MessageBlobStore.php

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<?php
class MessageBlobStore {

        public static function get( ResourceLoader $resourceLoader, $modules, $lang ) {
                wfProfileIn( __METHOD__ );
                if ( !count( $modules ) ) {
                        wfProfileOut( __METHOD__ );
                        return array();
                }
                // Try getting from the DB first
                $blobs = self::getFromDB( $resourceLoader, array_keys( $modules ), $lang );

                // Generate blobs for any missing modules and store them in the DB
                $missing = array_diff( array_keys( $modules ), array_keys( $blobs ) );
                foreach ( $missing as $name ) {
                        $blob = self::insertMessageBlob( $name, $modules[$name], $lang );
                        if ( $blob ) {
                                $blobs[$name] = $blob;
                        }
                }

                wfProfileOut( __METHOD__ );
                return $blobs;
        }

        public static function insertMessageBlob( $name, ResourceLoaderModule $module, $lang ) {
                $blob = self::generateMessageBlob( $module, $lang );

                if ( !$blob ) {
                        return false;
                }

                $dbw = wfGetDB( DB_MASTER );
                $success = $dbw->insert( 'msg_resource', array(
                                'mr_lang' => $lang,
                                'mr_resource' => $name,
                                'mr_blob' => $blob,
                                'mr_timestamp' => $dbw->timestamp()
                        ),
                        __METHOD__,
                        array( 'IGNORE' )
                );

                if ( $success ) {
                        if ( $dbw->affectedRows() == 0 ) {
                                // Blob was already present, fetch it
                                $blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
                                                'mr_resource' => $name,
                                                'mr_lang' => $lang,
                                        ),
                                        __METHOD__
                                );
                        } else {
                                // Update msg_resource_links
                                $rows = array();

                                foreach ( $module->getMessages() as $key ) {
                                        $rows[] = array(
                                                'mrl_resource' => $name,
                                                'mrl_message' => $key
                                        );
                                }
                                $dbw->insert( 'msg_resource_links', $rows,
                                        __METHOD__, array( 'IGNORE' )
                                );
                        }
                }

                return $blob;
        }

        public static function updateModule( $name, ResourceLoaderModule $module, $lang ) {
                $dbw = wfGetDB( DB_MASTER );
                $row = $dbw->selectRow( 'msg_resource', 'mr_blob',
                        array( 'mr_resource' => $name, 'mr_lang' => $lang ),
                        __METHOD__
                );
                if ( !$row ) {
                        return null;
                }

                // Save the old and new blobs for later
                $oldBlob = $row->mr_blob;
                $newBlob = self::generateMessageBlob( $module, $lang );
                
                $newRow = array(
                        'mr_resource' => $name,
                        'mr_lang' => $lang,
                        'mr_blob' => $newBlob,
                        'mr_timestamp' => $dbw->timestamp()
                );

                $dbw->replace( 'msg_resource',
                        array( array( 'mr_resource', 'mr_lang' ) ),
                        $newRow, __METHOD__
                );

                // Figure out which messages were added and removed
                $oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
                $newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
                $added = array_diff( $newMessages, $oldMessages );
                $removed = array_diff( $oldMessages, $newMessages );

                // Delete removed messages, insert added ones
                if ( $removed ) {
                        $dbw->delete( 'msg_resource_links', array(
                                        'mrl_resource' => $name,
                                        'mrl_message' => $removed
                                ), __METHOD__
                        );
                }

                $newLinksRows = array();

                foreach ( $added as $message ) {
                        $newLinksRows[] = array(
                                'mrl_resource' => $name,
                                'mrl_message' => $message
                        );
                }

                if ( $newLinksRows ) {
                        $dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
                                 array( 'IGNORE' ) // just in case
                        );
                }

                return $newBlob;
        }

        public static function updateMessage( $key ) {
                $dbw = wfGetDB( DB_MASTER );

                // Keep running until the updates queue is empty.
                // Due to update conflicts, the queue might not be emptied
                // in one iteration.
                $updates = null;
                do {
                        $updates = self::getUpdatesForMessage( $key, $updates );

