Example of Deploy a Replica Set in MongoDB

• Prepare Servers: Set up these three servers are mongo-primary, mongo-secondary, and mongo-arbiter.
• Install MongoDB: Install MongoDB on each server.

1. Configure Replica Set:

Start a MongoDB replica set with one primary node, one secondary node and one arbiter node on the same local machine for testing and development purposes.

# Start the Primary Node
mongod --replSet rs0 --port 27017 --dbpath /data/rs0 --bind_ip 127.0.0.1

# Start the First Secondary Node
mongod --replSet rs0 --port 27018 --dbpath /data/rs1 --bind_ip 127.0.0.1

# Start the Arbiter Node
mongod --replSet rs0 --port 27019 --dbpath /data/rs2 --bind_ip 127.0.0.1

2. Start MongoDB Instances:

Start MongoDB instances on each server.

Initialize Replica Set:

rs.initiate({
  _id: "rs0",
  members: [
    { _id: 0, host: "127.0.0.1:27017" },
    { _id: 1, host: "127.0.0.1:27018" },
    { _id: 2, host: "127.0.0.1:27019", arbiterOnly: true }
  ]
})

Output:

{
  "ok": 1,
  "$clusterTime": {
    "clusterTime": Timestamp(1637264328, 1),
    "signature": {
      "hash": BinData(0, "LAtUrh6VpBqrz0W9EYXL/DBLKpM="),
      "keyId": NumberLong("6957828764884994049")
    }
  },
  "operationTime": Timestamp(1637264328, 1)
}

Explanation: The rs.initiate() command initializes a MongoDB replica set named rs0 with three members: one primary node, one secondary node, and one arbiter node, all running on localhost but different ports

A MongoDB replica set configures MongoDB instances that collectively maintain the same dataset providing redundancy and high availability. This setup is fundamental for all production deployments. A replica set consists of several data-bearing nodes with one acting as the primary node and the others as secondary nodes. In this article, We will learn How to Deploy a Replica Set in MongoDB in detail.