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          * Get the message blobs for a set of modules
  34          * @param $modules array Array of module objects keyed by module name
  35          * @param $lang string Language code
  36          * @return array An array mapping module names to message blobs
  37          */
  38         public static function get( ResourceLoader $resourceLoader, $modules, $lang ) {
  39                 wfProfileIn( __METHOD__ );
  40                 if ( !count( $modules ) ) {
  41                         wfProfileOut( __METHOD__ );
  42                         return array();
  43                 }
  44                 // Try getting from the DB first
  45                 $blobs = self::getFromDB( $resourceLoader, array_keys( $modules ), $lang );
  46
  47                 // Generate blobs for any missing modules and store them in the DB
  48                 $missing = array_diff( array_keys( $modules ), array_keys( $blobs ) );
  49                 foreach ( $missing as $name ) {
  50                         $blob = self::insertMessageBlob( $name, $modules[$name], $lang );
  51                         if ( $blob ) {
  52                                 $blobs[$name] = $blob;
  53                         }
  54                 }
  55
  56                 wfProfileOut( __METHOD__ );
  57                 return $blobs;
  58         }
  59
  60         /**
  61          * Generate and insert a new message blob. If the blob was already
  62          * present, it is not regenerated; instead, the preexisting blob
  63          * is fetched and returned.
  64          * @param $module string Module name
  65          * @param $lang string Language code
  66          * @return mixed Message blob or false if the module has no messages
  67          */
  68         public static function insertMessageBlob( $name, ResourceLoaderModule $module, $lang ) {
  69                 $blob = self::generateMessageBlob( $module, $lang );
  70
  71                 if ( !$blob ) {
  72                         return false;
  73                 }
  74
  75                 $dbw = wfGetDB( DB_MASTER );
  76                 $success = $dbw->insert( 'msg_resource', array(
  77                                 'mr_lang' => $lang,
  78                                 'mr_resource' => $name,
  79                                 'mr_blob' => $blob,
  80                                 'mr_timestamp' => $dbw->timestamp()
  81                         ),
  82                         __METHOD__,
  83                         array( 'IGNORE' )
  84                 );
  85
  86                 if ( $success ) {
  87                         if ( $dbw->affectedRows() == 0 ) {
  88                                 // Blob was already present, fetch it
  89                                 $blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
  90                                                 'mr_resource' => $name,
  91                                                 'mr_lang' => $lang,
  92                                         ),
  93                                         __METHOD__
  94                                 );
  95                         } else {
  96                                 // Update msg_resource_links
  97                                 $rows = array();
  98
  99                                 foreach ( $module->getMessages() as $key ) {
 100                                         $rows[] = array(
 101                                                 'mrl_resource' => $name,
 102                                                 'mrl_message' => $key
 103                                         );
 104                                 }
 105                                 $dbw->insert( 'msg_resource_links', $rows,
 106                                         __METHOD__, array( 'IGNORE' )
 107                                 );
 108                         }
 109                 }
 110
 111                 return $blob;
 112         }
 113
 114         /**
 115          * Update all message blobs for a given module.
 116          * @param $module string Module name
 117          * @param $lang string Language code (optional)
 118          * @return mixed If $lang is set, the new message blob for that language is
 119          *    returned if present. Otherwise, null is returned.
 120          */
 121         public static function updateModule( $name, ResourceLoaderModule $module, $lang = null ) {
 122                 $retval = null;
 123
 124                 // Find all existing blobs for this module
 125                 $dbw = wfGetDB( DB_MASTER );
 126                 $res = $dbw->select( 'msg_resource',
 127                         array( 'mr_lang', 'mr_blob' ),
 128                         array( 'mr_resource' => $name ),
 129                         __METHOD__
 130                 );
 131
 132                 // Build the new msg_resource rows
 133                 $newRows = array();
 134                 $now = $dbw->timestamp();
 135                 // Save the last-processed old and new blobs for later
 136                 $oldBlob = $newBlob = null;
 137
 138                 foreach ( $res as $row ) {
 139                         $oldBlob = $row->mr_blob;
 140                         $newBlob = self::generateMessageBlob( $module, $row->mr_lang );
 141
 142                         if ( $row->mr_lang === $lang ) {
 143                                 $retval = $newBlob;
 144                         }
 145                         $newRows[] = array(
 146                                 'mr_resource' => $name,
 147                                 'mr_lang' => $row->mr_lang,
 148                                 'mr_blob' => $newBlob,
 149                                 'mr_timestamp' => $now
 150                         );
 151                 }
 152
 153                 $dbw->replace( 'msg_resource',
 154                         array( array( 'mr_resource', 'mr_lang' ) ),
 155                         $newRows, __METHOD__
 156                 );
 157
 158                 // Figure out which messages were added and removed
 159                 $oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
 160                 $newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
 161                 $added = array_diff( $newMessages, $oldMessages );
 162                 $removed = array_diff( $oldMessages, $newMessages );
 163
 164                 // Delete removed messages, insert added ones
 165                 if ( $removed ) {
 166                         $dbw->delete( 'msg_resource_links', array(
 167                                         'mrl_resource' => $name,
 168                                         'mrl_message' => $removed
 169                                 ), __METHOD__
 170                         );
 171                 }
 172
 173                 $newLinksRows = array();
 174
 175                 foreach ( $added as $message ) {
 176                         $newLinksRows[] = array(
 177                                 'mrl_resource' => $name,
 178                                 'mrl_message' => $message
 179                         );
 180                 }
 181
 182                 if ( $newLinksRows ) {
 183                         $dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
 184                                  array( 'IGNORE' ) // just in case
 185                         );
 186                 }
 187
 188                 return $retval;
 189         }
 190
 191         /**
 192          * Update a single message in all message blobs it occurs in.
