Updating Application

Writing database schema update playbook

The following url has the links to the database dumps

Database SQL Dumps

Lets write tasks to update schema for database

file: db.yml

---
  - name: playbook to configure db servers
    hosts: db
    become: yes
    roles:
      - { role: geerlingguy.mysql }
    tasks:
      - name: download database schema
        get_url:
          url: https://raw.githubusercontent.com/devopsdemoapps/devops-demo-app/master/data/devops-demo-1.0.sql
          dest: /tmp/devops-demo-1.0.sql
          mode: 0444
        tags: schema

      - name: Schema Migrate
        mysql_db:
          name: "{{ dbconn.db }}"
          login_host: "127.0.0.1"
          login_password: "{{ mysql_root_password }}"
          login_user: "root"
          state: import
          target: /tmp/devops-demo-1.0.sql
        tags: schema

where, * we have added task to download the schema file from a remote uri * load the schema using import state

Its important to use 1.0 as the schema version first time you run as it needs the initial tables.

Run it for the first time,

ansible-playbook db.yml  --vault-id prod@~/.vault_prod --tags=schema

Once the initial schema apply is done, update the tasks to use app.version for schema update as well

---
  - name: playbook to configure db servers
    hosts: db
    become: yes
    roles:
      - { role: geerlingguy.mysql }
    tasks:
      - name: download database schema
        get_url:
          url: https://raw.githubusercontent.com/devopsdemoapps/devops-demo-app/master/data/devops-demo-{{ app.version }}.sql
          dest: /tmp/devops-demo-{{ app.version }}.sql
          mode: 0444
        tags: schema

      - name: Schema Migrate
        mysql_db:
          name: "{{ dbconn.db }}"
          login_host: "127.0.0.1"
          login_password: "{{ mysql_root_password }}"
          login_user: "root"
          state: import
          target: /tmp/devops-demo-{{ app.version }}.sql
        tags: schema

Deployment Playbook

Strategy: * Rolling updates/zero downtime * Batch size = 1

Deployment strategy and sequence, * Update database schema * For each web server update * Disable load balancer traffic * Deploy new version of the application * Wait for the app to be available * Enable traffic from load balancer

Pre tasks

file: deployment.yml

- hosts: app
  become: yes
  vars:
    app:
      version: 1.6
  serial: 1

  pre_tasks:
    - name: take the app server out
      haproxy:
        host: '{{ inventory_hostname }}'
        state: disabled
      delegate_to: lb

  roles:
     - frontend

  post_tasks:
    - name: Wait 300 seconds for port 80 to be available
      wait_for:
        port: 80
        host: '{{ inventory_hostname }}'
        delay: 5
        timeout: 300
      connection: local
    - name: add server to loadbalancer
      haproxy:
        host: '{{ inventory_hostname }}'
        state: enabled
      delegate_to: lb

Deploy a new version with

ansible-playbook deployment.yml