Scalable Human Blog

In the era of microservices and distributed systems, it can be tempting to think of every service interaction in terms of HTTP calls. After all, HTTP is a widely understood protocol with a plethora of libraries and tools available for almost every language and platform. But is this a wise design choice? In this post, we will explore why placing an HTTP call in front of every service might not be the best idea.

1. Latency

Problem: Each HTTP call introduces additional latency. This is the time it takes to initiate the call, wait for the server to process the request, and then wait for the response to come back. Even in high-speed networks, this can add significant delays.

Impact: In a microservices architecture, where a single user request might result in multiple inter-service communications, this latency can multiply quickly. As more services are added or as the load increases, latency can escalate, affecting user experience.

2. Overhead

Problem: HTTP is a stateless, text-based protocol. Each request and response come with headers and other metadata, which can add up in terms of bytes transferred.

Impact: This overhead can put unnecessary strain on the network and increase the time it takes to process each request and response, especially when dealing with a large number of small-sized service interactions.

3. Unnecessary Complexity

Problem: Using HTTP for all service interactions forces you to handle a plethora of HTTP-specific concerns like status codes, headers, and URL routing for every single service, even if these concerns aren’t directly relevant to the service’s business logic.

Impact: Developers have to spend extra time and effort dealing with these concerns, making the system harder to maintain and evolve.

4. Tight Coupling

Problem: When services communicate via HTTP, they often become tightly coupled to the specifics of each other’s HTTP interfaces. A minor change in one service’s API can necessitate changes in all other services that communicate with it.

Impact: This can lead to a fragile system where changes become risky and slow to implement, defeating one of the main advantages of a microservices architecture: independent deployability.

5. Error Handling

Problem: HTTP error handling can be tricky. Different status codes, network failures, timeouts, and partial failures all introduce complexity.

Impact: Without careful design, this can lead to services that don’t handle errors gracefully, potentially causing cascading failures throughout the system.

6. Less Efficient Communication Mechanisms Available

Problem: Not all service interactions are best served by HTTP. Binary protocols, for example, can be much more efficient for certain types of interactions.

Impact: By defaulting to HTTP for everything, you might be missing out on more efficient communication mechanisms that could reduce costs, increase performance, and simplify development.

7. Security Concerns

Problem: Exposing every service via HTTP might open up additional attack vectors. Each HTTP endpoint is a potential point of vulnerability.

Impact: The security surface area increases, requiring more stringent security practices and potentially more complex infrastructure like API gateways.

Conclusion

While HTTP is an immensely valuable protocol and serves as the backbone of the modern web, it’s essential to understand its limitations and overheads. In a microservices architecture, it’s crucial to make intentional decisions about inter-service communication mechanisms based on the specific needs and constraints of the system. Blindly placing an HTTP call in front of every service can introduce unnecessary complexity, reduce system performance, and lead to more fragile and hard-to-maintain systems.

📚 Further Reading & Related Topics

If you’re exploring microservices communication and architectural best practices, these related articles will provide deeper insights:

• Selecting the Right API Gateway: Key Considerations for Your Architecture – Learn how API gateways can optimize service-to-service communication and mitigate the issues caused by excessive HTTP calls.

• To Message or REST? Understanding Kafka, RabbitMQ, and RESTful APIs – Explore alternative communication patterns such as message queues and event-driven architectures to reduce HTTP overhead.