Advanced Installation - Installing a Cluster | Installation and Configuration

Overview

A reference configuration implemented using Ansible playbooks is available as the advanced installation method for installing a OpenShift Container Platform cluster. Familiarity with Ansible is assumed, however you can use this configuration as a reference to create your own implementation using the configuration management tool of your choosing.

While RHEL Atomic Host is supported for running containerized OpenShift Container Platform services, the advanced installation method utilizes Ansible, which is not available in RHEL Atomic Host, and must therefore be run from a RHEL 7 system. The host initiating the installation does not need to be intended for inclusion in the OpenShift Container Platform cluster, but it can be.

Alternatively, you can use the quick installation method if you prefer an interactive installation experience.

To install OpenShift Container Platform as a stand-alone registry, see Installing a Stand-alone Registry.

Running Ansible playbooks with the --tags or --check options is not supported by Red Hat.

Before You Begin

Before installing OpenShift Container Platform, you must first see the Prerequisites and Host Preparation topics to prepare your hosts. This includes verifying system and environment requirements per component type and properly installing and configuring Docker. It also includes installing Ansible version 2.2.0 or later, as the advanced installation method is based on Ansible playbooks and as such requires directly invoking Ansible.

If you are interested in installing OpenShift Container Platform using the containerized method (optional for RHEL but required for RHEL Atomic Host), see RPM vs Containerized to ensure that you understand the differences between these methods, then return to this topic to continue.

After following the instructions in the Prerequisites topic and deciding between the RPM and containerized methods, you can continue in this topic to Configuring Ansible.

Configuring Ansible

The /etc/ansible/hosts file is Ansible’s inventory file for the playbook to use during the installation. The inventory file describes the configuration for your OpenShift Container Platform cluster. You must replace the default contents of the file with your desired configuration.

The following sections describe commonly-used variables to set in your inventory file during an advanced installation, followed by example inventory files you can use as a starting point for your installation. The examples 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 advanced installation.

Configuring Host Variables

To assign environment variables to hosts during the Ansible installation, indicate the desired variables in the /etc/ansible/hosts file after the host entry in the [masters] or [nodes] sections. For example:

[masters]
ec2-52-6-179-239.compute-1.amazonaws.com openshift_public_hostname=ose3-master.public.example.com

The following table describes variables for use with the Ansible installer that can be assigned to individual host entries:

Table 1. Host Variables
Variable	Purpose
`openshift_hostname`	This variable overrides the internal cluster host name for the system. Use this when the system’s default IP address does not resolve to the system host name.
`openshift_public_hostname`	This variable overrides the system’s public host name. Use this for cloud installations, or for hosts on networks using a network address translation (NAT).
`openshift_ip`	This variable overrides the cluster internal IP address for the system. Use this when using an interface that is not configured with the default route. This variable can also be used for etcd.
`openshift_public_ip`	This variable overrides the system’s public IP address. Use this for cloud installations, or for hosts on networks using a network address translation (NAT).
`containerized`	If set to true, containerized OpenShift Container Platform services are run on target master and node hosts instead of installed using RPM packages. If set to false or unset, the default RPM method is used. RHEL Atomic Host requires the containerized method, and is automatically selected for you based on the detection of the */run/ostree-booted* file. See RPM vs Containerized for more details. Containerized installations are supported starting in OpenShift Container Platform 3.1.1.
`openshift_node_labels`	This variable adds labels to nodes during installation. See Configuring Node Host Labels for more details.
`openshift_node_kubelet_args`	This variable is used to configure `kubeletArguments` on nodes, such as arguments used in container and image garbage collection, and to specify resources per node. `kubeletArguments` are key value pairs that are passed directly to the Kubelet that match the Kubelet’s command line arguments. `kubeletArguments` are not migrated or validated and may become invalid if used. These values override other settings in node configuration which may cause invalid configurations. Example usage: {'image-gc-high-threshold': ['90'],'image-gc-low-threshold': ['80']}.
`openshift_docker_options`	This variable configures additional Docker options within */etc/sysconfig/docker, such as options used in Managing Container Logs. Example usage: "--log-driver json-file --log-opt max-size=1M --log-opt max-file=3"*.
`openshift_schedulable`	This variable configures whether the host is marked as a schedulable node, meaning that it is available for placement of new pods. See Configuring Schedulability on masters.

