KEYCLOAK-7936 Prevent registration of the same node

The root cause is that NodesRegistrationManagement.tryRegister can be
called from multiple threads on the same node, so it can require
registration of the same node multiple times. Hence once it turns to
tasks that invoke sendRegistrationEvent (called sequentially), the same
check has been added to that method to prevent multiple invocations on
server side, or invocation upon undeployment/termination.

adapters/oidc/adapter-core/src/main/java/org/keycloak/adapters/NodesRegistrationManagement.java

@@ -23,10 +23,13 @@ import org.keycloak.common.util.Time;
 
 import java.io.IOException;
 import java.util.Collection;
+import java.util.LinkedList;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
 /**
  * @author <a href="mailto:mposolda@redhat.com">Marek Posolda</a>
@@ -36,7 +39,7 @@ public class NodesRegistrationManagement {
     private static final Logger log = Logger.getLogger(NodesRegistrationManagement.class);
 
     private final Map<String, NodeRegistrationContext> nodeRegistrations = new ConcurrentHashMap<String, NodeRegistrationContext>();
-    private final Executor executor = Executors.newSingleThreadExecutor();
+    private final ExecutorService executor = Executors.newSingleThreadExecutor();
 
     // Sending registration event during first request to application or if re-registration is needed
     public void tryRegister(final KeycloakDeployment resolvedDeployment) {
@@ -72,6 +75,8 @@ public class NodesRegistrationManagement {
      * Called during undeployment or server stop. De-register from all previously registered deployments
      */
     public void stop() {
+        executor.shutdownNow();
+
         Collection<NodeRegistrationContext> allRegistrations = nodeRegistrations.values();
         for (NodeRegistrationContext registration : allRegistrations) {
             sendUnregistrationEvent(registration.resolvedDeployment);
@@ -79,6 +84,17 @@ public class NodesRegistrationManagement {
     }
 
     protected void sendRegistrationEvent(KeycloakDeployment deployment) {
+        // This method is invoked from single-thread executor, so no synchronization is needed
+        // However, it could happen that the same deployment was submitted more than once to that executor
+        // Hence we need to recheck that the registration is really needed
+        final String registrationUri = deployment.getRegisterNodeUrl();
+        if (! needRefreshRegistration(registrationUri, deployment)) {
+            return;
+        }
+        if (Thread.currentThread().isInterrupted()) {
+            return;
+        }
+
         log.debug("Sending registration event right now");
 
         String host = HostUtils.getHostName();

services/src/main/java/org/keycloak/services/resources/ClientsManagementService.java

@@ -120,7 +120,12 @@ public class ClientsManagementService {
         event.client(client).detail(Details.NODE_HOST, nodeHost);
         logger.debugf("Registering cluster host '%s' for client '%s'", nodeHost, client.getClientId());
 
-        client.registerNode(nodeHost, Time.currentTime());
+        try {
+            client.registerNode(nodeHost, Time.currentTime());
+        } catch (RuntimeException e) {
+            event.error(e.getMessage());
+            throw e;
+        }
 
         event.success();