Unknown key for index template – How to solve this Elasticsearch error

Opster Team

July-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you try running the Elasticsearch Check-Up which can resolve issues that cause many errors.

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

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up to analyze Elasticsearch configuration and help resolve this error.

Log Context

Log “unknown key [{}] for index template”classname  is IndexTemplateMetadata.java We extracted the following from Elasticsearch source code for those seeking an in-depth context :

} else if ("aliases".equals(currentFieldName)) {
 while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
 } else {
 throw new ElasticsearchParseException("unknown key [{}] for index template"; currentFieldName);
 } else if (token == XContentParser.Token.START_ARRAY) {
 if ("mappings".equals(currentFieldName)) {
 while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
 Map mapping = parser.mapOrdered();


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