Image Version Policy

Images require a version number policy in order to maintain updates. See the Image Version Tag Policy section in the Architecture Guide for more information.

Configuring Cluster Variables

To assign environment variables during the Ansible install that apply more globally to your OpenShift Container Platform cluster overall, indicate the desired variables in the /etc/ansible/hosts file on separate, single lines within the [OSEv3:vars] section. For example:

[OSEv3:vars]

openshift_master_identity_providers=[{'name': 'htpasswd_auth',
'login': 'true', 'challenge': 'true',
'kind': 'HTPasswdPasswordIdentityProvider',
'filename': '/etc/origin/master/htpasswd'}]

openshift_master_default_subdomain=apps.test.example.com

The following table describes variables for use with the Ansible installer that can be assigned cluster-wide:

Table 2. Cluster Variables
Variable	Purpose
`ansible_ssh_user`	This variable sets the SSH user for the installer to use and defaults to root. This user should allow SSH-based authentication without requiring a password. If using SSH key-based authentication, then the key should be managed by an SSH agent.
`ansible_become`	If `ansible_ssh_user` is not root, this variable must be set to true and the user must be configured for passwordless sudo.
`debug_level`	This variable sets which INFO messages are logged to the `systemd-journald.service`. Set one of the following: `0` to log errors and warnings only `2` to log normal information (This is the default level.) `4` to log debugging-level information `6` to log API-level debugging information (request / response) `8` to log body-level API debugging information For more information on debug log levels, see Configuring Logging Levels.
`containerized`	If set to true, containerized OpenShift Container Platform services are run on all target master and node hosts in the cluster instead of installed using RPM packages. If set to false or unset, the default RPM method is used. RHEL Atomic Host requires the containerized method, and is automatically selected for you based on the detection of the */run/ostree-booted* file. See RPM vs Containerized for more details. Containerized installations are supported starting in OpenShift Container Platform 3.1.1.
`openshift_master_cluster_hostname`	This variable overrides the host name for the cluster, which defaults to the host name of the master.
`openshift_master_cluster_public_hostname`	This variable overrides the public host name for the cluster, which defaults to the host name of the master. If you use an external load balancer, specify the address of the external load balancer. For example: ---- openshift_master_cluster_public_hostname=openshift-ansible.public.example.com ----
`openshift_master_cluster_method`	Optional. This variable defines the HA method when deploying multiple masters. Supports the `native` method. See Multiple masters for more information.
`openshift_rolling_restart_mode`	This variable enables rolling restarts of HA masters (i.e., masters are taken down one at a time) when running the upgrade playbook directly. It defaults to `services`, which allows rolling restarts of services on the masters. It can instead be set to `system`, which enables rolling, full system restarts and also works for single master clusters.
`os_sdn_network_plugin_name`	This variable configures which OpenShift Container Platform SDN plug-in to use for the pod network, which defaults to redhat/openshift-ovs-subnet for the standard SDN plug-in. Set the variable to redhat/openshift-ovs-multitenant to use the multitenant plug-in.
