Mongo as a Replica Set

  Mongodb as a Replica Set

We would be creating mongodb as a replica set having 3 instances. One instance would be primary and the other 2 instances would be secondary.

For simplicity, I am going to have a replica set with 3 instances of mongodb running on the same server and thus to achieve this, all three mongodb instances would be running on different port numbers.

In production environment where in you have a dedicated mongodb instance running on a single server you can reuse the same port numbers.

1. Create data directories ( path where mongodb data would be stored in a file)

2. a. Start the first mongod instance

• Open command prompt and type the following press enter.

The above command associates the instance of mongodb to a replicaSet name "s0" and the starts the first instance of mongodb on port 37017 with oplogSize 100MB 

2. b. Similarly start the second instance of Mongodb

The above command associates the instance of mongodb to a replicaSet name "s0" and the starts the first instance of mongodb on port 37018 with oplogSize 100MB

2. c. Now start the third instance of Mongodb

The above command associates the instance of mongodb to a replicaSet name "s0" and the starts the first instance of mongodb on port 37019 with oplogSize 100MB

With all the 3 instances started, these 3 instances are independent of each other currently. We would now need to group these instances as a replica set. We do this with the help of a config object.