概述

MCP client的 spring-ai-starter-mcp-client 版本为1.0.0

客户端最初运行比较正常，但过一段时间请求时出现如下报错：
 

java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 20000ms in 'source(MonoDeferContextual)' (and no fallback has been configured)

reactor.core.Exceptions$ReactiveException: java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 20000ms in 'source(MonoDeferContextual)' (and no fallback has been configured)
	at reactor.core.Exceptions.propagate(Exceptions.java:410) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:102) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.Mono.block(Mono.java:1779) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at io.modelcontextprotocol.client.McpSyncClient.callTool(McpSyncClient.java:218) ~[mcp-0.10.0.jar!/:0.10.0]
	at org.springframework.ai.mcp.SyncMcpToolCallback.call(SyncMcpToolCallback.java:116) ~[spring-ai-mcp-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.mcp.SyncMcpToolCallback.call(SyncMcpToolCallback.java:126) ~[spring-ai-mcp-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.model.tool.DefaultToolCallingManager.lambda$executeToolCall$5(DefaultToolCallingManager.java:224) ~[spring-ai-model-1.0.0.jar!/:1.0.0]
	at io.micrometer.observation.Observation.observe(Observation.java:565) ~[micrometer-observation-1.13.13.jar!/:1.13.13]
	at org.springframework.ai.model.tool.DefaultToolCallingManager.executeToolCall(DefaultToolCallingManager.java:221) ~[spring-ai-model-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.model.tool.DefaultToolCallingManager.executeToolCalls(DefaultToolCallingManager.java:137) ~[spring-ai-model-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.openai.OpenAiChatModel.internalCall(OpenAiChatModel.java:244) ~[spring-ai-openai-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.openai.OpenAiChatModel.call(OpenAiChatModel.java:181) ~[spring-ai-openai-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.chat.client.advisor.ChatModelCallAdvisor.adviseCall(ChatModelCallAdvisor.java:54) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.chat.client.advisor.DefaultAroundAdvisorChain.lambda$nextCall$1(DefaultAroundAdvisorChain.java:110) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at io.micrometer.observation.Observation.observe(Observation.java:565) ~[micrometer-observation-1.13.13.jar!/:1.13.13]
	at org.springframework.ai.chat.client.advisor.DefaultAroundAdvisorChain.nextCall(DefaultAroundAdvisorChain.java:110) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.chat.client.DefaultChatClient$DefaultCallResponseSpec.lambda$doGetObservableChatClientResponse$1(DefaultChatClient.java:469) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at io.micrometer.observation.Observation.observe(Observation.java:565) ~[micrometer-observation-1.13.13.jar!/:1.13.13]
	at org.springframework.ai.chat.client.DefaultChatClient$DefaultCallResponseSpec.doGetObservableChatClientResponse(DefaultChatClient.java:467) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.chat.client.DefaultChatClient$DefaultCallResponseSpec.doGetObservableChatClientResponse(DefaultChatClient.java:446) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at org.springframework.ai.chat.client.DefaultChatClient$DefaultCallResponseSpec.content(DefaultChatClient.java:441) ~[spring-ai-client-chat-1.0.0.jar!/:1.0.0]
	at com.sieiot.ai.mcp.controller.McpClientController.aiPost(McpClientController.java:72) ~[!/:1.0]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[na:na]
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:255) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:188) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:926) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:831) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.19.jar!/:6.1.19]
	at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.19.jar!/:6.1.19]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:116) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:732) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:398) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:903) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1740) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1189) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:658) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.40.jar!/:na]
	at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]
	Suppressed: java.lang.Exception: #block terminated with an error
		at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:104) ~[reactor-core-3.6.16.jar!/:3.6.16]
		... 71 common frames omitted
Caused by: java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 20000ms in 'source(MonoDeferContextual)' (and no fallback has been configured)
	at reactor.core.publisher.FluxTimeout$TimeoutMainSubscriber.handleTimeout(FluxTimeout.java:296) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.FluxTimeout$TimeoutMainSubscriber.doTimeout(FluxTimeout.java:281) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.FluxTimeout$TimeoutTimeoutSubscriber.onNext(FluxTimeout.java:420) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.FluxOnErrorReturn$ReturnSubscriber.onNext(FluxOnErrorReturn.java:162) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.MonoDelay$MonoDelayRunnable.propagateDelay(MonoDelay.java:270) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.publisher.MonoDelay$MonoDelayRunnable.run(MonoDelay.java:285) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:68) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at reactor.core.scheduler.SchedulerTask.call(SchedulerTask.java:28) ~[reactor-core-3.6.16.jar!/:3.6.16]
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[na:na]
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[na:na]
	... 1 common frames omitted

解决方案

MCP Client为SSE client增加心跳，保持连接：

import io.modelcontextprotocol.client.McpSyncClient;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;

@Service
@Slf4j
public class McpHeartbeatService {
    private final List<McpSyncClient> mcpClients;

    public McpHeartbeatService(List<McpSyncClient> mcpClients) {
        this.mcpClients = mcpClients;
    }

    @Scheduled(fixedRate = 120000) // 每2分钟1次发送心跳
    public void sendHeartbeat() {
        try {
            log.info("McpSyncClient ping... ");
            this.mcpClients.parallelStream().forEach(client -> {client.ping();});
        } catch (Exception e) {
            log.warn("Heartbeat failed, triggering reconnect");
        }
    }

}