`openshift_master_identity_providers`	This variable overrides the identity provider, which defaults to Deny All.
`openshift_master_named_certificates`	These variables are used to configure custom certificates which are deployed as part of the installation. See Configuring Custom Certificates for more information.
`openshift_master_overwrite_named_certificates`
`openshift_master_session_name`	These variables override defaults for session options in the OAuth configuration. See Configuring Session Options for more information.
`openshift_master_session_max_seconds`
`openshift_master_session_auth_secrets`
`openshift_master_session_encryption_secrets`
`openshift_portal_net`	This variable configures the subnet in which services will be created within the OpenShift Container Platform SDN. This network block should be private and must not conflict with any existing network blocks in your infrastructure to which pods, nodes, or the master may require access to, or the installation will fail. Defaults to 172.30.0.0/16, and cannot be re-configured after deployment. If changing from the default, avoid 172.17.0.0/16, which the docker0 network bridge uses by default, or modify the docker0 network.
`openshift_master_default_subdomain`	This variable overrides the default subdomain to use for exposed routes.
`openshift_node_proxy_mode`	This variable specifies the service proxy mode to use: either iptables for the default, pure-iptables implementation, or userspace for the user space proxy.
`openshift_hosted_router_selector`	Default node selector for automatically deploying router pods. See Configuring Node Host Labels for details.
`openshift_registry_selector`	Default node selector for automatically deploying registry pods. See Configuring Node Host Labels for details.
`osm_default_node_selector`	This variable overrides the node selector that projects will use by default when placing pods.
`osm_cluster_network_cidr`	This variable overrides the SDN cluster network CIDR block. This is the network from which pod IPs are assigned. This network block should be a private block and must not conflict with existing network blocks in your infrastructure to which pods, nodes, or the master may require access. Defaults to 10.128.0.0/14 and cannot be arbitrarily re-configured after deployment, although certain changes to it can be made in the SDN master configuration.
`osm_host_subnet_length`	This variable specifies the size of the per host subnet allocated for pod IPs by OpenShift Container Platform SDN. Defaults to 9 which means that a subnet of size /23 is allocated to each host; for example, given the default 10.128.0.0/14 cluster network, this will allocate 10.128.0.0/23, 10.128.2.0/23, 10.128.4.0/23, and so on. This cannot be re-configured after deployment.
`openshift_docker_additional_registries`	OpenShift Container Platform adds the specified additional registry or registries to the Docker configuration.
`openshift_docker_insecure_registries`	OpenShift Container Platform adds the specified additional insecure registry or registries to the Docker configuration.
`openshift_docker_blocked_registries`	OpenShift Container Platform adds the specified blocked registry or registries to the Docker configuration.
`openshift_hosted_metrics_public_url`	This variable sets the host name for integration with the metrics console. The default is `https://hawkular-metrics.{{openshift_master_default_subdomain}}/hawkular/metrics` If you alter this variable, ensure the host name is accessible via your router.

