includes/MessageBlobStore.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @author Roan Kattouw
  19  * @author Trevor Parscal
  20  */
  21
  22 /**
  23  * This class provides access to the resource message blobs storage used by
  24  * the ResourceLoader.
  25  *
  26  * A message blob is a JSON object containing the interface messages for a
  27  * certain resource in a certain language. These message blobs are cached
  28  * in the msg_resource table and automatically invalidated when one of their
  29  * consistuent messages or the resource itself is changed.
  30  */
  31 class MessageBlobStore {
  32
  33         /**
  34          * Get the message blobs for a set of modules
  35          *
  36          * @param $resourceLoader ResourceLoader object
  37          * @param $modules array Array of module objects keyed by module name
  38          * @param $lang string Language code
  39          * @return array An array mapping module names to message blobs
  40          */
  41         public static function get( ResourceLoader $resourceLoader, $modules, $lang ) {
  42                 wfProfileIn( __METHOD__ );
  43                 if ( !count( $modules ) ) {
  44                         wfProfileOut( __METHOD__ );
  45                         return array();
  46                 }
  47                 // Try getting from the DB first
  48                 $blobs = self::getFromDB( $resourceLoader, array_keys( $modules ), $lang );
  49
  50                 // Generate blobs for any missing modules and store them in the DB
  51                 $missing = array_diff( array_keys( $modules ), array_keys( $blobs ) );
  52                 foreach ( $missing as $name ) {
  53                         $blob = self::insertMessageBlob( $name, $modules[$name], $lang );
  54                         if ( $blob ) {
  55                                 $blobs[$name] = $blob;
  56                         }
  57                 }
  58
  59                 wfProfileOut( __METHOD__ );
  60                 return $blobs;
  61         }
  62
  63         /**
  64          * Generate and insert a new message blob. If the blob was already
  65          * present, it is not regenerated; instead, the preexisting blob
  66          * is fetched and returned.
  67          *
  68          * @param $name String: module name
  69          * @param $module ResourceLoaderModule object
  70          * @param $lang String: language code
  71          * @return mixed Message blob or false if the module has no messages
  72          */
  73         public static function insertMessageBlob( $name, ResourceLoaderModule $module, $lang ) {
  74                 $blob = self::generateMessageBlob( $module, $lang );
  75
  76                 if ( !$blob ) {
  77                         return false;
  78                 }
  79
  80                 $dbw = wfGetDB( DB_MASTER );
  81                 $success = $dbw->insert( 'msg_resource', array(
  82                                 'mr_lang' => $lang,
  83                                 'mr_resource' => $name,
  84                                 'mr_blob' => $blob,
  85                                 'mr_timestamp' => $dbw->timestamp()
  86                         ),
  87                         __METHOD__,
  88                         array( 'IGNORE' )
  89                 );
  90
  91                 if ( $success ) {
  92                         if ( $dbw->affectedRows() == 0 ) {
  93                                 // Blob was already present, fetch it
  94                                 $blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
  95                                                 'mr_resource' => $name,
  96                                                 'mr_lang' => $lang,
  97                                         ),
  98                                         __METHOD__
  99                                 );
 100                         } else {
 101                                 // Update msg_resource_links
 102                                 $rows = array();
 103
 104                                 foreach ( $module->getMessages() as $key ) {
 105                                         $rows[] = array(
 106                                                 'mrl_resource' => $name,
 107                                                 'mrl_message' => $key
 108                                         );
 109                                 }
 110                                 $dbw->insert( 'msg_resource_links', $rows,
 111                                         __METHOD__, array( 'IGNORE' )
 112                                 );
 113                         }
 114                 }
 115
 116                 return $blob;
 117         }
 118
 119         /**
 120          * Update the message blob for a given module in a given language
 121          *
 122          * @param $name String: module name
 123          * @param $module ResourceLoaderModule object
 124          * @param $lang String: language code
 125          * @return String Regenerated message blob, or null if there was no blob for the given module/language pair
 126          */
