Spring Cloud服務短路Netflix Hystrix

服務短路

近義詞

服務容錯（Fault tolerance）：強調容忍錯誤，不至于整體故障
服務降級（downgrade）：強調服務非強依賴，不影響主要流程

以web工程為例

建立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();

    /**
     * 當方法執行時間超過 100 ms 時，觸發異常
     *
     * @return
     */
    @GetMapping("")
    public String index() throws Exception {

        long executeTime = random.nextInt(200);

        if (executeTime > 100) { // 執行時間超過了 100 ms
            throw new TimeoutException("Execution is timeout!");
        }

        return "Hello,World";
    }

}

異常處理

通過@RestControllerAdvice實作

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} 類似于AOP 攔截
 *
 */
@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依賴

<dependencyManagement>
        <dependencies>

            <!-- Spring Boot 依賴 -->
            <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 依賴 -->
            <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>

        <!-- 其他依賴省略 -->

        <!-- 依賴 Spring Cloud Netflix Hystrix -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</artifactId>
        </dependency>

    </dependencies>

使用 `@EnableHystrix` 實作服務提供方短路

修改應用user-service-provider的引導類：

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;

/**
 * 引導類
 *
 */
@SpringBootApplication
@EnableHystrix
public class UserServiceProviderApplication {

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

通過@HystrixCommand實作

增加getUsers（）方法到UserServiceProviderController

/**
     * 擷取所有使用者清單
     *
     * @return
     */
    @HystrixCommand(
            commandProperties = { // Command 配置
                    // 設定操作時間為 100 毫秒
                    @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "100")
            },
            fallbackMethod = "fallbackForGetUsers" // 設定 fallback 方法
    )
    @GetMapping("/user/list")
    public Collection<User> getUsers() throws InterruptedException {

        long executeTime = random.nextInt(200);

        // 通過休眠來模拟執行時間
        System.out.println("Execute Time : " + executeTime + " ms");

        Thread.sleep(executeTime);

        return userService.findAll();
    }

為getUsers（）添加fallback方法：

/**
     * {@link #getUsers()} 的 fallback 方法
     *
     * @return 空集合
     */
    public Collection<User> fallbackForGetUsers() {
        return Collections.emptyList();
    }

`@EnableCircuitBreaker` 實作服務調用方短路

調整user-ribbon-client，為UserRibbonController增加擷取使用者清單，實際調用user-service-provider"/user/list"REST接口

增加具備負載均衡

RestTemplate

在

UserRibbonClientApplication

增加

RestTemplate

申明

/**
     * 申明 具有負載均衡能力 {@link RestTemplate}
     * @return
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

實作服務調用

/**
     * 調用 user-service-provider "/user/list" REST 接口，并且直接傳回内容
     * 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

調整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;

/**
 * 引導類
 *
 * @author <a href="mailto:[email protected]">Mercy</a>
 * @since 0.0.1
 */
@SpringBootApplication
@RibbonClient("user-service-provider") // 指定目标應用名稱
@EnableCircuitBreaker // 使用服務短路
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 具有負載均衡能力 {@link RestTemplate}
     * @return
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

}

增加程式設計方式的短路實作

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:[email protected]">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;
    }

    /**
     * 主邏輯實作
     *
     * @return
     * @throws Exception
     */
    @Override
    protected Collection run() throws Exception {
        return restTemplate.getForObject("http://" + providerServiceName + "/user/list", Collection.class);
    }

    /**
     * Fallback 實作
     *
     * @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;

/**
 * 使用者 Ribbon Controller
 *
 * @author <a href="mailto:[email protected]">Mercy</a>
 * @since 0.0.1
 */
@RestController
public class UserRibbonController {

    /**
     * 負載均衡器用戶端
     */
    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Value("${provider.service.name}")
    private String providerServiceName;

    @Autowired
    private RestTemplate restTemplate;

    private UserRibbonClientHystrixCommand hystrixCommand;

    /**
     * 調用 user-service-provider "/user/list" REST 接口，并且直接傳回内容
     * 增加 短路功能
     */
    @GetMapping("/user-service-provider/user/list")
    public Collection<User> getUsersList() {
        return new UserRibbonClientHystrixCommand(providerServiceName, restTemplate).execute();
    }
}

為生産做準備

Netflix Hystrix Dashboard

建立hystrix-dashboard工程

<dependencies>

        <!-- 依賴 Hystrix Dashboard -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
        </dependency>

    </dependencies>

增加引導類

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 引導類
 *
 * @author <a href="mailto:[email protected]">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 應用
spring.application.name = hystrix-dashboard

## 服務端口
server.port = 10000

Spring Cloud服務短路Netflix Hystrix

服務短路

以web工程為例

Spring Cloud Netflix Hystrix

使用 `@EnableHystrix` 實作服務提供方短路

`@EnableCircuitBreaker` 實作服務調用方短路

改造 `UserRibbonController#getUsersList()` 方法

為生産做準備

Netflix Hystrix Dashboard

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Spring Cloud服務短路Netflix Hystrix

服務短路

以web工程為例

Spring Cloud Netflix Hystrix

使用 @EnableHystrix 實作服務提供方短路

@EnableCircuitBreaker 實作服務調用方短路

改造 UserRibbonController#getUsersList() 方法

為生産做準備

Netflix Hystrix Dashboard

繼續閱讀

使用 `@EnableHystrix` 實作服務提供方短路

`@EnableCircuitBreaker` 實作服務調用方短路

改造 `UserRibbonController#getUsersList()` 方法