No master known for action for shard entry – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch cannot find a master node to perform a specific action for a shard entry. 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, ensure the cluster settings are correct, or restart the master node. If the issue persists, consider increasing the or discovery.zen.minimum_master_nodes settings to improve cluster stability.

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

Log Context

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

        final ActionListener listener
    ) {
        ClusterStateObserver observer = new ClusterStateObserver(currentState; clusterService; null; logger; threadPool.getThreadContext());
        DiscoveryNode masterNode = currentState.nodes().getMasterNode();
        if (masterNode == null) {
            logger.warn("no master known for action [{}] for shard entry [{}]"; actionName; request);
            waitForNewMasterAndRetry(actionName; observer; request; listener);
        } else {
            logger.debug("sending [{}] to [{}] for shard entry [{}]"; actionName; masterNode.getId(); request);
            transportService.sendRequest(masterNode; actionName; request; new EmptyTransportResponseHandler(ThreadPool.Names.SAME) {


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