Chapter 6. Adding Hosts to an Existing Cluster

Re-run the installer with the install subcommand in interactive or unattended mode:

$ atomic-openshift-installer [-u] [-c </path/to/file>] install

The installer detects your current environment and allows you to either add an additional node or re-perform a clean install:

Gathering information from hosts...
Installed environment detected.
By default the installer only adds new nodes to an installed environment.
Do you want to (1) only add additional nodes or (2) perform a clean install?:

Choose (1) and follow the on-screen instructions to complete your desired task.

Ensure you have the latest playbooks by updating the atomic-openshift-utils package:

# yum update atomic-openshift-utils

Edit your /etc/ansible/hosts file and add new_<host_type> to the [OSEv3:children] section:

For example, to add a new node host, add new_nodes:

[OSEv3:children]
masters
nodes
new_nodes

To add new master hosts, add new_masters.

Create a [new_<host_type>] section much like an existing section, specifying host information for any new hosts you want to add. For example, when adding a new node:

[nodes]
master[1:3].example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"

[new_nodes]
node3.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"

See Configuring Host Variables for more options.

When adding new masters, hosts added to the [new_masters] section must also be added to the [new_nodes] section with the openshift_schedulable=false variable. This ensures the new master host is part of the OpenShift SDN and that pods are not scheduled for placement on them. For example:

[masters]
master[1:2].example.com

[new_masters]
master3.example.com

[nodes]
node[1:3].example.com openshift_node_labels="{'region': 'infra'}"
master[1:2].example.com openshift_schedulable=false

[new_nodes]
master3.example.com openshift_schedulable=false

Run the scaleup.yml playbook. If your inventory file is located somewhere other than the default of /etc/ansible/hosts, specify the location with the -i option.

For additional nodes:

# ansible-playbook [-i /path/to/file] \
    /usr/share/ansible/openshift-ansible/playbooks/byo/openshift-node/scaleup.yml

For additional masters:

# ansible-playbook [-i /path/to/file] \
    /usr/share/ansible/openshift-ansible/playbooks/byo/openshift-master/scaleup.yml

Finally, move any hosts you had defined in the [new_<host_type>] section into their appropriate section (but leave the [new_<host_type>] section definition itself in place) so that subsequent runs using this inventory file are aware of the nodes but do not handle them as new nodes. For example, when adding new nodes:

[nodes]
master[1:3].example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
node3.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"

[new_nodes]