Shard target shardId is already replicating – How to solve this OpenSearch exception

Opster Team

Aug-23, Version: 2.9-2.9

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Briefly, this error occurs when an attempt is made to replicate a shard that is already in the process of replication. This could be due to a configuration issue or a network problem causing the system to lose track of ongoing tasks. To resolve this, you can try the following: 1) Check the cluster health and ensure all nodes are properly connected. 2) Review the shard allocation settings and adjust if necessary. 3) If the issue persists, consider restarting the OpenSearch service to reset ongoing tasks. Always ensure to backup your data before making significant changes.

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This guide will help you check for common problems that cause the log ” Shard ” + target.shardId() + ” is already replicating ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: shard, indices, replication.

Log Context

Log “Shard ” + target.shardId() + ” is already replicating” class name is We extracted the following from OpenSearch source code for those seeking an in-depth context :

 final boolean isPresent = onGoingTargetEvents.values()
 .anyMatch(t -> t.equals(target.shardId()));
 if (isPresent) {
 throw new ReplicationFailedException("Shard " + target.shardId() + " is already replicating");
 } else {
 return start(target; activityTimeout);


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