MessageBlobStore.php

Go to the documentation of this file.

<?php
class MessageBlobStore {
    public static function getInstance() {
        static $instance = null;
        if ( $instance === null ) {
            $instance = new self;
        }

        return $instance;
    }

    public function get( ResourceLoader $resourceLoader, $modules, $lang ) {
        wfProfileIn( __METHOD__ );
        if ( !count( $modules ) ) {
            wfProfileOut( __METHOD__ );
            return array();
        }
        // Try getting from the DB first
        $blobs = $this->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 = $this->insertMessageBlob( $name, $modules[$name], $lang );
            if ( $blob ) {
                $blobs[$name] = $blob;
            }
        }

        wfProfileOut( __METHOD__ );
        return $blobs;
    }

    public function insertMessageBlob( $name, ResourceLoaderModule $module, $lang ) {
        $blob = $this->generateMessageBlob( $module, $lang );

        if ( !$blob ) {
            return false;
        }

        try {
            $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' )
                    );
                }
            }
        } catch ( Exception $e ) {
            wfDebug( __METHOD__ . " failed to update DB: $e\n" );
        }
        return $blob;
    }

    public 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 = $this->generateMessageBlob( $module, $lang );

        try {
            $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
                );
            }
        } catch ( Exception $e ) {
            wfDebug( __METHOD__ . " failed to update DB: $e\n" );
        }
        return $newBlob;
    }

    public function updateMessage( $key ) {
        try {
            $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 = $this->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.
        } catch ( Exception $e ) {
            wfDebug( __METHOD__ . " failed to update DB: $e\n" );
        }
    }

    public function clear() {
        // TODO: Give this some more thought
        try {
            // Not using TRUNCATE, because that needs extra permissions,
            // which maybe not granted to the database user.
            $dbw = wfGetDB( DB_MASTER );
            $dbw->delete( 'msg_resource', '*', __METHOD__ );
            $dbw->delete( 'msg_resource_links', '*', __METHOD__ );
        } catch ( Exception $e ) {
            wfDebug( __METHOD__ . " failed to update DB: $e\n" );
        }
    }

    private 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' => $this->reencodeBlob( $row->mr_blob, $key, $row->mr_lang )
            );
        }

        return $updates;
    }

    private function reencodeBlob( $blob, $key, $lang ) {
        $decoded = FormatJson::decode( $blob, true );
        $decoded[$key] = wfMessage( $key )->inLanguage( $lang )->plain();

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

    private function getFromDB( ResourceLoader $resourceLoader, $modules, $lang ) {
        $config = $resourceLoader->getConfig();
        $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 the CacheEpoch setting
            $keys = array_keys( FormatJson::decode( $row->mr_blob, true ) );
            $values = array_values( array_unique( $module->getMessages() ) );
            if ( $keys !== $values
                || wfTimestamp( TS_MW, $row->mr_timestamp ) <= $config->get( 'CacheEpoch' )
            ) {
                $retval[$row->mr_resource] = $this->updateModule( $row->mr_resource, $module, $lang );
            } else {
                $retval[$row->mr_resource] = $row->mr_blob;
            }
        }

        return $retval;
    }

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

        foreach ( $module->getMessages() as $key ) {
            $messages[$key] = wfMessage( $key )->inLanguage( $lang )->plain();
        }

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