今天就來小試身手，用 Ansible 部署 Nginx，在 Cloud Native 的開發中，平台(Cloud Provider)也會有 Load Balancer ，像是 AWS 的 NLB、ALB，或是早些年的 ELB。這裡的 Nginx 的作用，是在平台提供的 LB 後面，作 App Layer 的導流與 Reverse Proxy，見下圖。

圖片來源

我們會把每一個微服務要用到的 docker 獨立出來寫作一個 Yaml 檔，這樣的好處是，當你在堡壘機(bastion)上，要作目標環境(e.g. staging, production)作操作時，操作的彈性比較大，一個簡單的部署範例如下

$ cat roles/tasks/run_nginx.yaml 
- name: File | Remove Directories
  file:
    path: '{{ item }}'
    state: absent
    owner: centos
    group: centos
  with_items:
    - "{{ prd_dir }}/nginx/cert"
    - "{{ prd_dir }}/nginx/conf"
    - "{{ prd_dir }}/nginx/html"
    - "{{ prd_dir }}/nginx/log"
- name: File | Create Directories
  file:
    path: '{{ item }}'
    state: directory
    owner: centos
    group: centos
  with_items:
    - "{{ prd_dir }}/nginx/cert"
    - "{{ prd_dir }}/nginx/conf"
    - "{{ prd_dir }}/nginx/html"
    - "{{ prd_dir }}/nginx/log"
- name: Copy | Copy Cert File to Remote
  copy:
    src: "{{ dev_dir }}/files/cert.d/{{ item }}"
    dest: "{{ prd_dir }}/nginx/cert"
  with_items:
    - fullchain.pem
    - privkey.pem
    - ssl-dhparam.pem
- name: Copy | Copy Config File to Remote
  copy:
    src: "{{ dev_dir }}/files/conf.d/nginx.conf"
    dest: "{{ prd_dir }}/nginx/conf"
- name: Copy | Copy Maintenance HTML to Remote
  copy:
    src: "{{ dev_dir }}/files/html.d/maintenance.html"
    dest: "{{ prd_dir }}/nginx/html"
- name: Docker | Start nginx.mytodos
  docker_container:
    networks_cli_compatible: yes
    name: nginx.mytodos
    state: started
    domainname: nginx.mytodos
    image:  nginx:1.14.2-alpine
    networks:
      - name: mynet
        ipv4_address: 172.20.0.2
    ports:
      - '443:443' # port_on_host:port_on_docker
    restart: true
    volumes:
      - /usr/share/zoneinfo/UTC:/etc/localtime:ro
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
      - "{{ prd_dir }}/nginx/cert:/etc/nginx/cert.d:ro"
      - "{{ prd_dir }}/nginx/conf/:/etc/nginx/conf.d:ro"
      - "{{ prd_dir }}/nginx/html:/var/www/html:ro"
      - "{{ prd_dir }}/nginx/log:/var/log/nginx"