src/TtmServer/ElasticSearchTtmServer.php
<?php
declare( strict_types = 1 );
namespace MediaWiki\Extension\Translate\TtmServer;
use Elastica\Aggregation\Terms;
use Elastica\Client;
use Elastica\Document;
use Elastica\Exception\ExceptionInterface;
use Elastica\Index;
use Elastica\Mapping;
use Elastica\Query;
use Elastica\Query\BoolQuery;
use Elastica\Query\FunctionScore;
use Elastica\Query\MatchQuery;
use Elastica\Query\Term;
use Elastica\ResultSet;
use Elastica\Search;
use Exception;
use MediaWiki\Extension\Elastica\MWElasticUtils;
use MediaWiki\Extension\Translate\MessageLoading\MessageHandle;
use MediaWiki\Extension\Translate\TranslatorInterface\TranslationHelperException;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MediaWikiServices;
use MediaWiki\Title\Title;
use MediaWiki\WikiMap\WikiMap;
use RuntimeException;
use TTMServerBootstrap;
/**
* TtmServer backend based on ElasticSearch. Depends on Elastica.
* @author Niklas Laxström
* @license GPL-2.0-or-later
* @since 2014.04
* @ingroup TTMServer
*/
class ElasticSearchTtmServer
extends TtmServer
implements ReadableTtmServer, WritableTtmServer, SearchableTtmServer
{
/**
* @const int in case a write operation fails during a batch process
* this constant controls the number of times we will retry the same
* operation.
*/
private const BULK_INDEX_RETRY_ATTEMPTS = 5;
/**
* @const int time (seconds) to wait for the index to ready before
* starting to index. Since we wait for index status it can be relatively
* long especially if some nodes are restarted.
*/
private const WAIT_UNTIL_READY_TIMEOUT = 3600;
private ?Client $client = null;
/** Reference to the maintenance script to relay logging output. */
private ?TTMServerBootstrap $logger = null;
/** Used for reindex */
private bool $updateMapping = false;
public function isLocalSuggestion( array $suggestion ): bool {
return $suggestion['wiki'] === WikiMap::getCurrentWikiId();
}
public function expandLocation( array $suggestion ): string {
return $suggestion['uri'];
}
public function query( string $sourceLanguage, string $targetLanguage, string $text ): array {
try {
return $this->doQuery( $sourceLanguage, $targetLanguage, $text );
} catch ( Exception $e ) {
throw new TranslationHelperException( 'Elastica exception: ' . $e );
}
}
private function doQuery( string $sourceLanguage, string $targetLanguage, string $text ): array {
if ( !$this->useWikimediaExtraPlugin() ) {
// ElasticTTM is currently not compatible with elasticsearch 2.x/5.x
// It needs FuzzyLikeThis ported via the wmf extra plugin
throw new RuntimeException( 'The wikimedia extra plugin is mandatory.' );
}
/* Two query system:
* 1) Find all strings in source language that match text
* 2) Do another query for translations for those strings
*/
$connection = $this->getClient()->getConnection();
$oldTimeout = $connection->getTimeout();
$connection->setTimeout( 10 );
$fuzzyQuery = new FuzzyLikeThis();
$fuzzyQuery->setLikeText( $text );
$fuzzyQuery->addFieldNames( [ 'content' ] );
$boostQuery = new FunctionScore();
$boostQuery->addFunction(
'levenshtein_distance_score',
[
'text' => $text,
'field' => 'content'
]
);
$boostQuery->setBoostMode( FunctionScore::BOOST_MODE_REPLACE );
// Wrap the fuzzy query, so it can be used as a filter.
// This is slightly faster, as ES can throw away the scores by this query.
$bool = new BoolQuery();
$bool->addFilter( $fuzzyQuery );
$bool->addMust( $boostQuery );
$languageFilter = new Term();
$languageFilter->setTerm( 'language', $sourceLanguage );
$bool->addFilter( $languageFilter );
// The whole query
$query = new Query();
$query->setQuery( $bool );
// The interface usually displays three best candidates. These might
// come from more than three source things, if the translations are
// the same. In other words suggestions are grouped by the suggested
// translation. This algorithm might not find all suggestions, if the
// top N best matching source texts don't have equivalent translations
// in the target language, but worse matches which we did not fetch do.
// This code tries to balance between doing too many or too big queries
// and not fetching enough results to show all possible suggestions.
