No master known for assignment update – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 8.4-8.9

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Briefly, this error occurs when Elasticsearch cluster is unable to elect a master node. This could be due to network partitioning, high load, or configuration issues. To resolve this, ensure all nodes are reachable and operating under acceptable load. Check your cluster’s health and settings. If necessary, manually set a master node. Also, verify your discovery settings and ensure minimum_master_nodes is properly configured to prevent split-brain scenarios.

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

Log Context

Log “[{}] no master known for assignment update [{}]” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

    ) {
        ClusterState currentState = clusterService.state();
        ClusterStateObserver observer = new ClusterStateObserver(currentState; clusterService; null; logger; threadPool.getThreadContext());
        DiscoveryNode masterNode = currentState.nodes().getMasterNode();
        if (masterNode == null) {
            logger.warn("[{}] no master known for assignment update [{}]"; request.getDeploymentId(); request.getUpdate());
            waitForNewMasterAndRetry(observer; UpdateTrainedModelAssignmentRoutingInfoAction.INSTANCE; request; listener);


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