How Microservices Communicate with Each Other?
Introduction
In today’s software engineering, microservices architecture has become a popular choice for building scalable, flexible, and maintainable systems. A key challenge in designing and implementing microservices is ensuring that they can communicate effectively with each other. Microservices are designed to be loosely coupled, which means that each service should be able to operate independently and communicate with others when necessary.
How Microservices Communicate with Each Other
Microservices communicate with each other using various communication mechanisms. The choice of mechanism depends on the specific requirements of the system, the infrastructure, and the constraints of the project. Here are some of the common ways microservices communicate with each other:
Request-Response Pattern
The most common way for microservices to communicate with each other is by using the request-response pattern. In this pattern, a microservice requests some information or functionality from another microservice, and the second microservice responds with the requested information or performs the requested action. This pattern is often used when a microservice needs to send a request to another microservice, wait for a response, and use the response to continue processing.
Request-Response Pattern
| Microservice A | Microservice B | Request | Response |
|---|---|---|---|
| Customer Service | Payment Service | Get Order Details | Order Details |
| Inventory Service | Order Service | Check Availability | Available Quantity |
Event-Driven Architecture (EDA)
In an event-driven architecture, microservices publish and subscribe to events. When an event occurs in one microservice, it publishes the event to a message broker, which then forwards the event to the subscribed microservices. The subscribed microservices can then react to the event and perform the required actions.
Event-Driven Architecture (EDA)
| Microservice A | Event | Microservice B |
|---|---|---|
| Order Service | Order Placed | Inventory Service |
| Inventory Service | Product Stocked | Shipping Service |
| Payment Service | Payment Confirmed | Customer Service |
API Calls
Microservices can also communicate with each other by making API calls. This is similar to the request-response pattern, but the request and response are encoded in a specific data format, such as JSON or XML.
API Calls
| Microservice A | API Call | Microservice B | API Call |
|---|---|---|---|
| Customer Service | GetOrderDetails | Order Service | GetOrderDetails |
| Inventory Service | CheckAvailability | Product Service | GetProductDetails |
Message Queues
Message queues are a popular choice for microservices communication. In this approach, a microservice sends a message to a message queue, and another microservice consumes the message from the queue.
Message Queues
| Microservice A | Message | Microservice B | Consumer |
|---|---|---|---|
| Order Service | OrderDetails | Inventory Service | Inventory Consumer |
| Inventory Service | ProductStocked | Shipping Service | Shipping Consumer |
Gossip Protocol
Gossip protocol is a technique used for microservices to communicate with each other over a network. It’s commonly used in distributed systems, where microservices may need to discover other microservices or update each other about changes.
Gossip Protocol
| Microservice A | Peer | Event |
|---|---|---|
| Microservice X | Microservice Y | Change in Status |
Distributed Locks
Distributed locks are used to ensure that multiple microservices do not interfere with each other when accessing a shared resource.
Distributed Locks
| Microservice A | Lock | Lock Duration |
|---|---|---|
| Microservice X | Lock 1 | 5 minutes |
Service Discovery
Service discovery is the process of discovering the location of a microservice in a distributed system. It’s a crucial component of a microservices architecture, as it allows microservices to find each other and communicate effectively.
Service Discovery
| Microservice A | Service Discovery | Microservice B |
|---|---|---|
| Order Service | Eureka | Inventory Service |
| Inventory Service | Consul | Shipping Service |
Conclusion
In this article, we have discussed various ways in which microservices can communicate with each other. These mechanisms, including request-response pattern, event-driven architecture, API calls, message queues, gossip protocol, distributed locks, and service discovery, enable microservices to work together in harmony to build scalable and maintainable systems.