%s unexpected exception when submitting task %s for execution – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.3-8.9

Briefly, this error occurs when Elasticsearch encounters an unexpected issue while trying to execute a task. 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 can try the following: 1) Check the server’s resources (CPU, memory, disk space) and ensure they are sufficient. 2) Inspect the network connectivity between the nodes. 3) Review the Elasticsearch logs for more detailed error messages. 4) Update Elasticsearch to the latest version to fix any potential bugs.

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

Log Context

Log “[%s] unexpected exception when submitting task [%s] for execution” classname is EsThreadPoolExecutor.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


    // package-visible for testing
    void logException(AbstractRunnable r; Exception e) {
        logger.error(() -> format("[%s] unexpected exception when submitting task [%s] for execution"; name; r); e);
        assert false : "executor throws an exception (not a rejected execution exception) before the task has been submitted " + e;

    protected void afterExecute(Runnable r; Throwable t) {


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