JDK 11环境下WebClient调用抛出TimeoutException问题求助

在JDK 11（zulu-jdk11.0.14）环境中使用WebClient调用接口时，出现如下TimeoutException：

Caused by: java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 60000ms in 'source(MonoDefer)' (and no fallback has been configured)
        at reactor.core.publisher.FluxTimeout$TimeoutMainSubscriber.handleTimeout(FluxTimeout.java:295) ~[reactor-core-3.4.24.jar!/:3.4.24]

但在JDK 8（zulu8.61.0.18-sa-jdk8.0.331）环境下运行同一测试用例则完全正常，无异常出现。

应用基于Spring Boot 2.7.5构建，依赖spring-boot-starter-webflux，其中reactor-netty-http版本为1.0.24：

<dependency>
    <groupId>io.projectreactor.netty</groupId>
    <artifactId>reactor-netty-http</artifactId>
    <version>1.0.24</version>
</dependency>

观察到的现象 #

• 现象1：闲置连接异常关闭后，重新调用正常
  WebClient调用后闲置约30秒，连接会伴随SslCloseCompletionEvent(java.nio.channels.ClosedChannelException)关闭并注销：

2022-11-14 11:17:47.773 DEBUG 7600 --- [ctor-http-nio-3] reactor.netty.http.client.HttpClient     : [3d257d24, L:/xx.xx.xx.xx:64172 - R:nnctj2prxc4t.apps.internal.xxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 11:18:17.264 DEBUG 7600 --- [ctor-http-nio-3] reactor.netty.http.client.HttpClient     : [3d257d24, L:/xx.xx.xx.xx:64172 - R:nnctj2prxc4t.apps.internal.xxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 11:18:17.265 DEBUG 7600 --- [ctor-http-nio-3] reactor.netty.http.client.HttpClient     : [3d257d24, L:/xx.xx.xx.xx:64172 ! R:nnctj2prxc4t.apps.internal.xxxx.net/xx.xx.xx.xx:443] USER_EVENT: SslCloseCompletionEvent(java.nio.channels.ClosedChannelException)
2022-11-14 11:18:17.265 DEBUG 7600 --- [ctor-http-nio-3] reactor.netty.http.client.HttpClient     : [3d257d24, L:/xx.xx.xx.xx:64172 ! R:nnctj2prxc4t.apps.internal.xxxx.net/xx.xx.xx.xx:443] INACTIVE
2022-11-14 11:18:17.265 DEBUG 7600 --- [ctor-http-nio-3] reactor.netty.http.client.HttpClient     : [3d257d24, L:/xx.xx.xx.xx:64172 ! R:nnctj2prxc4t.apps.internal.xxxx.net/xx.xx.xx.xx:443] UNREGISTERED

此时再次发送请求，会注册新连接并调用成功：

2022-11-14 11:18:59.542 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d] REGISTERED
2022-11-14 11:18:59.630 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d] CONNECT: nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443
2022-11-14 11:18:59.743 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d, L:/xx.xx.xx.xx:64197 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] ACTIVE
2022-11-14 11:18:59.849 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d, L:/xx.xx.xx.xx:64197 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 11:18:59.858 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d, L:/xx.xx.xx.xx:64197 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] USER_EVENT: SslHandshakeCompletionEvent(SUCCESS)
2022-11-14 11:18:59.860 DEBUG 7600 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [476de49d-1, L:/xx.xx.xx.xx:64197 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] WRITE: 2023B 

• 现象2：连接正常关闭后，重新调用触发超时
  若连接伴随SslCloseCompletionEvent(SUCCESS)正常关闭并注销：

2022-11-14 09:10:41.295 DEBUG 21332 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [9a6b8e52, L:/xx.xx.xx.xx:56897 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] CLOSE
2022-11-14 09:10:41.303 DEBUG 21332 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [9a6b8e52, L:/xx.xx.xx.xx:56897 ! R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] USER_EVENT: SslCloseCompletionEvent(SUCCESS)
2022-11-14 09:10:41.303 DEBUG 21332 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [9a6b8e52, L:/xx.xx.xx.xx:56897 ! R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 09:10:41.303 DEBUG 21332 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [9a6b8e52, L:/xx.xx.xx.xx:56897 ! R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] INACTIVE
2022-11-14 09:10:41.303 DEBUG 21332 --- [ctor-http-nio-4] reactor.netty.http.client.HttpClient     : [9a6b8e52, L:/xx.xx.xx.xx:56897 ! R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] UNREGISTERED

