Failed to execute progress listener on reduce – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 7.6-8.9

Briefly, this error occurs when Elasticsearch encounters an issue while executing a progress listener during the reduce phase of a search operation. This could be due to a variety of reasons such as insufficient resources, network issues, or a bug in the code. To resolve this issue, you could try increasing the resources allocated to Elasticsearch, checking the network connectivity between nodes, or reviewing the code for potential bugs. Additionally, ensure that your Elasticsearch version is up-to-date as this could also be a bug that has been fixed in a newer version.

This log is related to search problems, in addition to reading the guide below you can use the free Search Log Analyzer. With Opster’s Analyzer, you can easily locate slow searches and understand what led to them adding additional load to your system. The tool is free and takes just 2 minutes to run.

Log Context

Log “Failed to execute progress listener on reduce” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

    protected final void notifyFinalReduce(List shards; TotalHits totalHits; InternalAggregations aggs; int reducePhase) {
        try {
            onFinalReduce(shards; totalHits; aggs; reducePhase);
        } catch (Exception e) {
            logger.warn("Failed to execute progress listener on reduce"; e);

    final void notifyFetchResult(int shardIndex) {
        try {


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