Encountered a retryable error. Will Retry with exponential backoff {:code=>400, :url=>"https://example.us-east-1.es.amazonaws.com:443/_bulk"}

Logstash Config file

input {
 elasticsearch {
 hosts => ["https://staing-example.com:443"]
 user => "userName"
 password => "password"
 index => "testingindex"
 size => 100
 scroll => "1m"
 }
}

filter {

}


output {
 amazon_es {
 hosts => ["https://example.us-east-1.es.amazonaws.com:443"]
 region => "us-east-1"
 aws_access_key_id => "access_key_id"
 aws_secret_access_key => "access_key_id"
 index => "testingindex"
}
}

Using Logstash to transferred from one elastic search server to amazon elastic search

For the above config, Logstash is continuously throwing

2019-10-10T16:00:51,232][ERROR][logstash.outputs.elasticsearch] Encountered a retryable error. Will Retry with exponential backoff {:code=>400, :url=>"https://example.us-east-1.es.amazonaws.com:443/_bulk"} [2019-10-10T16:00:52,127][ERROR][logstash.outputs.elasticsearch] Encountered a retryable error. Will Retry with exponential backoff {:code=>400, :url=>"https://example.us-east-1.es.amazonaws.com:443/_bulk"} [2019-10-10T16:00:52,317][ERROR][logstash.outputs.elasticsearch] Encountered a retryable error. Will Retry with exponential backoff {:code=>400, :url=>"https://example.us-east-1.es.amazonaws.com:443/_bulk"}

Don't know the reason why it is happening