Replica set configuration basics in MongoDB - Mini Project: Build & Apply

Replica set configuration basics

📖 Scenario: You are setting up a MongoDB replica set to ensure your database stays available even if one server goes down. A replica set is a group of MongoDB servers that keep the same data, so if one fails, another can take over.

🎯 Goal: Create a basic MongoDB replica set configuration with three members. You will define the replica set configuration document step-by-step, including the replica set name and the members with their IDs and hostnames.

📋 What You'll Learn

Create a variable called rsConfig to hold the replica set configuration document.

Add a _id field to rsConfig with the value "rs0" as the replica set name.

Add a members array to rsConfig with three members, each having an _id and host.

Add a priority field to the first member to make it the primary candidate.

💡 Why This Matters

🌍 Real World

Replica sets are used in MongoDB to provide high availability and data redundancy. Setting up the configuration correctly is essential for production databases.

💼 Career

Database administrators and backend engineers often configure replica sets to ensure database reliability and uptime.

1

Create the initial replica set configuration object

Create a variable called rsConfig and assign it an object with a single field _id set to the string "rs0".

MongoDB

// Create the replica set configuration object with _id 'rs0'
// Your code here

Need a hint?

The replica set configuration must have an _id field that names the replica set.

2

Add members array with three members

Add a members field to the rsConfig object. It should be an array with three objects. Each object must have an _id (0, 1, 2) and a host string: "mongo0:27017", "mongo1:27017", and "mongo2:27017" respectively.

MongoDB

var rsConfig = { _id: "rs0" };
// Add members array with three members to rsConfig
// Your code here

Need a hint?

The members field is an array of objects. Each member needs a unique _id and a host string with hostname and port.

3

Set priority for the first member

Add a priority field with value 2 to the first member object in the members array inside rsConfig. This makes it the preferred primary.

MongoDB

var rsConfig = {
  _id: "rs0",
  members: [
    { _id: 0, host: "mongo0:27017" },
    { _id: 1, host: "mongo1:27017" },
    { _id: 2, host: "mongo2:27017" }
  ]
};
// Add priority: 2 to the first member
// Your code here

Need a hint?

Set priority: 2 inside the first member object to make it the primary candidate.

4

Complete the replica set configuration

Ensure the rsConfig object is fully defined with _id as "rs0", a members array of three members with _id and host, and the first member has priority: 2.

MongoDB

var rsConfig = {
  _id: "rs0",
  members: [
    { _id: 0, host: "mongo0:27017", priority: 2 },
    { _id: 1, host: "mongo1:27017" },
    { _id: 2, host: "mongo2:27017" }
  ]
};
// Finalize the replica set configuration
// Your code here

Need a hint?

Check that the entire rsConfig object is correctly structured as a replica set configuration.