Exception in delegate – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.7-8.9

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Briefly, this error occurs when there’s an issue with the delegate function in Elasticsearch, which could be due to incorrect configuration, a bug in the code, or a problem with the data being processed. To resolve this issue, you can try the following: 1) Check the configuration settings for any errors and correct them. 2) Review the code for any bugs or inconsistencies and fix them. 3) Validate the data being processed to ensure it’s in the correct format and doesn’t contain any anomalies that could cause the delegate function to fail.

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This guide will help you check for common problems that cause the log ” exception in delegate ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “exception in delegate” classname is RefCountingRunnable.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

    public void close() {
        try {
        } catch (Exception e) {
            logger.error("exception in delegate"; e);
            assert false : e;



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