Unexpected exception from handler handleException – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.5-8.9

Briefly, this error occurs when Elasticsearch encounters an unexpected issue while processing a request, typically due to a bug in the code or an unhandled exception. To resolve this issue, you can try the following: 1) Check the Elasticsearch logs for more detailed error information. 2) Update Elasticsearch to the latest version, as the issue might have been fixed in a newer release. 3) Review your code to ensure it’s correctly handling exceptions. 4) If the error persists, consider seeking help from the Elasticsearch community or support, providing them with detailed information about the error.

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

Log Context

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

        try {
        } catch (Exception innerException) {
            // should not happen
            logger.error("unexpected exception from handler.handleException"; innerException);
            assert false : innerException;



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