No longer master source source – How to solve this OpenSearch exception

Opster Team

Aug-23, Version: 1-1.3

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Briefly, this error occurs when the OpenSearch cluster loses its master node. The master node is responsible for managing the state of the cluster, and if it fails or becomes unreachable, other nodes may not be able to perform their tasks. To resolve this issue, you can try the following: 1) Check the network connectivity between the nodes. 2) Increase the ‘discovery.zen.minimum_master_nodes’ setting to ensure a stable master node. 3) Ensure that the master node has sufficient resources (CPU, memory, disk space) to handle its tasks. 4) Check the OpenSearch logs for more detailed error information.

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

Log Context

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

 * called when the task was rejected because the local node is no longer master.
 * Used only for tasks submitted to {@link MasterService}.
 default void onNoLongerMaster(String source) {
 onFailure(source; new NotMasterException("no longer master. source: [" + source + "]"));
 }  /**
 * Called when the result of the {@link ClusterStateTaskExecutor#execute(ClusterState; List)} have been processed
 * properly by all listeners.


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