Hystrix的使用2-服務降級fallback
1.定義
我們可以給被調用的方法設置一個降級方法,在調用方法失敗或者超時後,Hystrix會調用這個降級方法。
2.代碼實現
2.1 父工程POM文件
<packaging>pom</packaging>
<modules>
<module>cloud-provider-payment-hystrix8001</module>
</modules>
<!-- 統一管理jar包版本 -->
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<junit.version>4.12</junit.version>
<log4j.version>1.2.17</log4j.version>
<lombok.version>1.16.18</lombok.version>
<spring.boot.version>2.2.2.RELEASE</spring.boot.version>
<spring.cloud.version>Hoxton.SR1</spring.cloud.version>
<liuhangs.cloud.api.version>1.0.0-SNAPSHOT</liuhangs.cloud.api.version>
</properties>
<distributionManagement>
<site>
<id>website</id>
<url>scp://webhost.company.com/www/website</url>
</site>
</distributionManagement>
<!-- 子模塊繼承之後,提供作用:鎖定版本 + 子module不用謝groupId和version -->
<dependencyManagement>
<dependencies>
<!--spring boot 2.2.2-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.2.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<!--spring cloud Hoxton.SR1-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Hoxton.SR1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<!--Spring cloud alibaba 2.1.0.RELEASE-->
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-alibaba-dependencies</artifactId>
<version>2.1.0.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
2.2 hystrix8001工程POM文件
我們新建cloud-provider-payment-hystrix8001服務提供者工程。下一節服務熔斷還會用到此工程。
<dependencies>
<!-- hystrix依賴 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<!-- 這是一個公共工程,定義了一些公用類 -->
<dependency>
<groupId>com.liuhangs.springcloud</groupId>
<artifactId>cloud-api-commons</artifactId>
<version>${liuhangs.cloud.api.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--監控-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
2.3 hystrix8001工程application.yml
server:
port: 8001
spring:
application:
# 服務名
name: cloud-provider-payment-hystrix
2.4 hystrix8001工程service
2.4.1 服務接口PaymentHystrixService
import com.liuhangs.springcloud.api.entities.CommonResult;
/**payment服務接口
*/
public interface PaymentHystrixService {
/**
* 正常方法
* @param id
* @return
*/
public CommonResult getPaymentOK(Long id);
/**
* 超時方法
* @param id
* @return
*/
public CommonResult getPaymentTimeOut(Long id);
}
2.4.1 服務實現類PaymentHystrixServiceImpl
在需要加入服務降級的方法上增加@HystrixCommand
註解,在註解中配置fallbackMethod
屬性值,來指定對應的服務降級方法。
import com.liuhangs.springcloud.api.entities.CommonResult;
import com.liuhangs.springcloud.payment.service.PaymentHystrixService;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import java.util.concurrent.TimeUnit;
import lombok.extern.slf4j.Slf4j;
/**這個類裏包含服務降級的測試
*/
@Service
@Slf4j
public class PaymentHystrixServiceImpl implements PaymentHystrixService {
@Value("${server.port}")
private String SERVER_PORT;
@Override
public CommonResult getPaymentOK(Long id)
{
return new CommonResult(200, "請求ID爲:" + id + ", 當前線程是:" + Thread.currentThread().getName() +
"," +
" " +
"服務端口:" +
SERVER_PORT);
}
/**
* 超過3000毫秒或者報錯就進入降級方法getPaymentTimeOutHandler
* @param id
* @return
*/
@HystrixCommand(fallbackMethod = "getPaymentTimeOutHandler", commandProperties =
{@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",
value = "3000")}) //@HystrixProperty中的配置表示調用此方法3秒後直接降級
@Override
public CommonResult getPaymentTimeOut(Long id)
{
//測試報錯進入降級方法
//int a = 1/0;
//測試超時進入降級方法
try
{
TimeUnit.MILLISECONDS.sleep(5000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
return new CommonResult(200, "請求ID爲:" + id + ", 當前線程是:" + Thread.currentThread().getName() + ", 服務端口:" +
SERVER_PORT + ", 線程睡眠3秒");
}
/**
* 服務降級後調用的方法
* @param id
* @return
*/
public CommonResult getPaymentTimeOutHandler(Long id)
{
return new CommonResult(200, "請求ID爲:" + id + ", 當前線程是:" + Thread.currentThread().getName() + ", 服務端口:" +
SERVER_PORT + ", 已經進入降級方法");
}
}
2.5 hystrix8001工程controller
import com.liuhangs.springcloud.api.entities.CommonResult;
import com.liuhangs.springcloud.api.entities.Payment;
import com.liuhangs.springcloud.payment.service.PaymentHystrixService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
/**服務降級測試controller
*/
@RequestMapping("provider/payment/hystrix")
@RestController
public class PaymentHystrixController {
@Autowired
private PaymentHystrixService paymentHystrixService;
@GetMapping("/ok/{id}")
public CommonResult getPaymentOK(@PathVariable("id") Long id)
{
return paymentHystrixService.getPaymentOK(id);
}
@GetMapping("/timeout/{id}")
public CommonResult getPaymentTimeOut(@PathVariable("id") Long id)
{
return paymentHystrixService.getPaymentTimeOut(id);
}
}
2.6 hystrix8001工程啓動類
/**服務啓動類
*/
@SpringBootApplication
@EnableCircuitBreaker //使用Hystrix需要開啓熔斷註解
public class PaymentHystrixStart8001 {
public static void main(String[] args)
{
SpringApplication.run(PaymentHystrixStart8001.class, args);
}
}
2.7 測試
啓動工程。
2.7.1 調用正常方法
在瀏覽器中訪問 http://localhost:8001/provider/payment/hystrix/ok/1 直接返回成功。
2.7.2 測試超時情況
PaymentHystrixServiceImpl#getPaymentTimeOut的方法配置了超時時間爲3000毫秒,但是在進入方法後睡眠了5000毫秒,調用這個方法會超時,就會進入@HystrixCommand註解配置的fallbackMethod降級方法。
在瀏覽器中輸入 http://localhost:8001/provider/payment/hystrix/timeout/1 鏈接,可以看到下圖的返回值:
我們可以看出先是一直在等待接口返回,到了3秒後進入降級方法。
2.7.3 測試報錯情況
我們註釋掉PaymentHystrixServiceImpl#getPaymentTimeOut方法中的睡眠5秒的代碼,將 //int a = 1/0; 代碼的註釋打開。重啓服務,在瀏覽器中輸入 http://localhost:8001/provider/payment/hystrix/timeout/1 鏈接,得到如下返回:
可以看到方法報錯,同樣進入降級方法。
3.代碼請見
https://github.com/ainydexiaohai/cloud2020