此时再次发送请求，虽注册新连接但仍触发TimeoutException：

2022-11-14 09:11:32.362 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d] REGISTERED
2022-11-14 09:11:32.424 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d] CONNECT: nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443
2022-11-14 09:11:32.528 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d, L:/xx.xx.xx.xx:56922 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] ACTIVE
2022-11-14 09:11:32.970 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d, L:/xx.xx.xx.xx:56922 - R:nnctj2prxc4t.apps.internal.xxxxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 09:11:33.063 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d, L:/xx.xx.xx.xx:56922 - R:nnctj2prxc4t.apps.internal.xxxxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 09:11:33.063 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d, L:/xx.xx.xx.xx:56922 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] READ COMPLETE
2022-11-14 09:11:33.165 DEBUG 21332 --- [ctor-http-nio-5] reactor.netty.http.client.HttpClient     : [ad2bc21d, L:/xx.xx.xx.xx:56922 - R:nnctj2prxc4t.apps.internal.xxxxx.net/xx.xx.xx.xx:443] USER_EVENT: SslHandshakeCompletionEvent(SUCCESS)
...

Caused by: java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 60000ms in 'source(MonoDefer)' (and no fallback has been configured)
        at reactor.core.publisher.FluxTimeout$TimeoutMainSubscriber.handleTimeout(FluxTimeout.java:295) ~[reactor-core-3.4.24.jar!/:3.4.24]

解决建议 #

1. 升级Reactor Netty版本 #

Reactor Netty 1.0.24存在部分JDK 11兼容性问题，建议升级至1.0.26或更高版本（Spring Boot 2.7.x兼容范围内），新版本修复了JDK 11下的连接管理和SSL相关bug。

修改依赖配置：

<dependency>
    <groupId>io.projectreactor.netty</groupId>
    <artifactId>reactor-netty-http</artifactId>
    <version>1.0.26</version>
</dependency>

2. 调整WebClient连接池配置 #

显式配置连接池的最大空闲时间和生命周期，避免复用已失效的连接：

import io.netty.channel.ChannelOption;
import io.netty.handler.timeout.ReadTimeoutHandler;
import io.netty.handler.timeout.WriteTimeoutHandler;
import reactor.netty.http.client.HttpClient;
import reactor.netty.resources.PoolResources;
import org.springframework.web.reactive.function.client.WebClient;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import java.time.Duration;

WebClient webClient = WebClient.builder()
        .clientConnector(new ReactorClientHttpConnector(
                HttpClient.create()
                        .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000)
                        .doOnConnected(conn -> conn
                                .addHandlerLast(new ReadTimeoutHandler(10))
                                .addHandlerLast(new WriteTimeoutHandler(10)))
                        .poolResources(PoolResources.fixed("webclient-pool", 10)
                                .maxIdleTime(Duration.ofSeconds(20))
                                .maxLifeTime(Duration.ofSeconds(60)))
        ))
        .build();

3. 添加请求重试机制 #

针对连接超时场景，添加重试策略，确保请求在连接失效时重新发起：

import reactor.util.retry.Retry;
import java.util.concurrent.TimeoutException;

webClient.get()
        .uri("/api/xxx")
        .retrieve()
        .bodyToMono(String.class)
        .retryWhen(Retry.fixedDelay(3, Duration.ofSeconds(1))
                .filter(throwable -> throwable instanceof TimeoutException))
        .block();

4. 调整JDK 11 SSL参数 #

JDK 11对SSL默认配置做了调整，可显式指定SSL provider或禁用某些特性：

import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.SslProvider;
import reactor.netty.http.client.HttpClient;

HttpClient httpClient = HttpClient.create()
        .secure(sslContextSpec -> sslContextSpec.sslContext(SslContextBuilder.forClient()
                .sslProvider(SslProvider.JDK)
                .build()));

内容的提问来源于stack exchange，提问作者user3787048