$sizeFirst = 100;
$sizeSecond = $sizeFirst * 5;
$query->setFrom( 0 );
$query->setSize( $sizeFirst );
$query->setParam( '_source', [ 'content' ] );
$cutoff = $this->config['cutoff'] ?? 0.65;
$query->setParam( 'min_score', $cutoff );
$query->setSort( [ '_score', 'wiki', 'localid' ] );
/* This query is doing two unrelated things:
* 1) Collect the message contents and scores so that they can
* be accessed later for the translations we found.
* 2) Build the query string for the query that fetches the translations.
*/
$contents = $scores = $terms = [];
do {
$resultset = $this->getIndex()->search( $query );
if ( count( $resultset ) === 0 ) {
break;
}
foreach ( $resultset->getResults() as $result ) {
$data = $result->getData();
$score = $result->getScore();
$sourceId = preg_replace( '~/[^/]+$~', '', $result->getId() );
$contents[$sourceId] = $data['content'];
$scores[$sourceId] = $score;
$terms[] = "$sourceId/$targetLanguage";
}
// Check if it looks like that we are hitting the long tail already.
// Otherwise, we'll do a query to fetch some more to reach a "sane"
// breaking point, i.e. include all suggestions with same content
// for reliable used X times statistics.
if ( count( array_unique( $scores ) ) > 5 ) {
break;
}
// Okay, We are now in second iteration of the loop. We already got
// lots of suggestions. We will give up for now even if it means we
// return in some sense incomplete results.
if ( count( $resultset ) === $sizeSecond ) {
break;
}
// After the first query, the smallest score is the new threshold.
// @phan-suppress-next-line PhanPossiblyUndeclaredVariable
$query->setParam( 'min_score', $score );
$query->setFrom( $query->getParam( 'size' ) + $query->getParam( 'from' ) );
$query->setSize( $sizeSecond );
// Break if we already got all hits
} while ( $resultset->getTotalHits() > count( $contents ) );
$suggestions = [];
// Skip second query if first query found nothing. Keeping only one return
// statement in this method to avoid forgetting to reset connection timeout
if ( $terms !== [] ) {
$idQuery = new Query\Terms( '_id', $terms );
$query = new Query( $idQuery );
$query->setSize( 25 );
$query->setParam( '_source', [ 'wiki', 'uri', 'content', 'localid' ] );
$resultset = $this->getIndex()->search( $query );
foreach ( $resultset->getResults() as $result ) {
$data = $result->getData();
// Construct the matching source id
$sourceId = preg_replace( '~/[^/]+$~', '', $result->getId() );
$suggestions[] = [
'source' => $contents[$sourceId],
'target' => $data['content'],
'context' => $data['localid'],
'quality' => $scores[$sourceId],
'wiki' => $data['wiki'],
'location' => $data['localid'] . '/' . $targetLanguage,
'uri' => $data['uri'],
];
}
// Ensure results are in quality order
uasort( $suggestions, static function ( $a, $b ) {
if ( $a['quality'] === $b['quality'] ) {
return 0;
}
return ( $a['quality'] < $b['quality'] ) ? 1 : -1;
} );
}
$connection->setTimeout( $oldTimeout );
return $suggestions;
}
/* Write functions */
public function update( MessageHandle $handle, ?string $targetText ): bool {
if ( !$handle->isValid() || $handle->getCode() === '' ) {
return false;
}
/* There are various different cases here:
* [new or updated] [fuzzy|non-fuzzy] [translation|definition]
* 1) We don't distinguish between new or updated here.
* 2) Delete old translation, but not definition
* 3) Insert new translation or definition, if non-fuzzy
* The definition should never be fuzzied anyway.
*
* These only apply to known messages.
