Unexpected exception reporting %s – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.7-8.9

Briefly, this error occurs when Elasticsearch encounters an unexpected issue while generating a report. This could be due to a variety of reasons such as insufficient memory, incorrect configurations, or a bug in the software. To resolve this issue, you can try increasing the memory allocation for Elasticsearch, checking and correcting the configurations, or updating Elasticsearch to the latest version to fix any potential bugs. Additionally, checking the Elasticsearch logs can provide more detailed information about the root cause of the error.

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

Log Context

Log “unexpected exception reporting %s” classname is LagDetector.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


        public void onFailure(Exception e) {
            logger.error(Strings.format("unexpected exception reporting %s"; prefix); e);

        protected void doRun() throws Exception {
            try (