Exception thrown by listener while notifying on ack timeout – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-8.9

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Briefly, this error occurs when a listener in Elasticsearch fails to receive an acknowledgment within a specified timeout period. This could be due to network issues, slow processing, or overloaded Elasticsearch cluster. To resolve this, you can increase the timeout period, optimize your queries for faster processing, or scale your Elasticsearch cluster to handle more load. Additionally, ensure your network connectivity is stable and reliable to prevent such timeouts.

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This guide will help you check for common problems that cause the log ” exception thrown by listener while notifying on ack timeout ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster.

Log Context

Log “exception thrown by listener while notifying on ack timeout” classname is MasterService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        public void onAckTimeout() {
            try (ThreadContext.StoredContext ignore = context.get()) {
            } catch (Exception e) {
                logger.error("exception thrown by listener while notifying on ack timeout"; e);

        public TimeValue ackTimeout() {
            return listener.ackTimeout();


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