KNOX-3332: Add listeners on gateway config changes

gateway-server/src/main/java/org/apache/knox/gateway/GatewayServer.java

@@ -28,6 +28,7 @@
 import org.apache.knox.gateway.audit.api.ResourceType;
 import org.apache.knox.gateway.audit.log4j.audit.AuditConstants;
 import org.apache.knox.gateway.config.GatewayConfig;
+import org.apache.knox.gateway.config.GatewayConfigChangeListener;
 import org.apache.knox.gateway.config.GatewayConfigurationException;
 import org.apache.knox.gateway.config.impl.GatewayConfigImpl;
 import org.apache.knox.gateway.deploy.DeploymentException;
@@ -127,6 +128,7 @@
 import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
@@ -148,6 +150,8 @@ public class GatewayServer {
   private static GatewayServer server;
   private static GatewayServices services;
 
+  private static final List<GatewayConfigChangeListener> configChangeListeners = new CopyOnWriteArrayList<>();
+
   private static Properties buildProperties;
 
   private static final ScheduledExecutorService exec = Executors.newSingleThreadScheduledExecutor();
@@ -239,6 +243,14 @@ public static synchronized GatewayServices getGatewayServices() {
     return services;
   }
 
+  public static void registerConfigChangeListener(GatewayConfigChangeListener listener) {
+    configChangeListeners.add(listener);
+  }
+
+  public static void unregisterConfigChangeListener(GatewayConfigChangeListener listener) {
+    configChangeListeners.remove(listener);
+  }
+
   private static void setupGatewayConfigRefresh(GatewayConfigImpl config) {
     Path resourcePath = Paths.get(config.getGatewayConfDir(), RELOADABLE_CONFIG_FILENAME);
     int refreshInterval = config.getConfigRefreshInterval();
@@ -261,6 +273,9 @@ private static synchronized void refreshGatewayConfig(GatewayConfigImpl config,
           lastReloadTime = lastModifiedTime;
           config.reloadConfiguration();
           log.refreshedGatewayConfig();
+          for (GatewayConfigChangeListener listener : configChangeListeners) {
+            listener.onGatewayConfigChanged(config);
+          }
         }
       }
     } catch (IOException e) {

gateway-server/src/main/java/org/apache/knox/gateway/services/DefaultGatewayServices.java

@@ -21,6 +21,7 @@
 import java.util.Map;
 
 import org.apache.knox.gateway.GatewayMessages;
+import org.apache.knox.gateway.GatewayServer;
 import org.apache.knox.gateway.config.GatewayConfig;
 import org.apache.knox.gateway.deploy.DeploymentContext;
 import org.apache.knox.gateway.descriptor.FilterParamDescriptor;
@@ -88,6 +89,7 @@ public void init(GatewayConfig config, Map<String,String> options) throws Servic
     if (config.isLDAPEnabled()) {
       KnoxLDAPService ldapService = new KnoxLDAPService();
       ldapService.init(config, options);
+      GatewayServer.registerConfigChangeListener(ldapService);
       addService(ServiceType.LDAP_SERVICE, ldapService);
     }
   }

gateway-server/src/main/java/org/apache/knox/gateway/services/ldap/KnoxLDAPServerManager.java

@@ -30,6 +30,7 @@
 import org.apache.directory.server.core.partition.ldif.LdifPartition;
 import org.apache.directory.server.ldap.LdapServer;
 import org.apache.directory.server.protocol.shared.transport.TcpTransport;
+import org.apache.knox.gateway.config.GatewayConfig;
 import org.apache.knox.gateway.i18n.messages.MessagesFactory;
 import org.apache.knox.gateway.services.ldap.backend.BackendFactory;
 import org.apache.knox.gateway.services.ldap.backend.LdapBackend;
@@ -56,21 +57,33 @@ public class KnoxLDAPServerManager {
     /**
      * Initialize the LDAP server with the given configuration
      *
-     * @param workDir Directory for LDAP data storage
-     * @param port Port for LDAP server to listen on
-     * @param baseDn Base DN for LDAP entries in the proxy server
-     * @param backendType Type of backend to use
-     * @param backendConfig Backend-specific configuration
-     * @param remoteBaseDn Base DN of the remote LDAP server (for proxy backends)
+     * @param config Gateway configuration
      */
-    public void initialize(File workDir, int port, String baseDn, String backendType, Map<String, String> backendConfig, String remoteBaseDn) throws Exception {
-        this.workDir = workDir;
-        this.port = port;
-        this.baseDn = baseDn;
-        this.remoteBaseDn = remoteBaseDn;
+    public void initialize(GatewayConfig config) throws Exception {
+        // Prepare work directory for LDAP data
+        File gatewayDataDir = new File(config.getGatewayDataDir());
+        this.workDir = new File(gatewayDataDir, "ldap-server");
 
