Web Application with Caching - deployed using Docker

This project is a basic web application written in python using Flask. It uses Postgres as it persistent storage layer and uses Redis as it caching layer. The application and all of its related components (i.e. postgres and redis instance) are deployed using Docker Compose.

The purpose of this project is to mainly demonstrate following concept in modern web app development:

• How to use in-memory caching to improve the performance of a web application. The project caches mapping of user email to its user id in Redis to optimize the performance of user id retrieval by email.
• How to build and deploy a self-contained web application with multiple services using Docker and Docker Compose.

Project Structure

Here is a brief overview of the project's structure:

• src/: This directory contains the main application code and related files.

  • app.py: This file contains our web application written using Flask.
  • db.py: This is a helper file to interact with the Postgres and Redis servers.
  • config.yaml: The configuration settings for the app.

• Dockerfile: This file is used to build the Docker image for our web application.

• docker-compose.yml: This file is used to define all the required services including our web-app and run them as multi-container Docker applications.

• .env: This file contains the environment variables required by the application.

• USERS_TABLE.psql: This file contains the SQL command to create the Users table in the Postgres DB.

• user_data.csv: This file contains 1M rows of random user data in CSV format, which can be loaded to the Users table.

Installation

Follow these steps to install and run the project using Docker Compose:

1. Install Docker and Docker Compose on your machine. Visit Docker's website for installation instructions.

2. Clone this repository to your local machine.

   git clone https://github.com/username/project.git

3. Navigate to the project directory.

   cd web-app-with-caching

4. Run the Docker Compose command to build and start the services defined in docker-compose.yml.

   docker-compose up [-d]

5. Load the User data in db container:

   • Copy the users.csv file to the db container using the following command:

     docker cp user_data.csv user-api-db:/

   • Open a new terminal window and navigate to the project directory.
   • Run the following command to login to the db container and connect to the Postgres database:

     docker exec -it user-api-db psql -U postgres user_db

   • Now create a table in the database using command given in the USERS_TABLE.sql file:

     CREATE TABLE Users (username varchar(20) PRIMARY KEY, name varchar(30) NOT NULL, email varchar(30) UNIQUE, dob date, passwordhash varchar);

   • Now import the data from the users.csv file to the Users table using following command:

     COPY Users FROM '/user_data.csv' DELIMITER ',' CSV HEADER;

Usage

Once the containers are up and running and data is loaded to the DB, you can access the web application by visiting http://localhost:5001 in your web browser. The application will display a greeting message saying Welcome to the User API Web-Application!.

List of request routes to interact with the application:

1. GET requests:

   • /users/<user_name> -> Returns the details of the user with the given user_name.
   • /users/email/<user_name> -> Returns the email of the user with the given user_name.
   • /users/username/<email> -> Returns the username of the user with the given email.

2. POST/PUT requests:

   • /users/email/<user_name> -> Updates the user's email address with value given in the request body. The request body should contain the new email address in JSON format i.e. {"email": "new_email_address"}. Note: The implementation of this request also handles the cache invalidation for the updated email.