How to split Nest.js microservices into separate projects?

Splitting Strategy

To address your query, here is a step-by-step approach for splitting an existing NestJS application into microservices. This process generally involves the following steps:

1. Identify Services: Identify which parts of the business logic can be extracted into standalone services. This is typically done based on business domains or functional areas.
2. Define Communication: Determine how services communicate with each other. NestJS supports various microservice communication protocols, such as TCP, Redis, RabbitMQ, and Kafka.
3. Refactor Code: Refactor the code to create standalone services. This involves moving business logic, controllers, services, and modules into new NestJS projects.
4. Handle Shared Code: Identify and handle shared code, such as libraries and utility functions, by placing them in a separate shared library for all services to use.
5. Data Management: Address data management issues, which may involve splitting databases or implementing API calls to access data.
6. Testing & Deployment: Ensure thorough testing before independently deploying each service. Then set up a CI/CD pipeline for automated deployment.

Practical Example

For example, consider an e-commerce application with features such as order processing, inventory management, and user management. The steps for splitting it into microservices might be as follows:

1. Identify Services:
   • Order Service: Manages order creation, updates, and queries.
   • Inventory Service: Manages product inventory.
   • User Service: Manages user information and authentication.
2. Define Communication:
   • Decide to use RabbitMQ as the message queue for asynchronous inter-service communication.
3. Refactor Code:
   • Create three new NestJS projects and migrate the corresponding controllers, services, modules, and entities to the respective projects.
4. Handle Shared Code:
   • If there are common functionalities, such as logging or authentication, create a shared library that all services can reference.
5. Data Management:
   • Each service has its own database instance, or retrieves data via API from other services.
6. Testing & Deployment:
   • Perform unit tests and integration tests for each service.
   • Set up a CI/CD pipeline to ensure each service can be deployed independently.

Summary

Splitting NestJS microservices is a thoughtful process involving architectural decisions, code refactoring, and infrastructure configuration. The above provides a high-level overview, but in practice, each step requires detailed planning and execution to ensure system robustness and maintainability.