5.Spring Cloud初相識-------Hystrix熔斷器
阿新 • • 發佈：2018-12-17
前言：
1.介紹Hystrix
在一個分散式系統裡，許多依賴不可避免的會呼叫失敗，比如超時、異常等，如何能夠保證在一個依賴出問題的情況下，不會導致整體服務失敗，這個就是Hystrix需要做的事情。Hystrix提供了熔斷、隔離、Fallback、cache、監控等功能，能夠在一個、或多個依賴同時出現問題時保證系統依然可用。
2.為什麼使用Hystrix
在分散式系統架構中多個系統之間通常是通過遠端RPC呼叫進行通訊，也就是 A 系統呼叫 B 系統服務，B 系統呼叫 C 系統的服務。當尾部應用 C 發生故障而系統 B 沒有服務降級時候可能會導致 B，甚至系統 A 癱瘓，這種現象被稱為雪崩現象。所以在系統設計時候要使用一定的降級策略，來保證當服務提供方服務不可用時候，服務呼叫方可以切換到降級後的策略進行執行。
實戰：
1.新建服務消費者：
（1）新增依賴
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.xm.cloud</groupId> <artifactId>cl_hello_consumer_hy</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>cl_hello_consumer_hy</name> <description>This is a Web about springcloud</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.6.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> <spring-cloud.version>Finchley.SR2</spring-cloud.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-hystrix</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>${spring-cloud.version}</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
（2）修改配置
eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/
eureka.client.register-with-eureka=false
feign.hystrix.enabled=true
（3）開啟註解
package com.xm.cloud; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.openfeign.EnableFeignClients; @EnableDiscoveryClient @EnableFeignClients @SpringBootApplication public class ClHelloConsumerHyApplication { public static void main(String[] args) { SpringApplication.run(ClHelloConsumerHyApplication.class, args); } }
（4）配置熔斷回撥工廠
package com.xm.cloud.fallback;
import org.springframework.stereotype.Component;
import com.xm.cloud.service.HelloService;
import feign.hystrix.FallbackFactory;
@Component
public class HelloServiceFallbackFactory implements FallbackFactory<HelloService> {
@Override
public HelloService create(Throwable cause) {
return new HelloService() {
@Override
public String sayHello() {
return "HelloService 異常！";
}
};
}
}
（5）新建Service
package com.xm.cloud.service;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import com.xm.cloud.fallback.HelloServiceFallbackFactory;
@FeignClient(value="CL-HELLO-PRODUCER",fallbackFactory=HelloServiceFallbackFactory.class)
public interface HelloService {
@GetMapping("/hello")
public String sayHello();
}
（6）新建Controller
package com.xm.cloud.controller;
import java.util.ArrayList;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.xm.cloud.service.HelloService;
@RestController
public class HelloController {
@Autowired
private HelloService helloService;
@GetMapping("/hello")
public List<String> sayHello() {
List<String> list = new ArrayList<String>();
for(int i=0;i<10;i++) {
list.add(helloService.sayHello());
}
return list;
}
}
2.新建服務提供者：
（1）新增依賴
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xm.cloud</groupId>
<artifactId>cl_hello_producer_hy</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>cl_hello_producer_hy</name>
<description>This is a Web about springcloud</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
（2）修改配置
server.port=8001
spring.application.name=cl-hello-producer
eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/（3）開啟註解
package com.xm.cloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@EnableDiscoveryClient
@EnableCircuitBreaker
@SpringBootApplication
public class ClHelloProducerHyApplication {
public static void main(String[] args) {
SpringApplication.run(ClHelloProducerHyApplication.class, args);
}
}
（4）新建Controller
package com.xm.cloud.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
@RestController
public class HelloController {
@GetMapping("/hello")
@HystrixCommand
public String sayHello() {
if(Math.random()>0.5) {
throw new RuntimeException();
} else {
return "Hello spring cloud!";
}
}
}
3.測試
執行：localhost:8080/hello
| 0 | "HelloService 異常！" |
|---|---|
| 1 | "Hello spring cloud!" |
| 2 | "HelloService 異常！" |
| 3 | "Hello spring cloud!" |
| 4 | "Hello spring cloud!" |
| 5 | "Hello spring cloud!" |
| 6 | "Hello spring cloud!" |
| 7 | "Hello spring cloud!" |
| 8 | "HelloService 異常！" |
| 9 | "Hello spring cloud!" |