MongoDB-ReplicaSet

A TP I had to do, it must use MongoDB ReplicaSet on Docker, can use any language to add CRUD operations.

How to install

1. Clone the repository
2. Run docker-compose up
3. Install Java 17 or higher

Scripts

• Run gradle :run --args=create for creating the users collection and adding fake data
• Run gradle :run --args=delete for deleting the first user with more than 70 years old
• Run gradle :run --args=search for searching all users with more than 30 years old
• Run gradle :run --args=update for adding all users 5 years to their age

Crud operations with Mongosh

Connecting to the database

First, here's how to connect to the database :

docker exec -it mongo1 bash

Replace mongo1 with mongo2 or mongo3 if you want to connect to the other nodes.

Then, you can connect to the database with the following command :

mongosh --host localhost --port 27017

Then, here's how to do CRUD operations :

Creating

db.users.insertOne({name: "John", age: 25})

Reading

db.users.find({age: {$gt: 30}})

Updating

db.users.updateOne({name: "John"}, {$set: {age: 30}})

Deleting :

db.users.deleteOne({name: "John"})

Differences between script and CLI CRUD operations

The main difference between the script and the CLI CRUD operations is that the script is more automated and can be run in one command, while the CLI operations require you to type each command manually. You can also define dynamic parameters in the script, while you can't do that in the CLI. The code also let us see the performance of the operations, while the CLI doesn't.

Difficulties encountered

The main difficulty I encountered was to set up the Replica Set with Docker Compose. I had to search for examples in GitHub, the main issue was to initialize the replica set with the right configuration. Using environment variables as my first approach was not working, I ended up removing them and use a bash script to initialize the Replica Set in an aside container.

Another issue I encountered was to connect to the database with code. I first created the entire code in JavaScript, but never succeeded to connect to the database. I had to rewrite everything from scratch in another language, I chose Kotlin.