Cloud-Computing-IA-2

Three-Tier Architecture with Docker

This guide will walk you through creating a three-tier application using a multi-container setup with Docker.

Author: Harsh Shah (21BCP359)

Medium Article: Dockerise Flask App with MongoDB

What is a Three-Tier Architecture?

A three-tier architecture is a well-established software application design pattern that organizes the application into three logical and physical tiers:

• Presentation Tier (e.g., HTML, CSS): This tier handles the user interface and presentation logic.
• Application Tier (e.g., Flask): This tier implements the business logic and interacts with the data tier.
• Data Tier (e.g., MongoDB): This tier stores and manages the application data.

Creating an Isolated Network

This command creates a new Docker network named myflaskmongonet that will be used by our application containers.

docker network create myflaskmongonet

Creating a MongoDB Container

You can pull the official MongoDB image from Docker Hub: https://hub.docker.com/_/mongo

docker pull mongo:latest

Running Mongo Container

This command runs a MongoDB container in detached mode (-d), maps the container’s port 27017 to the host’s port 27017 (-p), connects the container to the myflaskmongonet network (--network), and assigns the name 21bcp359_mongo to the container.

docker run -d -p 27017:27017 --network myflaskmongonet --name 21bcp359_mongo mongo:latest

Project Setup

For this example, we’ll use a project from GitHub: https://github.com/Soumi7/Mongo-Docker

These commands clone the Mongo-Docker repository, install the required Python packages, and run the Flask application. You should be able to access the application at http://localhost:5000/.

git clone https://github.com/Soumi7/Mongo-Docker.git

cd Mongo-Docker/

python -m pip install -r requirements.txt

python app.py

Navigate to http://localhost:5000/

Create Dockerfile in the root of your project

FROM python:3.8
ENV MONGODB_CONNSTRING="mongodb://localhost:27017"
COPY ./app_atlas.py /deploy/
COPY ./requirements.txt /deploy/
COPY ./templates /deploy/templates/
COPY ./static/css /deploy/static/css/
WORKDIR /deploy/
RUN pip3 install -r requirements.txt
EXPOSE 5000
ENTRYPOINT ["python", "app_atlas.py"]

Difference between RUN and CMD in Dockerfile:

RUN is used to execute commands during the build process of a Docker image, while CMD is used to specify the default command to run when a Docker container is started from the image.

Build Docker image using the following command

This command builds the image from the Dockerfile in the current directory and tags it with the name 21bcp359_flask_mongo.

docker build --tag 21bcp359_flask_mongo .

Run the Flask App Container

This command runs a container from the 21bcp359_flask_mongo image:

• Runs in detached mode (-d)
• Maps the container’s port 5000 to the host’s port 5000 (-p)
• Connects the container to the myflaskmongonet network (--network)
• Assigns the name 21bcp359_flaskapp to the container
• Runs the application in the background (-i) and allocates a pseudo-TTY (-t)

You should now be able to access your Flask application at http://localhost:5000/

docker run -dit -p 5000:5000 --name=21bcp359_flaskapp 21bcp359_flask_mongo

Web App Snapshots

Push to Dockerhub

docker tag 21bcp359_flask_mongo shaharsh624/21bcp359_flaskapp

docker push shaharsh624/21bcp359_flaskapp

Dockerhub Link

GitHub Project Link

---

Connect with me:

Portfolio: shaharsh.vercel.app
LinkedIn: harshshahdev
GitHub: shaharsh624

---