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

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when OpenSearch fails to execute a scheduled task on a specific thread pool due to issues like resource exhaustion, thread pool misconfiguration, or underlying system issues. To resolve this, you can increase the size of the thread pool, ensure the task isn’t consuming excessive resources, or check for any system-level problems that might be causing the thread pool to malfunction. Additionally, you can also review the task’s code for any potential bugs or inefficiencies that might be causing it to fail.

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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 OpenSearch concepts: task, thread, threadpool, pool.

Log Context

Log “failed to run scheduled task [{}] on thread pool [{}]” classname is
We extracted the following from OpenSearch 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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