Spring Cloud Gateway3.x自定义Spring Cloud Loadbalancer负载均衡策略以及实现动态负载均衡策略的方案

在Spring Cloud Gateway 3.x中，自定义Spring Cloud Loadbalancer的负载均衡策略需要实现ReactorLoadBalancer<ServiceInstance>接口，并提供一个自定义的LoadBalancerClientFilter。以下是一个简单的示例：

1. 实现ReactorLoadBalancer接口：

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.ReactorLoadBalancer;
import reactor.core.publisher.Mono;
 
public class CustomLoadBalancer implements ReactorLoadBalancer<ServiceInstance> {
    @Override
    public Mono<ServiceInstance> choose(Request request) {
        // 实现选择逻辑，返回ServiceInstance
        return Mono.empty(); // 示例中返回一个空的Mono，实际应用中应该根据请求选择合适的ServiceInstance
    }
 
    @Override
    public Mono<Void> notify(Request request, ServiceInstance instance, Throwable error) {
        // 实现负载均衡器通知逻辑，如记录访问成功或失败等
        return Mono.empty(); // 示例中返回一个空的Mono，实际应用中可能需要记录日志或者更新负载均衡器的内部状态
    }
}

2. 创建自定义的LoadBalancerClientFilter：

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.LoadBalancerClientFilter;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;
 
public class CustomLoadBalancerClientFilter extends LoadBalancerClientFilter {
    public CustomLoadBalancerClientFilter(ReactorLoadBalancer<ServiceInstance> loadBalancer) {
        super(loadBalancer);
    }
 
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        // 在调用父类filter之前可以添加额外的逻辑
        return super.filter(exchange, chain);
    }
}

3. 配置自定义的LoadBalancerClientFilter：

import org.springframework.cloud.gateway.filter.factory.GatewayFilterFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
@Configuration
public class GatewayConfig {
    @Bean
    public GatewayFilterFactory loadBalancer() {
        // 返回自定义的LoadBalancerClientFilter Bean
        return new GatewayFilterFactory() {
            @Override
            public GatewayFilter apply(Object config) {
                return (exchange, chain) -> new CustomLoadBalancerClientFilter(new CustomLoadBalancer()).filter(exchange, chain);
            }
        };
    }
}

4. 在\`app