Not a primary shard can t move to replica – How to solve this OpenSearch exception

Opster Team

Aug-23, Version: 2.4-2.9

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Briefly, this error occurs when OpenSearch tries to move data from a primary shard to a replica shard, but fails. This could be due to a network issue, a configuration error, or a lack of resources. To resolve this, you can try to manually relocate the shard, check your cluster health and ensure it’s green, or increase the resources available to OpenSearch. If the issue persists, you may need to reindex your data or check your shard allocation settings.

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This guide will help you check for common problems that cause the log ” Not a primary shard; can’t move to replica ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: cluster, routing.

Log Context

Log “Not a primary shard; can’t move to replica” class name is We extracted the following from OpenSearch source code for those seeking an in-depth context :

 * @throws IllegalShardRoutingStateException if shard is already a replica
 public ShardRouting moveActivePrimaryToReplica() {
 assert active() : "expected an active shard " + this;
 if (!primary) {
 throw new IllegalShardRoutingStateException(this; "Not a primary shard; can't move to replica");
 return new ShardRouting(


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