SpringCloud第七节内容精简（上），Hystrix断路器和服务降级
Hystrix是一个用于处理分布式系统的延迟和容错的开源库，在分布式系统里，许多依赖不可避免的会调用失败，如超时，异常灯，Hystrix能够保证 在一个以来出问题的情况下，不会导致整体服务失败，避免级联故障 ，以提高分布式系统的弹性。
通过断路器的故障监控，向调用方返回一个符合预期的，可处理的备选响应，而不是 长时间的等待或者抛出调用方无法处理的异常，这样就保证了服务调用方的现成不会被长时间，不必要的占用，避免故障在分布式系统中的蔓延，乃至雪崩。
分为服务降级，服务熔断，服务限流
以下是服务降级
创建项目
8001的hystrix项目，注意这里是feign配合hystrix学习
pom
cloud2020
com.atguigu.springcloud
1.0-SNAPSHOT
4.0.0
cloud-provider-hystrix-payment8001
org.springframework.cloud
spring-cloud-starter-netflix-hystrix
org.springframework.cloud
spring-cloud-starter-netflix-eureka-client
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-actuator
com.atguigu.springcloud
cloud-api-commons
${project.version}
org.springframework.boot
spring-boot-devtools
runtime
true
org.projectlombok
lombok
true
org.springframework.boot
spring-boot-starter-test
test
service层
@Service
public class PaymentService {
public String paymentInfo_Ok(Integer id){
return "线程池："+Thread.currentThread().getName()+"paymentInfo_ok,id:"+id;
}
public String paymentInfo_TimeOut(Integer id){
try {
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "线程池："+Thread.currentThread().getName()+"paymentInfo_TimeOut,id:"+id+"耗时3秒";
}
}控制器
@RestController
@Slf4j
public class PaymentController {
@Resource
private PaymentService paymentService;
@Value("${server.port")
private String serverPost;
@GetMapping("/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id){
String result = paymentService.paymentInfo_Ok(id);
log.info("******result"+result);
return result;
}
@GetMapping("/payment/hystrix/timeout/{id}")
public String paymentInfo_TimeOut(@PathVariable("id") Integer id){
String result = paymentService.paymentInfo_TimeOut(id);
log.info("******result"+result);
return result;
}
}启动类
@SpringBootApplication
@EnableEurekaClient
public class PaymentHystrixMain8001 {
public static void main(String[] args) {
SpringApplication.run(PaymentHystrixMain8001.class,args);
}
}然后借助JMeter压力测试
https://blog.csdn.net/bailaoshi666/article/details/107067478
80项目模块
pom
cloud2020
com.atguigu.springcloud
1.0-SNAPSHOT
4.0.0
cloud-consumer-feign-hystrix-order80
org.springframework.cloud
spring-cloud-starter-openfeign
org.springframework.cloud
spring-cloud-starter-netflix-hystrix
org.springframework.cloud
spring-cloud-starter-netflix-eureka-client
com.atguigu.springcloud
cloud-api-commons
${project.version}
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-actuator
org.springframework.boot
spring-boot-devtools
runtime
true
org.projectlombok
lombok
true
org.springframework.boot
spring-boot-starter-test
test
service层，一定要feign注解加接口啊
@Component
@FeignClient(value = "CLOUD-PROVIDER-HYSTRIX-PAYMENT")
public interface PaymentHystrixService {
@GetMapping("/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id);
@GetMapping("/payment/hystrix/timeout/{id}")
public String paymentInfo_TimeOut(@PathVariable("id") Integer id);
}
application.yml
server:
port: 80
eureka:
client:
register-with-eureka: false
service-url:
defaultZone: http://eureka7001.com:7001/eureka/
feign:
hystrix:
enabled: true控制器
@RestController
@Slf4j
public class OrderHystrixController {
@Resource
private PaymentHystrixService paymentHystrixService;
@GetMapping("/consumer/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_Ok(id);
}
@GetMapping("/consumer/payment/hystrix/timeout/{id}")
public String paymentInfo_TimeOut(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_TimeOut(id);
}
}
压力8001接口测试再走80接口会报超时错误
写降级方法
修改8001的service层，超时3秒走另一个
@Service
public class PaymentService {
public String paymentInfo_Ok(Integer id){
return "线程池："+Thread.currentThread().getName()+"paymentInfo_ok,id:"+id;
}
@HystrixCommand(fallbackMethod = "paymentInfo_TimeOutHandler",commandProperties = {
@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="3000")
})
public String paymentInfo_TimeOut(Integer id){
try {
