Building distributed applications based on Spring Cloud

With the rapid development of Internet applications, distributed architecture has become a mainstream trend in modern application development. The advantage of distributed applications is that they can better handle problems such as high concurrency and large data volumes, and improve the reliability, scalability and flexibility of applications. As one of the most popular microservice frameworks at present, Spring Cloud's flexibility and ease of use make more developers choose to build distributed applications based on Spring Cloud. This article will share relevant knowledge about building distributed applications based on Spring Cloud based on practical experience.

1. Introduction to Spring Cloud

Spring Cloud is a microservice architecture development framework based on Spring Boot. It provides a complete set of distributed system development tools for Spring Boot applications, including configuration management, Components such as service discovery, circuit breakers, intelligent routing, micro-agents, and control buses help developers quickly build distributed systems. Spring Cloud is very popular in the Spring community, and more and more companies are using Spring Cloud to build their own microservice applications.

2. Distributed application architecture

From single application to distributed application, the architecture has changed significantly. In distributed applications, a large system is split into several microservices. Each microservice has its own independent functions and business logic. The microservices communicate through RPC, HTTP and other protocols, working independently and collaborating with each other. In the entire distributed system, the support of service registration center, configuration center, load balancing, gateway and other components is often required.

3. Spring Cloud application components

1. Service registration and discovery

Spring Cloud Eureka is the service registration and discovery component in Spring Cloud. In a distributed architecture, All services need to be registered in Eureka Server and query the addresses of other services through Eureka Client, thus realizing automatic discovery and load balancing of services. In actual applications, we often introduce Eureka Client dependencies in each microservice to realize service registration and discovery.

2. Configuration Center

Spring Cloud Config is the configuration center management component of Spring Cloud. Its function is to centrally manage configuration files and put the configuration files of all microservices in one It is managed locally and the configuration is obtained through HTTP or git protocol. This avoids errors caused by manually modifying configuration files.

3. Load Balancing

Spring Cloud Ribbon is a client-side load balancer based on HTTP and TCP. It is responsible for handling communication between services and distributing requests according to specified rules. to different instances to improve system performance and reliability. In Spring Cloud applications, we can use Ribbon's default load balancing strategy or customize the load balancing strategy as needed.

4. Circuit breaker

Spring Cloud Hystrix is ​​a circuit breaker component used to manage distributed systems. It mainly implements the ability to protect distributed systems and prevent infectious faults from causing system collapse. . When the failure rate of the requested service reaches a certain threshold, Hystrix will automatically cut off the service and quickly enable fallback logic to reduce the impact on other services.

5. Gateway

Spring Cloud Gateway is the API gateway component in Spring Cloud. It can route and uniformly process all microservice requests, improving the maintainability and security of the system. and scalable, but it does not depend on any specific protocol or implementation, so it can be used in any scenario that requires API routing processing.

4. Practical application

1. Build a service registration center

The service registration center is the basic component of the entire microservice architecture, so we first need to build an Eureka Server as Service registration center. In Spring Cloud, we can build Eureka Server by adding the following dependencies.

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>

Add the following content in the configuration file to start Eureka Server.

server.port=8761
eureka.instance.hostname=localhost
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

2. Create a service provider

The service provider is where we actually write business logic. When implementing the service provider, we can add the following dependencies to realize the registration function of the service .

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

In the configuration file, we need to specify the address of the Eureka Server.

eureka.client.service-url.default-zone=http://localhost:8761/eureka/

After writing the business logic, we need to register it with the Eureka Server when the service starts.

@SpringBootApplication
@EnableDiscoveryClient
public class ProviderApplication {
    public static void main(String[] args) {
        SpringApplication.run(ProviderApplication.class, args);
    }
}

3. Create a service consumer

The service consumer is where the interface provided by the service provider is called. When implementing the service consumer, we can add the following dependencies to realize the service Discover features.

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

    org.springframework.cloud
    spring-cloud-starter-netflix-ribbon

In the configuration file, we also need to specify the address of the Eureka Server.

eureka.client.service-url.default-zone=http://localhost:8761/eureka/

After writing the business logic, we need to call the interface provided by the service provider through RestTemplate and other methods.

@Service
public class ConsumerService {
    @Autowired
    private RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "fallback")
    public String helloService() {
        return restTemplate.getForObject("http://PROVIDER-SERVICE/hello", String.class);
    }

    public String fallback() {
        return "error";
    }
}

5. Summary

This article introduces the relevant knowledge of building distributed applications based on Spring Cloud, and shares the actual application process based on practice. Spring Cloud provides a complete set of distributed architecture solutions, which provides great convenience for us to develop distributed applications. Through learning and practice, we can better master and apply Spring Cloud to build our own distributed applications.

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