Capstone Project - Spring Microservices - E-commerce Application

[akash-coded]

Project Title: Ecommerce Platform

The purpose of this project is to design and implement a microservices-based e-commerce platform using Spring Boot, following all principles of microservices, integrating various patterns, asynchronous communications, testing strategies, and DevOps practices.

Project Modules:

1. Product Catalog Service
2. Order Processing Service
3. Customer Service
4. Inventory Service
5. Payment Service

1. Modelled Around Business Domain:
Each service represents a different bounded context in the ecommerce domain and implements related functionality.

2. Culture Of Automation:
Automate everything possible, from testing (unit, integration tests) to building (Maven or Gradle), to deployment (using CI/CD pipelines in Jenkins).

3. Hide Implementation Details:
Services communicate using well-defined APIs, hiding the details of their implementation. Services should adhere to the single responsibility principle.

4. Decentralize All The Things:
Each service should be independent and autonomous, responsible for its own database, and capable of being developed, deployed, and scaled individually.

5. Deploy Independently:
Each service should be containerized (using Docker) and managed independently. Use Kubernetes for orchestration, enabling independent deployment and scaling.

6. Consumer First:
Design APIs keeping the consumers in mind. Use tools like Swagger for API documentation. Implement Client-side Load Balancing using Netflix Ribbon.

7. Isolate Failure:
Use the Circuit Breaker pattern to prevent failures from cascading. Implement it using Hystrix.

8. Highly Observable:
Integrate with tools like Zipkin for tracing, Prometheus for monitoring, and ELK Stack for logs.

9. Understanding of Twelve-Factor App:
Adhere to the principles of the Twelve-Factor App in the application design, like codebase, dependencies, configuration, backing services, build-release-run, etc.

10. Microservices Patterns:

• Use the Strangler Pattern to gradually replace parts of the monolithic legacy system, if any.
• Use the Proxy Pattern for communication between services.
• Implement an Aggregator to combine responses from multiple services.
• Use the API Gateway pattern to provide a single entry point for all clients.
• Implement Chained (Chain of Responsibility) Patterns for tasks involving multiple steps or tasks that can be performed independently of the calling client.
• Use Saga Pattern to manage transactions that span multiple services.
• Use Sidecar Pattern for cross-cutting concerns like logging, monitoring, etc.
• Implement Database per service pattern to ensure loose coupling and independence.

11. Asynchronous Communications:

• Use message-driven architectures where appropriate, utilizing ActiveMQ, RabbitMQ, or Kafka.
• Services should be designed to handle both synchronous and asynchronous communication.

12. Microservices Testing (Optional):

• Unit Testing: Use JUnit and Mockito.
• Integration Testing: Use Spring Boot's support for integration testing.
• End-to-End Testing: Use Selenium or similar tools.
• Leverage Jenkins to create a DevOps pipeline for automated testing.

13. Microservices and DevOps (Optional):

• Resource Provisioning: Use Terraform for IaC.
• CI/CD pipelines: Use Jenkins for creating CI/CD pipelines.
• Minimal Downtime Deployments: Use Kubernetes for zero-downtime deployments, Blue-Green deployments, or Canary deployments.

The platform you build will be a robust, resilient, and highly scalable e-commerce platform. It will leverage the best practices of microservice architecture, using a modern tech stack and various patterns to ensure a successful implementation. Remember to follow the principles and patterns where they make sense and not to follow them dogmatically.

Steps for reference

Step 1: Setup Development Environment

• Install Java JDK (version 11 or newer).
• Install an IDE such as IntelliJ IDEA or Eclipse.
• Install Docker and Kubernetes, which are needed for containerization and orchestration.
• Install Maven or Gradle for building your project.
• Set up a Git repository for version control.

Step 2: Create Spring Boot Projects

• For each of the services (Product Catalog, Order Processing, Customer Service, Inventory, Payment), create a separate Spring Boot project. You can do this using Spring Initializr: https://start.spring.io/
• Make sure to add the Web, JPA, and appropriate SQL database dependencies.

