During the development of your business, the volume of data stored in your Elasticsearch cluster and the number of access requests for the cluster continue to change. In this case, you may need to perform cluster update operations such as scale-out, scale-in, version upgrades, or node migration. To implement the operations, Elasticsearch provides two cluster update methods: in-place update and blue-green update. This topic describes the two methods.
- Before you perform a cluster update operation, we recommend that you make sure that each index in your cluster has at least one replica shard. This improves the stability of your cluster.
- When you make a change to a multi-zone cluster, make sure that the number of replica shards of each index in the cluster is less than the number of zones in which the cluster is deployed. After the change is complete, you can manually increase the number of replica shards based on your business requirements. For more information about how to change the number of replica shards of indexes in a cluster, see Index Templates.
Cluster update methods
|Cluster update method||Description||Use scenario||Limit|
|In-place update||The system performs a rolling update for the nodes that you want to update. This process does not involve data migration, and the time that is required for this process is not affected by the data volume of your cluster. However, the performance of your cluster may be affected.||Your cluster encounters a performance bottleneck, and you want to complete a cluster update at the earliest opportunity.||The in-place update method may affect the performance of your cluster. We recommend that you use this method during off-peak hours.|
|Blue-green update||The system adds the same number of nodes to your cluster, seamlessly migrates data from the original nodes to the new nodes, and removes the original nodes from the cluster. This process is seamless but time-consuming, and the IP addresses of nodes are changed.||