Install and Run Mongodb using Ansible

Introduction

As a person who has to do several on-premise deployments, at a place where docker is not accepted yet, I have had several issues installing mongodb. Even if I am installing it in the same environment, or upgrading it, I face several problems regarding permissions, ownerships, lockfiles etc.
In this article I will share an automated way through which you can install mongodb (version 4.2). Yes, we will be using ansible.

Pre-requisites

You need to have ansible installed on your system.

Hosts

When you run an ansible-playbook command, you may or may not mention the host file which has the all the required host information. Lets create a new file named mongo-hosts and enter name of all the servers on which you need mongodb installed

mongo-hosts

[local]
localhost       ansible_connection=local

[mongo-server-1]
XX.YY.ZZ.AA   ansible_connection=ssh  ansible_user=user

[mongo-server-2]
XX.YY.ZZ.BB   ansible_connection=ssh ansible_user=user

[mongo-servers:children]
local
mongo-server-1
mongo-server-2

We have mentioned all the instances, with their connection type and username.
Here you can see that I have grouped all the servers at the end. So anywhere mongo-servers is mentioned in playbook,All the child instances will be considered.

Playbook - mongo-playbook.yml

- hosts: mongo-servers
  become: true
  serial: 1

  tasks:
    - name: Install aptitude using apt
      apt:
        name: aptitude
        state: latest
        update_cache: yes

    - name: Import public key
      apt_key:
        url: 'https://www.mongodb.org/static/pgp/server-4.2.asc'
        state: present

    - name: Add repository
      apt_repository:
        filename: '/etc/apt/sources.list.d/mongodb-org-4.2.list'
        repo: 'deb https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.2 multiverse'
        state: present
        update_cache: yes

    - name: Install mongoDB
      apt:
        name: mongodb-org
        state: present
        update_cache: yes

    - name: Ensure mongodb is running and and enabled to start automatically on reboots
      service:
        name: mongod
        enabled: yes
        state: started

So here as we can see

hosts represent the instances on which this playbook will run.

become parameter is a privilege escalation setting as some commands we would only be able to run if the user is sudo. Note: These commands are only possible if the user through which ansible logs into the server is a sudo user.

serial parameter is for controlling how the playbook will be executed. In our case, this would mean that we are going to run the playbook on all the servers serially.

tasks are the steps that ansible will take on each server. These are the commands that we generally run to install mongodb manually.

Execution:

ansible-playbook mongo-playbook.yml -vvvv -i ./mongo-hosts

-vvvv is used to run the ansible playbook in verbose mode.
If we dont mention the hosts file(using i flag) , ansible-playbook will pick from the default one. In case of Ubuntu, that is /var/ansible/hosts

And thats it! This is a really basic case which only touches a simple installation. Let me know if you need examples of more complex ones (Primary,secondary,arbiter or the same using docker)