Step 3: Implement Business Logic for Each Service

• Each service should be designed around a business domain. Create entities, repositories, services, and controllers for each of them.

Step 4: Containerize Your Services

• Create a Dockerfile for each of your services. This will define how the Docker image for that service should be built.
• Build the Docker image for each service and test it by running it locally.

Step 5: Create Kubernetes Configuration

• For each service, create a Kubernetes Deployment and Service configuration.
• The Deployment specifies how the application should be deployed, including the Docker image to use, the number of replicas, etc.
• The Service exposes the application to the network, allowing it to be accessed.

Step 6: Implement API Gateway

• Use Spring Cloud Gateway or Netflix Zuul to implement the API Gateway pattern.
• The API Gateway will serve as the single entry point for client requests and will route requests to the appropriate microservice.

Step 7: Implement Service Discovery

• Use Netflix Eureka or Kubernetes native service discovery.
• Each service will register itself with the service discovery component, and can use it to find other services.

Step 8: Implement Circuit Breaker

• Use Netflix Hystrix to implement the Circuit Breaker pattern.
• This pattern will prevent failures in one service from cascading to other services.

Step 9: Implement Database Per Service Pattern

• Each service should have its own dedicated database. This could be a different database server or a different database on the same server, depending on your requirements.

Step 10: Implement Asynchronous Communication

• Use RabbitMQ, ActiveMQ, or Kafka for asynchronous communication.
• This is especially important for operations that are time-consuming and can be processed in the background.

Step 11: Implement Testing (Optional)

• Unit Testing: Use JUnit and Mockito.
• Integration Testing: Use Spring Boot Test.
• End-to-End Testing: Use Selenium.

Step 12: Implement DevOps (Optional)

• Set up a Jenkins server for CI/CD.
• Create Jenkins pipelines that build your project, run tests, build Docker images, and deploy them to Kubernetes.

Step 13: Implement Observability (Optional)

• Set up an ELK (Elasticsearch, Logstash, Kibana) stack for centralized logging.
• Set up Prometheus and Grafana for monitoring.
• Use Zipkin or Jaeger for distributed tracing.

This is a broad overview of the steps you should follow. Each step is a significant amount of work and requires a detailed understanding of various technologies. However, with this roadmap, you should be able to start building your e-commerce platform based on microservices using Spring Boot. Always remember to start small, test as you go, and incrementally add complexity as you get comfortable with each technology.

---

Project Implementation: Ecommerce Platform Using Spring Boot Microservices

Introduction

This implementation manual is tailored for building an E-commerce Platform using Spring Boot, structured around microservices architecture. The goal is to adhere to microservices principles, integrate various patterns, support asynchronous communications, and apply DevOps practices for a robust, scalable, and maintainable system.

Project Modules Overview

1. Product Catalog Service: Manages product listings, details, and categories.
2. Order Processing Service: Handles customer orders, order statuses, and history.
3. Customer Service: Manages customer profiles, preferences, and authentication.
4. Inventory Service: Keeps track of product stock levels and inventory updates.
5. Payment Service: Processes payments, refunds, and financial records.

---

Guidelines and Principles

1. Business Domain Modeling: Each service focuses on a specific domain aspect, ensuring clear boundaries and responsibilities.

2. Culture of Automation:

   • Automate testing using JUnit and Mockito for unit tests, and Spring Boot Test for integration tests.
   • Use Maven/Gradle for automated builds.
   • Implement CI/CD pipelines using Jenkins for automated deployment.

3. API Design and Single Responsibility Principle:

   • Design clear, well-documented APIs using Swagger.
   • Ensure each service adheres to the single responsibility principle.

4. Decentralization and Service Autonomy:

   • Each service manages its own database (MySQL, PostgreSQL, or MongoDB).
   • Services are developed and deployed independently.

