springcloud学习之ribbon负载均衡

矫情吗；* 2024-04-18 13:33 77阅读 0赞

ribbon负责实现服务的负载均衡。

Spring cloud有两种服务调用方式，一种是ribbon+restTemplate，另一种是feign

ribbon简单使用如下：

1、引入依赖

<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
    </dependency>

2、在springboot中注入一个RestTemplate，增加@LoadBalanced注解

@Bean
        @LoadBalanced
        public RestTemplate restTemplate(){
            return new RestTemplate();
        }

3、调用方式

在需要调用服务的地方注入一个RestTemplate。在url处写服务ID就可以，ribbon会帮我们解析成IP与端口地址。

@RequestMapping("{userId}")
        public String getAll2(@PathVariable("userId") String id) {
            String url = "http://search-service/"+id;
            System.out.println(url);
            return restTemplate.getForObject(url, String.class);;
        }

4、@LoadBalanced注解会自动实现负载均衡和服务的IP端口解析源码追踪如下：

ribbon之所以能实现这些功能主要依靠的是LoadBalancer的拦截器。查看LoadBalancerInterceptor类

public class LoadBalancerInterceptor implements ClientHttpRequestInterceptor {
    
    	private LoadBalancerClient loadBalancer;
    	private LoadBalancerRequestFactory requestFactory;
    
    	public LoadBalancerInterceptor(LoadBalancerClient loadBalancer, LoadBalancerRequestFactory requestFactory) {
    		this.loadBalancer = loadBalancer;
    		this.requestFactory = requestFactory;
    	}
    
    	public LoadBalancerInterceptor(LoadBalancerClient loadBalancer) {
    		// for backwards compatibility
    		this(loadBalancer, new LoadBalancerRequestFactory(loadBalancer));
    	}
    
    	@Override
    	public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
    			final ClientHttpRequestExecution execution) throws IOException {
    		final URI originalUri = request.getURI();
    		String serviceName = originalUri.getHost();
    		Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);
    		return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
    	}
    }

进入execute方法，在originalUri.getHost();之后会负载均衡选择出对应的服务和端口IP。默认ribbon的负载均衡策略是

IRule DEFAULT\_RULE = new RoundRobinRule();是一种线性负载均衡策略，是一种轮询的方式，通过计数器与模的计算选择服务。

当然可以更改成其他的策略

在配置文件中配置即可

service-name: #服务name
      ribbon:
        NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule #更改为随机的策略