How to add a node for high availability

in Overview and setup

Lewis Stonier

Published: Aug 3, 2023|Last updated: Aug 9, 2023

How to add a node for high availability

This guide is for adding a node to an OPC cluster and configuring it for high availability.

This mode will add a secondary node to the cluster which is automatically placed in standy mode. The standby nodes will be unavailable for normal use and will remain on standby until you manually promote it to a main node.

GUI Method

Warning

The cluster is designed to have nodes added that have a clean install of the On-Premise-Controller and no helpdesk instances on.
If you are adding a node that already has a Deskpro helpdesk instance already present, this can lead to errors and the overwriting of any data on the standby node.

From the cluster menu, go to the Secondary node card and click 'Add Ssecondary Node'

The next menu will prompt for the node details.

IP Address - The IP address of the node being added

Port - the SSH port that is in use

User name - The user you are configuring HA for, this can be the root user or a custom SSH user

Note

If you are setting a custom user you will need to make sure that they are in the below user groups as well as adding the user to the /etc/sudoers file on each node in the cluster: deskpro_admin adm sudo

Authorization Method - For initial node setup we support both password and SSH key (guide) methods for the initial configuration. The cluster setup will add it's own SSH key pairs for the service once the node is added.

Once the configuration is filled out, click 'save' and the OPC will run through connectivity checks then configure the node, adding it to the cluster.

Clicking continue will take you back to the cluster menu where the new node will be listed in the secondary node card.

You can repeat this process for any other additional nodes you want to add.

CLI Method

Warning

The cluster is designed to have nodes added that have a clean install of the On-Premise-Controller and no helpdesk instances on. If you are adding a node that already has a Deskpro helpdesk instance already present, this can lead to errors and the overwriting of any data on the standby node.

To add a node to a cluster on the command line you need to run the node add command on the main node in the cluster. You can only add a new node to the cluster from the main node.

For initial node setup we support both password and SSH key (guide) methods for the initial configuration. The cluster setup will add it's own SSH key pairs for the service once the node is added.

Using SSH Key pairs You will need to setup SSH key pairs between all the servers in your cluster before setting up the cluster with this method. If using a user other than root please change the --ssh-user field to match your custom user.

opc cluster node add --ssh-host IPADDRESS --ssh-user root --ssh-key-path ~/.ssh/KEYFILE
 copy

Using Password auth You can use password auth to connect the nodes of the cluster. If using a user other than root please change the --ssh-user field to match your custom user.

opc cluster node add --ssh-host IPADDRESS --ssh-user root --ssh-password PASSWORD
 copy

Once the configuration is filled out, click 'save' and the OPC will run through connectivity checks then configure the node, adding it to the cluster.