5. Containerization and Orchestration:

   • Use Docker for containerizing services.
   • Employ Kubernetes for managing and scaling services.

6. Consumer-First Approach:

   • Design APIs with a focus on the end-user experience.
   • Implement client-side load balancing using Netflix Ribbon.

7. Failure Isolation:

   • Use Hystrix for the Circuit Breaker pattern to prevent cascading failures.

8. Observability:

   • Implement Zipkin for distributed tracing.
   • Use Prometheus for monitoring and ELK Stack for logging.

9. Twelve-Factor App Compliance:

   • Follow the principles of the Twelve-Factor App methodology in application design.

10. Microservices Patterns:

    • Apply various microservices patterns like Strangler, Proxy, Aggregator, API Gateway, Chained patterns, Saga, Sidecar, and Database per service.

11. Asynchronous Communication:

    • Use messaging systems like ActiveMQ, RabbitMQ, or Kafka for asynchronous communication between services.

---

Detailed Scenarios for Implementation

Scenario 1: Product Catalog Update

• Problem: A batch of new products needs to be added to the Product Catalog Service.
• Task: Implement an automated process to add new products, ensuring inventory and payment services are notified of changes.
• Techniques: Use message queues (Kafka) for broadcasting product updates.

Scenario 2: Handling High Order Volume

• Problem: Order Processing Service becomes overwhelmed during peak shopping periods.
• Task: Ensure the service scales to handle high demand and maintains performance.
• Techniques: Implement auto-scaling in Kubernetes. Use asynchronous messaging for order processing.

Scenario 3: Customer Profile Synchronization

• Problem: Customer profile updates in Customer Service need to reflect in Order Processing Service.
• Task: Synchronize customer data across services without direct coupling.
• Techniques: Use event-driven architecture. Publish customer update events that other services can subscribe to.

Scenario 4: Inventory Shortage Notification

• Problem: Inventory Service detects a shortage of a popular product.
• Task: Notify the Product Catalog Service and Customer Service about the shortage.
• Techniques: Publish an InventoryShortage event. Implement event handlers in respective services.

Scenario 5: Payment Service Timeout

• Problem: Payment Service experiences a timeout during transaction processing.
• Task: Implement a strategy to handle timeouts and ensure transaction consistency.
• Techniques: Use the Circuit Breaker pattern with Hystrix. Implement a fallback mechanism, possibly queuing the transaction for later processing.

Continuing with more detailed scenarios for the E-commerce Platform using Spring Boot Microservices:

Scenario 6: Distributed Transaction During Order Placement

• Problem: An order placement involves multiple services, and any failure in the process should not leave the system in an inconsistent state.
• Task: Implement a saga to manage the distributed transaction across services.
• Techniques:
  • Start the saga in Order Processing Service.
  • Coordinate steps between Inventory, Payment, and Customer services.
  • Use compensating transactions for each step to handle failures.

Scenario 7: Real-time Updates in Product Catalog

• Problem: Real-time updates are required in the Product Catalog when a product's price or availability changes.
• Task: Implement an event-driven mechanism to update the Product Catalog in real-time.
• Techniques:
  • Inventory Service publishes events on stock changes.
  • Product Catalog Service listens to these events and updates the product details accordingly.

Scenario 8: Automated Refund Process

• Problem: Automatic refunds need to be processed in case of order cancellations.
• Task: Automate the refund process while ensuring data consistency across services.
• Techniques:
  • Implement a saga in Order Processing Service to handle order cancellations and initiate refunds.
  • Coordinate with the Payment Service for processing refunds.

Scenario 9: User Authentication and Authorization

• Problem: Secure and efficient user authentication and authorization are needed.
• Task: Implement a security mechanism for user authentication and authorization.
• Techniques:
  • Use Spring Security and OAuth2 for securing endpoints.
  • Implement JWT tokens for stateless authentication.

