Failed to send shard started to – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

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Briefly, this error occurs when Elasticsearch is unable to notify the cluster that a shard has started. This could be due to network issues, node failures, or configuration problems. To resolve this issue, you can try the following: 1) Check the network connectivity between the nodes in the cluster. 2) Verify the health of the nodes and restart any that are failing. 3) Review the cluster settings and correct any misconfigurations. 4) If the problem persists, consider increasing the timeout settings for shard operations.

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This guide will help you check for common problems that cause the log ” failed to send shard started to [{}] ” 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 “failed to send shard started to [{}]” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

         logger.debug("{} sending shard started for {}"; shardRoutingEntry.shardRouting.shardId(); shardRoutingEntry);
                SHARD_STARTED_ACTION_NAME; new ShardRoutingEntry(shardRouting; indexUUID; reason; null); new EmptyTransportResponseHandler(ThreadPool.Names.SAME) {
                    public void handleException(TransportException exp) {
                        logger.warn("failed to send shard started to [{}]"; exp; masterNode);



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