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);
}
}
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