微服务SpringCloud开弓之Ribbon负载均衡调用《六》

1、概述

• 是什么
  

• 官网资料

​ 地址

Ribbon目前也进入维护模式

• 用途

  LB(负载均衡)

• 集中式LB
  
• 进程内LB

2、Ribbon负载均衡演示

• 架构说明

  

总结:

Ribbon其实就是一个软负载均衡的客户端组件, 他可以和其他所需请求的客户端结合使用,和eureka结合只是其中一个实例.

• RestTemplate的使用

  • 官网
    

  • getForObject方法/getForEntity方法

      @GetMapping("/consumer/payment/get/{id}")
        public CommonResult<Payment> getPayment(@PathVariable("id") Long id) {
            return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
    }
            
        @GetMapping("/consumer/payment/getForEntity/{id}")
        public CommonResult<Payment> getPayment2(@PathVariable("id") Long id) {
            ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
    
            if (entity.getStatusCode().is2xxSuccessful()) {
                log.info("#############" + entity.getStatusCodeValue() + "################\t" + entity.getHeaders());
                return entity.getBody();
            } else {
                return new CommonResult<>(444, "操作失败");
            }
    }
    

  • postForObject/postEntity

     @GetMapping("/consumer/payment/create")
        public CommonResult<Payment> create(Payment payment) {
            return restTemplate.postForObject(PAYMENT_URL + "/payment/create", payment, CommonResult.class);
        }
    

3、Ribbon核心组件IRule

IRule:根据特定算法从服务列表中选取一个要访问的服务

如何替换

• 修改cloud-consumer-order80

• 注意配置细节

• 新建package

• 上面包下新建MySelfRule规则类

  @Configuration
  public class MySelfRule {
  
      @Bean
      public IRule myRule() {
  
          // 定义为随机
          return new RandomRule();
      }
  }
  

• 主启动类添加@RibbonClient

  @SpringBootApplication
  @EnableEurekaClient
  @RibbonClient(name = "CLOUD-PAYMENT-SERVICE", configuration = MySelfRule.class)
  public class OrderMain80 {
      public static void main(String[] args) {
          SpringApplication.run(OrderMain80.class, args);
      }
  }
  

• 测试

  http://localhost/consumer/payment/get/31

4、Ribbon负载均衡算法

• 原理

• 源码

      public Server choose(ILoadBalancer lb, Object key) {
          if (lb == null) {
              log.warn("no load balancer");
              return null;
          } else {
              Server server = null;
              int count = 0;
  
              while(true) {
                  if (server == null && count++ < 10) {
                      List<Server> reachableServers = lb.getReachableServers();
                      List<Server> allServers = lb.getAllServers();
                      int upCount = reachableServers.size();
                      int serverCount = allServers.size();
                      if (upCount != 0 && serverCount != 0) {
                          int nextServerIndex = this.incrementAndGetModulo(serverCount);
                          server = (Server)allServers.get(nextServerIndex);
                          if (server == null) {
                              Thread.yield();
                          } else {
                              if (server.isAlive() && server.isReadyToServe()) {
                                  return server;
                              }
  
                              server = null;
                          }
                          continue;
                      }
  
                      log.warn("No up servers available from load balancer: " + lb);
                      return null;
                  }
  
                  if (count >= 10) {
                      log.warn("No available alive servers after 10 tries from load balancer: " + lb);
                  }
  
                  return server;
              }
          }
      }
  
      private int incrementAndGetModulo(int modulo) {
          int current;
          int next;
          do {
              current = this.nextServerCyclicCounter.get();
              next = (current + 1) % modulo;
          } while(!this.nextServerCyclicCounter.compareAndSet(current, next));
  
          return next;
      }
  

• 自己试着写一个本地负载均衡器

  • 7001/7002集群启动

  • 8001/8002集群启动

    1、controller改造

    @GetMapping(value = "/payment/lb")
    public String getPaymentLB() {
        return serverPort;
    }
    

  • 80订单微服务改造

    1、ApplicationContextBean去掉注解@LoadBalanced

    2、LoadBalancer接口

    public interface LoadBalancer {
        ServiceInstance  instance(List<ServiceInstance> serviceInstances);
    }
    

    3、MyLB

    @Component
    public class MyLB implements LoadBalancer {
        private AtomicInteger atomicInteger = new AtomicInteger(0);
        public final int getAndIncrement() {
            int current;
            int next;
            do {
                current = this.atomicInteger.get();
                next = current >= 214743647 ? 0 : current + 1;
            }while (!this.atomicInteger.compareAndSet(current,next));
            System.out.println("##############naext:"+next);
    
            return next;
        }
        @Override
        public ServiceInstance instance(List<ServiceInstance> serviceInstances) {
            int  index= getAndIncrement() % serviceInstances.size();
    
            return serviceInstances.get(index);
        }
    }
    
    

**4、OrderController**

```java
  @Resource
    private DiscoveryClient discoveryClient;
  @Resource
    private LoadBalancer loadBalancer;

    @GetMapping(value = "/consumer/payment/lb")
    public String getPaymentLB() {
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PROVIDER-SERVICE");
        if (instances == null || instances.size() <= 0){
            return  null;
        }

        ServiceInstance serviceInstance = loadBalancer.instance(instances);
        URI uri = serviceInstance.getUri();
        return  restTemplate.getForObject(uri+"/payment/lb",String.class);
    }

```

**5、测试**

http://localhost/consumer/payment/lb

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