No longer master failing t source – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 8.3-8.7

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Briefly, this error occurs when a node in Elasticsearch cluster that was previously acting as a master is no longer in that role. This could be due to network issues, resource constraints, or configuration problems. To resolve this issue, you can check the cluster health and logs to identify any network or resource issues. If there are configuration issues, ensure that the ‘discovery.zen.minimum_master_nodes’ setting is correctly configured. Also, consider increasing the ‘discovery.zen.ping_timeout’ if network latency is high. Lastly, ensure that your cluster has a sufficient number of master-eligible nodes.

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This guide will help you check for common problems that cause the log ” no longer master; failing [” + t.source() + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster.

Log Context

Log “no longer master; failing [” + t.source() + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 logger.debug("executing cluster state update for [{}]"; summary);
 final ClusterState previousClusterState = state();  if (previousClusterState.nodes().isLocalNodeElectedMaster() == false && executor.runOnlyOnMaster()) {
 logger.debug("failing [{}]: local node is no longer master"; summary);
 updateTasks.forEach(t -> t.onFailure(new NotMasterException("no longer master; failing [" + t.source() + "]"); () -> {}));
 }  final long computationStartTime = threadPool.rawRelativeTimeInMillis();
 final var executionResults =;


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