在做Sentinel的时候，Sentinel能够监控到服务，但是不管怎么访问接口，都实时监控都为空白，查看日志，报错信息如下：
2020-05-11 16:19:28 [http-nio-8080-exec-1] ERROR c.a.c.s.d.client.SentinelApiClient - Error when fetching items from api: jsonTree -> root
java.util.concurrent.ExecutionException: java.net.ConnectException: Connection timed out: no further information
at java.util.concurrent.CompletableFuture.reportGet(Unknown Source)
at java.util.concurrent.CompletableFuture.get(Unknown Source)
at com.alibaba.csp.sentinel.dashboard.client.SentinelApiClient.fetchItems(SentinelApiClient.java:374)
at com.alibaba.csp.sentinel.dashboard.client.SentinelApiClient.fetchResourceOfMachine(SentinelApiClient.java:441)
at com.alibaba.csp.sentinel.dashboard.controller.ResourceController.fetchResourceChainListOfMachine(ResourceController.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.alibaba.csp.sentinel.adapter.servlet.CommonFilter.doFilter(CommonFilter.java:110)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.alibaba.csp.sentinel.dashboard.auth.LoginAuthenticationFilter.doFilter(LoginAuthenticationFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.ConnectException: Connection timed out: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvent(DefaultConnectingIOReactor.java:171)
at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvents(DefaultConnectingIOReactor.java:145)
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:348)
at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:194)
at org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64)
... 1 common frames omitted
Sentinel界面界面如下，此时已经调用过接口了：
解决办法如下：
查看官网链接
还有些其他的：
在通过cmd来启动jar时添加参数，Dproject.name=xxxx （该端口号自己指定），我这里指定的是8889``
java -jar sentinel-dashboard-1.7.0.jar -Dproject.name=8889
同样的yml文件也需要进行修改！
spring:
application:
name: cloudalibaba-sentinel-service
cloud:
nacos:
discovery:
#Nacos服务注册中心地址
server-addr: localhost:8848
sentinel:
transport:
#配置sentinel dashboard地址
dashboard: localhost:8080
#默认8719端口，假如被占用会自动从8719开始依次+1扫描，直至找到未被占用的端口
port: 8889
management:
endpoints:
web:
exposure:
include: '*'
之后即可监控到服务！
希望可以帮助到大家，谢谢！