ICU folding was enabled yesterday on en, fr, el and he wikis.
It seems to have triggered an issue in elastic that causes many suggester indices to fail:
[2017-01-25 03:27:18,654][DEBUG][action.bulk ] [elastic1044] [enwiktionary_titlesuggest_1485314643][1] failed to execute bulk item (index) index {[enwiktionary_titlesuggest_1485314643][titlesuggest][3057103t], source[{"batch_id":1485314639,"suggest":{"input":["はーい"],"output":"3057103:t:はーい","weight":160700},"suggest-stop":{"input":["はーい"],"output":"3057103:t:はーい","weight":160700}}]}
[enwiktionary_titlesuggest_1485314643][[enwiktionary_titlesuggest_1485314643][1]] IndexFailedEngineException[Index failed for [titlesuggest#3057103t]]; nested: IllegalStateException[from state (0) already had transitions added];
at org.elasticsearch.index.engine.InternalEngine.index(InternalEngine.java:462)
at org.elasticsearch.index.shard.IndexShard.index(IndexShard.java:601)
at org.elasticsearch.index.engine.Engine$Index.execute(Engine.java:836)
at org.elasticsearch.action.index.TransportIndexAction.executeIndexRequestOnPrimary(TransportIndexAction.java:237)
at org.elasticsearch.action.bulk.TransportShardBulkAction.shardIndexOperation(TransportShardBulkAction.java:327)
at org.elasticsearch.action.bulk.TransportShardBulkAction.shardOperationOnPrimary(TransportShardBulkAction.java:120)
at org.elasticsearch.action.bulk.TransportShardBulkAction.shardOperationOnPrimary(TransportShardBulkAction.java:68)
at org.elasticsearch.action.support.replication.TransportReplicationAction$PrimaryPhase.doRun(TransportReplicationAction.java:639)
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
at org.elasticsearch.action.support.replication.TransportReplicationAction$PrimaryOperationTransportHandler.messageReceived(TransportReplicationAction.java:279)
at org.elasticsearch.action.support.replication.TransportReplicationAction$PrimaryOperationTransportHandler.messageReceived(TransportReplicationAction.java:271)
at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:75)
at org.elasticsearch.transport.TransportService$4.doRun(TransportService.java:376)
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: from state (0) already had transitions added
at org.apache.lucene.util.automaton.Automaton.addTransition(Automaton.java:182)
at org.apache.lucene.search.suggest.analyzing.XAnalyzingSuggester.replaceSep(XAnalyzingSuggester.java:335)
at org.apache.lucene.search.suggest.analyzing.XAnalyzingSuggester.toAutomaton(XAnalyzingSuggester.java:954)
at org.apache.lucene.search.suggest.analyzing.XAnalyzingSuggester.toFiniteStrings(XAnalyzingSuggester.java:973)
at org.elasticsearch.search.suggest.completion.AnalyzingCompletionLookupProvider.toFiniteStrings(AnalyzingCompletionLookupProvider.java:403)
at org.elasticsearch.search.suggest.completion.CompletionTokenStream.incrementToken(CompletionTokenStream.java:63)
at org.apache.lucene.index.DefaultIndexingChain$PerField.invert(DefaultIndexingChain.java:634)
at org.apache.lucene.index.DefaultIndexingChain.processField(DefaultIndexingChain.java:365)
at org.apache.lucene.index.DefaultIndexingChain.processDocument(DefaultIndexingChain.java:321)
at org.apache.lucene.index.DocumentsWriterPerThread.updateDocument(DocumentsWriterPerThread.java:234)
at org.apache.lucene.index.DocumentsWriter.updateDocument(DocumentsWriter.java:450)
at org.apache.lucene.index.IndexWriter.updateDocument(IndexWriter.java:1477)
at org.apache.lucene.index.IndexWriter.addDocument(IndexWriter.java:1256)
at org.elasticsearch.index.engine.InternalEngine.innerIndex(InternalEngine.java:530)
at org.elasticsearch.index.engine.InternalEngine.index(InternalEngine.java:457)
... 16 moreIt's unclear yet, but it sounds like a bug in elastic, I'll revert the patch to activate ICU and try to find a workaround.