分布式系统的延时和故障容错之Spring Cloud Hystrix
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本示例主要介绍 Spring Cloud 系列中的 Eureka,如何使用Hystrix熔断器容错保护我们的应用程序。
在微服务架构中,系统被拆分成很多个服务单元,各个服务单元的应用通过 HTTP 相互调用、依赖,在某个服务由于网络或其他原因自身出现故障、延迟时,调用方也会出现延迟。若调用方请求不断增加,可能会形成任务积压,最终导致调用方服务瘫痪,服务不可用现象逐渐放大。
解决方案
Spring Cloud Hystrix 是一个专用于服务熔断处理的开源项目,实现了一系列服务保护措施,当依赖的服务方出现故障不可用时,hystrix实现服务降级、服务熔断等功能,对延迟和故障提供强大的容错能力,从而防止故障进一步扩大。
Hystrix 主要作用介绍
- 保护和控制底层服务的高延迟和失效对上层服务的影响。
- 避免复杂分布式中服务失效的雪崩效应。在大型的分布式系统中,存在各种复杂的依赖关系。如果某个服务失效,很可能会对其他服务造成影响,形成连锁反应。
- 快速失效和迅速恢复。以Spring为例,一般在实现controller的时候,都会以同步的逻辑调用依赖的服务。如果服务失效,而且没有客户端失效机制,就会导致请求长时间的阻塞。如果不能快速的发现失效,而就很难通过高可用机制或者负载均衡实现迅速的恢复。
- 实现服务降级。这一点是从用户体验来考虑的,一个预定义默认返回会比请求卡死或者500好很多。
- 实现了服务监控、报警和运维控制。Hystrix Dashboard和Turbine可以配合Hystrix完成这些功能。
Hystrix 主要特性:
服务熔断
Hystrix 会记录各个服务的请求信息,通过 成功、失败、拒绝、超时 等统计信息判断是否打开断路器,将某个服务的请求进行熔断。一段时间后切换到半开路状态,如果后面的请求正常则关闭断路器,否则继续打开断路器。
服务降级
服务降级是请求失败时的后备方法,故障时执行降级逻辑。
线程隔离
Hystrix 通过线程池实现资源的隔离,确保对某一服务的调用在出现故障时不会对其他服务造成影响。
代码实现
创建三个项目来完成示例,分别为:服务注册中心hystrix-eureka-server,服务提供者hystrix-service-provider,服务消费者hystrix-service-consumer
1.创建hystrix-eureka-server服务注册中心
pom.xml配置
<?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.easy</groupId>
<artifactId>hystrix-eureka-server</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hystrix-eureka-server</name>
<description>Demo project for Spring Boot</description>
<parent>
<artifactId>cloud-hystrix</artifactId>
<groupId>com.easy</groupId>
<version>1.0.0</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
application.yml配置文件
server:
port: 8761
spring:
application:
name: eureka-server
eureka:
instance:
hostname: localhost # eureka 实例名称
client:
register-with-eureka: false # 不向注册中心注册自己
fetch-registry: false # 是否检索服务
service-url:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/ # 注册中心访问地址
HystrixEurekaServerApplication.java启动类
package com.easy.eurekaServer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
@EnableEurekaServer
@SpringBootApplication
public class HystrixEurekaServerApplication {
public static void main(String[] args) {
SpringApplication.run(HystrixEurekaServerApplication.class, args);
}
}
2.创建hystrix-service-provider服务提供者
pom.xml配置
<?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.easy</groupId>
<artifactId>hystrix-service-provider</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hystrix-service-provider</name>
<description>Demo project for Spring Boot</description>
<parent>
<artifactId>cloud-hystrix</artifactId>
<groupId>com.easy</groupId>
<version>1.0.0</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
application.yml配置文件
spring:
application:
name: hystrix-service-provider
eureka:
client:
service-url:
defaultZone: http://localhost:8761/eureka/
# 实例一
server:
port: 8081
HelloController.java提供一个hello接口
package com.easy.serviceProvider.web;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@GetMapping("hello")
public String hello(@RequestParam String p1, @RequestParam String p2) throws Exception {
// 用来测试服务超时的情况
// int sleepTime = new Random().nextInt(2000);
// System.out.println("hello sleep " + sleepTime);
// Thread.sleep(sleepTime);
return "hello, " + p1 + ", " + p2;
}
}
最后贴上启动类HystrixServiceProviderApplication.java
package com.easy.serviceProvider;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@EnableDiscoveryClient
@SpringBootApplication
public class HystrixServiceProviderApplication {
public static void main(String[] args) {
SpringApplication.run(HystrixServiceProviderApplication.class, args);
}
}
3.创建hystrix-service-consumer服务消费者
pom.xml配置
<?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.easy</groupId>
<artifactId>hystrix-service-consumer</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hystrix-service-consumer</name>
<description>Demo project for Spring Boot</description>
<parent>
<artifactId>cloud-hystrix</artifactId>
<groupId>com.easy</groupId>
<version>1.0.0</version>
</parent>
<dependencies>
<!-- eureka 客户端 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<!-- ribbon -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-ribbon</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-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
application.yml配置文件
spring:
application:
name: hystrix-eureka-server
eureka:
client:
service-url:
defaultZone: http://localhost:8761/eureka/
hystrix:
command:
default:
execution:
isolation:
thread:
timeoutInMilliseconds: 1000 # 默认超时时间
相关代码
异常处理类NotFallbackException.java
package com.easy.serviceConsumer.exception;
public class NotFallbackException extends Exception {
}
服务层HelloService.java
package com.easy.serviceConsumer.service;
import com.easy.serviceConsumer.exception.NotFallbackException;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class HelloService {
@Autowired
RestTemplate restTemplate;
private static final String HELLO_SERVICE = "http://hystrix-service-provider/";
@HystrixCommand(fallbackMethod = "helloFallback", ignoreExceptions = {NotFallbackException.class}
, groupKey = "hello", commandKey = "str", threadPoolKey = "helloStr")
public String hello(String p1, String p2) {
return restTemplate.getForObject(HELLO_SERVICE + "hello?p1=" + p1 + "&p2=" + p2, String.class);
}
private String helloFallback(String p1, String p2, Throwable e) {
System.out.println("class: " + e.getClass());
return "error, " + p1 + ", " + p2;
}
}
控制器ConsumerController.java
package com.easy.serviceConsumer.web;
import com.easy.serviceConsumer.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class ConsumerController {
@Autowired
HelloService helloService;
@GetMapping("hello")
public String hello(@RequestParam String p1, @RequestParam String p2) {
System.out.println("hello");
return helloService.hello(p1, p2);
}
}
4.启动类HystrixServiceConsumerApplication.java
package com.easy.serviceConsumer;
import org.springframework.boot.SpringApplication;
import org.springframework.cloud.client.SpringCloudApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringCloudApplication
public class HystrixServiceConsumerApplication {
@Bean
@LoadBalanced
RestTemplate restTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(HystrixServiceConsumerApplication.class, args);
}
}
使用示例
分别运行3个服务,HystrixEurekaServerApplication.java(服务注册中心),HystrixServiceProviderApplication.java(服务提供者),HystrixServiceConsumerApplication.java(服务消费者)
- 1.访问 http://localhost:8080/hello?p1=a&p2=b ,正常情况下响应为 hello, a, b
- 2.关闭 hystrix-service-provider 或在 sleepTime 超过 1000ms 时,访问 http://localhost:8080/hello?p1=a&p2=b,执行降级逻辑,返回 error, a, b
资料
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SpringCloud---服务容错保护---Spring Cloud Hystrix