Scenario 10: Load Balancing under Heavy Traffic

• Problem: Services need to efficiently handle increased loads during peak traffic times.
• Task: Ensure services can handle load spikes without performance degradation.
• Techniques:
  • Implement Netflix Ribbon for client-side load balancing.
  • Use Kubernetes’ horizontal pod autoscaler for dynamic scaling.

---

Scenario 11: Centralized Configuration Management

• Problem: Managing configurations across multiple services and environments.
• Task: Centralize configuration management.
• Techniques:
  • Use Spring Cloud Config for externalizing and managing application configurations.
  • Store environment-specific configurations in a version-controlled repository.

Scenario 12: Legacy System Integration

• Problem: The new platform needs to integrate with a legacy system for certain functionalities.
• Task: Gradually replace the legacy system functionalities.
• Techniques:
  • Apply the Strangler pattern to incrementally migrate functionalities.
  • Use a Proxy service to manage communication with the legacy system.

Scenario 13: Handling Partial Failures in Checkout Process

• Problem: A failure in one part of the checkout process should not affect the overall transaction.
• Task: Handle partial failures gracefully in the checkout process.
• Techniques:
  • Use the Saga pattern for managing the checkout process.
  • Implement compensating transactions to revert any partial changes in case of a failure.

Scenario 14: Data Consistency Across Bounded Contexts

• Problem: Ensuring data consistency across different bounded contexts (services).
• Task: Implement a mechanism to maintain data consistency.
• Techniques:
  • Use event-driven architecture to propagate data changes across services.
  • Implement eventual consistency where immediate consistency is not critical.

Scenario 15: Service Monitoring and Tracing

• Problem: Monitoring and tracing transactions across multiple microservices.
• Task: Implement tools for monitoring and tracing.
• Techniques:
  • Integrate Zipkin for distributed tracing to track requests across services.
  • Use Prometheus for monitoring service performance and health.

These scenarios cover a broad spectrum of challenges and tasks that a development team would encounter in building a complex, microservices-based E-commerce platform. They encompass various aspects of system design, including transaction management, inter-service communication, scalability, security, and observability, offering a comprehensive learning experience in microservices architecture.

---

E-commerce Platform Microservices: Event Flow, Actions, and CQRS

Product Catalog Service

• Events Produced: ProductAdded, ProductUpdated, ProductRemoved.
• Actions:
  • On adding a new product, publish ProductAdded.
  • On updating product details, publish ProductUpdated.
  • On removing a product, publish ProductRemoved.
• Events Consumed: N/A.
• CQRS Implementation: Command side for product management, Query side for product retrieval.

Order Processing Service

• Events Produced: OrderPlaced, OrderCancelled, OrderUpdated.
• Actions:
  • On placing an order, publish OrderPlaced.
  • On canceling an order, publish OrderCancelled.
  • On updating an order (like status change), publish OrderUpdated.
• Events Consumed: ProductRemoved, PaymentProcessed.
• CQRS Implementation: Command side for processing orders, Query side for order tracking.

Customer Service

• Events Produced: CustomerProfileUpdated.
• Actions:
  • On updating customer profiles, publish CustomerProfileUpdated.
• Events Consumed: OrderPlaced, OrderCancelled.
• CQRS Implementation: Command side for customer data updates, Query side for customer data retrieval.

Inventory Service

• Events Produced: InventoryUpdated.
• Actions:
  • On changes in inventory, publish InventoryUpdated.
• Events Consumed: ProductAdded, OrderPlaced, OrderCancelled.
• CQRS Implementation: Command side for inventory updates, Query side for inventory queries.

Payment Service

• Events Produced: PaymentProcessed, RefundProcessed.
• Actions:
  • On successful payment, publish PaymentProcessed.
  • On processing a refund, publish RefundProcessed.
• Events Consumed: OrderPlaced, OrderCancelled.
• CQRS Implementation: Command side for transaction processing.

