[logstash.outputsCould not index event to Elasticsearch."error {"type"=>"mapper_parsing_exception", "reason"=>"object mapping for [host] tried to parse field [host] as object, but found a concrete value"

[Badger]

See this answer. Once you have indexed an document in which [host] is an object (probably containing [host][name]) any event that in which [host] is text will be rejected.