11.7. Configuring a high availability cluster with resource constraints using system roles

Procedure

1. Store your sensitive variables in an encrypted file:

   1. Create the vault:

      $ ansible-vault create ~/vault.yml
      New Vault password: <vault_password>
      Confirm New Vault password: <vault_password>

   2. After the ansible-vault create command opens an editor, enter the sensitive data in the <key>: <value> format:

      cluster_password: <cluster_password>

   3. Save the changes, and close the editor. Ansible encrypts the data in the vault.

2. Create a playbook file, for example, ~/playbook.yml, with the following content:

   ---
   - name: Create a high availability cluster
     hosts: node1 node2
     vars_files:
       - ~/vault.yml
     tasks:
       - name: Create cluster with resource constraints
         ansible.builtin.include_role:
           name: redhat.rhel_system_roles.ha_cluster
         vars:
           ha_cluster_cluster_name: my-new-cluster
           ha_cluster_hacluster_password: "{{ cluster_password }}"
           ha_cluster_manage_firewall: true
           ha_cluster_manage_selinux: true
           # In order to use constraints, we need resources
           # the constraints will apply to.
           ha_cluster_resource_primitives:
             - id: xvm-fencing
               agent: 'stonith:fence_xvm'
               instance_attrs:
                 - attrs:
                     - name: pcmk_host_list
                       value: node1 node2
             - id: dummy-1
               agent: 'ocf:pacemaker:Dummy'
             - id: dummy-2
               agent: 'ocf:pacemaker:Dummy'
             - id: dummy-3
               agent: 'ocf:pacemaker:Dummy'
             - id: dummy-4
               agent: 'ocf:pacemaker:Dummy'
             - id: dummy-5
               agent: 'ocf:pacemaker:Dummy'
             - id: dummy-6
               agent: 'ocf:pacemaker:Dummy'
           # location constraints
           ha_cluster_constraints_location:
             # resource ID and node name
             - resource:
                 id: dummy-1
               node: node1
               options:
                 - name: score
                   value: 20
             # resource pattern and node name
             - resource:
                 pattern: dummy-\d+
               node: node1
               options:
                 - name: score
                   value: 10
             # resource ID and rule
             - resource:
                 id: dummy-2
               rule: '#uname eq node2 and date in_range 2022-01-01 to 2022-02-28'
             # resource pattern and rule
             - resource:
                 pattern: dummy-\d+
               rule: node-type eq weekend and date-spec weekdays=6-7
           # colocation constraints
           ha_cluster_constraints_colocation:
             # simple constraint
             - resource_leader:
                 id: dummy-3
               resource_follower:
                 id: dummy-4
               options:
                 - name: score
                   value: -5
             # set constraint
             - resource_sets:
                 - resource_ids:
                     - dummy-1
                     - dummy-2
                 - resource_ids:
                     - dummy-5
                     - dummy-6
                   options:
                     - name: sequential
                       value: "false"
               options:
                 - name: score
                   value: 20
           # order constraints
           ha_cluster_constraints_order:
             # simple constraint
             - resource_first:
                 id: dummy-1
               resource_then:
                 id: dummy-6
               options:
                 - name: symmetrical
                   value: "false"
             # set constraint
             - resource_sets:
                 - resource_ids:
                     - dummy-1
                     - dummy-2
                   options:
                     - name: require-all
                       value: "false"
                     - name: sequential
                       value: "false"
                 - resource_ids:
                     - dummy-3
                 - resource_ids:
                     - dummy-4
                     - dummy-5
                   options:
                     - name: sequential
                       value: "false"
           # ticket constraints
           ha_cluster_constraints_ticket:
             # simple constraint
             - resource:
                 id: dummy-1
               ticket: ticket1
               options:
                 - name: loss-policy
                   value: stop
             # set constraint
             - resource_sets:
                 - resource_ids:
                     - dummy-3
                     - dummy-4
                     - dummy-5
               ticket: ticket2
               options:
                 - name: loss-policy
                   value: fence

   The settings specified in the example playbook include the following:

   ha_cluster_cluster_name: <cluster_name>

   The name of the cluster you are creating.

   ha_cluster_hacluster_password: <password>

   The password of the hacluster user. The hacluster user has full access to a cluster.

   ha_cluster_manage_firewall: true

   A variable that determines whether the ha_cluster RHEL system role manages the firewall.

   ha_cluster_manage_selinux: true

   A variable that determines whether the ha_cluster RHEL system role manages the ports of the firewall high availability service using the selinux RHEL system role.

   ha_cluster_resource_primitives: <cluster_resources>

   A list of resource definitions for the Pacemaker resources configured by the ha_cluster RHEL system role, including fencing

   ha_cluster_constraints_location: <location_constraints>

   A variable that defines resource location constraints.

   ha_cluster_constraints_colocation: <colocation_constraints>

   A variable that defines resource colocation constraints.

   ha_cluster_constraints_order: <order_constraints>

   A variable that defines resource order constraints.

   ha_cluster_constraints_ticket: <ticket_constraints>

   A variable that defines Booth ticket constraints.

3. Validate the playbook syntax:

   $ ansible-playbook --syntax-check --ask-vault-pass ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

4. Run the playbook:

   $ ansible-playbook --ask-vault-pass ~/playbook.yml