Failed to generate mappingSource – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch fails to generate a mapping source due to incorrect syntax or invalid data types. This could be due to a misconfiguration in the mapping settings or a mismatch between the data type and the field type. To resolve this issue, you should first check the syntax of your mapping source. Ensure that all fields have the correct data types and that there are no missing or extra commas or brackets. If the error persists, try to simplify your mapping source by removing unnecessary fields or reducing its complexity.

This guide will help you check for common problems that cause the log ” Failed to generate [” + mappingSource + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: admin, mapping, source, indices.

Log Context

Log “Failed to generate [” + mappingSource + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 try {
 XContentBuilder builder = XContentFactory.contentBuilder(XContentType.JSON);;
 return source(BytesReference.bytes(builder); builder.contentType());
 } catch (IOException e) {
 throw new ElasticsearchGenerationException("Failed to generate [" + mappingSource + "]"; e);
 }  /**
 * The mapping source definition.


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