Keycloak NullPointerException in DefaultHostnameProvider when authenticating - docker

Question

I'm stucking in this quite some weeks and I hope you can give me some hints.
I have a Docker-infrastructure where I have a backend in a container and keycloak (18.0.0 / latest version) running in another container. When my Backend tries to handle a request the authentication in Keycloak returns with a response code 500.
When I look at the logs in the keycloak-container I see a NullPointerException:`
2022-05-24 11:52:39,789 ERROR [org.keycloak.services.error.KeycloakErrorHandler] (executor-thread-4) Uncaught server error: java.lang.NullPointerException
at org.keycloak.quarkus.runtime.hostname.DefaultHostnameProvider.isHostFromFrontEndUrl(DefaultHostnameProvider.java:158)
at org.keycloak.quarkus.runtime.hostname.DefaultHostnameProvider.forNonStrictBackChannel(DefaultHostnameProvider.java:132)
at org.keycloak.quarkus.runtime.hostname.DefaultHostnameProvider.getScheme(DefaultHostnameProvider.java:60)
at org.keycloak.models.KeycloakUriInfo.<init>(KeycloakUriInfo.java:46)
at org.keycloak.services.DefaultKeycloakContext.getUri(DefaultKeycloakContext.java:78)
at org.keycloak.protocol.oidc.OIDCWellKnownProvider.getConfig(OIDCWellKnownProvider.java:111)
at org.keycloak.services.resources.RealmsResource.getWellKnown(RealmsResource.java:267)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:170)
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:130)
at org.jboss.resteasy.core.ResourceMethodInvoker.internalInvokeOnTarget(ResourceMethodInvoker.java:660)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTargetAfterFilter(ResourceMethodInvoker.java:524)
at org.jboss.resteasy.core.ResourceMethodInvoker.lambda$invokeOnTarget$2(ResourceMethodInvoker.java:474)
at org.jboss.resteasy.core.interception.jaxrs.PreMatchContainerRequestContext.filter(PreMatchContainerRequestContext.java:364)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:476)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:434)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:408)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:69)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:492)
at org.jboss.resteasy.core.SynchronousDispatcher.lambda$invoke$4(SynchronousDispatcher.java:261)
at org.jboss.resteasy.core.SynchronousDispatcher.lambda$preprocess$0(SynchronousDispatcher.java:161)
at org.jboss.resteasy.core.interception.jaxrs.PreMatchContainerRequestContext.filter(PreMatchContainerRequestContext.java:364)
at org.jboss.resteasy.core.SynchronousDispatcher.preprocess(SynchronousDispatcher.java:164)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:247)
at io.quarkus.resteasy.runtime.standalone.RequestDispatcher.service(RequestDispatcher.java:73)
at io.quarkus.resteasy.runtime.standalone.VertxRequestHandler.dispatch(VertxRequestHandler.java:151)
at io.quarkus.resteasy.runtime.standalone.VertxRequestHandler.handle(VertxRequestHandler.java:82)
at io.quarkus.resteasy.runtime.standalone.VertxRequestHandler.handle(VertxRequestHandler.java:42)
at io.vertx.ext.web.impl.RouteState.handleContext(RouteState.java:1212)
at io.vertx.ext.web.impl.RoutingContextImplBase.iterateNext(RoutingContextImplBase.java:163)
at io.vertx.ext.web.impl.RoutingContextWrapper.next(RoutingContextWrapper.java:201)
at io.quarkus.vertx.http.runtime.StaticResourcesRecorder$2.handle(StaticResourcesRecorder.java:67)
at io.quarkus.vertx.http.runtime.StaticResourcesRecorder$2.handle(StaticResourcesRecorder.java:55)
at io.vertx.ext.web.impl.RouteState.handleContext(RouteState.java:1212)
at io.vertx.ext.web.impl.RoutingContextImplBase.iterateNext(RoutingContextImplBase.java:163)
at io.vertx.ext.web.impl.RoutingContextWrapper.next(RoutingContextWrapper.java:201)
at io.quarkus.vertx.http.runtime.VertxHttpRecorder$5.handle(VertxHttpRecorder.java:380)
at io.quarkus.vertx.http.runtime.VertxHttpRecorder$5.handle(VertxHttpRecorder.java:358)
at io.vertx.ext.web.impl.RouteState.handleContext(RouteState.java:1212)
at io.vertx.ext.web.impl.RoutingContextImplBase.iterateNext(RoutingContextImplBase.java:163)
at io.vertx.ext.web.impl.RoutingContextWrapper.next(RoutingContextWrapper.java:201)
at org.keycloak.quarkus.runtime.integration.web.QuarkusRequestFilter.lambda$createBlockingHandler$1(QuarkusRequestFilter.java:71)
at io.vertx.core.impl.ContextImpl.lambda$null$0(ContextImpl.java:159)
at io.vertx.core.impl.AbstractContext.dispatch(AbstractContext.java:100)
at io.vertx.core.impl.ContextImpl.lambda$executeBlocking$1(ContextImpl.java:157)
at io.quarkus.vertx.core.runtime.VertxCoreRecorder$13.runWith(VertxCoreRecorder.java:543)
at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2449)
at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1478)
at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:29)
at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:29)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.base/java.lang.Thread.run(Thread.java:829)
The URL my backend is sending the request to is: http://keycloak:8080/auth/realms/my-realm/.well-known/openid-configuration
When I execute this request in the keycloak-container I get the same error.
When I execute this request with localhost instead of the container-name in the keycloak-container everything works fine.
I don’t know what I’m doing wrong

Answer 1

I found the problem in my configuration.
My backend was communictating with keycloak through the internal name and keycloak was setup with the public name of the host.
When I set to get everything working with the IP of the host (not tha name of the host as it is not accessible in the containers) everything is working as expected.