You can manually add or remove read-only nodes after you create a PolarDB cluster.

Background information

A PolarDB cluster can contain up to 15 read-only nodes. Each cluster must have at least one read-only node to ensure high availability. All nodes in a cluster have the same specifications.

Billing methods of nodes

You are charged for newly added nodes based on the following billing methods:
  • If nodes are added to a subscription cluster, you are charged based on the subscription billing method.
  • If nodes are added to a pay-as-you-go cluster, you are charged on an hourly basis.
Note
  • You can release subscription or pay-as-you-go read-only nodes at any time. After you release the nodes, the system refunds fees for the remaining subscription period or stops billing. For more information, see Configuration change fees.
  • Only the node specifications of the added nodes are charged. For more information, see Specifications and pricing. The storage fee is charged based on the amount of the used storage, regardless of the number of nodes.

Precautions

  • You can add or remove read-only nodes only when the cluster does not have pending configuration changes.
  • To avoid misoperations, only one read-only node can be added or removed at a time. To add or remove multiple read-only nodes, repeat the operation for multiple times.
  • It takes about five minutes to add or remove a node.

Add a read-only node

  1. Log on to the PolarDB console.
  2. In the upper-left corner of the console, select the region where the cluster is deployed.
  3. You can use the following methods to go to the Add/Remove Node dialog box.
    • Find the cluster and click Add/Remove Node in the Actions column.Clusters
    • Find the cluster, click the cluster ID, and then click Add/Remove Node on the Overview page.Overview page
  4. Select Add Node and click OK.
    Add/Remove Node
  5. Click the Add a read-only node icon to add a read-only node. Read and agree to the service agreement by selecting the check box, and click Buy Now to complete the payment.

Remove a read-only node

  1. Log on to the PolarDB console.
  2. In the upper-left corner of the console, select the region where the cluster is deployed.
  3. You can use the following methods to go to the Add/Remove Node dialog box.
    • Find the cluster and click Add/Remove Node in the Actions column.Clusters
    • Find the cluster, click the cluster ID, and then click Add/Remove Node on the Overview page.Overview page
  4. Select Remove Node and click OK.
    Add/Remove Node
  5. Click the Minus sign (-) icon next to the node that you want to remove. In the dialog box that appears, click OK.
    Note You must retain at least one read-only node in the cluster to ensure high availability.
  6. Read and agree to the service agreement by selecting the check box, and click OK.

Related API operations

API Description
CreateDBNodes Adds nodes to a specified PolarDB cluster.
ModifyDBNodeClass Changes the specifications of nodes in a specified PolarDB cluster.
RestartDBNode Restarts a specified node in a PolarDB cluster.
DeleteDBNodes Removes a specified node from a PolarDB cluster.