Configuring a Registry Location

If you are using an image registry other than the default at registry.access.redhat.com, specify the desired registry within the /etc/ansible/hosts file.

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

Table 3. Registry Variables
Variable	Purpose
`oreg_url`	Set to the alternate image location. Necessary if you are not using the default registry at `registry.access.redhat.com`.
`openshift_examples_modify_imagestreams`	Set to `true` if pointing to a registry other than the default. Modifies the image stream location to the value of `oreg_url`.

Configuring Global Proxy Options

If your hosts require use of a HTTP or HTTPS proxy in order to connect to external hosts, there are many components that must be configured to use the proxy, including masters, Docker, and builds. Node services only connect to the master API requiring no external access and therefore do not need to be configured to use a proxy.

In order to simplify this configuration, the following Ansible variables can be specified at a cluster or host level to apply these settings uniformly across your environment.

See Configuring Global Build Defaults and Overrides for more information on how the proxy environment is defined for builds.

Table 4. Cluster Proxy Variables
Variable	Purpose
`openshift_http_proxy`	This variable specifies the `HTTP_PROXY` environment variable for masters and the Docker daemon.
`openshift_https_proxy`	This variable specifices the `HTTPS_PROXY` environment variable for masters and the Docker daemon.
`openshift_no_proxy`	This variable is used to set the `NO_PROXY` environment variable for masters and the Docker daemon. This value should be set to a comma separated list of host names or wildcard host names that should not use the defined proxy. This list will be augmented with the list of all defined OpenShift Container Platform host names by default.
`openshift_generate_no_proxy_hosts`	This boolean variable specifies whether or not the names of all defined OpenShift hosts and `.cluster.local` should be automatically appended to the `NO_PROXY` list. Defaults to true; set it to false* to override this option.
`openshift_builddefaults_http_proxy`	This variable defines the `HTTP_PROXY` environment variable inserted into builds using the `BuildDefaults` admission controller. If `openshift_http_proxy` is set, this variable will inherit that value; you only need to set this if you want your builds to use a different value.
`openshift_builddefaults_https_proxy`	This variable defines the `HTTPS_PROXY` environment variable inserted into builds using the `BuildDefaults` admission controller. If `openshift_https_proxy` is set, this variable will inherit that value; you only need to set this if you want your builds to use a different value.
`openshift_builddefaults_no_proxy`	This variable defines the `NO_PROXY` environment variable inserted into builds using the `BuildDefaults` admission controller. If `openshift_no_proxy` is set, this variable will inherit that value; you only need to set this if you want your builds to use a different value.
`openshift_builddefaults_git_http_proxy`	This variable defines the HTTP proxy used by `git clone` operations during a build, defined using the `BuildDefaults` admission controller. If `openshift_builddefaults_http_proxy` is set, this variable will inherit that value; you only need to set this if you want your `git clone` operations to use a different value.
`openshift_builddefaults_git_https_proxy`	This variable defines the HTTPS proxy used by `git clone` operations during a build, defined using the `BuildDefaults` admission controller. If `openshift_builddefaults_https_proxy` is set, this variable will inherit that value; you only need to set this if you want your `git clone` operations to use a different value.

Configuring Schedulability on masters

Any hosts you designate as masters during the installation process should also be configured as nodes so that the masters are configured as part of the OpenShift SDN. You must do so by adding entries for these hosts to the [nodes] section:

[nodes]
master.example.com

In order to ensure that your masters are not burdened with running pods, they are automatically marked unschedulable by default by the installer, meaning that new pods cannot be placed on the hosts. This is the same as setting the openshift_schedulable=false host variable.

You can manually set a master host to schedulable during installation using the openshift_schedulable=true host variable, though this is not recommended in production environments:

[nodes]
master.example.com openshift_schedulable=true

If you want to change the schedulability of a host post-installation, see Marking Nodes as Unschedulable or Schedulable.

Configuring Node Host Labels

You can assign labels to node hosts during the Ansible install by configuring the /etc/ansible/hosts file. Labels are useful for determining the placement of pods onto nodes using the scheduler. Other than region=infra (discussed in Configuring Dedicated Infrastructure Nodes), the actual label names and values are arbitrary and can be assigned however you see fit per your cluster’s requirements.

To assign labels to a node host during an Ansible install, use the openshift_node_labels variable with the desired labels added to the desired node host entry in the [nodes] section. In the following example, labels are set for a region called primary and a zone called east:

[nodes]
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"

Configuring Dedicated Infrastructure Nodes

The openshift_router_selector and openshift_registry_selector Ansible settings determine the label selectors used when placing registry and router pods. They are set to region=infra by default:

# default selectors for router and registry services
# openshift_router_selector='region=infra'
# openshift_registry_selector='region=infra'

The default router and registry will be automatically deployed during installation if nodes exist in the [nodes] section that match the selector settings. For example:

[nodes]
infra-node1.example.com openshift_node_labels="{'region': 'infra','zone': 'default'}"

The registry and router are only able to run on node hosts with the region=infra label. Ensure that at least one node host in your OpenShift Container Platform environment has the region=infra label.

It is recommended for production environments that you maintain dedicated infrastructure nodes where the registry and router pods can run separately from pods used for user applications.

