Fatal error in thread exiting – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-7.5

Briefly, this error occurs when a severe problem arises in a thread causing it to exit abruptly. This could be due to issues like memory leaks, resource exhaustion, or unhandled exceptions. To resolve this, you can: 1) Check the Elasticsearch logs for more detailed error messages that might indicate the root cause. 2) Monitor the system’s resources to ensure there’s enough memory and CPU. 3) Review your code for unhandled exceptions and fix them. 4) If the error persists, consider upgrading Elasticsearch to the latest version as it might be a bug that’s been fixed in newer versions.

This guide will help you check for common problems that cause the log ” fatal error in thread [{}]; exiting ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: bootstrap, thread.

Log Context

Log “fatal error in thread [{}]; exiting” classname is ElasticsearchUncaughtExceptionHandler.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

    static boolean isFatalUncaught(Throwable e) {
        return e instanceof Error;

    void onFatalUncaught(final String threadName; final Throwable t) {
        logger.error(() -> new ParameterizedMessage("fatal error in thread [{}]; exiting"; threadName); t);

    void onNonFatalUncaught(final String threadName; final Throwable t) {
        logger.warn(() -> new ParameterizedMessage("uncaught exception in thread [{}]"; threadName); t);


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