With the rapid development of the Internet, more and more businesses need to support high concurrency, high availability, and high performance, which poses new challenges to traditional monolithic architectures and database storage methods. The microservice architecture solves many problems faced by the traditional monolithic architecture in a distributed environment by dividing the system into multiple independent small services.

In the microservice architecture, each functional unit is an independent service, and services call each other in various ways. It is inevitable to face problems such as exceptions and failures between services. In response to this situation, we need to introduce some mechanisms to ensure the availability and stability of the system, including service interruption and degradation.

Service circuit breaker

Service circuit breaker is a common fault-tolerance mechanism. When the error rate of a service exceeds a certain threshold, the circuit breaker will open, disconnecting the mutual calls between services, and return A preset default response.

Circuits can effectively handle abnormal situations in a short period of time, prevent incorrect responses from being transmitted to the upstream system, avoid upstream and downstream systems from dragging each other down, and improve the availability of the entire system. Generally, service circuit breaker can be achieved through Hystrix that comes with Spring Cloud.

Steps to use Hystrix:

1.Introduce Hystrix dependency

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

2.Add the @EnableCircuitBreaker annotation on the main class

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

3.Use @ HystrixCommand annotation handles service degradation and circuit breaker

@HystrixCommand(fallbackMethod = "defaultProcess")
public String process(String data) {
    // 服务调用
}

public String defaultProcess(String data) {
    // 熔断和降级处理
}

Service degradation

Since the default response of service circuit breaker may not match the actual business scenario, we also need to introduce a service degradation mechanism. When the service is abnormal or circuit breaker, Instead of throwing an exception or returning an error result, return the preset default response.

When services are downgraded, corresponding processing strategies need to be formulated based on actual business needs. For example, cached data, default values, exception prompts, etc. can be returned when services are downgraded to minimize the impact on users.

The steps to implement service downgrade using Spring Cloud are similar to service circuit breaker. You need to use the @HystrixCommand annotation in the resource class and specify the method corresponding to the fallbackMethod attribute to implement service degradation.

@HystrixCommand(fallbackMethod = "defaultGetData")
public String getData(String id) {
    // 服务调用
}

public String defaultGetData(String id) {
    // 服务降级处理
}

In short, in the microservice architecture, circuit breakers and downgrade mechanisms are very important fault tolerance mechanisms. Spring Cloud provides Hystrix to support this mechanism. When faced with service failures or abnormalities, we should perform circuit breaker and downgrade processing in a timely manner to avoid the spread of faults, thereby ensuring system availability and robustness.

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