Spring Cloud（九）Ribbon 服务调用

悠悠 2022-11-25 10:02 171阅读 0赞

**Table of Contents**

1.Ribbon介绍

2.pom.xml中添加依赖

3.@LoadBalanced 开启负载均衡

4.Ribbon负载规则

5.自定义负载的算法CAS+自旋锁

--------------------

### 1.Ribbon介绍 ###

**[https://github.com/Netflix/ribbon][https_github.com_Netflix_ribbon]**

Spring Cloud Ribbon是一个基于HTTP和TCP的**客户端负载均衡工具**，它基于Netflix Ribbon实现。通过Spring Cloud的封装，可以让我们轻松地将面向服务的REST模版请求自动转换成客户端负载均衡的服务调用。Spring Cloud Ribbon虽然只是一个**工具类框架**，它不像服务注册中心、配置中心、API网关那样需要独立部署，但是它几乎存在于每一个Spring Cloud构建的微服务和基础设施中。因为微服务间的调用，API网关的请求转发等内容，实际上都是通过Ribbon来实现的。同时，**Feign**也是基于Ribbon实现的工具。

**LB负载均衡(Load Balance)：**  
        简单的说就是将用户的请求平雄的分配到多个服务上,从而达到系统的HA (高可用)。常见的负载均衡有软件Nginx, LVS,硬件F5等。  
**Ribbon本地负载均衡客户端（集中式LB）VS Nginx服务端负载均衡（进程内LB）区别：**  
        Nginx是服务器负载均衡,客户端所有请求都会交给nginx,然后由nginx实现转发请求。即负载均衡是由服务端实现。  
        Ribbon本地负载均衡,在调用微服务接口时候,会在注册中心上获取注册信息服务列表之后缓存到 JVM 本地,从而在本地实现RPC 远程服务调用技术。

### 2.pom.xml中添加依赖 ###

spring-cloud-starter-netflix-eureka-client中已经含有spring-cloud-starter-netflix-ribbon，无需重复引入

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70][]

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### 3.@LoadBalanced 开启负载均衡 ###

![20200807173334198.png][]

### 4.Ribbon**负载规则** ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 2][]

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**默认为轮询规则：**

公式：实际调用服务器位置下标 = rest接口第几次请求次数 % 服务器集群总数量 ；

每次服务器重启后，rest接口计数从1开始。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 4][]

**替换负载规则：**

写 配置类 和 主启动类加@RibbonClien

注意：不能被 @ComponentScan 扫描到，即不能和主启动类同一个包。

![20200807175923415.png][]

//@Configuration
    public class RibbonRule {
    
        @Bean
        public IRule iRule(){
            return new RandomRule();
        }
    }

@RibbonClient(name = "PAYMENT-SERVICE",configuration = RibbonRule.class)
    @EnableEurekaClient
    @SpringBootApplication
    public class Order80 {
        public static void main(String[] args) {
            SpringApplication.run(Order80.class,args);
        }
    }

### 5.自定义**负载的算法**CAS+自旋锁 ###

8001、8002服务controller层加上

@GetMapping("get/LB")
        public String getPaymentLB() {
            return serverPort;
        }

80去除 @LoadBalanced

自定义 LoadBalancer

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

@Component
    public class LoadBalancerImpl implements LoadBalancer {
    
        private AtomicInteger nextServerCyclicCounter;
    
        public LoadBalancerImpl() {
            nextServerCyclicCounter = new AtomicInteger(0);
        }
    
        private int incrementAndGetModulo() {
            for (; ; ) {//自旋锁
                int current = nextServerCyclicCounter.get();
    //            int next = (current + 1) % modulo;
                int next = current >= Integer.MAX_VALUE ? 0 : current + 1;
                if (nextServerCyclicCounter.compareAndSet(current, next))
                    return next;
            }
        }
    
        @Override
        public ServiceInstance instance(List<ServiceInstance> instances) {
            int index = incrementAndGetModulo() % instances.size();
            return instances.get(index);
        }
    
    }

@Autowired
        private RestTemplate restTemplate;
    
        @Autowired
        private LoadBalancer loadBalancer;
        @Autowired
        private DiscoveryClient discoveryClient;
    
        @GetMapping("get/LB")
        public String getPaymentLB() {
            List<ServiceInstance> instances = discoveryClient.getInstances("PAYMENT-SERVICE");
            if (instances == null || instances.size() < 1) {
                return null;
            }
            ServiceInstance instance = loadBalancer.instance(instances);
            URI uri = instance.getUri();
            return restTemplate.getForObject(uri + "/payment/get/LB", String.class);
        }

[https_github.com_Netflix_ribbon]: https://github.com/Netflix/ribbon
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