Spring Cloud LoadBalancer 负载均衡策略与缓存机制

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.Response;
import org.springframework.cloud.client.loadbalancer.ServiceInstanceSupplier;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
 
public class CachingServiceInstanceSupplier implements ServiceInstanceSupplier {
 
    private final ServiceInstanceSupplier delegate;
    private final AtomicInteger index = new AtomicInteger();
    private List<Response<ServiceInstance>> instances;
 
    public CachingServiceInstanceSupplier(ServiceInstanceSupplier delegate) {
        this.delegate = delegate;
    }
 
    @Override
    public Response<ServiceInstance> get() {
        if (instances == null) {
            instances = delegate.get().getData();
        }
        int size = instances.size();
        if (size == 0) {
            return Response.empty();
        }
        int nextIndex = Math.abs(index.getAndIncrement() % size);
        return Response.success(instances.get(nextIndex).getData());
    }
}

这个代码实例展示了如何实现一个简单的轮询负载均衡策略，其中使用了AtomicInteger来保证线程安全，并且实现了ServiceInstanceSupplier接口。这个实现会缓存服务实例列表，并在每次请求时返回下一个实例。如果没有可用的服务实例，它将返回一个空的响应。这个例子是教学用途，实际应用中应该考虑更复杂的负载均衡策略和服务实例状态管理。