Add nodes to cluster

New nodes that are properly configured are provisioned automatically. When you start a node with the address of at least one other running node in the wsrep_cluster_address variable, this node automatically joins and synchronizes with the cluster.

Note

Existing data and configuration will be replaced to align with those of the DONOR node. To minimize traffic overhead, avoid joining multiple nodes simultaneously.

Percona XtraDB Cluster uses Percona XtraBackup for State Snapshot Transfer and the wsrep_sst_method variable is always set to xtrabackup-v2.

Generate and Copy SSL Certificates

Before starting the nodes, ensure that you generate the SSL certificates on the first node. All nodes must use identical key and certificate files to ensure a consistent security setup. Store the certificates in /etc/, not in the data directory. After generating the certificates, copy them to all other nodes.

1. Generate the SSL certificates on the first node:

   [root@pxc1 ~]# openssl req -newkey rsa:2048 -nodes -keyout /etc/server-key.pem \
   -x509 -days 365 -out /etc/server-cert.pem
   

2. Copy the SSL certificates to the other nodes:

   [root@pxc1 ~]# scp /etc/server-key.pem pxc2:/etc/
   [root@pxc1 ~]# scp /etc/server-cert.pem pxc2:/etc/
   [root@pxc1 ~]# scp /etc/server-key.pem pxc3:/etc/
   [root@pxc1 ~]# scp /etc/server-cert.pem pxc3:/etc/
   

Start the second node

Start the second node using the following command:

[root@pxc2 ~]# systemctl start mysql

After the server starts, it receives SST automatically.

To check the status of the second node, run the following:

mysql@pxc2> show status like 'wsrep%';

Expected output

+----------------------------------+--------------------------------------------------+
| Variable_name                    | Value                                            |
+----------------------------------+--------------------------------------------------+
| wsrep_local_state_uuid           | a08247c1-5807-11ea-b285-e3a50c8efb41             |
| ...                              | ...                                              |
| wsrep_local_state                | 4                                                |
| wsrep_local_state_comment        | Synced                                           |
| ...                              |                                                  |
| wsrep_cluster_size               | 2                                                |
| wsrep_cluster_status             | Primary                                          |
| wsrep_connected                  | ON                                               |
| ...                              | ...                                              |
| wsrep_provider_capabilities      | :MULTI_MASTER:CERTIFICATION: ...                 |
| wsrep_provider_name              | Galera                                           |
| wsrep_provider_vendor            | Codership Oy <[email protected]>                |
| wsrep_provider_version           | 4.3(r752664d)                                    |
| wsrep_ready                      | ON                                               |
| ...                              | ...                                              | 
+----------------------------------+--------------------------------------------------+
75 rows in set (0.00 sec)

The output of SHOW STATUS shows that the new node has been successfully added to the cluster. The cluster size is now 2 nodes, it is the primary component, and it is fully connected and ready to receive write-set replication.

If the state of the second node is Synced as in the previous example, then the node received full SST is synchronized with the cluster, and you can proceed to add the next node.

Note

If the state of the node is Joiner, it means that SST hasn’t finished. Do not add new nodes until all others are in Synced state.

Starting the Third Node

To add the third node, start it as usual:

[root@pxc3 ~]# systemctl start mysql

To check the status of the third node, run the following:

mysql@pxc3> show status like 'wsrep%';

The output shows that the new node has been successfully added to the cluster. Cluster size is now 3 nodes, it is the primary component, and it is fully connected and ready to receive write-set replication.

Expected output

+----------------------------+--------------------------------------+
| Variable_name              | Value                                |
+----------------------------+--------------------------------------+
| wsrep_local_state_uuid     | c2883338-834d-11e2-0800-03c9c68e41ec |
| ...                        | ...                                  |
| wsrep_local_state          | 4                                    |
| wsrep_local_state_comment  | Synced                               |
| ...                        | ...                                  |
| wsrep_cluster_size         | 3                                    |
| wsrep_cluster_status       | Primary                              |
| wsrep_connected            | ON                                   |
| ...                        | ...                                  |
| wsrep_ready                | ON                                   |
+----------------------------+--------------------------------------+
40 rows in set (0.01 sec)

Next steps

When you add all nodes to the cluster, you can verify replication by running queries and manipulating data on nodes to see if these changes are synchronized across the cluster.