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 mixed $value The user-supplied value
  16          * @param mixed $deps 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 object $cache A cache object such as $wgMemc
  70          * @param string $key The cache key
  71          * @param integer $expiry The expiry timestamp or interval in seconds
  72          * @param mixed $callback The callback for generating the value, or false
  73          * @param array $callbackParams The function parameters for the callback
  74          * @param array $deps 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 string $filename The name of the file, preferably fully qualified
 124          * @param mixed $timestamp 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 loadDependencyValues() {
 138                 if ( is_null( $this->timestamp ) ) {
 139                         if ( !file_exists( $this->filename ) ) {
 140                                 # Dependency on a non-existent file
 141                                 # This is a valid concept!
 142                                 $this->timestamp = false;
 143                         } else {
 144                                 $this->timestamp = filemtime( $this->filename );
 145                         }
 146                 }
 147         }
 148
 149         function isExpired() {
 150                 if ( !file_exists( $this->filename ) ) {
 151                         if ( $this->timestamp === false ) {
 152                                 # Still nonexistent
 153                                 return false;
 154                         } else {
 155                                 # Deleted
 156                                 wfDebug( "Dependency triggered: {$this->filename} deleted.\n" );
 157                                 return true;
 158                         }
 159                 } else {
 160                         $lastmod = filemtime( $this->filename );
 161                         if ( $lastmod > $this->timestamp ) {
 162                                 # Modified or created
 163                                 wfDebug( "Dependency triggered: {$this->filename} changed.\n" );
 164                                 return true;
 165                         } else {
 166                                 # Not modified
 167                                 return false;
 168                         }
 169                 }
 170         }
 171 }
 172
 173 /**
 174  * @ingroup Cache
 175  */
 176 class TitleDependency extends CacheDependency {
 177         var $titleObj;
 178         var $ns, $dbk;
 179         var $touched;
 180
 181         /**
 182          * Construct a title dependency
 183          * @param Title $title
 184          */
 185         function __construct( Title $title ) {
 186                 $this->titleObj = $title;
 187                 $this->ns = $title->getNamespace();
 188                 $this->dbk = $title->getDBkey();
 189         }
 190
 191         function loadDependencyValues() {
 192                 $this->touched = $this->getTitle()->getTouched();
 193         }
 194
 195         /**
 196          * Get rid of bulky Title object for sleep
 197          */
 198         function __sleep() {
 199                 return array( 'ns', 'dbk', 'touched' );
 200         }
 201
 202         function getTitle() {
 203                 if ( !isset( $this->titleObj ) ) {
 204                         $this->titleObj = Title::makeTitle( $this->ns, $this->dbk );
 205                 }
 206                 return $this->titleObj;
 207         }
 208
 209         function isExpired() {
 210                 $touched = $this->getTitle()->getTouched();
 211                 if ( $this->touched === false ) {
 212                         if ( $touched === false ) {
 213                                 # Still missing
 214                                 return false;
 215                         } else {
 216                                 # Created
 217                                 return true;
 218                         }
 219                 } elseif ( $touched === false ) {
 220                         # Deleted
 221                         return true;
 222                 } elseif ( $touched > $this->touched ) {
 223                         # Updated
 224                         return true;
 225                 } else {
 226                         # Unmodified
 227                         return false;
 228                 }
 229         }
 230 }
 231
 232 /**
 233  * @ingroup Cache
 234  */
 235 class TitleListDependency extends CacheDependency {
 236         var $linkBatch;
 237         var $timestamps;
 238
 239         /**
 240          * Construct a dependency on a list of titles
 241          */
 242         function __construct( LinkBatch $linkBatch ) {
 243                 $this->linkBatch = $linkBatch;
 244         }
 245
 246         function calculateTimestamps() {
 247                 # Initialise values to false
 248                 $timestamps = array();
 249                 foreach ( $this->getLinkBatch()->data as $ns => $dbks ) {
 250                         if ( count( $dbks ) > 0 ) {
 251                                 $timestamps[$ns] = array();
 252                                 foreach ( $dbks as $dbk => $value ) {
 253                                         $timestamps[$ns][$dbk] = false;
 254                                 }
 255                         }
 256                 }
 257
 258                 # Do the query
 259                 if ( count( $timestamps ) ) {
 260                         $dbr = wfGetDB( DB_SLAVE );
 261                         $where = $this->getLinkBatch()->constructSet( 'page', $dbr );
 262                         $res = $dbr->select( 'page',
 263                                 array( 'page_namespace', 'page_title', 'page_touched' ),
 264                                 $where, __METHOD__ );
 265                         while ( $row = $dbr->fetchObject( $res ) ) {
 266                                 $timestamps[$row->page_namespace][$row->page_title] = $row->page_touched;
 267                         }
 268                 }
 269                 return $timestamps;
 270         }
 271
 272         function loadDependencyValues() {
 273                 $this->timestamps = $this->calculateTimestamps();
 274         }
 275
 276         function __sleep() {
 277                 return array( 'timestamps' );
 278         }
 279
 280         function getLinkBatch() {
 281                 if ( !isset( $this->linkBatch ) ){
 282                         $this->linkBatch = new LinkBatch;
 283                         $this->linkBatch->setArray( $this->timestamps );
 284                 }
 285                 return $this->linkBatch;
 286         }
 287
 288         function isExpired() {
 289                 $newTimestamps = $this->calculateTimestamps();
 290                 foreach ( $this->timestamps as $ns => $dbks ) {
 291                         foreach ( $dbks as $dbk => $oldTimestamp ) {
 292                                 $newTimestamp = $newTimestamps[$ns][$dbk];
 293                                 if ( $oldTimestamp === false ) {
 294                                         if ( $newTimestamp === false ) {
 295                                                 # Still missing
 296                                         } else {
 297                                                 # Created
 298                                                 return true;
 299                                         }
 300                                 } elseif ( $newTimestamp === false ) {
 301                                         # Deleted
 302                                         return true;
 303                                 } elseif ( $newTimestamp > $oldTimestamp ) {
 304                                         # Updated
 305                                         return true;
 306                                 } else {
 307                                         # Unmodified
 308                                 }
 309                         }
 310                 }
 311                 return false;
 312         }
 313 }
 314
 315 /**
 316  * @ingroup Cache
 317  */
 318 class GlobalDependency extends CacheDependency {
 319         var $name, $value;
 320
 321         function __construct( $name ) {
 322                 $this->name = $name;
 323                 $this->value = $GLOBALS[$name];
 324         }
 325
 326         function isExpired() {
 327                 return $GLOBALS[$this->name] != $this->value;
 328         }
 329 }
 330
 331 /**
 332  * @ingroup Cache
 333  */
 334 class ConstantDependency extends CacheDependency {
 335         var $name, $value;
 336
 337         function __construct( $name ) {
 338                 $this->name = $name;
 339                 $this->value = constant( $name );
 340         }
 341
 342         function isExpired() {
 343                 return constant( $this->name ) != $this->value;
 344         }
 345 }