User Management and Email Service System

This project is a software study solution involving two primary APIs, implemented using Spring Boot 3 and Java 17. The system is designed for managing users and sending emails asynchronously through RabbitMQ messages with CloudAMQP.

Messaging Behavior Strategy

The core of this project is built upon a resilient message handling strategy that ensures reliability and robustness in asynchronous communication. Below are the key strategies implemented:

Persistent Messages

Messages sent to RabbitMQ are marked as persistent, ensuring they are not lost during broker restarts and are stored on disk for durability.

Durable Queues

Queues are declared as durable, which means they will survive a broker restart, preserving the state and contents of the queue.

Manual Message Acknowledgments

Our consumer, the EmailService API, implements manual message acknowledgments, ensuring messages are only acknowledged after successful processing. This prevents message loss in case of service failures.

Dead Letter Exchanges (DLX)

We utilize Dead Letter Exchanges for handling messages that cannot be processed immediately. Messages that fail to process or exceed a retry limit are rerouted to a designated DLX queue for further inspection or later reprocessing.

Message Retry Mechanism

A retry mechanism with a delay is implemented for messages that fail to process. By utilizing the x-dead-letter-exchange and x-message-ttl queue arguments, we introduce a delay before a failed message is retried, allowing temporary issues to be resolved and maintaining the integrity of message processing.

These strategies form the backbone of our robust message-driven architecture, ensuring our services remain resilient and reliable.

The system is designed for managing users and sending emails asynchronously through RabbitMQ messages with CloudAMQP.

Architecture Diagram

System Components

UserService API

• Technology: Java 17
• Framework: Spring Boot 3
• Database: PostgreSQL (user_db)
• Primary Endpoint:
  • POST /user: Endpoint for adding new users.

EmailService API

• Technology: Java 17
• Framework: Spring Boot 3
• Database: PostgreSQL (email_db)

Asynchronous Communication

The APIs communicate asynchronously via RabbitMQ, using CloudAMQP as the message broker.

Workflow

1. User Addition:

   • An external client sends a request to add a new user via the /user endpoint of the UserService API.
   • UserService processes the request, persists user data in user_db, and notifies RabbitMQ about the new user's creation.

2. Email Processing:

   • EmailService listens to the RabbitMQ queue.
   • Upon receiving a message about a new user, it persists the information in email_db.
   • An email is then sent to the new user via SMTP, using Gmail's service.

Configuration and Installation

Detailed instructions.