 193          * @param $key string Message key
 194          */
 195         public static function updateMessage( $key ) {
 196                 $dbw = wfGetDB( DB_MASTER );
 197
 198                 // Keep running until the updates queue is empty.
 199                 // Due to update conflicts, the queue might not be emptied
 200                 // in one iteration.
 201                 $updates = null;
 202                 do {
 203                         $updates = self::getUpdatesForMessage( $key, $updates );
 204
 205                         foreach ( $updates as $key => $update ) {
 206                                 // Update the row on the condition that it
 207                                 // didn't change since we fetched it by putting
 208                                 // the timestamp in the WHERE clause.
 209                                 $success = $dbw->update( 'msg_resource',
 210                                         array(
 211                                                 'mr_blob' => $update['newBlob'],
 212                                                 'mr_timestamp' => $dbw->timestamp() ),
 213                                         array(
 214                                                 'mr_resource' => $update['resource'],
 215                                                 'mr_lang' => $update['lang'],
 216                                                 'mr_timestamp' => $update['timestamp'] ),
 217                                         __METHOD__
 218                                 );
 219
 220                                 // Only requeue conflicted updates.
 221                                 // If update() returned false, don't retry, for
 222                                 // fear of getting into an infinite loop
 223                                 if ( !( $success && $dbw->affectedRows() == 0 ) ) {
 224                                         // Not conflicted
 225                                         unset( $updates[$key] );
 226                                 }
 227                         }
 228                 } while ( count( $updates ) );
 229
 230                 // No need to update msg_resource_links because we didn't add
 231                 // or remove any messages, we just changed their contents.
 232         }
 233
 234         public static function clear() {
 235                 // TODO: Give this some more thought
 236                 // TODO: Is TRUNCATE better?
 237                 $dbw = wfGetDB( DB_MASTER );
 238                 $dbw->delete( 'msg_resource', '*', __METHOD__ );
 239                 $dbw->delete( 'msg_resource_links', '*', __METHOD__ );
 240         }
 241
 242         /**
 243          * Create an update queue for updateMessage()
 244          * @param $key string Message key
 245          * @param $prevUpdates array Updates queue to refresh or null to build a fresh update queue
 246          * @return array Updates queue
 247          */
 248         private static function getUpdatesForMessage( $key, $prevUpdates = null ) {
 249                 $dbw = wfGetDB( DB_MASTER );
 250
 251                 if ( is_null( $prevUpdates ) ) {
 252                         // Fetch all blobs referencing $key
 253                         $res = $dbw->select(
 254                                 array( 'msg_resource', 'msg_resource_links' ),
 255                                 array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
 256                                 array( 'mrl_message' => $key, 'mr_resource=mrl_resource' ),
 257                                 __METHOD__
 258                         );
 259                 } else {
 260                         // Refetch the blobs referenced by $prevUpdates
 261
 262                         // Reorganize the (resource, lang) pairs in the format
 263                         // expected by makeWhereFrom2d()
 264                         $twoD = array();
 265
 266                         foreach ( $prevUpdates as $update ) {
 267                                 $twoD[$update['resource']][$update['lang']] = true;
 268                         }
 269
 270                         $res = $dbw->select( 'msg_resource',
 271                                 array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
 272                                 $dbw->makeWhereFrom2d( $twoD, 'mr_resource', 'mr_lang' ),
 273                                 __METHOD__
 274                         );
 275                 }
 276
 277                 // Build the new updates queue
 278                 $updates = array();
 279
 280                 foreach ( $res as $row ) {
 281                         $updates[] = array(
 282                                 'resource' => $row->mr_resource,
 283                                 'lang' => $row->mr_lang,
 284                                 'timestamp' => $row->mr_timestamp,
 285                                 'newBlob' => self::reencodeBlob( $row->mr_blob, $key, $row->mr_lang )
 286                         );
 287                 }
 288
 289                 return $updates;
 290         }
 291
 292         /**
 293          * Reencode a message blob with the updated value for a message
 294          * @param $blob string Message blob (JSON object)
 295          * @param $key string Message key
 296          * @param $lang string Language code
 297          * @return Message blob with $key replaced with its new value
 298          */
 299         private static function reencodeBlob( $blob, $key, $lang ) {
 300                 $decoded = FormatJson::decode( $blob, true );
 301                 $decoded[$key] = wfMsgExt( $key, array( 'language' => $lang ) );
 302
 303                 return FormatJson::encode( $decoded );
 304         }
 305
 306         /**
 307          * Get the message blobs for a set of modules from the database.
 308          * Modules whose blobs are not in the database are silently dropped.
 309          * @param $modules array 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 ) ) !== $module->getMessages() ||
 332                                         wfTimestamp( TS_MW, $row->mr_timestamp ) <= $wgCacheEpoch ) {
 333                                 $retval[$row->mr_resource] = self::updateModule( $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          * @param $module string Module name
 345          * @param $lang string Language code
 346          * @return string JSON object
 347          */
 348         private static function generateMessageBlob( ResourceLoaderModule $module, $lang ) {
 349                 $messages = array();
 350
 351                 foreach ( $module->getMessages() as $key ) {
 352                         $messages[$key] = wfMsgExt( $key, array( 'language' => $lang ) );
 353                 }
 354
 355                 return FormatJson::encode( $messages );
 356         }
 357 }