You cannot directly set hot standby nodes when you create a cluster. You can only enable the failover with hot standby feature for existing read-only nodes in your cluster.

Prerequisites

  • Only Cluster Edition of PolarDB for MySQL supports the failover with hot standby feature. One of the following PolarDB for MySQL clusters is created:
    • A PolarDB for MySQL 5.6 cluster whose revision version is 5.6.1.0.35 or later
    • A PolarDB for MySQL 5.7 cluster whose revision version is 5.7.1.0.24 or later
    • A PolarDB for MySQL 8.0.1 cluster whose revision version is 8.0.1.1.29 or later
    • A PolarDB for MySQL 8.0.2 cluster whose revision version is 8.0.2.2.12 or later
  • PolarDB for MySQL PolarProxy must be 2.8.1 or later. For more information about how to view and update the PolarProxy version, see Upgrade the cluster version.

Precautions

  • If the failover with hot standby feature is not enabled for read-only nodes, your services may be interrupted for about 20 to 30 seconds when failover occurs. Therefore, make sure that your applications can be automatically reconnected to the cluster. If the hot standby feature is enabled for read-only nodes, failover can be completed within 3 to 10 seconds.
  • The specifications of hot standby nodes must be the same as those of the primary node.
  • The failover with hot standby feature cannot be enabled along with the in-memory column index feature. If a cluster contains a read-only column store node, you cannot enable the failover with hot standby feature on any read-only nodes in the cluster.
  • The transaction resumable upload feature must be separately enabled. To enable this feature, you must set the loose_innodb_trx_resume parameter to ON on the Parameters page in the PolarDB console. For more information, see Specify cluster and node parameters.

Procedure

  1. Log on to the PolarDB console.
  2. In the upper-left corner of the console, select the region in which the cluster that you want to manage is deployed.
  3. Find the cluster and click the cluster ID.
  4. In the Database Nodes section of the Overview page, click the Failover icon in the upper-right corner of the section to switch views.
  5. In the Database Nodes section, find the read-only node for which you want to enable hot standby and click Enable Hot Standby in the Actions column.
    Enable the failover with hot standby feature
    Note When the failover with hot standby feature is enabled for the first time, all nodes in the cluster are restarted one by one. When the failover with hot standby feature is enabled or disabled in the future, the nodes will not be restarted.