How can a Couchbase cluster be expanded or reduced?

The Couchbase cluster can be scaled up or down by adding or removing nodes. Below are the specific steps:

Expand cluster:

1. Install the Couchbase Server software on the machine where you want to add a new node.
2. Open the Couchbase Web Console and click on the “Servers” tab.
3. Click on the “Add Server” button and enter the IP address and administrator credentials for the new node.
4. Select the type of service you want to add (such as data node or query node) in the pop-up dialog box, then click the “Add Server” button.
5. New nodes will be added to the cluster, which will automatically start receiving data and balancing the load.

Reduce cluster size.

1. Open the Couchbase Web console on the node to be removed and click on the “Servers” tab.
2. Click on the name of the node you want to remove, then click on the “Remove Server” button in the dialog box that pops up.
3. Confirming the operation to remove the node, the system will automatically remove the data and load from the node, and exclude it from the cluster.

Make sure that all nodes can communicate properly and back up data to prevent data loss when expanding and shrinking the cluster. Also, ensure that the hardware configuration and network settings of new nodes match those of existing nodes to maintain the performance and stability of the entire cluster.