Joining nodes to a Subscriber-only group v5.6

If you have no subscriber-only groups in your PGD cluster, you must create the groups following the process in Creating Subscriber-only groups and nodes. After you have created a subscriber-only group, you can join subscriber-only nodes to it.

Joining a node to an existing subscriber-only group

Unlike joining a node to a new subscriber-only group, joining a node to an existing subscriber-only group is a simpler process.

First create the new node as a subscriber-only node. Run the following SQL command on the new node:

select bdr.create_node('so-node-2', 'host=so-host-2 dbname=bdrdb port=5444', 'subscriber-only');

or more explicitly with parameter names:

select bdr.create_node(node_name:='so-node-2',
        dsn:='host=so-host-2 dbname=bdrdb port=5444',
        node_type:='subscriber-only');

This command creates a new node named so-node-2 on host so-host-2 and configures it as a subscriber-only node. The node won't be able to join the cluster until joins a group. The DSN h

Now in creating a new subscriber-only group, you created a group named sogroup and added a subscriber-only node called so-node-1 on a host shost-1. It used a node in an existing data group to facilitate that join. Now that the group exists, the node join can leverage the existing node in the group to manage the join. In this case, shost-1, you can use the following SQL command on shost-2 to join it to the sogroup group:

select bdr.join_node_group('host=shost-1 dbname=bdrdb port=5444','sogroup');

or more explicitly with parameter names:

select bdr.join_node_group(dsn:='host=shost-1 dbname=bdrdb port=5444',
        node_group_name:='sogroup');

This command instructs the new node to join the sogroup group. As it has no knowledge of the cluster topology, it connects to the node specified in the DSN to receive the necessary information to join the group.

Once the new node has joined the group, it will begin replicating changes from the other nodes in the cluster.

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