                         if ( $newTimestamp === false ) {
 282                                                 # Still missing
 283                                         } else {
 284                                                 # Created
 285                                                 return true;
 286                                         }
 287                                 } elseif ( $newTimestamp === false ) {
 288                                         # Deleted
 289                                         return true;
 290                                 } elseif ( $newTimestamp > $oldTimestamp ) {
 291                                         # Updated
 292                                         return true;
 293                                 } else {
 294                                         # Unmodified
 295                                 }
 296                         }
 297                 }
 298                 return false;
 299         }
 300 }
 301
 302 class GlobalDependency extends CacheDependency {
 303         var $name, $value;
 304
 305         function __construct( $name ) {
 306                 $this->name = $name;
 307                 $this->value = $GLOBALS[$name];
 308         }
 309
 310         function isExpired() {
 311                 return $GLOBALS[$this->name] != $this->value;
 312         }
 313 }
 314
 315 class ConstantDependency extends CacheDependency {
 316         var $name, $value;
 317
 318         function __construct( $name ) {
 319                 $this->name = $name;
 320                 $this->value = constant( $name );
 321         }
 322
 323         function isExpired() {
 324                 return constant( $this->name ) != $this->value;
 325         }
 326 }
 327
 328 ?>