API Gateway pattern : Why? When to use ?
API Gateway is a server that acts as an entry point for APIs. It provides a centralized way for managing, and optimizing API communication.
API Gateway pattern
The API Gateway pattern is a design pattern used in software architecture. which uses API gateway server as single entry point for all clients.
- This pattern is recommended if you want to build a complex or large microservices-based application with multiple clients.
- This server acts as a gateway for incoming requests and helps provide various services such as authorization, rate limiting, caching, logging..
When to use API Gateway pattern ?
Have Diverse Client Base: Used to Simplify Client Interaction.
- When your system serves various clients (e.g., web applications, mobile apps, third-party integrations), an API Gateway can simplify the client experience by providing a unified API.
- By presenting a simplified and consistent API to clients, it hides the complexities of the underlying microservices.
Handle cross-cutting concern : when you need Centralized way to handle cross-cutting concerns ( security, monitoring, analytics .. )
- When your system requires centralized security management, including authentication, authorization, and encryption.
- When you need centralized monitoring, logging, and analytics to gain insights into the usage and performance of your APIs.
Traffic Management
- When load balancing, rate limiting, or traffic shaping is essential to ensure the reliability and performance of your microservices.
Key features of API Gateway :
Authentication and Authorization: The API Gateway handles authentication and authorization on behalf of the microservices. It ensures that only authenticated and authorized requests are forwarded to the underlying services, enhancing security.
Protocol Translation: The API Gateway can handle different communication protocols, translating requests from one protocol to another.
Request Routing: It can route requests to the appropriate microservices based on the request’s path, method, or other criteria. It allows for flexible and dynamic routing of incoming requests.
Rate Limiting
Caching: It can implement caching mechanisms to store and retrieve frequently requested data
Logging and Monitoring
— Logging: API Gateways can log requests and responses, providing a centralized point for monitoring and debugging.
— Analytics: Collects data on API usage, helping with performance monitoring, and making informed decisions about scaling.
SSL/TLS termination: It can manage SSL/TLS termination, encrypting and decrypting requests before forwarding them to microservices.
Error Handling
Transformation and Enrichment:
— Request/Response Transformation: It can transform requests and responses to adapt to different data formats or versions.
— Data Enrichment: Allows adding or enriching data before it reaches the microservices, reducing the burden on individual services.
Alternatives to API gateway
- Direct Communication (Decentralized):
— In this approach, services communicate directly with each other without an intermediary API Gateway.
— Each microservice is responsible for handling its own API requests and responses.
— This can reduce the single point of failure but may require additional effort in managing communication complexities.
2. Service Mesh:
— Service meshes, like Istio or Linkerd, provide a dedicated infrastructure layer for handling service-to-service communication.
— They offer features such as load balancing, service discovery, and traffic management without the need for a central API Gateway.
— This approach is particularly beneficial for microservices deployments with a high level of complexity and inter-service communication.
3. Backend for Frontend (BFF):
— The Backend for Frontend pattern involves creating separate backend services tailored for specific frontend applications or user interfaces.
— Instead of a centralized API Gateway, each frontend application communicates with its dedicated backend service.
— This allows for better customization of APIs based on the requirements of each frontend application.
4. GraphQL Federation:
— GraphQL Federation allows for a decentralized approach to handling API requests.
— Microservices expose their own GraphQL endpoints, and a federated gateway stitches these schemas together.
— This approach offers flexibility and can cater to specific client needs without relying on a monolithic API Gateway.
5. Edge Services:
— Content Delivery Networks (CDNs) and edge computing platforms can be leveraged for handling authentication, caching, and routing closer to the end-users.
PS : It’s common for a combination of these patterns to be used in a microservices architecture.
tldr
API gateway pattern has some benefits:
- Insulates the clients from the problem of determining the locations of service instances
- Simplifies the client by moving logic for calling multiple services from the client to API gateway
- Translates from a “standard” public web-friendly API protocol to whatever protocols are used internally
API gateway pattern has some drawbacks:
- Increased complexity/cost — the API gateway is yet another moving part that must be developed, deployed and managed
- Increased response time due to the additional network hop through the API gateway
