No known master node – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.17

Briefly, this error occurs when Elasticsearch cannot find a master node in the cluster. This could be due to network issues, configuration errors, or the master node being down. To resolve this, you can check the network connectivity between nodes, verify the cluster settings in the Elasticsearch configuration file, or ensure the master node is running and not overloaded. If the master node is down, you may need to promote a data node to be the new master.

This guide will help you check for common problems that cause the log ” no known master node ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: master, node, plugin.

Log Context

Log “no known master node” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 final DiscoveryNodes nodes = state.nodes();
 if (request.isLocal() == false && nodes.isLocalNodeElectedMaster() == false) {
 // Delegates close job to elected master node; so it becomes the coordinating node.
 // See comment in OpenJobAction.Transport class for more information.
 if (nodes.getMasterNode() == null) {
 listener.onFailure(new MasterNotDiscoveredException("no known master node"));
 } else {