GUACAMOLE-1224: Add events for overall webapp startup/shutdown.

guacamole-ext/src/main/java/org/apache/guacamole/net/event/ApplicationShutdownEvent.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.net.event;
+
+import org.apache.guacamole.net.auth.AuthenticationProvider;
+import org.apache.guacamole.net.auth.UserContext;
+import org.apache.guacamole.net.event.listener.Listener;
+
+/**
+ * Event that is dispatched when the web application has nearly completely shut
+ * down, including the authentication/authorization portion of extensions. Any
+ * installed extensions are still loaded (such that they may receive this event
+ * via {@link Listener#handleEvent(java.lang.Object)}, but their authentication
+ * providers will have been shut down via {@link AuthenticationProvider#shutdown()},
+ * and resources from user sessions will have been closed and released via
+ * {@link UserContext#invalidate()}.
+ */
+public interface ApplicationShutdownEvent {
+}

guacamole-ext/src/main/java/org/apache/guacamole/net/event/ApplicationStartedEvent.java

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.net.event;
+
+/**
+ * Event that is dispatched when the web application has finished starting up,
+ * including all extensions. This event indicates only that the web application
+ * startup process has completed and all extensions have been loaded. It does
+ * not indicate whether all extensions have started successfully.
+ */
+public interface ApplicationStartedEvent {
+}

guacamole/src/main/java/org/apache/guacamole/GuacamoleServletContextListener.java

@@ -35,11 +35,14 @@ import org.apache.guacamole.environment.LocalEnvironment;
 import org.apache.guacamole.extension.ExtensionModule;
 import org.apache.guacamole.log.LogModule;
 import org.apache.guacamole.net.auth.AuthenticationProvider;
+import org.apache.guacamole.net.event.ApplicationShutdownEvent;
+import org.apache.guacamole.net.event.ApplicationStartedEvent;
 import org.apache.guacamole.properties.BooleanGuacamoleProperty;
 import org.apache.guacamole.properties.FileGuacamoleProperties;
 import org.apache.guacamole.rest.RESTServiceModule;
 import org.apache.guacamole.rest.auth.HashTokenSessionMap;
 import org.apache.guacamole.rest.auth.TokenSessionMap;
+import org.apache.guacamole.rest.event.ListenerService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -126,6 +129,12 @@ public class GuacamoleServletContextListener extends GuiceServletContextListener
     @Inject
     private List<File> temporaryFiles;
 
+    /**
+     * Service for dispatching events to registered listeners.
+     */
+    @Inject
+    private ListenerService listenerService;
+
     /**
      * Internal reference to the Guice injector that was lazily created when
      * getInjector() was first invoked.
@@ -179,6 +188,17 @@ public class GuacamoleServletContextListener extends GuiceServletContextListener
         // Store reference to injector for use by Jersey and HK2 bridge
         servletContextEvent.getServletContext().setAttribute(GUICE_INJECTOR, injector);
 
+        // Inform any listeners that application startup has completed
+        try {
+            listenerService.handleEvent(new ApplicationStartedEvent() {
+                // The application startup event currently has no content
+            });
+        }
+        catch (GuacamoleException e) {
+            logger.error("An extension listening for application startup failed: {}", e.getMessage());
+            logger.debug("Extension failed internally while handling the application startup event.", e);
+        }
+
     }
 
     @Override
@@ -228,19 +248,36 @@ public class GuacamoleServletContextListener extends GuiceServletContextListener
             // Clean up reference to Guice injector
             servletContextEvent.getServletContext().removeAttribute(GUICE_INJECTOR);
 
-            // Shutdown TokenSessionMap
+            // Shutdown TokenSessionMap, invalidating all sessions (logging all
+            // users out)
             if (sessionMap != null)
                 sessionMap.shutdown();
 
-            // Unload all extensions
+            // Unload authentication for all extensions
             if (authProviders != null) {
                 for (AuthenticationProvider authProvider : authProviders)
                     authProvider.shutdown();
             }
 
+            // Inform any listeners that application shutdown has completed
+            try {
+                listenerService.handleEvent(new ApplicationShutdownEvent() {
+                    // The application shutdown event currently has no content
+                });
+            }
+            catch (GuacamoleException e) {
+                logger.error("An extension listening for application shutdown failed: {}", e.getMessage());
+                logger.debug("Extension failed internally while handling the application shutdown event.", e);
+            }
+
         }
         finally {
 
+            // NOTE: This temporary file cleanup must happen AFTER firing the
+            // ApplicationShutdownEvent, or an extension that relies on a .jar
+            // file among those temporary files might fail internally when
+            // attempting to process the event.
+
             // Regardless of what may succeed/fail here, always attempt to
             // clean up ALL temporary files
             if (temporaryFiles != null)

guacamole/src/main/java/org/apache/guacamole/event/EventLoggingListener.java

@@ -22,6 +22,8 @@ package org.apache.guacamole.event;
 import javax.annotation.Nonnull;
 import org.apache.guacamole.GuacamoleException;
 import org.apache.guacamole.GuacamoleResourceNotFoundException;
+import org.apache.guacamole.net.event.ApplicationShutdownEvent;
+import org.apache.guacamole.net.event.ApplicationStartedEvent;
 import org.apache.guacamole.net.event.DirectoryEvent;
 import org.apache.guacamole.net.event.DirectoryFailureEvent;
 import org.apache.guacamole.net.event.DirectorySuccessEvent;
@@ -115,12 +117,19 @@ public class EventLoggingListener implements Listener {
     @Override
     public void handleEvent(@Nonnull Object event) throws GuacamoleException {
 
+        // General object creation/modification/deletion
         if (event instanceof DirectorySuccessEvent)
             logSuccess((DirectorySuccessEvent<?>) event);
-
         else if (event instanceof DirectoryFailureEvent)
             logFailure((DirectoryFailureEvent<?>) event);
 
+        // Application startup/shutdown
+        else if (event instanceof ApplicationStartedEvent)
+            logger.info("The Apache Guacamole web application has started.");
+        else if (event instanceof ApplicationShutdownEvent)
+            logger.info("The Apache Guacamole web application has shut down.");
+
+        // Unknown events
         else
             logger.debug("Ignoring unknown/unimplemented event type: {}",
                     event.getClass());