As described in Configuring Schedulability on masters, master hosts are marked unschedulable by default. If you label a master host with region=infra and have no other dedicated infrastructure nodes, you must also explicitly mark these master hosts as schedulable. Otherwise, the registry and router pods cannot be placed anywhere:

[nodes]
master.example.com openshift_node_labels="{'region': 'infra','zone': 'default'}" openshift_schedulable=true

Configuring Session Options

Session options in the OAuth configuration are configurable in the inventory file. By default, Ansible populates a sessionSecretsFile with generated authentication and encryption secrets so that sessions generated by one master can be decoded by the others. The default location is /etc/origin/master/session-secrets.yaml, and this file will only be re-created if deleted on all masters.

You can set the session name and maximum number of seconds with openshift_master_session_name and openshift_master_session_max_seconds:

openshift_master_session_name=ssn
openshift_master_session_max_seconds=3600

If provided, openshift_master_session_auth_secrets and openshift_master_encryption_secrets must be equal length.

For openshift_master_session_auth_secrets, used to authenticate sessions using HMAC, it is recommended to use secrets with 32 or 64 bytes:

openshift_master_session_auth_secrets=['DONT+USE+THIS+SECRET+b4NV+pmZNSO']

For openshift_master_encryption_secrets, used to encrypt sessions, secrets must be 16, 24, or 32 characters long, to select AES-128, AES-192, or AES-256:

openshift_master_session_encryption_secrets=['DONT+USE+THIS+SECRET+b4NV+pmZNSO']

Configuring Custom Certificates

Custom serving certificates for the public host names of the OpenShift Container Platform API and web console can be deployed during an advanced installation and are configurable in the inventory file.

Custom certificates should only be configured for the host name associated with the publicmasterURL which can be set using openshift_master_cluster_public_hostname. Using a custom serving certificate for the host name associated with the masterURL (openshift_master_cluster_hostname) will result in TLS errors as infrastructure components will attempt to contact the master API using the internal masterURL host.

Certificate and key file paths can be configured using the openshift_master_named_certificates cluster variable:

openshift_master_named_certificates=[{"certfile": "/path/to/custom1.crt", "keyfile": "/path/to/custom1.key"}]

File paths must be local to the system where Ansible will be run. Certificates are copied to master hosts and are deployed within the /etc/origin/master/named_certificates/ directory.

Ansible detects a certificate’s Common Name and Subject Alternative Names. Detected names can be overridden by providing the "names" key when setting openshift_master_named_certificates:

openshift_master_named_certificates=[{"certfile": "/path/to/custom1.crt", "keyfile": "/path/to/custom1.key", "names": ["public-master-host.com"]}]

Certificates configured using openshift_master_named_certificates are cached on masters, meaning that each additional Ansible run with a different set of certificates results in all previously deployed certificates remaining in place on master hosts and within the master configuration file.

If you would like openshift_master_named_certificates to be overwritten with the provided value (or no value), specify the openshift_master_overwrite_named_certificates cluster variable:

openshift_master_overwrite_named_certificates=true

For a more complete example, consider the following cluster variables in an inventory file:

openshift_master_cluster_method=native
openshift_master_cluster_hostname=lb-internal.openshift.com
openshift_master_cluster_public_hostname=custom.openshift.com

To overwrite the certificates on a subsequent Ansible run, you could set the following:

openshift_master_named_certificates=[{"certfile": "/root/STAR.openshift.com.crt", "keyfile": "/root/STAR.openshift.com.key", "names": ["custom.openshift.com"]}]
openshift_master_overwrite_named_certificates=true

Configuring Deployment Type

Various defaults used throughout the playbooks and roles in this repository are set based on the deployment type configuration (usually defined in an Ansible hosts file).

Ensure the deployment_type parameter in your inventory file is set to openshift-enterprise.

Configuring Cluster Metrics

Cluster metrics are not set to automatically deploy by default. Set the following to enable cluster metrics when using the advanced install:

[OSEv3:vars]

openshift_hosted_metrics_deploy=true

In accordance with upstream Kubernetes rules, metrics can be collected only on the default interface of eth0.

