Failed to parse rules expression expected to be an object but found instead – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.15

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Briefly, this error occurs when Elasticsearch expects a certain data type (an object) in the rules expression, but encounters a different data type instead. This mismatch can cause parsing to fail. To resolve this issue, you should check the data type of the input in your rules expression. Ensure that it matches the expected data type (object). If necessary, convert the data type or adjust your rules expression to handle the actual data type. Also, validate your JSON structure to ensure it’s correctly formatted.

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This guide will help you check for common problems that cause the log ” failed to parse rules expression. expected [{}] to be an object but found [{}] instead ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: parser, rest-high-level, client.

Log Context

Log “failed to parse rules expression. expected [{}] to be an object but found [{}] instead” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 token = parser.nextToken();
 } else {
 token = parser.currentToken();
 if (token != XContentParser.Token.START_OBJECT) {
 throw new ElasticsearchParseException("failed to parse rules expression. expected [{}] to be an object but found [{}] instead";
 objectName; token);
 }  final String fieldName = fieldName(objectName; parser);
 final RoleMapperExpression expr = parseExpression(parser; fieldName; objectName);


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