Overview

After getting to know the basics of configuring your own inventory file, you can review the following example inventories which describe various environment topographies, including using multiple masters for high availability. You can choose an example that matches your requirements, modify it to match your own environment, and use it as your inventory file when running the installation.

The following example inventories use the default set of node groups when setting openshift_node_group_name per host in the [nodes] group. To define and use your own custom node group definitions, set the openshift_node_groups variable in the inventory file. See Defining Node Groups and Host Mappings for details.

Single Master Examples

You can configure an environment with a single master and multiple nodes, and either a single or multiple number of etcd hosts.

Moving from a single master cluster to multiple masters after installation is not supported.

Single Master, Single etcd, and Multiple Nodes

The following table describes an example environment for a single master (with a single etcd instance running as a static pod on the same host), two nodes for hosting user applications, and two nodes with the node-role.kubernetes.io/infra=true label for hosting dedicated infrastructure:

Host Name Component/Role(s) to Install

master.example.com

Master, etcd, and node

node1.example.com

Compute node

node2.example.com

infra-node1.example.com

Infrastructure node

infra-node2.example.com

You can see these example hosts present in the [masters], [etcd], and [nodes] sections of the following example inventory file:

Single Master, Single etcd, and Multiple Nodes Inventory File
# Create an OSEv3 group that contains the masters, nodes, and etcd groups
[OSEv3:children]
masters
nodes
etcd

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
# SSH user, this user should allow ssh based auth without requiring a password
ansible_ssh_user=root

# If ansible_ssh_user is not root, ansible_become must be set to true
#ansible_become=true

openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# uncomment the following to enable htpasswd authentication; defaults to DenyAllPasswordIdentityProvider
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider'}]

# host group for masters
[masters]
master.example.com

# host group for etcd
[etcd]
master.example.com

# host group for nodes, includes region info
[nodes]
master.example.com openshift_node_group_name='node-config-master'
node1.example.com openshift_node_group_name='node-config-compute'
node2.example.com openshift_node_group_name='node-config-compute'
infra-node1.example.com openshift_node_group_name='node-config-infra'
infra-node2.example.com openshift_node_group_name='node-config-infra'

See Configuring Node Host Labels to ensure you understand the default node selector requirements and node label considerations beginning in OpenShift Container Platform 3.9.

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

Single Master, Multiple etcd, and Multiple Nodes

The following table describes an example environment for a single master, three etcd hosts, two nodes for hosting user applications, and two nodes with the node-role.kubernetes.io/infra=true label for hosting dedicated infrastructure:

Host Name Component/Role(s) to Install

master.example.com

Master and node

etcd1.example.com

etcd

etcd2.example.com

etcd3.example.com

node1.example.com

Compute node

node2.example.com

infra-node1.example.com

Dedicated infrastructure node

infra-node2.example.com

You can see these example hosts present in the [masters], [nodes], and [etcd] sections of the following example inventory file:

Single Master, Multiple etcd, and Multiple Nodes Inventory File
# Create an OSEv3 group that contains the masters, nodes, and etcd groups
[OSEv3:children]
masters
nodes
etcd

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# uncomment the following to enable htpasswd authentication; defaults to DenyAllPasswordIdentityProvider
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider'}]

# host group for masters
[masters]
master.example.com

# host group for etcd
[etcd]
etcd1.example.com
etcd2.example.com
etcd3.example.com

# host group for nodes, includes region info
[nodes]
master.example.com openshift_node_group_name='node-config-master'
node1.example.com openshift_node_group_name='node-config-compute'
node2.example.com openshift_node_group_name='node-config-compute'
infra-node1.example.com openshift_node_group_name='node-config-infra'
infra-node2.example.com openshift_node_group_name='node-config-infra'

See Configuring Node Host Labels to ensure you understand the default node selector requirements and node label considerations beginning in OpenShift Container Platform 3.9.

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

Multiple Masters Examples

You can configure an environment with multiple masters, multiple etcd hosts, and multiple nodes. Configuring multiple masters for high availability (HA) ensures that the cluster has no single point of failure.

Moving from a single master cluster to multiple masters after installation is not supported.

When configuring multiple masters, the cluster installation process supports the native high availability (HA) method. This method leverages the native HA master capabilities built into OpenShift Container Platform and can be combined with any load balancing solution.

If a host is defined in the [lb] section of the inventory file, Ansible installs and configures HAProxy automatically as the load balancing solution. If no host is defined, it is assumed you have pre-configured an external load balancing solution of your choice to balance the master API (port 8443) on all master hosts.

This HAProxy load balancer is intended to demonstrate the API server’s HA mode and is not recommended for production environments. If you are deploying to a cloud provider, Red Hat recommends deploying a cloud-native TCP-based load balancer or take other steps to provide a highly available load balancer.

For an external load balancing solution, you must have:

  • A pre-created load balancer virtual IP (VIP) configured for SSL passthrough.

  • A VIP listening on the port specified by the openshift_master_api_port value (8443 by default) and proxying back to all master hosts on that port.

  • A domain name for VIP registered in DNS.

    • The domain name will become the value of both openshift_master_cluster_public_hostname and openshift_master_cluster_hostname in the OpenShift Container Platform installer.

See the External Load Balancer Integrations example in Github for more information. For more on the high availability master architecture, see Kubernetes Infrastructure.

