服务短路
近义词
- 服务容错(Fault tolerance):强调容忍错误,不至于整体故障
- 服务降级(downgrade):强调服务非强依赖,不影响主要流程
以web工程为例
创建DemoRestController
package com.segmentfault.spring.cloud.lesson8.web.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Random;
import java.util.concurrent.TimeoutException;
/**
* Demo RestController
*
*/
@RestController
public class DemoRestController {
private final static Random random = new Random();
/**
* 当方法执行时间超过 100 ms 时,触发异常
*
* @return
*/
@GetMapping("")
public String index() throws Exception {
long executeTime = random.nextInt(200);
if (executeTime > 100) { // 执行时间超过了 100 ms
throw new TimeoutException("Execution is timeout!");
}
return "Hello,World";
}
}
异常处理
通过@RestControllerAdvice实现
package com.segmentfault.spring.cloud.lesson8.web.controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import java.util.concurrent.TimeoutException;
/**
* {@link DemoRestController} 类似于AOP 拦截
*
*/
@RestControllerAdvice(assignableTypes = DemoRestController.class)
public class DemoRestControllerAdvice {
@ExceptionHandler(TimeoutException.class)
public Object faultToleranceTimeout(Throwable throwable) {
return throwable.getMessage();
}
}
Spring Cloud Netflix Hystrix
增加Maven依赖
<dependencyManagement>
<dependencies>
<!-- Spring Boot 依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>1.5.8.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<!-- Spring Cloud 依赖 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Dalston.SR4</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- 其他依赖省略 -->
<!-- 依赖 Spring Cloud Netflix Hystrix -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
</dependencies>
使用@EnableHystrix
实现服务提供方短路
修改应用user-service-provider的引导类:
package com.segumentfault.spring.cloud.lesson8.user.service;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
/**
* 引导类
*
*/
@SpringBootApplication
@EnableHystrix
public class UserServiceProviderApplication {
public static void main(String[] args) {
SpringApplication.run(UserServiceProviderApplication.class, args);
}
}
通过@HystrixCommand实现
增加getUsers()方法到UserServiceProviderController
/**
* 获取所有用户列表
*
* @return
*/
@HystrixCommand(
commandProperties = { // Command 配置
// 设置操作时间为 100 毫秒
@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "100")
},
fallbackMethod = "fallbackForGetUsers" // 设置 fallback 方法
)
@GetMapping("/user/list")
public Collection<User> getUsers() throws InterruptedException {
long executeTime = random.nextInt(200);
// 通过休眠来模拟执行时间
System.out.println("Execute Time : " + executeTime + " ms");
Thread.sleep(executeTime);
return userService.findAll();
}
为getUsers()添加fallback方法:
/**
* {@link #getUsers()} 的 fallback 方法
*
* @return 空集合
*/
public Collection<User> fallbackForGetUsers() {
return Collections.emptyList();
}
使用@EnableCircuitBreaker
实现服务调用方短路
调整user-ribbon-client,为UserRibbonController增加获取用户列表,实际调用user-service-provider"/user/list"REST接口
增加具备负载均衡RestTemplate
在UserRibbonClientApplication
增加RestTemplate
申明
/**
* 申明 具有负载均衡能力 {@link RestTemplate}
* @return
*/
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
实现服务调用
/**
* 调用 user-service-provider "/user/list" REST 接口,并且直接返回内容
* 增加 短路功能
*/
@GetMapping("/user-service-provider/user/list")
public Collection<User> getUsersList() {
return restTemplate.getForObject("http://" + providerServiceName + "/user/list", Collection.class);
}
激活@EnableCircuitBreaker
调整UserRibbonClientApplication:
package com.segumentfault.spring.cloud.lesson8.user.ribbon.client;
import com.netflix.loadbalancer.IRule;
import com.segumentfault.spring.cloud.lesson8.user.ribbon.client.rule.MyRule;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
/**
* 引导类
*
* @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
* @since 0.0.1
*/
@SpringBootApplication
@RibbonClient("user-service-provider") // 指定目标应用名称
@EnableCircuitBreaker // 使用服务短路
public class UserRibbonClientApplication {
public static void main(String[] args) {
SpringApplication.run(UserRibbonClientApplication.class, args);
}
/**
* 将 {@link MyRule} 暴露成 {@link Bean}
*
* @return {@link MyRule}
*/
@Bean
public IRule myRule() {
return new MyRule();
}
/**
* 申明 具有负载均衡能力 {@link RestTemplate}
* @return
*/
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
增加编程方式的短路实现
package com.segumentfault.spring.cloud.lesson8.user.ribbon.client.hystrix;
import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import org.springframework.web.client.RestTemplate;
import java.util.Collection;
import java.util.Collections;
/**
* User Ribbon Client HystrixCommand
*
* @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
* @since 0.0.1
*/
public class UserRibbonClientHystrixCommand extends HystrixCommand<Collection> {
private final String providerServiceName;
private final RestTemplate restTemplate;
public UserRibbonClientHystrixCommand(String providerServiceName, RestTemplate restTemplate) {
super(HystrixCommandGroupKey.Factory.asKey(
"User-Ribbon-Client"),
100);
this.providerServiceName = providerServiceName;
this.restTemplate = restTemplate;
}
/**
* 主逻辑实现
*
* @return
* @throws Exception
*/
@Override
protected Collection run() throws Exception {
return restTemplate.getForObject("http://" + providerServiceName + "/user/list", Collection.class);
}
/**
* Fallback 实现
*
* @return 空集合
*/
protected Collection getFallback() {
return Collections.emptyList();
}
}
改造UserRibbonController#getUsersList()
方法
package com.segumentfault.spring.cloud.lesson8.user.ribbon.client.web.controller;
import com.segumentfault.spring.cloud.lesson8.domain.User;
import com.segumentfault.spring.cloud.lesson8.user.ribbon.client.hystrix.UserRibbonClientHystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import javax.annotation.PostConstruct;
import java.io.IOException;
import java.util.Collection;
/**
* 用户 Ribbon Controller
*
* @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
* @since 0.0.1
*/
@RestController
public class UserRibbonController {
/**
* 负载均衡器客户端
*/
@Autowired
private LoadBalancerClient loadBalancerClient;
@Value("${provider.service.name}")
private String providerServiceName;
@Autowired
private RestTemplate restTemplate;
private UserRibbonClientHystrixCommand hystrixCommand;
/**
* 调用 user-service-provider "/user/list" REST 接口,并且直接返回内容
* 增加 短路功能
*/
@GetMapping("/user-service-provider/user/list")
public Collection<User> getUsersList() {
return new UserRibbonClientHystrixCommand(providerServiceName, restTemplate).execute();
}
}
为生产做准备
Netflix Hystrix Dashboard
创建hystrix-dashboard工程
增加Maven依赖
<dependencies>
<!-- 依赖 Hystrix Dashboard -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
</dependency>
</dependencies>
增加引导类
package com.segumentfault.spring.cloud.lesson8.hystrix.dashboard;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
/**
* Hystrix Dashboard 引导类
*
* @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
* @since 0.0.1
*/
@SpringBootApplication
@EnableHystrixDashboard
public class HystrixDashboardApplication {
public static void main(String[] args) {
SpringApplication.run(HystrixDashboardApplication.class, args);
}
}
增加application.properties
## Hystrix Dashboard 应用
spring.application.name = hystrix-dashboard
## 服务端口
server.port = 10000