Ribbon负载均衡服务调用

1.概述

       1.1主要功能是提供客户端的软件负载均衡算法和服务调用。在配置文件中列出Load Balancer后面的所有机器，Ribbon会自动帮助你基于某种规则去连接这些机器。

       1.2集中式负载均衡：即在服务的消费方和服务的提供方之间独立的LB设施（可以使硬件，也可以是软件）由改设施负责把访问请求通过某种策略转发到服务提供方

       1.3进程内LB：将LB逻辑集成到消费方，消费方从服务中心获取可用地址，然后选择合适的服务器使用，Ribbon就属于进程是LB 

2.Ribbon负载均衡演示

利用RestTemplate+Ribbon+Eureka来实现负载均衡

 该依赖在eureka里面已经注册过了，所以不需要单独引入

@Configuration
public class ApplicationContextConfig {
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

@RestController
@Slf4j
public class OrderController {

    public static final String PAYMENT_URL="http://CLOUD-PAYMENT-SERVICE";
    @Resource
    private RestTemplate restTemplate;


    @Resource
    private LoadBalancer loadBalancer;

    @Resource
    private DiscoveryClient discoveryClient;

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

    @GetMapping(value = "/consumer/payment/get/{id}")
    public CommonResult<Payment> getPayment(@PathVariable("id")Long id){
        return restTemplate.getForObject(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);
    }

    @GetMapping(value = "/consumer/payment/getEntity/{id}")
    public CommonResult<Payment> getPayment2(@PathVariable("id")Long id){

        ResponseEntity<CommonResult> forEntity = restTemplate.getForEntity(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
        if(forEntity.getStatusCode().is2xxSuccessful()){
            return forEntity.getBody();
        }else {
            return new CommonResult<>(444,"");
        }

    }

    @GetMapping(value = "/consumer/payment/lb")
    public String getPaymentLB(){
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        if (instances == null || instances.size() <= 0){
            return null;
        }
        ServiceInstance serviceInstance = loadBalancer.instances(instances);
        URI uri = serviceInstance.getUri();
        return restTemplate.getForObject(uri+"/payment/lb",String.class);
    }


}

ps：实现远程调用加负载均衡必须要进行服务注册，否者会调用失败

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 

更改规则方法：首先在主启动扫描不到（@SpringBootApplication注解下面包含一个@ComponentScan注解，不可以被这个注解扫描到）新建一个规则类，然后再主启动下添加一个注解

@Configuration
public class MySelfRule {

    @Bean
    public IRule myRule(){
        return new RandomRule();//定义为随机规则
    }
}

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

}
 
 

4.手写负载均衡算法

首先在定义restTemplate的地方去掉@LoadBalanced

然后定义接口

public interface LoadBalancer {
     //收集服务器总共有多少台能够提供服务的机器，并放到list里面
    ServiceInstance instances(List<ServiceInstance> serviceInstances);

}
 
 

@Component
public class MyLB implements LoadBalancer {

    private AtomicInteger atomicInteger = new AtomicInteger(0);

    //坐标
    private final int getAndIncrement(){
        int current;
        int next;
        do {
            current = this.atomicInteger.get();
            next = current >= 2147483647 ? 0 : current + 1;
        }while (!this.atomicInteger.compareAndSet(current,next));  //第一个参数是期望值，第二个参数是修改值是
        System.out.println("*******第几次访问，次数next: "+next);
        return next;
    }

    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstances) {  //得到机器的列表
       int index = getAndIncrement() % serviceInstances.size(); //得到服务器的下标位置
        return serviceInstances.get(index);
    }
}
 

@GetMapping(value = "/consumer/payment/lb")
     public String getPaymentLB(){
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        if (instances == null || instances.size() <= 0){
            return null;
        }
        ServiceInstance serviceInstance = loadBalancer.instances(instances);
        URI uri = serviceInstance.getUri();
        return restTemplate.getForObject(uri+"/payment/lb",String.class);
    }
}