Elasticsearch 6.0 multiple types problem

Check out this upgrading advice or this sticky in the Logstash subforum.

What you need to do is explicitly set document_type in the elasticsearch output, like this:

elasticsearch {
  hosts => [ "localhost:9200" ]
  index => 'fg-%{+YYYY.MM.dd}'
  document_type => doc
}

This may not work for any existing indexes, as there will already be a type defined in the mapping of those indexes, but it will work for all new indexes.