*/
$sourceLanguage = $handle->getGroup()->getSourceLanguage();
// Do not delete definitions, because the translations are attached to that
if ( $handle->getCode() !== $sourceLanguage ) {
$localid = $handle->getTitleForBase()->getPrefixedText();
$this->deleteByQuery( $this->getIndex(), Query::create(
( new BoolQuery() )
->addFilter( new Term( [ 'wiki' => WikiMap::getCurrentWikiId() ] ) )
->addFilter( new Term( [ 'language' => $handle->getCode() ] ) )
->addFilter( new Term( [ 'localid' => $localid ] ) ) ) );
}
// If translation was made fuzzy, we do not need to add anything
if ( $targetText === null ) {
return true;
}
// source language is null, skip doing rest of the stuff
if ( $sourceLanguage === null ) {
return true;
}
$revId = $handle->getTitleForLanguage( $sourceLanguage )->getLatestRevID();
$doc = $this->createDocument( $handle, $targetText, $revId );
$fname = __METHOD__;
MWElasticUtils::withRetry( self::BULK_INDEX_RETRY_ATTEMPTS,
function () use ( $doc ) {
$this->getIndex()->addDocuments( [ $doc ] );
},
static function ( $e, $errors ) use ( $fname ) {
$c = get_class( $e );
$msg = $e->getMessage();
error_log( $fname . ": update failed ($c: $msg); retrying." );
sleep( 10 );
}
);
return true;
}
private function createDocument( MessageHandle $handle, string $text, int $revId ): Document {
$language = $handle->getCode();
$localid = $handle->getTitleForBase()->getPrefixedText();
$wiki = WikiMap::getCurrentWikiId();
$globalid = "$wiki-$localid-$revId/$language";
$data = [
'wiki' => $wiki,
'uri' => $handle->getTitle()->getCanonicalURL(),
'localid' => $localid,
'language' => $language,
'content' => $text,
'group' => $handle->getGroupIds(),
];
return new Document( $globalid, $data, '_doc' );
}
/** @param bool $rebuild Deletes index first if already exists */
private function createIndex( bool $rebuild ): void {
$indexSettings = [
'settings' => [
'index' => [
'number_of_shards' => $this->getShardCount(),
'analysis' => [
'filter' => [
'prefix_filter' => [
'type' => 'edge_ngram',
'min_gram' => 2,
'max_gram' => 20
]
],
'analyzer' => [
'prefix' => [
'type' => 'custom',
'tokenizer' => 'standard',
'filter' => [ 'lowercase', 'prefix_filter' ]
],
'casesensitive' => [
'tokenizer' => 'standard'
]
]
]
],
],
];
$replicas = $this->getReplicaCount();
$key = str_contains( $replicas, '-' ) ? 'auto_expand_replicas' : 'number_of_replicas';
$indexSettings['settings']['index'][$key] = $replicas;
$this->getIndex()->create( $indexSettings, $rebuild );
}
/**
* Begin the bootstrap process.
* @throws RuntimeException
*/
public function beginBootstrap(): void {
$this->checkElasticsearchVersion();
$index = $this->getIndex();
if ( $this->updateMapping ) {
$this->logOutput( 'Updating the index mappings...' );
$this->createIndex( true );
} elseif ( !$index->exists() ) {
$this->createIndex( false );
}
$settings = $index->getSettings();
$settings->setRefreshInterval( '-1' );
$this->deleteByQuery( $this->getIndex(), Query::create(
( new Term() )->setTerm( 'wiki', WikiMap::getCurrentWikiId() ) ) );
$properties = [
'wiki' => [ 'type' => 'keyword' ],
'localid' => [ 'type' => 'keyword' ],
'uri' => [ 'type' => 'keyword' ],
'language' => [ 'type' => 'keyword' ],
'group' => [ 'type' => 'keyword' ],
'content' => [
'type' => 'text',
'fields' => [
'content' => [
'type' => 'text',
'term_vector' => 'yes'
],
'prefix_complete' => [
'type' => 'text',
'analyzer' => 'prefix',
'search_analyzer' => 'standard',
'term_vector' => 'yes'
],
'case_sensitive' => [
'type' => 'text',
'analyzer' => 'casesensitive',
'term_vector' => 'yes'
]
]
],
];
$mapping = new Mapping( $properties );
$mapping->send( $index, [ 'include_type_name' => 'false' ] );
$this->waitUntilReady();
}
public function beginBatch(): void {
}
/**
* @param array[] $batch
* @phan-param array<int,array{0:MessageHandle,1:string,2:string}> $batch
*/
public function batchInsertDefinitions( array $batch ): void {
$lb = MediaWikiServices::getInstance()->getLinkBatchFactory()->newLinkBatch();
foreach ( $batch as $data ) {
$lb->addObj( $data[0]->getTitle() );
}
$lb->execute();
$this->batchInsertTranslations( $batch );
}
public function batchInsertTranslations( array $batch ): void {
$docs = [];
foreach ( $batch as $data ) {
[ $handle, $sourceLanguage, $text ] = $data;
$revId = $handle->getTitleForLanguage( $sourceLanguage )->getLatestRevID();
$docs[] = $this->createDocument( $handle, $text, $revId );
}
MWElasticUtils::withRetry( self::BULK_INDEX_RETRY_ATTEMPTS,
function () use ( $docs ) {
$this->getIndex()->addDocuments( $docs );
},
function ( $e, $errors ) {
$c = get_class( $e );
$msg = $e->getMessage();
$this->logOutput( "Batch failed ($c: $msg), trying again in 10 seconds" );