-        // Initialize backend
+        // Get configuration
+        this.port = config.getLDAPPort();
+        this.baseDn = config.getLDAPBaseDN();
+        String backendType = config.getLDAPBackendType();
+
+        // Get backend-specific configuration using prefixed properties
+        Map<String, String> backendConfig = config.getLDAPBackendConfig(backendType);
+
+        // Add common configuration
         backendConfig.put("baseDn", baseDn);
+
+        // Add legacy dataFile property for backwards compatibility with file backend
+        if ("file".equalsIgnoreCase(backendType) && !backendConfig.containsKey("dataFile")) {
+            backendConfig.put("dataFile", config.getLDAPBackendDataFile());
+        }
+
+        // For proxy backends, extract remoteBaseDn if present
+        this.remoteBaseDn = backendConfig.get("remoteBaseDn");
+
+        // Initialize backend
         backend = BackendFactory.createBackend(backendType, backendConfig);
 
         // Clean up previous run if it didn't shut down cleanly

gateway-server/src/main/java/org/apache/knox/gateway/services/ldap/KnoxLDAPService.java

@@ -18,18 +18,18 @@
 package org.apache.knox.gateway.services.ldap;
 
 import org.apache.knox.gateway.config.GatewayConfig;
+import org.apache.knox.gateway.config.GatewayConfigChangeListener;
 import org.apache.knox.gateway.i18n.messages.MessagesFactory;
 import org.apache.knox.gateway.services.Service;
 import org.apache.knox.gateway.services.ServiceLifecycleException;
 
-import java.io.File;
 import java.util.Map;
 
 /**
  * Knox LDAP Service - provides an embedded LDAP server with pluggable backends
  * for user and group lookups.
  */
-public class KnoxLDAPService implements Service {
+public class KnoxLDAPService implements Service, GatewayConfigChangeListener {
     private static final LdapMessages LOG = MessagesFactory.get(LdapMessages.class);
 
     private KnoxLDAPServerManager ldapServerManager;
@@ -46,32 +46,7 @@ public void init(GatewayConfig config, Map<String, String> options) throws Servi
         try {
             // Initialize the LDAP server manager with configuration
             ldapServerManager = new KnoxLDAPServerManager();
-
-            // Prepare work directory for LDAP data
-            File gatewayDataDir = new File(config.getGatewayDataDir());
-            File ldapWorkDir = new File(gatewayDataDir, "ldap-server");
-
-            // Get configuration
-            int port = config.getLDAPPort();
-            String baseDn = config.getLDAPBaseDN();
-            String backendType = config.getLDAPBackendType();
-
-            // Get backend-specific configuration using prefixed properties
-            Map<String, String> backendConfig = config.getLDAPBackendConfig(backendType);
-
-            // Add common configuration
-            backendConfig.put("baseDn", baseDn);
-
-            // Add legacy dataFile property for backwards compatibility with file backend
-            if ("file".equalsIgnoreCase(backendType) && !backendConfig.containsKey("dataFile")) {
-                backendConfig.put("dataFile", config.getLDAPBackendDataFile());
-            }
-
-            // For proxy backends, extract remoteBaseDn if present
-            String remoteBaseDn = backendConfig.get("remoteBaseDn");
-
-            // Initialize but don't start yet
-            ldapServerManager.initialize(ldapWorkDir, port, baseDn, backendType, backendConfig, remoteBaseDn);
+            ldapServerManager.initialize(config);
 
