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