---

Compensating Transactions and Saga Choreography

Scenario 1: Failed Payment Processing

• Flow: Order Placement → Payment Failure → Order Cancellation
• Compensating Transaction: If payment fails in Payment Service, trigger a compensating transaction in Order Processing Service to cancel the order and update inventory in Inventory Service.
• CQRS Impact: Command sides of Payment and Order Services roll back changes, while their Query sides provide updated transaction status.

Scenario 2: Inventory Shortage Post Order Placement

• Flow: Order Placement → Inventory Shortage Detected → Order Cancellation and Refund
• Compensating Transaction: Post order placement, if Inventory Service detects a shortage, it initiates a compensating transaction to cancel the order in Order Processing Service and process a refund in Payment Service.

Scenario 3: Customer Profile Update Failure

• Flow: Customer Updates Profile → Failure in Update → Revert Changes
• Compensating Transaction: If Customer Service fails to update the profile, ensure the previous state is restored, and the customer is notified of the failure.

Scenario 4: Product Catalog Sync Issue

• Flow: Product Update in Catalog → Sync Failure with Inventory → Revert Catalog Update
• Compensating Transaction: If Inventory Service cannot sync with a product update, trigger a rollback in Product Catalog Service to maintain consistency.

Scenario 5: Order Cancellation Failure

• Flow: Customer Initiates Order Cancellation → Failure in Processing → Escalation
• Compensating Transaction: If the order cancellation fails in Order Processing Service, escalate the issue for manual intervention and notify the customer.

---

Circuit Breaker Usage Scenarios

Scenario 1: Overloaded Customer Service

• Trigger: High request volume to Customer Service.
• Circuit Breaker: In services interacting with Customer Service.
• Action: Use fallback methods to serve cached customer data or simplified responses.

Scenario 2: Payment Service Timeout

• Trigger: Payment Service times out during transaction processing.
• Circuit Breaker: Implemented in Order Processing Service for payment calls.
• Action: Queue the payment request and attempt later, informing the customer about the delay.

---

Flow of Events Between Microservices for CQRS

• Command Side: Services like Order Processing and Payment handle create, update, and delete operations, emitting events post transactions.
• Query Side: Services like Customer Service and Inventory Service consume events to update their query models, ensuring real-time data representation.

Relationships Between Command and Query Sides in CQRS

• In the Product Catalog Service:
  • Command Side: Handles addition, update, and removal of products.
  • Query Side: Provides up-to-date product listings and details, updated through events from the command side.
• In the Order Processing Service:
  • Command Side: Manages order placement, updates, and cancellations.
  • Query Side: Offers real-time order tracking, updated via events like OrderPlaced and OrderCancelled.
• In the Customer Service:
  • Command Side: Manages updates to customer profiles.
  • Query Side: Provides access to customer details, history, and preferences, updated through events related to orders and profile changes.

---

Detailed Scenarios for Inter-Service Communications and Design Patterns

Scenario 6: Implementing the Strangler Pattern

• Context: Gradually transitioning from a legacy system to the new microservices architecture.
• Implementation: Introduce an API Gateway to redirect certain requests to new services while keeping others on the legacy system. Slowly increase the scope of requests handled by new services.

Scenario 7: Utilizing the API Gateway Pattern

• Context: Managing incoming traffic efficiently and securely.
• Implementation: Deploy Spring Cloud Gateway or Zuul as an entry point. Configure routes, load balancing, and security measures like authentication and rate limiting.

Scenario 8: Proxy Pattern for Third-Party Integrations

• Context: Integrating with external services for payment processing.
• Implementation: Create a Proxy Service that interfaces with the third-party payment gateway, adding an extra layer for handling retries, error logging, and response transformations.

