Unknown cause – How to solve this Elasticsearch error

Opster Team

March-22, Version: 1.7-8.0

Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many configuration errors.

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This guide will help you check for common problems that cause the log ” unknown cause ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: rest.

Log Context

Log “unknown cause”classname  is RestController.java We extracted the following from Elasticsearch source code for those seeking an in-depth context :

public void dispatchBadRequest(final RestChannel channel; final ThreadContext threadContext; final Throwable cause) {
 try {
 final Exception e;
 if (cause == null) {
 e = new ElasticsearchException("unknown cause");
 } else if (cause instanceof Exception) {
 e = (Exception) cause;
 } else {
 e = new ElasticsearchException(cause);


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