Specified foreach object was not a an array collection – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.3-8.9

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Briefly, this error occurs when Elasticsearch tries to iterate over an object that is not an array or collection. This usually happens when you’re using a “foreach” processor in an ingest pipeline and the field you’re trying to iterate over is not an array. To resolve this issue, you can either ensure that the field is an array or collection before using the “foreach” processor, or you can add a conditional check in your pipeline to skip the “foreach” processor if the field is not an array.

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This guide will help you check for common problems that cause the log ” specified foreach object was not a an array/collection: [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “specified foreach object was not a an array/collection: [{}]” class name is ActionWrapper.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 } else if (object == null) {
 throw new ElasticsearchException("specified foreach object was null: [{}]"; path);
 } else {
 throw new ElasticsearchException("specified foreach object was not a an array/collection: [{}]"; path);
 }  // check if we have mixed results; then set to partial failure
 final Set statuses = results.stream().map(Action.Result::status).collect(Collectors.toSet());
 Action.Result.Status status;


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