 127         public static function updateModule( $name, ResourceLoaderModule $module, $lang ) {
 128                 $dbw = wfGetDB( DB_MASTER );
 129                 $row = $dbw->selectRow( 'msg_resource', 'mr_blob',
 130                         array( 'mr_resource' => $name, 'mr_lang' => $lang ),
 131                         __METHOD__
 132                 );
 133                 if ( !$row ) {
 134                         return null;
 135                 }
 136
 137                 // Save the old and new blobs for later
 138                 $oldBlob = $row->mr_blob;
 139                 $newBlob = self::generateMessageBlob( $module, $lang );
 140
 141                 $newRow = array(
 142                         'mr_resource' => $name,
 143                         'mr_lang' => $lang,
 144                         'mr_blob' => $newBlob,
 145                         'mr_timestamp' => $dbw->timestamp()
 146                 );
 147
 148                 $dbw->replace( 'msg_resource',
 149                         array( array( 'mr_resource', 'mr_lang' ) ),
 150                         $newRow, __METHOD__
 151                 );
 152
 153                 // Figure out which messages were added and removed
 154                 $oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
 155                 $newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
 156                 $added = array_diff( $newMessages, $oldMessages );
 157                 $removed = array_diff( $oldMessages, $newMessages );
 158
 159                 // Delete removed messages, insert added ones
 160                 if ( $removed ) {
 161                         $dbw->delete( 'msg_resource_links', array(
 162                                         'mrl_resource' => $name,
 163                                         'mrl_message' => $removed
 164                                 ), __METHOD__
 165                         );
 166                 }
 167
 168                 $newLinksRows = array();
 169
 170                 foreach ( $added as $message ) {
 171                         $newLinksRows[] = array(
 172                                 'mrl_resource' => $name,
 173                                 'mrl_message' => $message
 174                         );
 175                 }
 176
 177                 if ( $newLinksRows ) {
 178                         $dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
 179                                  array( 'IGNORE' ) // just in case
 180                         );
 181                 }
 182
 183                 return $newBlob;
 184         }
 185
 186         /**
 187          * Update a single message in all message blobs it occurs in.
 188          *
 189          * @param $key String: message key
 190          */
 191         public static function updateMessage( $key ) {
 192                 $dbw = wfGetDB( DB_MASTER );
 193
 194                 // Keep running until the updates queue is empty.
 195                 // Due to update conflicts, the queue might not be emptied
 196                 // in one iteration.
 197                 $updates = null;
 198                 do {
 199                         $updates = self::getUpdatesForMessage( $key, $updates );
 200
 201                         foreach ( $updates as $k => $update ) {
 202                                 // Update the row on the condition that it
 203                                 // didn't change since we fetched it by putting
 204                                 // the timestamp in the WHERE clause.
 205                                 $success = $dbw->update( 'msg_resource',
 206                                         array(
 207                                                 'mr_blob' => $update['newBlob'],
 208                                                 'mr_timestamp' => $dbw->timestamp() ),
 209                                         array(
 210                                                 'mr_resource' => $update['resource'],
 211                                                 'mr_lang' => $update['lang'],
 212                                                 'mr_timestamp' => $update['timestamp'] ),
 213                                         __METHOD__
 214                                 );
 215
 216                                 // Only requeue conflicted updates.
 217                                 // If update() returned false, don't retry, for
 218                                 // fear of getting into an infinite loop
 219                                 if ( !( $success && $dbw->affectedRows() == 0 ) ) {
 220                                         // Not conflicted
 221                                         unset( $updates[$k] );
 222                                 }
 223                         }
 224                 } while ( count( $updates ) );
 225
 226                 // No need to update msg_resource_links because we didn't add
 227                 // or remove any messages, we just changed their contents.
 228         }
 229
 230         public static function clear() {
 231                 // TODO: Give this some more thought
 232                 // TODO: Is TRUNCATE better?
