Can t send shard started for no master known – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

Briefly, this error occurs when Elasticsearch cannot find a master node in the cluster to send the shard started event. This could be due to network issues, configuration errors, or the master node being down. To resolve this issue, you can check the network connectivity between nodes, ensure that the correct master node is specified in the configuration, or restart the master node if it’s down. Additionally, you can also increase the timeout or set the discovery.zen.minimum_master_nodes to a lower value.

This guide will help you check for common problems that cause the log ” {} can’t send shard started for {}; no master known. ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cluster and shard.

Log Context

Log “{} can’t send shard started for {}; no master known.” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


    public void shardStarted(final ShardRouting shardRouting; String indexUUID; final String reason) {
        DiscoveryNode masterNode = clusterService.state().nodes().masterNode();
        if (masterNode == null) {
            logger.warn("{} can't send shard started for {}; no master known."; shardRouting.shardId(); shardRouting);
        shardStarted(shardRouting; indexUUID; reason; masterNode);


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