Microservice system design - service fusing and degradation design

Abstract

OpenFeign The call between microservices is completed , And in the case of multi instance clusters , Adjust the load policy to deal with concurrent calls . Network product development , The network may sometimes be unavailable , The service may also be unavailable , When the calling service is slow or unavailable , A large backlog of requests , Will be the last straw to overwhelm the camel of the system .

One 、Hystrix Principle

It is the basic component of a low delay fault tolerance mechanism provided by distributed systems , Provide current limiting 、 service degradation 、 System fuse protection 、 Fast failure and other dimensions to ensure the stability of micro services .Hystrix It's also Netflix Part of the kit .

Unfortunately 1.5.18 After the release, it entered maintenance mode , Officials offer alternatives ：resilience4j , This test uses Hystrix ultimate , If you need a higher version , It is suggested that resilience4j , I won't give you too much introduction here , It will be replaced by another important component ——Sentinel To replace Hystrix.

1.1 introduce Hystrix

use starter Way to introduce

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

feignClient The function of circuit breaker has been integrated by default in , But it needs to be opened in the configuration file , Ability to open . stay application.properties Open in hystrix switch ：

#hystrix enable
feign.hystrix.enabled=true

Go back to the previous FeignClient Code , Add... In comments fallback Property value , Add corresponding fallback Calling class .

@FeignClient(value = "card-service", fallback = MemberCardServiceFallback.class)
public interface MemberCardClient {

    @RequestMapping(value = "/card/addCard", method = RequestMethod.POST)
    public CommonResult<Integer> addCard(@RequestParam(value = "json") String json) throws BusinessException;

    @RequestMapping(value = "/card/updateCard", method = RequestMethod.POST)
    public CommonResult<Integer> updateCard(@RequestParam(value = "json") String json) throws BusinessException;
}

To write MemberCardServiceFallback Method , Is a common service implementation class , increase @Component annotation .

@Component
@Slf4j
public class MemberCardServiceFallback implements MemberCardClient {

    @Override
    public CommonResult<Integer> addCard(String json) throws BusinessException {
        CommonResult<Integer> result = new CommonResult<>("parking-card service not available! ");
        log.warn("parking-card service not available! ");
        return result;
    }

    @Override
    public CommonResult<Integer> updateCard(String json) throws BusinessException {
        CommonResult<Integer> result = new CommonResult<>("parking-card service not available! ");
        log.warn("parking-card service not available! ");
        return result;
    }

}

1.2 test Hystrix

The function has been completed according to the normal process in the previous chapter ： After the member opens , Integral generation , There will be no startup " Points sub service ", See what the effect will be .( The default service registry has been started , It will not be specifically mentioned here and in the subsequent demonstrations )

1. Start only parking-member A sub service
2. open parking-member Sub service swagger-ui Interface , Call the member binding mobile number interface ( Or adopt PostMan Tools )

Under normal circumstances, it will directly call fallback Interface , Fast failure , Response caller . At this point, the integration module service will be started , Call again , In the correct case, it is no longer called fallback Method , Instead, the integration service interface is called normally , Shown below ：

1.3 Graphical monitoring Hystrix

Through the above application , We can already Hystrix Normal integration into the function development process , But after all Hystrix What is the real-time running status ？ Is there any way to see Hystrix The indicators of ？ Here we introduce Hystrix Dashboard ( The dashboard ), adopt UI The way , Check the health status quickly .

Add instrument panel table item ： We are parking-base-serv Under the project , Create a new one called parking-hystrix-dashboard Spring Boot Sub project , It's for you Hystrix Instrument cluster monitoring . modify pom.xml file , Add dependencies ：

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>

Add... In the project startup class @EnableHystrixDashboard annotation , Turn on the instrument cluster function

@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrixDashboard
public class ParkingHystrixDashboardApplication {

    public static void main(String[] args) {
        SpringApplication.run(ParkingHystrixDashboardApplication.class, args);
    }

}

Start project , Open the address ：http://localhost:10093/hystrix, The following interface appears to indicate normal operation .

Adjust the monitored items ： In the member service, in the process of calling the points service interface , use Feign To initiate a remote call , At the same time fallback service degradation 、 Fast fail function , The main objective of this monitoring is this function . stay parking-member project config Code package , increase Hystrix Configuration of data flow ：

@Configuration
public class HystrixConfig {

    @Bean
    public ServletRegistrationBean<HystrixMetricsStreamServlet> getServlet() {
        HystrixMetricsStreamServlet servlet = new HystrixMetricsStreamServlet();
        ServletRegistrationBean<HystrixMetricsStreamServlet> bean = new ServletRegistrationBean<>(servlet);
        bean.addUrlMappings("/hystrix.stream");
        bean.setName("HystrixMetricsStreamServlet");
        return bean;
    }
}

After starting , Open the Hystrix Data acquisition address ：http://localhost:10060/hystrix.stream, The initial state , The page will keep outputting ping The case of null value , Only use Hystrix When relevant functions are requested , To output data normally JSON Format data , As shown in the screenshot ：

The output of the above figure is not friendly , There is no way to intuitively analyze Hystrix Application of components , At this point, our dashboard project comes in handy .

Dashboard interpretation ： Address http://localhost:10060/hystrix.stream Input to dashboard The data in the page is captured in the address bar ,Delay Items can have default values ,Titile Items can be given a new name , So that we can identify . alike , Related functions have only been performed , The instrument cluster can display normally , The following figure shows that the points service is not started , The direct invocation of member services leads to all failures .

 

Two 、sentinel Principle

Blog reference