In mule, we are connecting to analytics jar file. So, the error is actually originating from the Java file itself. If nothing is changing from ES 2.3 to ES 5.5, we should ideally not get any error in sending analytics. The only thing we changed in the ES host.
I really apologize for not giving the complete context. Will try to clarify.
We built our API's on Mulesoft platform and asynchronously send the logs to a jar file. In this java file, we send the multiple log files to elasticsearch using bulk api. The elasticsearch cluster to which the data is being ingested is currently on 2.3 version. We have the data in elasticsearch and we are able to see the data in kibana as well.
Today, we spinned another ES cluster which is on version 5.5 and updated the Java code to reflect this change to new URL. This is the only change we did and now, we are unable to see the data in the new Elasticsearch cluster.
The only logs we have are the one's we listed above. I don't think it is related to mulesoft because, the issue happens only when the ES version is changing. It should be either something to do with the way we insert data using Elasticsearch Java client or the api we are using to push data to Elasticsearch.