Cant send shard failed 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 failed 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 failed for {}; no master known.” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


    public void shardFailed(final ShardRouting shardRouting; final String indexUUID; final String message; 
Nullable final Throwable failure) {
        DiscoveryNode masterNode = clusterService.state().nodes().masterNode();
        if (masterNode == null) {
            logger.warn("can't send shard failed for {}; no master known."; shardRouting);
        innerShardFailed(shardRouting; indexUUID; masterNode; message; failure);


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