sleep( 10 );
}
);
}
public function endBatch(): void {
}
public function endBootstrap(): void {
$index = $this->getIndex();
$index->refresh();
$index->forcemerge();
$index->getSettings()->setRefreshInterval( '5s' );
}
public function getClient(): Client {
if ( $this->client === null ) {
if ( isset( $this->config['config'] ) ) {
$this->client = new Client( $this->config['config'] );
} else {
$this->client = new Client();
}
}
return $this->client;
}
/** @return true if the backend is configured with the wikimedia extra plugin */
public function useWikimediaExtraPlugin(): bool {
return isset( $this->config['use_wikimedia_extra'] ) && $this->config['use_wikimedia_extra'];
}
private function getIndexName(): string {
return $this->config['index'] ?? 'ttmserver';
}
public function getIndex(): Index {
return $this->getClient()
->getIndex( $this->getIndexName() );
}
private function getShardCount(): int {
return $this->config['shards'] ?? 1;
}
private function getReplicaCount(): string {
return $this->config['replicas'] ?? '0-2';
}
private function waitUntilReady(): void {
$statuses = MWElasticUtils::waitForGreen(
$this->getClient(),
$this->getIndexName(),
self::WAIT_UNTIL_READY_TIMEOUT );
$this->logOutput( "Waiting for the index to go green..." );
foreach ( $statuses as $message ) {
$this->logOutput( $message );
}
if ( !$statuses->getReturn() ) {
die( "Timeout! Please check server logs for {$this->getIndexName()}." );
}
}
public function setLogger( TTMServerBootstrap $logger ): void {
$this->logger = $logger;
}
// Can it get any uglier?
private function logOutput( string $text ): void {
if ( $this->logger !== null ) {
$this->logger->statusLine( "$text\n" );
}
}
public function setDoReIndex(): void {
$this->updateMapping = true;
}
/** Parse query string and build the search query */
private function parseQueryString( string $queryString, array $opts ): array {
$fields = $highlights = [];
$terms = preg_split( '/\s+/', $queryString );
$match = $opts['match'];
$case = $opts['case'];
// Map each word in the query string with its corresponding field
foreach ( $terms as $term ) {
$prefix = strstr( $term, '*', true );
if ( $prefix ) {
// For wildcard search
$fields['content.prefix_complete'][] = $prefix;
} elseif ( $case === '1' ) {
// For case-sensitive search
$fields['content.case_sensitive'][] = $term;
} else {
$fields['content'][] = $term;
}
}
// Allow searching either by message content or message id (page name
// without language subpage) with exact match only.
$searchQuery = new BoolQuery();
foreach ( $fields as $analyzer => $words ) {
foreach ( $words as $word ) {
$boolQuery = new BoolQuery();
$contentQuery = new MatchQuery();
$contentQuery->setFieldQuery( $analyzer, $word );
$boolQuery->addShould( $contentQuery );
$messageQuery = new Term();
$messageQuery->setTerm( 'localid', $word );
$boolQuery->addShould( $messageQuery );
if ( $match === 'all' ) {
$searchQuery->addMust( $boolQuery );
} else {
$searchQuery->addShould( $boolQuery );
}
// Fields for highlighting
$highlights[$analyzer] = [
'number_of_fragments' => 0
];
// Allow searching by exact message title (page name with
// language subpage).
$title = Title::newFromText( $word );
if ( !$title ) {
continue;
}
$handle = new MessageHandle( $title );
if ( $handle->isValid() && $handle->getCode() !== '' ) {
$localid = $handle->getTitleForBase()->getPrefixedText();
$boolQuery = new BoolQuery();
$messageId = new Term();
$messageId->setTerm( 'localid', $localid );
$boolQuery->addMust( $messageId );
$searchQuery->addShould( $boolQuery );
}
}
}
return [ $searchQuery, $highlights ];
}
/** Search interface */
public function createSearch( string $queryString, array $opts, array $highlight ): Search {
$query = new Query();
[ $searchQuery, $highlights ] = $this->parseQueryString( $queryString, $opts );
$query->setQuery( $searchQuery );
$language = new Terms( 'language' );
$language->setField( 'language' );
$language->setSize( 500 );
$query->addAggregation( $language );
$group = new Terms( 'group' );
$group->setField( 'group' );
// Would like to prioritize the top level groups and not show subgroups
// if the top group has only few hits, but that doesn't seem to be possile.
$group->setSize( 500 );
$query->addAggregation( $group );
$query->setSize( $opts['limit'] );
$query->setFrom( $opts['offset'] );
// BoolAnd filters are executed in sequence per document. Bool filters with
// multiple must clauses are executed by converting each filter into a bit
// field then anding them together. The latter is normally faster if either
// of the subfilters are reused. May not make a difference in this context.
