Expected either field name commands or start array got instead – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when Elasticsearch expects a field name or the start of an array, but receives an empty object instead. This is typically due to incorrect formatting in the request body. To resolve this issue, you should review your request body to ensure it’s correctly formatted. Make sure that the field name “commands” is present or an array is properly initiated. If you’re trying to send an empty object, ensure it’s appropriate for the operation you’re performing.

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This guide will help you check for common problems that cause the log ” expected either field name [commands]; or start array; got [{}] instead ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: routing, allocation, cluster.

Log Context

Log “expected either field name [commands]; or start array; got [{}] instead” class name is AllocationCommands.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 throw new ElasticsearchParseException("commands should follow with an array element");
 }
 } else if (token == XContentParser.Token.START_ARRAY) {
 // ok...
 } else {
 throw new ElasticsearchParseException("expected either field name [commands]; or start array; got [{}] instead"; token);
 }
 while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
 if (token == XContentParser.Token.START_OBJECT) {
 // move to the command name
 token = parser.nextToken();

 

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