Unknown node nodeId – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when Elasticsearch tries to perform an operation on a node that it doesn’t recognize or that doesn’t exist in the cluster. This could be due to a misconfiguration, a node being down, or a network issue. To resolve this, you can check the cluster’s health and configuration, ensure all nodes are up and running, and verify network connectivity. If the node is no longer part of the cluster, you may need to update your configuration or scripts to remove references to the unknown node.

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This guide will help you check for common problems that cause the log ” unknown node [” + nodeId + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: node, replication.

Log Context

Log “unknown node [” + nodeId + “]” class name is TransportReplicationAction.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 final ActionListener listener
 ) {
 String nodeId = replica.currentNodeId();
 final DiscoveryNode node = clusterService.state().nodes().get(nodeId);
 if (node == null) {
 listener.onFailure(new NoNodeAvailableException("unknown node [" + nodeId + "]"));
 final ConcreteReplicaRequest replicaRequest = new ConcreteReplicaRequest<>(


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