after migrating from 5.4 to 6.4.2 when i try to run logstash.conf file using
bin/logstash --debug -f logstash-XXXX.conf
[2018-11-17T22:33:02,516][WARN ][logstash.outputs.elasticsearch] Could not index event to Elasticsearch. {:status=>400, :action=>["index", {:_id=>nil, :_index=>"logstash-XXXX-2018.11.18", :_type=>"doc", :_routing=>nil}, #LogStash::Event:0x54f9f901], :response=>{"index"=>{"_index"=>"logstash-XXXX-2018.11.18", "_type"=>"doc", "_id"=>nil, "status"=>400, "error"=>{"type"=>"mapper_parsing_exception", "reason"=>"Failed to parse mapping [default]: Enabling [_all] is disabled in 6.0. As a replacement, you can use [copy_to] on mapping fields to create your own catch all field.", "caused_by"=>{"type"=>"illegal_argument_exception", "reason"=>"Enabling [_all] is disabled in 6.0. As a replacement, you can use [copy_to] on mapping fields to create your own catch all field."}}}}}