如何关闭Spring WebClient所用Netty HttpClient的DNS连接重试机制？

高版本Reactor Netty（适配Spring Boot 2.7.10+ / 3.0+） #

直接通过内置配置参数关闭多IP重试逻辑，仅需在构造HttpClient时设置maxAddressesPerHost为1即可：

import reactor.netty.http.client.HttpClient;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.web.reactive.function.client.WebClient;

// 构造自定义HttpClient
HttpClient httpClient = HttpClient.create()
        // 限制每个域名仅保留1个解析到的IP，无多余IP可供重试
        .resolver(nameResolverSpec -> nameResolverSpec.maxAddressesPerHost(1));

// 注入到WebClient中使用
WebClient webClient = WebClient.builder()
        .clientConnector(new ReactorClientHttpConnector(httpClient))
        .build();

该配置是你提到的reactor-netty issue #1822落地的官方特性，配置后域名解析仅返回第一条记录，首次连接失败直接抛出错误，不会触发后续IP的连接尝试。

低版本Reactor Netty兼容方案 #

如果使用的版本未提供上述配置项，可自定义地址解析器仅返回首个解析IP：

import io.netty.resolver.AddressResolver;
import io.netty.resolver.DefaultAddressResolverGroup;
import io.netty.resolver.InetNameResolver;
import io.netty.util.concurrent.EventExecutor;
import reactor.netty.http.client.HttpClient;
import java.net.InetSocketAddress;
import java.util.List;

public class SingleIpResolverGroup extends DefaultAddressResolverGroup {
    public static final SingleIpResolverGroup INSTANCE = new SingleIpResolverGroup();

    @Override
    protected AddressResolver<InetSocketAddress> newResolver(EventExecutor executor) {
        InetNameResolver baseResolver = (InetNameResolver) super.newResolver(executor);
        return baseResolver.asAddressResolver(addr -> {
            List<InetSocketAddress> allResolved = baseResolver.resolveAll(addr).getNow(null);
            return allResolved == null || allResolved.isEmpty() ? List.of() : List.of(allResolved.get(0));
        });
    }
}

// 配置到HttpClient
HttpClient httpClient = HttpClient.create()
        .resolver(SingleIpResolverGroup.INSTANCE);

内容的提问来源于stack exchange，提问作者reperion