Foreach object was an empty list could not run any action – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.3-8.9

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Briefly, this error occurs when a foreach processor in an Elasticsearch ingest pipeline tries to process an empty list. The foreach processor is designed to perform specified operations on each item in a list. If the list is empty, it cannot perform any action, hence the error. To resolve this issue, you can either ensure that the list is never empty by adding a check before the foreach processor or handle the empty list scenario within the foreach processor by using an “ignore_failure” option. This will allow the pipeline to continue processing even if the list is empty.

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This guide will help you check for common problems that cause the log ” foreach object [{}] was an empty list; could not run any action ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.

Log Context

Log “foreach object [{}] was an empty list; could not run any action” class name is ActionWrapper.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 List results = new ArrayList<>();
 Object object = ObjectPath.eval(path; toMap(ctx));
 int runs = 0;
 if (object instanceof Collection collection) {
 if (collection.isEmpty()) {
 throw new ElasticsearchException("foreach object [{}] was an empty list; could not run any action"; path);
 } else {
 for (Object o : collection) {
 if (runs >= maxIterations) {
 break;
 }

 

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