Adding or Deleting a Standby Node ​

Availability ​

This feature is available since openGauss 2.0.0.

Introduction ​

Standby nodes can be added and deleted.

Benefits ​

If the read pressure of the primary node is high or you want to improve the disaster recovery capability of the database, you need to add a standby node. If some standby nodes in a cluster are faulty and cannot be recovered within a short period of time, you can delete the faulty nodes to ensure that the cluster is running properly.

Description ​

openGauss can be scaled out from a single node or one primary and multiple standbys to one primary and eight standbys. Cascaded standby nodes can be added. Standby nodes can be added when a faulty standby node exists in the cluster. One primary and multiple standbys can be scaled in to a single node. A faulty standby node can be deleted.

Standby nodes can be added or deleted online without affecting the primary node.

Enhancements ​

None.

Constraints ​

For adding a standby node:

• Ensure that the openGauss image package exists on the primary node.

• Ensure that the same users and user groups as those on the primary node have been created on the new standby node.

• Ensure that the mutual trust of user root and the database management user has been established between the existing database nodes and the new nodes.

• Ensure that the XML file has been properly configured and information about the standby node to be scaled has been added to the installed database configuration file.

• Ensure that only user root is authorized to run the scale-out command.

• Do not run the gs_dropnode command on the primary node to delete other standby nodes at the same time.

• Ensure that the environment variables of the primary node have been imported before the scale-out command is run.

• Ensure that the operating system of the new standby node is the same as that of the primary node.

• Do not perform an primary/standby switchover or failover on other standby nodes at the same time.

For deleting a standby node:

• Delete the standby node only on the primary node.
• Do not perform an primary/standby switchover or failover on other standby nodes at the same time.
• Do not run the gs_expansion command on the primary node for scale-out at the same time.
• Do not run the gs_dropnode command twice at the same time.
• Before deletion, ensure that the database management user trust relationship has been established between the primary and standby nodes.
• Run this command as a database administrator.
• Before running commands, run the source command to import environment variables of the primary node.

Dependencies ​

None.