The cluster installation process does not currently support multiple HAProxy load balancers in an active-passive setup. See the Load Balancer Administration documentation for post-installation amendments.

To configure multiple masters, refer to Multiple Masters with Multiple etcd

Multiple Masters Using Native HA with External Clustered etcd

The following describes an example environment for three masters using the native HA method:, one HAProxy load balancer, three etcd hosts, two nodes for hosting user applications, and two nodes with the node-role.kubernetes.io/infra=true label for hosting dedicated infrastructure:

Host Name Component/Role(s) to Install

master1.example.com

Master (clustered using native HA) and node

master2.example.com

master3.example.com

lb.example.com

HAProxy to load balance API master endpoints

etcd1.example.com

etcd

etcd2.example.com

etcd3.example.com

node1.example.com

Compute node

node2.example.com

infra-node1.example.com

Dedicated infrastructure node

infra-node2.example.com

You can see these example hosts present in the [masters], [etcd], [lb], and [nodes] sections of the following example inventory file:

Multiple Masters Using HAProxy Inventory File
# Create an OSEv3 group that contains the master, nodes, etcd, and lb groups.
# The lb group lets Ansible configure HAProxy as the load balancing solution.
# Comment lb out if your load balancer is pre-configured.
[OSEv3:children]
masters
nodes
etcd
lb

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# uncomment the following to enable htpasswd authentication; defaults to DenyAllPasswordIdentityProvider
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider'}]

# Native high availbility cluster method with optional load balancer.
# If no lb group is defined installer assumes that a load balancer has
# been preconfigured. For installation the value of
# openshift_master_cluster_hostname must resolve to the load balancer
# or to one or all of the masters defined in the inventory if no load
# balancer is present.
openshift_master_cluster_method=native
openshift_master_cluster_hostname=openshift-internal.example.com
openshift_master_cluster_public_hostname=openshift-cluster.example.com

# apply updated node defaults
openshift_node_groups=[{'name': 'node-config-all-in-one', 'labels': ['node-role.kubernetes.io/master=true', 'node-role.kubernetes.io/infra=true', 'node-role.kubernetes.io/compute=true'], 'edits': [{ 'key': 'kubeletArguments.pods-per-core','value': ['20']}]}]

# host group for masters
[masters]
master1.example.com
master2.example.com
master3.example.com

# host group for etcd
[etcd]
etcd1.example.com
etcd2.example.com
etcd3.example.com

# Specify load balancer host
[lb]
lb.example.com

# host group for nodes, includes region info
[nodes]
master[1:3].example.com openshift_node_group_name='node-config-master'
node1.example.com openshift_node_group_name='node-config-compute'
node2.example.com openshift_node_group_name='node-config-compute'
infra-node1.example.com openshift_node_group_name='node-config-infra'
infra-node2.example.com openshift_node_group_name='node-config-infra'

See Configuring Node Host Labels to ensure you understand the default node selector requirements and node label considerations beginning in OpenShift Container Platform 3.9.

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

Multiple Masters Using Native HA with Co-located Clustered etcd

The following describes an example environment for three masters using the native HA method (with etcd running as a static pod on each host), one HAProxy load balancer, two nodes for hosting user applications, and two nodes with the node-role.kubernetes.io/infra=true label for hosting dedicated infrastructure:

Host Name Component/Role(s) to Install

master1.example.com

Master (clustered using native HA) and node with etcd running as a static pod on each host

master2.example.com

master3.example.com

lb.example.com

HAProxy to load balance API master endpoints

node1.example.com

Compute node

node2.example.com

infra-node1.example.com

Dedicated infrastructure node

infra-node2.example.com

You can see these example hosts present in the [masters], [etcd], [lb], and [nodes] sections of the following example inventory file:

# Create an OSEv3 group that contains the master, nodes, etcd, and lb groups.
# The lb group lets Ansible configure HAProxy as the load balancing solution.
# Comment lb out if your load balancer is pre-configured.
[OSEv3:children]
masters
nodes
etcd
lb

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# uncomment the following to enable htpasswd authentication; defaults to DenyAllPasswordIdentityProvider
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider'}]

# Native high availability cluster method with optional load balancer.
# If no lb group is defined installer assumes that a load balancer has
# been preconfigured. For installation the value of
# openshift_master_cluster_hostname must resolve to the load balancer
# or to one or all of the masters defined in the inventory if no load
# balancer is present.
openshift_master_cluster_method=native
openshift_master_cluster_hostname=openshift-internal.example.com
openshift_master_cluster_public_hostname=openshift-cluster.example.com

# host group for masters
[masters]
master1.example.com
master2.example.com
master3.example.com

# host group for etcd
[etcd]
master1.example.com
master2.example.com
master3.example.com

# Specify load balancer host
[lb]
lb.example.com

# host group for nodes, includes region info
[nodes]
master[1:3].example.com openshift_node_group_name='node-config-master'
node1.example.com openshift_node_group_name='node-config-compute'
node2.example.com openshift_node_group_name='node-config-compute'
infra-node1.example.com openshift_node_group_name='node-config-infra'
infra-node2.example.com openshift_node_group_name='node-config-infra'

See Configuring Node Host Labels to ensure you understand the default node selector requirements and node label considerations beginning in OpenShift Container Platform 3.9.

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.