Failed to run scheduled task on thread pool – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-7.15

Briefly, this error occurs when Elasticsearch is unable to execute a scheduled task due to issues like high CPU usage, insufficient memory, or thread pool saturation. To resolve this, you can optimize your queries to reduce CPU usage, increase your server’s memory, or adjust the thread pool settings in Elasticsearch. Additionally, ensure that your tasks are not scheduled too closely together to avoid overloading the system.

This guide will help you check for common problems that cause the log ” failed to run scheduled task [{}] on thread pool [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: threadpool, task, pool, thread.

Log Context

Log “failed to run scheduled task [{}] on thread pool [{}]” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                    if (logger.isDebugEnabled()) {
                        logger.debug(() -> new ParameterizedMessage("scheduled task [{}] was rejected on thread pool [{}]";
                                command; executor); e);
                (e) -> logger.warn(() -> new ParameterizedMessage("failed to run scheduled task [{}] on thread pool [{}]";
                        command; executor); e));

    protected final void stopCachedTimeThread() {
        cachedTimeThread.running = false;


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