Start a vanilla Elasticsearch 6.5 server, without language analyzer plugins. (This is to force errors when indexing Liferay documents.)
Add any content with multi language fields (web articles, document files etc.)
Perform a full reindex.
Observed: Elasticsearch errors in the Elasticsearch console (missing language analyzers).
Observed: Documents are not indexed; zero search results.
Expected: Elasticsearch errors in Liferay logs, when "log exceptions only" is enabled; Liferay exceptions in Liferay logs, when "log exceptions only" is disabled.
Observed: No indication of why documents are missing; No errors of any kind in Liferay logs.
Go to Control Panel > Configuration > System Settings > Search > Elasticsearch 6, paste into Additional Type Mappings:
Go to Control Panel > Configuration > Search, Reindex all search indexes.
Go to Control Panel > Configuration > Custom Fields > Document > Add a Text Field called "test", under Advanced Properties, select searchable AS TEXT
Go to Document and Media > Add a Document ("File Upload") called "doc" and in the Test custom field, put the word text
Publish the document and see ERROR in tomcat logs
For additional logging, Go to Control Panel > Configuration > Server Administration > Log Levels, set "com.liferay.portal.search.elasticsearch6" to WARN