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