Scenario 9: Aggregator Pattern for Unified Customer Dashboard

• Context: Creating a dashboard showing customer's orders, preferences, and recommendations.
• Implementation: Implement an Aggregator microservice that collates data from Customer, Order, and Product Catalog services to present a unified view.

Scenario 10: Implementing Chained Patterns for Order Fulfillment

• Context: Processing an order involves multiple steps handled by different services.
• Implementation: Chain Order, Inventory, and Payment services. The completion of one step triggers the next service in the chain, ensuring a seamless order fulfillment process.

---

Asynchronous Communication Strategies

Scenario 11: Asynchronous Order Processing

• Context: Decoupling order placement from actual processing.
• Implementation: Use Kafka to queue order requests. Order Processing Service consumes messages asynchronously, allowing for better load handling.

Scenario 12: Event-Driven Inventory Updates

• Context: Real-time inventory updates post order confirmation or cancellation.
• Implementation: Inventory Service listens to events from Order Processing Service to update stock levels asynchronously.

---

Failure Scenarios and Circuit Breaker Implementation

Scenario 13: Inventory Service Downtime

• Trigger: Inventory Service becomes temporarily unavailable.
• Circuit Breaker: In Product Catalog Service when accessing inventory data.
• Action: Provide fallback responses based on cached data or predefined rules until the Inventory Service is back online.

Scenario 14: External Communication Failure

• Trigger: Failure in communicating with external shipping services.
• Circuit Breaker: In Order Processing Service during shipping request handling.
• Action: Queue shipping requests and process them once the external service is available again.

---

Conclusion

These scenarios, patterns, and strategies provide a roadmap for developing a sophisticated E-commerce Platform using Spring Boot microservices. They emphasize the importance of designing a system that is resilient, scalable, and capable of handling real-world challenges in e-commerce operations. By implementing these guidelines, developers will gain valuable insights into microservices architecture, enabling them to build advanced, enterprise-level applications.

[kuttiram]

@akash-coded - Can you please share the overall theory whiteboard that you used during the training hours and the demo project that you created. Really, it will help us.

Thanks,
Ramesh Kumar

[akash-coded]

Sorry for the delay. I was on a hiatus post the training. I have shared it all. I have been trying to upload it to the repo. But there are some merge conflicts to be addressed. Hope you have received the whiteboards.

[akash-coded]

@kuttiram Sorry for the delay. I was on a hiatus post the training. I have shared it all. I have been trying to upload it to the repo. But there are some merge conflicts to be addressed. Hope you have received the whiteboards.

[kuttiram]

@akash-coded - Not yet Akash. can you please help me to get that. Thanks

[vinayak355]

Dear @akash-coded Just I have submitted the final project assignment on the 'E-commerce Application' in the learning portal.
I request you to please evaluate the same.

[cppbeginner]

Hey Akash, I created one producer (order), to consumers (inventory and payment), however only one listener reads the message. Can you help here.

[niroshkumar]

Dear @akash-coded , I have submitted the partial in the portal, but now I have completed the whole project and uploaded the source code in the GitHub link below. Please consider this version for my final project evaluation.

https://github.com/niroshkumar/TCS_NIROSH_CapstoneProject/tree/Crypto-2021

Thanks
Niroshkumar
+1 9055502922

[RnNilesh]

Dear @akash-coded I have submitted the final project assignment on the 'E-commerce Application' in the learning portal. I have implemented few more fun here , attaching zip file, I request you to please evaluate the same.
CapstoneProject_Nilesh.zip

[BibhuOfficial]

Hi Akash, waiting for your response on my issue I was facing related to api-gateway. Also please find attached the project.
capstone.zip

Bibhu Rath(TCS)

[VidyaChelluri]

Hi Akash

Please find the solution for capstone project attached.

Thanks
Vidya Madhuri Chelluri
(TCS)
capstone.zip

[Bhagavathg88]

Hi Akash, I have uploaded the project in LMS. Added few more tasks and uploading it here.
Capstone Project - Assignment.docx