Failed to notify response handler on exception action %s – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.3-8.9

Briefly, this error occurs when Elasticsearch fails to notify the response handler about an exception during a specific action. This could be due to a network issue, a node failure, or a problem with the response handler itself. To resolve this issue, you can try restarting the Elasticsearch node, checking the network connection, or debugging the response handler to identify any potential issues. Additionally, ensure that your Elasticsearch cluster is properly configured and that all nodes are functioning correctly.

This guide will help you check for common problems that cause the log ” failed to notify response handler on exception; action: %s ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: response, handler.

Log Context

Log “failed to notify response handler on exception; action: %s” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                logger.debug(() -> format("failed to notify response handler on rejection; action: %s"; contextToNotify.action()); e);

            public void onFailure(Exception e) {
                logger.warn(() -> format("failed to notify response handler on exception; action: %s"; contextToNotify.action()); e);

            protected void doRun() {


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