ERROR logstash.outputs.elasticsearch Encountered a retryable error. Will Retry with exponential backoff code=>400

[2018-01-24T17:33:38,541][ERROR][logstash.outputs.elasticsearch] Encountered a retryable error.
Will Retry with exponential backoff  {:code=>400, :url=>"http://xx.xx.xx.xx:9200/_bulk"}

output {
  elasticsearch {
    manage_template => false
    hosts => ["xx.xx.xx.xx:9200"]
    index => "%{[@metadata][indexname]}-%{+YYYY.MM.dd}"
    document_type => "xxxxxxxxxxxx_mapping"
  }
}