Metrics Storage

The openshift_hosted_metrics_storage_kind variable must be set in order to use persistent storage. If openshift_hosted_metrics_storage_kind is not set, then cluster metrics data is stored in an EmptyDir volume, which will be deleted when the Cassandra pod terminates.

There are three options for enabling cluster metrics storage when using the advanced install:

Option A - NFS Host Group

When the following variables are set, an NFS volume is created during an advanced install with path <nfs_directory>/<volume_name> on the host within the [nfs] host group. For example, the volume path using these options would be /exports/metrics:

[OSEv3:vars]

openshift_hosted_metrics_storage_kind=nfs
openshift_hosted_metrics_storage_access_modes=['ReadWriteOnce']
openshift_hosted_metrics_storage_nfs_directory=/exports
openshift_hosted_metrics_storage_nfs_options='*(rw,root_squash)'
openshift_hosted_metrics_storage_volume_name=metrics
openshift_hosted_metrics_storage_volume_size=10Gi

Option B - External NFS Host

To use an external NFS volume, one must already exist with a path of <nfs_directory>/<volume_name> on the storage host.

[OSEv3:vars]

openshift_hosted_metrics_storage_kind=nfs
openshift_hosted_metrics_storage_access_modes=['ReadWriteOnce']
openshift_hosted_metrics_storage_host=nfs.example.com
openshift_hosted_metrics_storage_nfs_directory=/exports
openshift_hosted_metrics_storage_volume_name=metrics
openshift_hosted_metrics_storage_volume_size=10Gi

The remote volume path using the following options would be nfs.example.com:/exports/metrics.

Option C - Dynamic

Use the following variable if your OpenShift Container Platform environment supports dynamic volume provisioning for your cloud platform:

[OSEv3:vars]

#openshift_hosted_metrics_storage_kind=dynamic

Single master Examples

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

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

Single master and Multiple Nodes

The following table describes an example environment for a single master (with embedded etcd) and two nodes:

Host Name	Infrastructure Component to Install
master.example.com	master and node
node1.example.com	Node
node2.example.com

Host Name

Infrastructure Component to Install

master.example.com

master and node

node1.example.com

Node

node2.example.com

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

Example 1. Single master and Multiple Nodes Inventory File

# Create an OSEv3 group that contains the masters and nodes groups
[OSEv3:children]
masters
nodes

# 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

deployment_type=openshift-enterprise

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

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

# host group for nodes, includes region info
[nodes]
master.example.com
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

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, and two nodes:

Host Name	Infrastructure Component to Install
master.example.com	master and node
etcd1.example.com	etcd
etcd2.example.com
etcd3.example.com
node1.example.com	Node
node2.example.com

Host Name

Infrastructure Component to Install

master.example.com

master and node

etcd1.example.com

etcd

etcd2.example.com

etcd3.example.com

node1.example.com

Node

node2.example.com

When specifying multiple etcd hosts, external etcd is installed and configured. Clustering of OpenShift Container Platform’s embedded etcd is not supported.

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

Example 2. 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
deployment_type=openshift-enterprise

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

# 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
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

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 advanced installation supports the following high availability (HA) method:

native

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 a load balancing solution of your choice to balance the master API (port 8443) on all master hosts.

For your pre-configured load balancing solution, you must have:

A pre-created load balancer VIP configured for SSL passthrough.
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 External Load Balancer Integrations for more information.

For more on the high availability master architecture, see Kubernetes Infrastructure.

Note the following when using the native HA method:

The advanced installation method does not currently support multiple HAProxy load balancers in an active-passive setup. See the Load Balancer Administration documentation for post-installation amendments.
In a HAProxy setup, controller manager servers run as standalone processes. They elect their active leader with a lease stored in etcd. The lease expires after 30 seconds by default. If a failure happens on an active controller server, it will take up to this number of seconds to elect another leader. The interval can be configured with the osm_controller_lease_ttl variable.

To configure multiple masters, refer to the following section.

