SuggestHelper#updateSuggester updates suggester by doing a build() on a newly created instance of AnalyzingInfixSuggester. But it never closes the suggester instance, which, in turn, leads to un-closed reader. With FS based directory (when copy-on-write is enabled), this leads to leaking file handles. FSDirectory does get closed on GC though.
The issue was reported by Marcel Reutegger