ansible - deploy a 3 tiers application on 3 different machines -


i have basic application with:
- db
- api (connected db)
- front end (connected http api)

i'd 3 services run on 3 differents machines. i'm using ansible perform i'm not quite sure how define environment variables each layer knows how connect underlying one.

  • api needs db_host , db_port connect db. needs provided port own usage.

  • front end needs api_host , api_port connect api. needs provided port own usage.

inventory.ini 

[www] 192.168.1.120  [api] 192.168.1.120  [db] 192.168.1.120  [myproj:children] www api db  [myproj:vars] db_host=192.168.1.120      // needed api db_port=27017              // needed api api_host=192.168.1.120     // needed front-end api_port=8000              // needed api + front-end www_port=8001              // needed front-end

note: test use 1 vagrant vm 3 machines distinct in production.

playbooks.yml 

---   - hosts: db   sudo: true   roles:     - common     - db - hosts: api   sudo: true   roles:     - common     - api - hosts: www   sudo: true   roles:     - common     - www

example api roles: (roles/api/tasks/main.yml) 

--- - name: clone api   git: repo=git@github.com:...  - name: install api packages   ...  - name: start api    sudo: false   shell: npm start   args:     chdir: /var/app   environment:     port: ???     db_host: ???     db_port: ???

i'd have db_host / db_port / port setup hostvars not manage retrieve variable i've set in inventory. way handle ? should declare variables somewhere else ?

i think can refactoring. having variables in inventory file against ansible best prices. page describes optimal layout of playbooks http://docs.ansible.com/playbooks_best_practices.html#content-organization

furthermore, in inventory file www, api , db group names. can this:

[www] web01 ansible_ssh_host=192.168.1.120  [api] api01 ansible_ssh_host=192.168.1.120  [db] db01 ansible_ssh_host=192.168.1.120

this way can refer servers using bit friendlier names, making playbooks more readable.

as getting, example database ip, can use host facts extract such: 

{{ hostvars[db01]['ansible_eth0']['ipv4']['address'] }}

or, if want via index group:

{{ hostvars[groups['db'][0]]['ansible_eth0']['ipv4']['address'] }}

you should take @ other facts ansible collects , see if there suits use-case.


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