TimeUnit.SECONDS.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "线程池："+Thread.currentThread().getName()+"paymentInfo_TimeOut,id:"+id+"耗时5秒";
}
public String paymentInfo_TimeOutHandler(Integer id){
return "线程池："+Thread.currentThread().getName()+"paymentInfo_TimeOutHandler,id:"+id+"拦截方法";
}
}
启动类要加@EnableCircuitBreaker即可
@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class PaymentHystrixMain8001 {
public static void main(String[] args) {
SpringApplication.run(PaymentHystrixMain8001.class,args);
}
}方法改成int age = 10/0计算错误也可以拦截
另外关于Hystrix的注解，建议修改完重启微服务，热部署对于这个注解不是及时反应
一般在项目中，断路器Hystrix一般是写在消费者，就是80端口的服务。所以下面来为80项目添加断路器
其实主要就是application.yml加启动，启动类加注解，服务加注解
application.yml
server:
port: 80
eureka:
client:
register-with-eureka: false
service-url:
defaultZone: http://eureka7001.com:7001/eureka/
feign:
hystrix:
enabled: true启动类
@SpringBootApplication
@EnableFeignClients
@EnableHystrix
public class OrderHystrixMain80 {
public static void main(String[] args) {
SpringApplication.run(OrderHystrixMain80.class,args);
}
}控制器
@RestController
@Slf4j
public class OrderHystrixController {
@Resource
private PaymentHystrixService paymentHystrixService;
@GetMapping("/consumer/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_Ok(id);
}
@GetMapping("/consumer/payment/hystrix/timeout/{id}")
@HystrixCommand(fallbackMethod = "paymentTimeOutFallbackMethod",commandProperties = {
@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="1500")
})
public String paymentInfo_TimeOut(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_TimeOut(id);
}
public String paymentTimeOutFallbackMethod(@PathVariable("id") Integer id){
return "我是消费者80，对方系统繁忙";
}
}效果。写上int age = 10/0。效果如下
这里让我想到个问题 ，为什么 8001的断路器写在service层，而80的断路器在控制层。
后来发现原来是，视频老师偷懒，8001的service层是class层，实际就是平常的serviceImpl层，可以写实现，也可以写控制器上。而80项目的service是interface，接口，只能写在serviceImpl，但是视频中为了简便，没有serviceImpl，直接控制器实现，所以这就是写在控制器的原因，其实写serviceImpl即可 。仔细查看项目，8001的service层（实际是serviceImpl层）加了 @Service注解。而80项目的 service层加了 @Component扫描。
之后，我修改了8001，把断路器从service层（实际是serviceImpl层）移动到了控制层，效果依旧可以。从80访问依旧走80的callback
接下来考虑到效率问题，如何1对多的断路器，就是默认断路器
主要是 @DefaultProperties 和 @HystrixCommand
代码只修改这个。要注意这个默认的断路器方法不能写参数
@RestController
@Slf4j
@DefaultProperties(defaultFallback = "payment_Global_FallbackMethod")
public class OrderHystrixController {
@Resource
private PaymentHystrixService paymentHystrixService;
@GetMapping("/consumer/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_Ok(id);
}
@GetMapping("/consumer/payment/hystrix/timeout/{id}")
/*@HystrixCommand(fallbackMethod = "paymentTimeOutFallbackMethod",commandProperties = {
@HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="1000")
})*/
@HystrixCommand
public String paymentInfo_TimeOut(@PathVariable("id") Integer id){
return paymentHystrixService.paymentInfo_TimeOut(id);
}
public String paymentTimeOutFallbackMethod(@PathVariable("id") Integer id){
return "我是消费者80，对方系统繁忙";
}
public String payment_Global_FallbackMethod(){
return "我是消费者80的全局断路器";
}
}效果如下
考虑完1对多的断路器，要考虑如何写代码解耦，更优化
写个类，继承service层并扫描进spring
@Component
public class PaymentFallbackService implements PaymentHystrixService {
@Override
public String paymentInfo_Ok(Integer id) {
return "PaymentFallbackService-okokkokokokok";
}
@Override
public String paymentInfo_TimeOut(Integer id) {
return "PaymentFallbackService.timeoutimeout";
}
}
service层加fallback
@Component
@FeignClient(value = "CLOUD-PROVIDER-HYSTRIX-PAYMENT",fallback = PaymentFallbackService.class)
public interface PaymentHystrixService {
@GetMapping("/payment/hystrix/ok/{id}")
public String paymentInfo_Ok(@PathVariable("id") Integer id);
@GetMapping("/payment/hystrix/timeout/{id}")
public String paymentInfo_TimeOut(@PathVariable("id") Integer id);
}
注意application.yml要开启
server:
port: 80
eureka:
client:
register-with-eureka: false
service-url:
defaultZone: http://eureka7001.com:7001/eureka/
feign:
hystrix:
enabled: true
效果图
