LoadBalancerClient作为负载均衡客户端,用于进行负载均衡逻辑,从服务列表中选择出一个服务地址进行调用,其内部方法为下图显示:
在LoadBalancerClient种存在两个execute()方法,均是用来执行请求的,reconstructURI()是用来重构URL。对于LoadBalancerClient在Spring Cloud LoadBalancer中实现类则是BlockingLoadBalancerClient。BlockingLoadBalancerClient存在两个choose()方法,其实现的是图1-1中的ServiceInstanceChooser接口种的两个choose()方法(图1-2):
在上述图片中通过通过工厂类LoadBalancerClientFactory获取具体的负载均衡器实例,后面的loadBalancer.choose(request)调用(图1-3)接口choose()方法实现根据负载均衡算法选择下一个服务器完成负载均衡。
图1-3可以看出ReactorLoadBalancer接口继承ReactiveLoadBalancer接口,ReactorLoadBalancer接口后续又被ReactorServiceInstanceLoadBalancer继承且其实现了两个方法,分别是:RandomLoadBalancer(随机负载均衡器)和RoundRobinLoadBalancer(轮询负载均衡器)。
根据图1-4类图显示,我们只需要在自定义配置轮询方法时重定义ReactorServiceInstanceLoadBalancer接口即可,如下例子:
@Configuration
public class MyLoadBalancerConfig {
@Bean
public ReactorServiceInstanceLoadBalancer reactorServiceInstanceLoadBalancer(Environment environment, LoadBalancerClientFactory loadBalancerClientFactory) {
String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
//返回随机轮询负载均衡方式
return new RandomLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
}
}
但是如果我们要自定义轮询算法该如何做呢?根据上面可以知道LoadBalancerClientFactory是创建客户机、负载均衡器和客户机配置实例的工厂。它根据客户端名称创建一个Spring ApplicationContext,并从中提取所需的bean(官方解释)。因此我们进入到LoadBalancerClientFactory类中:
我们需要去实现它的子接口ReactorServiceInstanceLoadBalancer,因为去获取负载均衡器实例的时候,是通过去容器中查找ReactorServiceInstanceLoadBalancer类型的bean来实现的,参照RandomLoadBalancer我们进行仿写
public class CustomRandomLoadBalancerClient implements ReactorServiceInstanceLoadBalancer {
// 服务列表
private ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
public CustomRandomLoadBalancerClient(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
}
@Override
public Mono<Response<ServiceInstance>> choose(Request request) {
ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider.getIfAvailable();
return supplier.get().next().map(this::getInstanceResponse);
}
/**
* 使用随机数获取服务
* @param instances
* @return
*/
private Response<ServiceInstance> getInstanceResponse(
List<ServiceInstance> instances) {
System.out.println("进来了");
if (instances.isEmpty()) {
return new EmptyResponse();
}
System.out.println("进行随机选取服务");
// 随机算法
int size = instances.size();
Random random = new Random();
ServiceInstance instance = instances.get(random.nextInt(size));
return new DefaultResponse(instance);
}
}
自定义配置类:
@Configuration
public class MyLoadBalancerConfig {
// 参数 serviceInstanceListSupplierProvider 会自动注入
@Bean
public ReactorServiceInstanceLoadBalancer customLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
return new CustomRandomLoadBalancerClient(serviceInstanceListSupplierProvider);
}
}
在项目启动类上添加@LoadBalancerClient注解:name值一定要使用服务端配置的服务名(spring.application.name),通过configuration指定自定义的配置
@SpringBootApplication
@LoadBalancerClient(name = "myServer", configuration = MyLoadBalancerConfig.class)
public class BlockClientApplication {
public static void main(String[] args) {
SpringApplication.run(BlockClientApplication.class, args);
}
}
参考:https://www.cnblogs.com/linchenguang/p/15656603.html
https://blog.csdn.net/weixin_50518271/article/details/111449560
https://blog.csdn.net/qq_31142237/article/details/90486836