$filters = new BoolQuery();
$language = $opts['language'];
if ( $language !== '' ) {
$languageFilter = new Term();
$languageFilter->setTerm( 'language', $language );
$filters->addFilter( $languageFilter );
}
$group = $opts['group'];
if ( $group !== '' ) {
$groupFilter = new Term();
$groupFilter->setTerm( 'group', $group );
$filters->addFilter( $groupFilter );
}
// Check that we have at least one filter to avoid invalid query errors.
if ( $language !== '' || $group !== '' ) {
// TODO: This seems wrong, but perhaps for aggregation purposes?
// should make $search a must clause and use the bool query
// as main.
$query->setPostFilter( $filters );
}
[ $pre, $post ] = $highlight;
$query->setHighlight( [
// The value must be an object
'pre_tags' => [ $pre ],
'post_tags' => [ $post ],
'fields' => $highlights,
] );
return $this->getIndex()->createSearch( $query );
}
/**
* Search interface
* @throws TtmServerException
*/
public function search( string $queryString, array $opts, array $highlight ): ResultSet {
$search = $this->createSearch( $queryString, $opts, $highlight );
try {
return $search->search();
} catch ( ExceptionInterface $e ) {
throw new TtmServerException( $e->getMessage() );
}
}
/** @inheritDoc */
public function getFacets( $resultset ): array {
$this->assertResultSetInstance( $resultset );
$aggs = $resultset->getAggregations();
'@phan-var array[][][] $aggs';
$ret = [
'language' => [],
'group' => []
];
foreach ( $aggs as $type => $info ) {
foreach ( $info['buckets'] as $row ) {
$ret[$type][$row['key']] = $row['doc_count'];
}
}
return $ret;
}
/** @inheritDoc */
public function getTotalHits( $resultset ): int {
$this->assertResultSetInstance( $resultset );
return $resultset->getTotalHits();
}
/** @inheritDoc */
public function getDocuments( $resultset ): array {
$this->assertResultSetInstance( $resultset );
$ret = [];
foreach ( $resultset->getResults() as $document ) {
$data = $document->getData();
$hl = $document->getHighlights();
if ( isset( $hl['content.prefix_complete'][0] ) ) {
$data['content'] = $hl['content.prefix_complete'][0];
} elseif ( isset( $hl['content.case_sensitive'][0] ) ) {
$data['content'] = $hl['content.case_sensitive'][0];
} elseif ( isset( $hl['content'][0] ) ) {
$data['content'] = $hl['content'][0];
}
$ret[] = $data;
}
return $ret;
}
/**
* Delete docs by query by using the scroll API.
* TODO: Elastica\Index::deleteByQuery() ? was removed
* in 2.x and returned in 5.x.
* @throws RuntimeException
*/
private function deleteByQuery( Index $sourceIndex, Query $query ): void {
try {
MWElasticUtils::deleteByQuery( $sourceIndex, $query, /* $allowConflicts = */ true );
} catch ( Exception $e ) {
LoggerFactory::getInstance( 'ElasticSearchTtmServer' )->error(
'Problem encountered during deletion.',
[ 'exception' => $e ]
);
throw new RuntimeException( "Problem encountered during deletion.\n" . $e );
}
}
/* @throws RuntimeException */
private function getElasticsearchVersion(): string {
$response = $this->getClient()->request( '' );
if ( !$response->isOK() ) {
throw new RuntimeException( "Cannot fetch elasticsearch version: " . $response->getError() );
}
$result = $response->getData();
if ( !isset( $result['version']['number'] ) ) {
throw new RuntimeException( 'Unable to determine elasticsearch version, aborting.' );
}
return $result[ 'version' ][ 'number' ];
}
private function checkElasticsearchVersion(): void {
$version = $this->getElasticsearchVersion();
if ( !str_starts_with( $version, '6.8' ) && !str_starts_with( $version, '7.' ) ) {
throw new RuntimeException( "Only Elasticsearch 6.8.x and 7.x are supported. Your version: $version." );
}
}
/** @param mixed $resultSet */
private function assertResultSetInstance( $resultSet ): void {
if ( $resultSet instanceof ResultSet ) {
return;
}
throw new RuntimeException(
"Expected resultset to be an instance of " . ResultSet::class
);
}
}
// Translation memory configuration ($wgTranslateTranslationServices) uses class as ElasticSearchTTMServer
// See: https://www.mediawiki.org/wiki/Help:Extension:Translate/Translation_memories#Configuration
class_alias( ElasticSearchTtmServer::class, "ElasticSearchTTMServer" );