[ISSUE] Requesting `/` on `client-service` in `kubernetes-guide` throws UnknownHostException

[desmond27]

Article and Module Links
https://www.baeldung.com/spring-cloud-kubernetes
https://github.com/eugenp/tutorials/tree/master/spring-cloud-modules/spring-cloud-kubernetes

Describe the Issue
When building and deploying the application on Minikube using the deployment-travel-service.sh script, attempting to access the / URI on the client-service throws this error:

17:42:36.277 [http-nio-8080-exec-8] ERROR o.a.c.c.C.[.[.[.[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://myapp-discoveryserver/apps": myapp-discoveryserver: Name does not resolve; nested exception is java.net.UnknownHostException: myapp-discoveryserver: Name does not resolve] with root cause
java.net.UnknownHostException: myapp-discoveryserver: Name does not resolve
	at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
	at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:929)
	at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1324)
	at java.net.InetAddress.getAllByName0(InetAddress.java:1277)
	at java.net.InetAddress.getAllByName(InetAddress.java:1193)
	at java.net.InetAddress.getAllByName(InetAddress.java:1127)
	at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:45)
	at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:112)
	at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:376)
	at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:393)
	at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236)
	at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
	at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
	at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
	at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
	at org.springframework.http.client.HttpComponentsClientHttpRequest.executeInternal(HttpComponentsClientHttpRequest.java:87)
	at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
	at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:66)
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:782)
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:717)
	at org.springframework.web.client.RestTemplate.getForEntity(RestTemplate.java:367)
	at org.springframework.cloud.kubernetes.discovery.KubernetesDiscoveryClient.getServices(KubernetesDiscoveryClient.java:65)
	at org.springframework.cloud.client.discovery.composite.CompositeDiscoveryClient.getServices(CompositeDiscoveryClient.java:67)
	at com.baeldung.spring.cloud.kubernetes.client.ClientController.load(ClientController.java:42)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:529)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:96)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:768)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:389)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

I think a discovery server needs to be running with URL http://myapp-discoveryserver as per the property spring.cloud.kubernetes.discovery.discovery-server-url in the application.properties file:

spring:
  application.name: client-service
  cloud:
    kubernetes:
      reload:
        enabled: true
      discovery:
        enabled: true
        all-namespaces: false
        primary-port-name: "default-http"
        discovery-server-url: "http://myapp-discoveryserver"
        include-not-ready-addresses: true

To Reproduce
Steps to reproduce the behavior:

1. Go to this path: spring-cloud-modules/spring-cloud-kubernetes/kubernetes-guide
2. Run minikube start with appropriate driver.
3. Run the script deployment-travel-client.sh
4. Run minikube service list to see the URL of the client-service service.
5. Run http://<The URL from the service list>/ in a browser. It will return a 500 error.
6. Check the deployment or pod logs for client-service.

Expected Behavior
There is no error and we should get a response displaying the message from the config map, response body from travel-agency-service and a list of services returned by the discovery client.

Screenshots
N/A

Environment (please complete the following information):

• OS: Linux
• Browser: Firefox
• Version: 120

Additional Context
None

[ulisseslima]

Hey, @desmond27.

Thanks for the feedback. We'll look into this.

This issue will remain open until then.

[youngledo]

This guide is a bit of a hole, and there is no pre-description of "Spring Cloud Kubernetes Discovery Server". For details, see:

• https://stackoverflow.com/questions/75153698/spring-cloud-kubernetes-discovery-discovery-server-url-what-is-the-correct-url
• https://spring.io/blog/2021/10/26/new-features-for-spring-cloud-kubernetes-in-spring-cloud-2021-0-0-m3