About this task

In an AtScale cluster, a master database instance must always be running on one of the nodes. However, there are times when the node that is running the master database instance needs to be brought offline for maintenance or for other reasons.

By following this procedure, you can cause a standby database instance to become the master, and cause the current master database instance to become a standby. After making this switch, you can take offline the node that formerly was running the master database instance.

Restriction: This procedure works only for AtScale clusters that have no more than two nodes.

Procedure

1. On each node (the order of nodes does not matter), run the following commands to terminate all connections to the AtScale database:

   /opt/atscale/bin/atscale_stop_apps
   /opt/atscale/bin/atscale_service_control stop egress
   

2. On either node, run the following command to find out which node is currently running the master (Leader) database instance:

   /opt/atscale/current/bin/database/postgres_nodes
   

   The output is a table that looks like this:

   Cluster	Member	Host	Role	State	TL	Lag in MB
   atscale_postgres_cluster	atscale-01	atscale-01:10520	Leader	running	1
   atscale_postgres_cluster	atscale-02	atscale-02:10520		running	1

3. On either node, run the following command to move the master (Leader) to the other node:

   /opt/atscale/current/bin/database/standby_switchover
   

4. Once the master (Leader) has been moved to the other node, run the following commands on both nodes to restart the AtScale egress and apps services:

   1. First, run this command:

      /opt/atscale/bin/atscale_service_control start egress
      

   2. Then, run this command:

      /opt/atscale/bin/atscale_start_apps
      

What to do next

You can now take offline the node that was previously running the master database instance. To do this, see the section Starting and Stopping AtScale Services Manually in the topic Managing AtScale Services.