Ansible Playbook for MongoDB Shard

Introduction

MongoDB is a popular NoSQL database that provides high performance, scalability, and flexibility. In large-scale deployments, it is common to use sharding to distribute the data across multiple servers. Ansible, an open-source automation tool, can be used to automate the configuration and deployment of MongoDB sharded clusters.

In this article, we will explore how to use Ansible playbooks to set up a MongoDB sharded cluster. We will cover the basic architecture of a sharded cluster, the key components involved, and provide code examples for each step.

Prerequisites

Before we begin, make sure you have the following prerequisites:

  • Ansible installed on your machine
  • Access to multiple servers or virtual machines to set up the cluster
  • Basic knowledge of MongoDB and Ansible

MongoDB Sharded Cluster Architecture

A MongoDB sharded cluster consists of the following key components:

  1. Shards: These are individual MongoDB instances that store a subset of the data. Each shard can be a standalone MongoDB server or a replica set.

  2. Config servers: These servers store metadata about the cluster configuration, such as the sharding key ranges and the mapping of chunks to shards. A minimum of three config servers is recommended for production clusters.

  3. Query routers: Also known as mongos instances, these are the entry point for client applications to access the sharded cluster. They route queries to the appropriate shards and handle the aggregation of results.

The following diagram illustrates the architecture of a MongoDB sharded cluster:

stateDiagram
    [*] --> ConfigServers
    ConfigServers --> Shards
    ConfigServers --> Mongos
    Mongos --> Shards

Setting up the MongoDB Sharded Cluster

Now, let's dive into how to set up a MongoDB sharded cluster using Ansible playbooks.

Step 1: Inventory Configuration

Create an inventory file, typically named hosts.ini, which lists all the servers participating in the cluster. Here is an example of how the inventory file might look:

[table]
| Hostname | IP Address  |
|----------|-------------|
| shard1   | 10.0.0.1    |
| shard2   | 10.0.0.2    |
| shard3   | 10.0.0.3    |
| config1  | 10.0.0.4    |
| config2  | 10.0.0.5    |
| config3  | 10.0.0.6    |
| mongos   | 10.0.0.7    |

Step 2: Playbook Configuration

Create a playbook file, let's name it mongodb-shard.yml, to define the tasks required to set up the MongoDB sharded cluster. Here is an example playbook:

- name: Install MongoDB
  hosts: shard1, shard2, shard3, config1, config2, config3, mongos
  tasks:
    - name: Install MongoDB packages
      apt:
        name: mongodb
        state: present

- name: Configure Shards
  hosts: shard1, shard2, shard3
  tasks:
    - name: Start MongoDB service
      service:
        name: mongod
        state: started

- name: Configure Config Servers
  hosts: config1, config2, config3
  tasks:
    - name: Start MongoDB service
      service:
        name: mongod
        state: started

- name: Configure Query Routers
  hosts: mongos
  tasks:
    - name: Start mongos service
      service:
        name: mongos
        state: started

Step 3: Running the Playbook

To run the playbook and set up the MongoDB sharded cluster, use the following command:

ansible-playbook -i hosts.ini mongodb-shard.yml

This will execute each task defined in the playbook on the corresponding servers.

Conclusion

In this article, we have explored how to use Ansible playbooks to set up a MongoDB sharded cluster. We discussed the architecture of a sharded cluster, its key components, and provided a step-by-step guide with code examples.

Ansible allows for the automation of complex tasks, such as the deployment and configuration of MongoDB sharded clusters. By using Ansible playbooks, you can easily scale your MongoDB infrastructure and ensure consistency across multiple servers.

Remember to adjust the playbook according to your specific requirements and add more advanced configurations as needed. Happy sharding!

References:

  • [Ansible Documentation](
  • [MongoDB Sharding Documentation](