cant send shard started for ; no master known. – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.

This guide will help you check for common problems that cause the log ” cant 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.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up to analyze Elasticsearch configuration and help resolve this error.

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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