 233                 $dbw = wfGetDB( DB_MASTER );
 234                 $dbw->delete( 'msg_resource', '*', __METHOD__ );
 235                 $dbw->delete( 'msg_resource_links', '*', __METHOD__ );
 236         }
 237
 238         /**
 239          * Create an update queue for updateMessage()
 240          *
 241          * @param $key String: message key
 242          * @param $prevUpdates Array: updates queue to refresh or null to build a fresh update queue
 243          * @return Array: updates queue
 244          */
 245         private static function getUpdatesForMessage( $key, $prevUpdates = null ) {
 246                 $dbw = wfGetDB( DB_MASTER );
 247
 248                 if ( is_null( $prevUpdates ) ) {
 249                         // Fetch all blobs referencing $key
 250                         $res = $dbw->select(
 251                                 array( 'msg_resource', 'msg_resource_links' ),
 252                                 array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
 253                                 array( 'mrl_message' => $key, 'mr_resource=mrl_resource' ),
 254                                 __METHOD__
 255                         );
 256                 } else {
 257                         // Refetch the blobs referenced by $prevUpdates
 258
 259                         // Reorganize the (resource, lang) pairs in the format
 260                         // expected by makeWhereFrom2d()
 261                         $twoD = array();
 262
 263                         foreach ( $prevUpdates as $update ) {
 264                                 $twoD[$update['resource']][$update['lang']] = true;
 265                         }
 266
 267                         $res = $dbw->select( 'msg_resource',
 268                                 array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
 269                                 $dbw->makeWhereFrom2d( $twoD, 'mr_resource', 'mr_lang' ),
 270                                 __METHOD__
 271                         );
 272                 }
 273
 274                 // Build the new updates queue
 275                 $updates = array();
 276
 277                 foreach ( $res as $row ) {
 278                         $updates[] = array(
 279                                 'resource' => $row->mr_resource,
 280                                 'lang' => $row->mr_lang,
 281                                 'timestamp' => $row->mr_timestamp,
 282                                 'newBlob' => self::reencodeBlob( $row->mr_blob, $key, $row->mr_lang )
 283                         );
 284                 }
 285
 286                 return $updates;
 287         }
 288
 289         /**
 290          * Reencode a message blob with the updated value for a message
 291          *
 292          * @param $blob String: message blob (JSON object)
 293          * @param $key String: message key
 294          * @param $lang String: language code
 295          * @return Message blob with $key replaced with its new value
 296          */
 297         private static function reencodeBlob( $blob, $key, $lang ) {
 298                 $decoded = FormatJson::decode( $blob, true );
 299                 $decoded[$key] = wfMsgExt( $key, array( 'language' => $lang ) );
 300
 301                 return FormatJson::encode( (object)$decoded );
 302         }
 303
 304         /**
 305          * Get the message blobs for a set of modules from the database.
 306          * Modules whose blobs are not in the database are silently dropped.
 307          *
 308          * @param $resourceLoader ResourceLoader object
 309          * @param $modules Array of module names
 310          * @param $lang String: language code
 311          * @return array Array mapping module names to blobs
 312          */
 313         private static function getFromDB( ResourceLoader $resourceLoader, $modules, $lang ) {
 314                 global $wgCacheEpoch;
 315                 $retval = array();
 316                 $dbr = wfGetDB( DB_SLAVE );
 317                 $res = $dbr->select( 'msg_resource',
 318                         array( 'mr_blob', 'mr_resource', 'mr_timestamp' ),
 319                         array( 'mr_resource' => $modules, 'mr_lang' => $lang ),
 320                         __METHOD__
 321                 );
 322
 323                 foreach ( $res as $row ) {
 324                         $module = $resourceLoader->getModule( $row->mr_resource );
 325                         if ( !$module ) {
 326                                 // This shouldn't be possible
 327                                 throw new MWException( __METHOD__ . ' passed an invalid module name' );
 328                         }
 329                         // Update the module's blobs if the set of messages changed or if the blob is
 330                         // older than $wgCacheEpoch
 331                         if ( array_keys( FormatJson::decode( $row->mr_blob, true ) ) !== array_values( array_unique( $module->getMessages() ) ) ||
 332                                         wfTimestamp( TS_MW, $row->mr_timestamp ) <= $wgCacheEpoch ) {
 333                                 $retval[$row->mr_resource] = self::updateModule( $row->mr_resource, $module, $lang );
 334                         } else {
 335                                 $retval[$row->mr_resource] = $row->mr_blob;
 336                         }
 337                 }
 338
 339                 return $retval;
 340         }
 341
 342         /**
 343          * Generate the message blob for a given module in a given language.
 344          *
 345          * @param $module ResourceLoaderModule object
 346          * @param $lang String: language code
 347          * @return String: JSON object
 348          */
 349         private static function generateMessageBlob( ResourceLoaderModule $module, $lang ) {
 350                 $messages = array();
 351
 352                 foreach ( $module->getMessages() as $key ) {
 353                         $messages[$key] = wfMsgExt( $key, array( 'language' => $lang ) );
 354                 }
 355
 356                 return FormatJson::encode( (object)$messages );
 357         }
 358 }