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Lab 6: Comprehensive Review

Optional Bonus Lab

If time permits, students can work through this bonus lab. In lab six we will apply some of what we learned to accomplish a new task: performing a rolling OS upgrade of our web servers, with the help of an OpenStack loadbalancer.

This playbook should handle:

  • Checking if a server has any pending package updates

  • Removing the server from the load balancer pool

  • Update packages and reboot the host

  • Add the server back in to the pool when back online

First, a couple of hints to get your started. You can retrieve information about the current load balancer and pool with the following:

$ openstack loadbalancer show weblb
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| admin_state_up      | True                                 |
| created_at          | 2018-10-21T15:22:00                  |
| description         |                                      |
| flavor              |                                      |
| id                  | f9d18367-0c5b-481a-b72c-dc5eddcf1c44 |
| listeners           | c756d025-bac8-46c9-a7f3-7d40f2e5b9ca |
| name                | weblb                                |
| operating_status    | ONLINE                               |
| pools               | 37d58607-a4ec-480c-a388-3a92e60d3482 |
| project_id          | b0796a9f0938466b9e9771c01d5bd2ba     |
| provider            | amphora                              |
| provisioning_status | ACTIVE                               |
| updated_at          | 2018-10-21T15:23:41                  |
| vip_address         | 172.24.4.11                          |
| vip_network_id      | 29e88081-d40f-4463-8bd6-f13a511aed5a |
| vip_port_id         | 46d724fa-8770-473e-8da1-832cae8ae569 |
| vip_qos_policy_id   | None                                 |
| vip_subnet_id       | 4908af3c-075b-4024-8186-32a5286d8e1a |
+---------------------+--------------------------------------+
$ openstack loadbalancer pool show weblb_pool
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| admin_state_up      | True                                 |
| created_at          | 2018-10-21T15:23:24                  |
| description         |                                      |
| healthmonitor_id    |                                      |
| id                  | 37d58607-a4ec-480c-a388-3a92e60d3482 |
| lb_algorithm        | ROUND_ROBIN                          |
| listeners           | c756d025-bac8-46c9-a7f3-7d40f2e5b9ca |
| loadbalancers       | f9d18367-0c5b-481a-b72c-dc5eddcf1c44 |
| members             | 54dc0cc0-cb0f-4303-bc41-9fefca2a438e |
|                     | b297a100-69f9-475b-8e3c-1c48d1366acd |
| name                | weblb_pool                           |
| operating_status    | ONLINE                               |
| project_id          | b0796a9f0938466b9e9771c01d5bd2ba     |
| protocol            | HTTP                                 |
| provisioning_status | ACTIVE                               |
| session_persistence | None                                 |
| updated_at          | 2018-10-21T15:23:41                  |
+---------------------+--------------------------------------+

Ansible now includes a number of modules for dealing with OpenStack load balancers. They can be found here.

The serial keyword can be handy for controlling the number of hosts managed at one time.

Assignment: Attempt to create a playbook.yml file that accomplishes all the task bullets. Ensure to take advantage of the Ansible documentation for clues on how to complete each task and also via command-line make use of the ansible-doc command for examples.

Example of using ansible-doc:

$ ansible-doc os_member

The above command would provide documentation on how to use the OpenStack os_member module.

Note
 While testing and running your playbook, you can observe which host is serving each request by `curl`ing the load balancer IP: 
$ curl 172.24.4.11 2>&1 | grep 'served by:'
      served by: web1.novalocal
$ curl 172.24.4.11 2>&1 | grep 'served by:'
      served by: web0.novalocal

Answer to comprehensive review

---
- name: perform a rolling OS upgrade of web nodes
  hosts: web
  gather_facts: true
  user: centos
  serial: 1
  tasks:
  - name: check for pending updates
    yum:
      list: updates
    register: yum_update
  - block:
      - name: remove web server from pool
        os_member:
          state: absent
          name: '{{ ansible_hostname }}'
          pool: weblb_pool
        delegate_to: localhost
      - name: update packages
        package:
          name: '*'
          state: latest
        become: true
      - name: reboot server
        shell: sleep 5 && reboot &
        async: 1
        poll: 0
      - name: wait for server
        wait_for_connection:
          connect_timeout: 20
          sleep: 5
          delay: 5
          timeout: 600
        become: true
      - name: put server back in pool
        os_member:
          state: present
          name: '{{ ansible_hostname }}'
          pool: weblb_pool
          address: '{{ ansible_default_ipv4.address }}'
          protocol_port: 80
        delegate_to: localhost
    when:
    - yum_update.results | length > 0
...