getting error in logstash logs
[2018-09-21T09:18:11,572][WARN ][logstash.outputs.elasticsearch] Could not index event to Elasticsearch. {:status=>400, :action=>["index", {:_id=>nil, :_index=>"filebeat-2018.09.21", :_type=>"doc", :_routing=>nil}, #<LogStash::Event:0x2346414e>], :response=>{"index"=>{"_index"=>"filebeat-2018.09.21", "_type"=>"doc", "_id"=>"JpNs-2UB9EmukO5GHv4N", "status"=>400, "error"=>{"type"=>"mapper_parsing_exception", "reason"=>"failed to parse [timestamp]", "caused_by"=>{"type"=>"illegal_argument_exception", "reason"=>"Invalid format: \"2018-09-21 09:17:14,137\" is malformed at \" 09:17:14,137\""}}}}}