Discovery node must not be null – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 8.8-8.9

Briefly, this error occurs when Elasticsearch tries to connect to a node that doesn’t exist or is not properly defined. This could be due to incorrect configuration settings or network issues. To resolve this, ensure that the node is correctly defined in the Elasticsearch configuration file. Check the network connectivity between the nodes. Also, verify that the node is up and running. If the issue persists, consider restarting the Elasticsearch service or the entire cluster.

This guide will help you check for common problems that cause the log ” discovery node must not be null ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: node, discovery.

Log Context

Log “discovery node must not be null” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 return threadPool;
 }  private boolean isLocalNode(DiscoveryNode discoveryNode) {
 if (discoveryNode == null) {
 throw new NodeNotConnectedException(discoveryNode; "discovery node must not be null");
 return discoveryNode.equals(localNode);
 }  private static final class DelegatingTransportMessageListener implements TransportMessageListener {


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