how to set mongodb replica set using ansible

Question

Need to set up mongo dB replica set in 3 instances,one can be primary and rest two will be secondary. Anyone can suggest me about how can I write the playbook.

Have started mongo shell in three servers and initiate the replication name

'''replication: replSetName: "testingrs"'''

Answer 1

Ansible provides already plugin for it: community.mongodb.mongodb_replicaset

When I deployed my MongoDB sharded cluster, the plugin was still version 1.0 and had many limitations. We also had some problems with installing pymongo , so I developed the tasks manually. However, I think with current version there is no need anymore to write the tasks by your own.

Anyway, my playbook looks like this:

- name: Check if Replicaset is already initialized
  shell: 
    cmd: "/usr/bin/mongo --norc --quiet localhost:{{ ports.config }}"
    executable: /bin/bash
    stdin: "rs.status().codeName" 
  register: result
  changed_when: false
  check_mode: no

- set_fact:
    rs_initiate: |      
      {% set members = [] %}
      {% for host in groups['config'] | sort %}
      {% set m = {'_id': loop.index0 } %}
      {% set _ = m.update({'host': host + '.' + domain + ':' + ports.config | string }) %}
      {% set _ = members.append(m) %}
      {% endfor %}
      {% set init = {'_id': replica_set.conf} %}
      {% set _ = init.update({'members': members}) %}
      {{ init }} 
    rs: |
      {% set i = (result.stdout == 'NotYetInitialized') %}
      {% for host in ansible_play_hosts %}
      {% set i = i and (hostvars[host].result.stdout == 'NotYetInitialized') %}
      {% endfor %}
      {{ {'NotYetInitialized': i} }}

- name: Init Replicaset
  shell: 
    cmd: "/usr/bin/mongo --norc --quiet localhost:{{ ports.config }}"
    executable: /bin/bash
    stdin: |
      rs.initiate({{ rs_initiate | to_json }})
      rs.status()
      while (! db.isMaster().ismaster ) sleep(1000) 
  when: rs.NotYetInitialized and inventory_hostname_short == (groups['config'] | sort | first) 

One issue I had was to deal with authentication, because when you deploy a MongoDB from scratch then no user exist. Thus when you like to run the playbook multiple times, you have to distinct with and without authentication.

My playbook contains these tasks:

  - name: Check if authentication is enabled
    shell: 
      cmd: "/usr/bin/mongo --norc --quiet localhost:{{ ports.router }}"
      executable: /bin/bash
      stdin: "rs.status().codeName" 
    register: result
    ignore_errors: yes
    changed_when: false
    when: inventory_hostname_short == (groups['application'] | sort | first)

  - name: Authenticate if needed
    set_fact:
      authenticate: "{{ (result.stdout == 'Unauthorized') | ternary('-u admin -p ' + password[env].admin + ' --authenticationDatabase admin','') }}"
    when: inventory_hostname_short == (groups['application'] | sort | first)

  - name: Create users
    shell: 
      cmd: "/usr/bin/mongo {{ authenticate }} --norc --quiet localhost:{{ ports.router }}"
      executable: /bin/bash
      stdin: |
        admin = db.getSiblingDB("admin")
        admin.createUser({ user: "admin", pwd: "{{ password[env].admin }}", roles: ["root"] })
        admin.auth("admin", "{{ password[env].admin }}")
        // create more users if needed
        admin.createUser(...)
    when: inventory_hostname_short == (groups['application'] | sort | first)