         } catch (Exception e) {
             throw new ServiceLifecycleException("Failed to initialize LDAP service", e);
@@ -107,6 +82,26 @@ public void stop() throws ServiceLifecycleException {
         }
     }
 
+    @Override
+    public void onGatewayConfigChanged(GatewayConfig config) {
+        LOG.ldapReloadingConfig();
+        try {
+            this.enabled = config.isLDAPEnabled();
+
+            if (this.enabled) {
+                this.ldapServerManager = this.ldapServerManager == null ? new KnoxLDAPServerManager() : this.ldapServerManager;
+                ldapServerManager.stop();
+                ldapServerManager.initialize(config);
+                ldapServerManager.start();
+            } else if (ldapServerManager != null) {
+                ldapServerManager.stop();
+                ldapServerManager = null;
+            }
+        } catch (Exception e) {
+            LOG.ldapServiceReloadFailed(e);
+        }
+    }
+
     /**
      * Get the port the LDAP server is listening on
      */

gateway-server/src/main/java/org/apache/knox/gateway/services/ldap/LdapMessages.java

@@ -102,4 +102,12 @@ public interface LdapMessages {
 
     @Message(level = MessageLevel.WARN, text = "LDAP authentication failed for user: {0}")
     void ldapAuthFailed(String user, @StackTrace(level = MessageLevel.INFO) Throwable cause);
+
+    @Message(level = MessageLevel.INFO,
+            text = "Reloading LDAP configuration")
+    void ldapReloadingConfig();
+
+    @Message(level = MessageLevel.ERROR,
+            text = "Failed to reload LDAP service: {0}")
+    void ldapServiceReloadFailed(@StackTrace(level = MessageLevel.DEBUG) Exception e);
 }

gateway-server/src/test/java/org/apache/knox/gateway/GatewayServerTest.java

@@ -17,6 +17,7 @@
  */
 package org.apache.knox.gateway;
 
+import org.apache.knox.gateway.config.GatewayConfigChangeListener;
 import org.apache.knox.gateway.config.impl.GatewayConfigImpl;
 import org.easymock.EasyMock;
 import org.junit.Rule;
@@ -32,6 +33,7 @@
 import java.nio.file.attribute.FileTime;
 
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 public class GatewayServerTest {
 
@@ -95,4 +97,34 @@ public void testRefreshGatewayConfig() throws Exception {
     refreshMethod.invoke(null, config, configFile.toPath());
     EasyMock.verify(config);
   }
+
+  @Test
+  public void testGatewayConfigChangeListener() throws Exception {
+    GatewayConfigImpl config = EasyMock.createNiceMock(GatewayConfigImpl.class);
+    File configFile = folder.newFile("gateway-reloadable-listener.xml");
+    try (PrintWriter writer = new PrintWriter(configFile, StandardCharsets.UTF_8)) {
+      writer.println("<configuration></configuration>");
+    }
+
+    final boolean[] notified = {false};
+    GatewayConfigChangeListener listener = (c) -> notified[0] = true;
+
+    GatewayServer.registerConfigChangeListener(listener);
+
+    try {
+      Method refreshMethod = GatewayServer.class.getDeclaredMethod("refreshGatewayConfig", GatewayConfigImpl.class, Path.class);
+      refreshMethod.setAccessible(true);
+
+      // Reset lastReloadTime to ensure refresh happens
+      Field lastReloadTimeField = GatewayServer.class.getDeclaredField("lastReloadTime");
+      lastReloadTimeField.setAccessible(true);
+      lastReloadTimeField.set(null, null);
+
+      refreshMethod.invoke(null, config, configFile.toPath());
+
+      assertTrue("Listener should have been notified", notified[0]);
+    } finally {
+      GatewayServer.unregisterConfigChangeListener(listener);
+    }
+  }
 }