When I run extensions/CirrusSearch/maintenance/updateSuggesterIndex.php for the first time under MediaWiki 1.27.1, I get this error (which includes the sentence, "This is always a bug in CirrusSearch." hence this ticket).
$ php updateSuggesterIndex.php Scanning available plugins... kopf Picking analyzer...english Fetching Elasticsearch version...1.7.4...ok Inferring index identifier...wikidb-vpw__titlesuggest_first Index does not exist yet cannot recycle. Inferring index identifier...wikidb-vpw__titlesuggest_first Setting index identifier...wikidb-vpw__titlesuggest_1479240582 2016-11-15 15:09:42 Unexpected Elasticsearch failure. Elasticsearch failed in an unexpected way. This is always a bug in CirrusSearch. Error type: Elastica\Exception\ResponseException Message: IndexCreationException[[wikidb-vpw__titlesuggest_1479240582] failed to create index]; nested: ElasticsearchIllegalArgumentException[failed to find token filter type [icu_normalizer] for [icu_normalizer]]; nested: NoClassSettingsException[Failed to load class setting [type] with value [icu_normalizer]]; nested: ClassNotFoundException[org.elasticsearch.index.analysis.icunormalizer.IcuNormalizerTokenFilterFactory]; Trace: #0 /home/wiki/wiki/wiki/vendor/ruflin/elastica/lib/Elastica/Request.php(171): Elastica\Transport\Http->exec(Object(Elastica\Request), Array) #1 /home/wiki/wiki/wiki/vendor/ruflin/elastica/lib/Elastica/Client.php(621): Elastica\Request->send() #2 /home/wiki/wiki/wiki/vendor/ruflin/elastica/lib/Elastica/Index.php(496): Elastica\Client->request('wikidb-vpw__tit...', 'PUT', Array, Array) #3 /home/wiki/wiki/wiki/extensions/CirrusSearch/maintenance/updateSuggesterIndex.php(706): Elastica\Index->request('wikidb-vpw__tit...', 'PUT', Array, Array) #4 /home/wiki/wiki/wiki/extensions/CirrusSearch/maintenance/updateSuggesterIndex.php(301): CirrusSearch\Maintenance\UpdateSuggesterIndex->createIndex() #5 /home/wiki/wiki/wiki/extensions/CirrusSearch/maintenance/updateSuggesterIndex.php(231): CirrusSearch\Maintenance\UpdateSuggesterIndex->rebuild() #6 /home/wiki/wiki/wiki/maintenance/doMaintenance.php(103): CirrusSearch\Maintenance\UpdateSuggesterIndex->execute() #7 /home/wiki/wiki/wiki/extensions/CirrusSearch/maintenance/updateSuggesterIndex.php(809): require_once('/home/wiki/wiki...') #8 {main}
I ran composer update but it didn't make a difference.