Multiple masters with Multiple etcd, and Using Native HA

The following describes an example environment for three masters, one HAProxy load balancer, three etcd hosts, and two nodes using the native HA method:

Host Name	Infrastructure Component 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	Node
node2.example.com

Host Name

Infrastructure Component 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

Node

node2.example.com

When specifying multiple etcd hosts, external etcd is installed and configured. Clustering of OpenShift Container Platform’s embedded etcd is not supported.

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

Example 3. 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
deployment_type=openshift-enterprise

# Uncomment the following to enable htpasswd authentication; defaults to
# DenyAllPasswordIdentityProvider.
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider', 'filename': '/etc/origin/master/htpasswd'}]

# 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_kubelet_args={'pods-per-core': ['10'], 'max-pods': ['250'], 'image-gc-high-threshold': ['90'], 'image-gc-low-threshold': ['80']}

# override the default controller lease ttl
#osm_controller_lease_ttl=30

# enable ntp on masters to ensure proper failover
openshift_clock_enabled=true

# 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
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

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

Multiple masters with master and etcd on the Same Host, and Using Native HA

The following describes an example environment for three masters with etcd on each host, one HAProxy load balancer, and two nodes using the native HA method:

Host Name	Infrastructure Component to Install
master1.example.com	master (clustered using native HA) and node with etcd on each host
master2.example.com
master3.example.com
lb.example.com	HAProxy to load balance API master endpoints
node1.example.com	Node
node2.example.com

Host Name

Infrastructure Component to Install

master1.example.com

master (clustered using native HA) and node with etcd on each host

master2.example.com

master3.example.com

lb.example.com

HAProxy to load balance API master endpoints

node1.example.com

Node

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
deployment_type=openshift-enterprise

# Uncomment the following to enable htpasswd authentication; defaults to
# DenyAllPasswordIdentityProvider.
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider', 'filename': '/etc/origin/master/htpasswd'}]

# 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

# override the default controller lease ttl
#osm_controller_lease_ttl=30

# 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
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

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

Running the Advanced Installation

After you have configured Ansible by defining an inventory file in /etc/ansible/hosts, you can run the advanced installation using the following playbook:

# ansible-playbook /usr/share/ansible/openshift-ansible/playbooks/byo/config.yml

If for any reason the installation fails, before re-running the installer, see Known Issues to check for any specific instructions or workarounds.

The installer caches playbook configuration values for 10 minutes, by default. If you change any system, network, or inventory configuration, and then re-run the installer within that 10 minute period, the new values are not used, and the previous values are used instead. You can delete the contents of the cache, which is defined by the fact_caching_connection value in the /etc/ansible/ansible.cfg file.

Due to a known issue, after running the installation, if NFS volumes are provisioned for any component, the following directories might be created whether their components are being deployed to NFS volumes or not:

/exports/logging-es
/exports/logging-es-ops/
/exports/metrics/
/exports/prometheus
/exports/prometheus-alertbuffer/
/exports/prometheus-alertmanager/

You can delete these directories after installation, as needed.

Verifying the Installation

After the installation completes:

Verify that the master is started and nodes are registered and reporting in Ready status. On the master host, run the following as root:

# oc get nodes

NAME                        STATUS                     AGE
master.example.com          Ready,SchedulingDisabled   165d
node1.example.com           Ready                      165d
node2.example.com           Ready                      165d

To verify that the web console is installed correctly, use the master host name and the console port number to access the console with a web browser.

For example, for a master host with a hostname of master.openshift.com and using the default port of 8443, the web console would be found at:
```
https://master.openshift.com:8443/console
```
Now that the install has been verified, run the following command on each master and node host to add the atomic-openshift packages back to the list of yum excludes on the host:
```
# atomic-openshift-excluder exclude
```

The default port for the console is 8443. If this was changed during the installation, the port can be found at openshift_master_console_port in the /etc/ansible/hosts file.