                        foreach ( $updates as $k => $update ) {
                                // Update the row on the condition that it
                                // didn't change since we fetched it by putting
                                // the timestamp in the WHERE clause.
                                $success = $dbw->update( 'msg_resource',
                                        array(
                                                'mr_blob' => $update['newBlob'],
                                                'mr_timestamp' => $dbw->timestamp() ),
                                        array(
                                                'mr_resource' => $update['resource'],
                                                'mr_lang' => $update['lang'],
                                                'mr_timestamp' => $update['timestamp'] ),
                                        __METHOD__
                                );

                                // Only requeue conflicted updates.
                                // If update() returned false, don't retry, for
                                // fear of getting into an infinite loop
                                if ( !( $success && $dbw->affectedRows() == 0 ) ) {
                                        // Not conflicted
                                        unset( $updates[$k] );
                                }
                        }
                } while ( count( $updates ) );

                // No need to update msg_resource_links because we didn't add
                // or remove any messages, we just changed their contents.
        }

        public static function clear() {
                // TODO: Give this some more thought
                // TODO: Is TRUNCATE better?
                $dbw = wfGetDB( DB_MASTER );
                $dbw->delete( 'msg_resource', '*', __METHOD__ );
                $dbw->delete( 'msg_resource_links', '*', __METHOD__ );
        }

        private static function getUpdatesForMessage( $key, $prevUpdates = null ) {
                $dbw = wfGetDB( DB_MASTER );

                if ( is_null( $prevUpdates ) ) {
                        // Fetch all blobs referencing $key
                        $res = $dbw->select(
                                array( 'msg_resource', 'msg_resource_links' ),
                                array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
                                array( 'mrl_message' => $key, 'mr_resource=mrl_resource' ),
                                __METHOD__
                        );
                } else {
                        // Refetch the blobs referenced by $prevUpdates

                        // Reorganize the (resource, lang) pairs in the format
                        // expected by makeWhereFrom2d()
                        $twoD = array();

                        foreach ( $prevUpdates as $update ) {
                                $twoD[$update['resource']][$update['lang']] = true;
                        }

                        $res = $dbw->select( 'msg_resource',
                                array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
                                $dbw->makeWhereFrom2d( $twoD, 'mr_resource', 'mr_lang' ),
                                __METHOD__
                        );
                }

                // Build the new updates queue
                $updates = array();

                foreach ( $res as $row ) {
                        $updates[] = array(
                                'resource' => $row->mr_resource,
                                'lang' => $row->mr_lang,
                                'timestamp' => $row->mr_timestamp,
                                'newBlob' => self::reencodeBlob( $row->mr_blob, $key, $row->mr_lang )
                        );
                }

                return $updates;
        }

        private static function reencodeBlob( $blob, $key, $lang ) {
                $decoded = FormatJson::decode( $blob, true );
                $decoded[$key] = wfMsgExt( $key, array( 'language' => $lang ) );

                return FormatJson::encode( (object)$decoded );
        }

        private static function getFromDB( ResourceLoader $resourceLoader, $modules, $lang ) {
                global $wgCacheEpoch;
                $retval = array();
                $dbr = wfGetDB( DB_SLAVE );
                $res = $dbr->select( 'msg_resource',
                        array( 'mr_blob', 'mr_resource', 'mr_timestamp' ),
                        array( 'mr_resource' => $modules, 'mr_lang' => $lang ),
                        __METHOD__
                );

                foreach ( $res as $row ) {
                        $module = $resourceLoader->getModule( $row->mr_resource );
                        if ( !$module ) {
                                // This shouldn't be possible
                                throw new MWException( __METHOD__ . ' passed an invalid module name' );
                        }
                        // Update the module's blobs if the set of messages changed or if the blob is
                        // older than $wgCacheEpoch
                        if ( array_keys( FormatJson::decode( $row->mr_blob, true ) ) !== array_values( array_unique( $module->getMessages() ) ) ||
                                        wfTimestamp( TS_MW, $row->mr_timestamp ) <= $wgCacheEpoch ) {
                                $retval[$row->mr_resource] = self::updateModule( $row->mr_resource, $module, $lang );
                        } else {
                                $retval[$row->mr_resource] = $row->mr_blob;
                        }
                }

                return $retval;
        }

        private static function generateMessageBlob( ResourceLoaderModule $module, $lang ) {
                $messages = array();

                foreach ( $module->getMessages() as $key ) {
                        $messages[$key] = wfMsgExt( $key, array( 'language' => $lang ) );
                }

                return FormatJson::encode( (object)$messages );
        }
}