学习内容：

一.使用openFeign

1.创建模块

2.导入依赖

<dependencies>
    <!-- Open Feign -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    <!-- eureka Client -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <dependency><!-- 引入自己定义的api通用包，可以使用Payment支付Entity -->
        <groupId>com.krisswen.cloud</groupId>
        <artifactId>cloud-api-commons</artifactId>
        <version>${project.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <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-devtools</artifactId>
        <scope>runtime</scope>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

3.编写配置文件

server:
  port: 80
spring:
  application:
    name: cloud-consumer-feign-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/

4.编写启动类

@SpringBootApplication
@EnableFeignClients //开启使用feign客户端的功能
public class CustomerFeignMain80 {
    public static void main(String[] args) {
        SpringApplication.run(CustomerFeignMain80.class,args);
    }
}

5.编写controller

@RestController
public class CustomerFeignController {

    @Autowired
    PaymentFeignService paymentFeignService;

    @GetMapping("consumer/feign/payment/{id}")
    public CommonResult<Payment> getPaymentById(@PathVariable("id") Long id){
        return paymentFeignService.getPaymentById(id);
    }
}
//localhost/consumer/feign/payment/1

二、Hystrix断路器

1.Hystrix断路器是什么？

Hystix是Netflix开源的一个延迟和容错库，用于隔离访问远程服务、第三方库，防止出现级联失败。
在微服务I发生异常，请求阻塞，用户不会得到响应，则tomcat的这个线程不会释放，于是越来越多的用户请求到来，越来越多的线程会阻塞，服务器支持的线程和并发数有限，请求一直阻塞，会导致服务器资源耗尽，从而导致所有其它服务都不可用，形成雪崩效应。

2.Hystrix的几个重要概念
（1）服务降级：
服务器忙碌或者网络拥堵时，不让客户端等待并立刻返回一个友好提示，fallback(备选方案)。触发服务降级的情况:

（2）服务熔断：

（3）服务限流

3.Hystrix案例

先创建新模块

接着导入依赖

<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>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
        <optional>true</optional>
    </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>
    <dependency>
        <!-- 引入自己定义的api通用包，可以使用Payment支付Entity -->
        <groupId>com.krisswen.cloud</groupId>
        <artifactId>cloud-api-commons</artifactId>
        <version>${project.version}</version>
    </dependency>
</dependencies>

然后编写配置文件

server:
  port: 8001
spring:
  application:
    name: cloud-payment-service  #服务名称
eureka:
  client:
    # 注册进 Eureka 的服务中心
    register-with-eureka: true
    # 检索 服务中心 的其它服务
    fetch-registry: true
    service-url:
      # 设置与 Eureka Server 交互的地址
      defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/

接着编写启动类

@SpringBootApplication
@DiscoveryClient
public class HystrixPaymentApplication {
    public static void main(String[] args) {
        SpringApplication.run(HystrixPaymentApplication.class,args);
    }
}

然后是service

@Service
public class PaymentService {

    /**
     * 可以正常访问的方法
     * @param id
     * @return
     */
    public String paymentInfo_Ok(Integer id){
        return "线程池：" + Thread.currentThread().getName() + "  ，paymentInfo_OK，id:" + id;
    }

    /**
     超时访问的方法
     */
    public String paymentInfo_Timeout(Integer id){
        int interTime = 3;
        try{
            TimeUnit.SECONDS.sleep(interTime);
        }catch (Exception e){
            e.printStackTrace();
        }
        return "线程池：" + Thread.currentThread().getName() + "  ，paymentInfo_Timeout，id:" + id + "耗时" + interTime + "秒钟";
    }
}

最后是controller

@RestController
@Slf4j
public class PaymentController {

    @Autowired
    PaymentService paymentService;

    @Value("${server.port}")
    private String serverPort;

    @GetMapping("/payment/hystrix/{id}")
    public String paymentInfo_OK(@PathVariable("id")Integer id){
        log.info("paymentInfo_OKKKKOKKK");
        return paymentService.paymentInfo_Ok(id);
    }

    @GetMapping("/payment/hystrix/timeout/{id}")
    public String paymentInfo_Timeout(@PathVariable("id")Integer id){
        log.info("paymentInfo_timeout");
        return paymentService.paymentInfo_Timeout(id);
    }
}

三、模拟高并发

定义cloud-customer-feign-hystrix-order80
然后导入依赖

<dependencies>
    <!-- OpenFeign -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    <!--eureka-client-->
    <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>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
        <optional>true</optional>
    </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>
    <dependency><!-- 引入自己定义的api通用包，可以使用Payment支付Entity -->
        <groupId>com.krisswen.cloud</groupId>
        <artifactId>cloud-api-commons</artifactId>
        <version>${project.version}</version>
    </dependency>
</dependencies>

然后配置文件

server:
  port: 80
spring:
  application:
    name: cloud-customer-feign-hystrix-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/

随后编写启动类

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients // 开启Feign客户端
public class HystrixOrderApplication80 {
    public static void main(String[] args) {
        SpringApplication.run(HystrixOrderApplication80.class, args);
    }
}

再编写feign客户端

@Component
@FeignClient(value = "cloud-payment-service")
public interface OrderService {

    @GetMapping("/payment/hystrix/{id}")
    public String paymentInfo_OK(@PathVariable("id")Integer id);

    @GetMapping("/payment/hystrix/timeout/{id}")
    public String paymentInfo_Timeout(@PathVariable("id")Integer id);
}

最后是controller

@RestController
@Slf4j
public class OrderController {

    @Autowired
    OrderService orderService;

    @GetMapping("/consumer/payment/hystrix/{id}")
    public String paymentInfo_OK(@PathVariable("id")Integer id){
        log.info("paymentInfo_OKKKKOKKK");
        return orderService.paymentInfo_OK(id);
    }

    @GetMapping("/consumer/payment/hystrix/timeout/{id}")
    public String paymentInfo_Timeout(@PathVariable("id")Integer id){
        log.info("paymentInfo_timeout");
        return orderService.paymentInfo_Timeout(id);
    }
}

四、服务降级

• 服务提供方设置局部服务降级
• 服务降级放在消费端，即消费者端，但是提供者端同样适用。
• 提供者设置自身调用超时的峰值，峰值内正常运行，超出峰值需要有兜底的方法处理，作服务降级fallback。

具体案例待明天总结