Multiple etcd Hosts

If you installed multiple etcd hosts:

First, verify that the etcd package, which provides the etcdctl command, is installed:
```
# yum install etcd
```

On a etcd host, verify the etcd cluster health, substituting for the FQDNs of your etcd hosts in the following:

# etcdctl -C \
    https://etcd1.example.com:2379,https://etcd2.example.com:2379,https://etcd3.example.com:2379 \
    --ca-file=/etc/origin/master/master.etcd-ca.crt \
    --cert-file=/etc/origin/master/master.etcd-client.crt \
    --key-file=/etc/origin/master/master.etcd-client.key cluster-health

Also verify the member list is correct:

# etcdctl -C \
    https://etcd1.example.com:2379,https://etcd2.example.com:2379,https://etcd3.example.com:2379 \
    --ca-file=/etc/origin/master/master.etcd-ca.crt \
    --cert-file=/etc/origin/master/master.etcd-client.crt \
    --key-file=/etc/origin/master/master.etcd-client.key member list

Multiple masters Using HAProxy

If you installed multiple masters using HAProxy as a load balancer, browse to the following URL according to your [lb] section definition and check HAProxy’s status:

http://<lb_hostname>:9000

You can verify your installation by consulting the HAProxy Configuration documentation.

Optionally Securing Builds

Running docker build is a privileged process, so the container has more access to the node than might be considered acceptable in some multi-tenant environments. If you do not trust your users, you can use a more secure option at the time of installation. Disable Docker builds on the cluster and require that users build images outside of the cluster. See Securing Builds by Strategy for more information on this optional process.

Uninstalling OpenShift Container Platform

You can uninstall OpenShift Container Platform hosts in your cluster by running the uninstall.yml playbook. This playbook deletes OpenShift Container Platform content installed by Ansible, including:

Configuration
Containers
Default templates and image streams
Images
RPM packages

The playbook will delete content for any hosts defined in the inventory file that you specify when running the playbook. If you want to uninstall OpenShift Container Platform across all hosts in your cluster, run the playbook using the inventory file you used when installing OpenShift Container Platform initially or ran most recently:

# ansible-playbook [-i /path/to/file] \
    /usr/share/ansible/openshift-ansible/playbooks/adhoc/uninstall.yml

Uninstalling Nodes

You can also uninstall node components from specific hosts using the uninstall.yml playbook while leaving the remaining hosts and cluster alone:

This method should only be used when attempting to uninstall specific node hosts and not for specific masters or etcd hosts, which would require further configuration changes within the cluster.

First follow the steps in Deleting Nodes to remove the node object from the cluster, then continue with the remaining steps in this procedure.
Create a different inventory file that only references those hosts. For example, to only delete content from one node:
[OSEv3:children] nodes (1) [OSEv3:vars] ansible_ssh_user=root deployment_type=openshift-enterprise [nodes] node3.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}" (2)
1 Only include the sections that pertain to the hosts you are interested in uninstalling.

2 Only include hosts that you want to uninstall.

Specify that new inventory file using the -i option when running the uninstall.yml playbook:

# ansible-playbook -i /path/to/new/file \
    /usr/share/ansible/openshift-ansible/playbooks/adhoc/uninstall.yml

When the playbook completes, all OpenShift Container Platform content should be removed from any specified hosts.

Known Issues

On failover in multiple master clusters, it is possible for the controller manager to overcorrect, which causes the system to run more pods than what was intended. However, this is a transient event and the system does correct itself over time. See https://github.com/kubernetes/kubernetes/issues/10030 for details.
On failure of the Ansible installer, you must start from a clean operating system installation. If you are using virtual machines, start from a fresh image. If you are using bare metal machines, see Uninstalling OpenShift Container Platform for instructions.

What’s Next?

Now that you have a working OpenShift Container Platform instance, you can:

Configure authentication; by default, authentication is set to Deny All.
Deploy an integrated Docker registry.
Deploy a router.

1	Only include the sections that pertain to the hosts you are interested in uninstalling.
2	Only include hosts that you want to uninstall.