GUAC-867: Add periodic keep-alive ping to ensure the session does not perish while a connection is active.

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/SessionKeepAlive.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2014 Glyptodon LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package org.glyptodon.guacamole.net.basic;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import org.glyptodon.guacamole.net.auth.UserContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Dummy servlet which provides an endpoint for arbitrary requests intended to
+ * simply keep the HTTP session from expiring.
+ *
+ * @author Michael Jumper
+ */
+public class SessionKeepAlive extends RestrictedHttpServlet {
+
+    /**
+     * Logger for this class.
+     */
+    private final Logger logger = LoggerFactory.getLogger(SessionKeepAlive.class);
+
+    @Override
+    protected void restrictedService(
+            UserContext context,
+            HttpServletRequest request, HttpServletResponse response) {
+
+        // Do nothing
+        logger.trace("Keep-alive signal received.");
+        
+    }
+
+}

guacamole/src/main/webapp/WEB-INF/web.xml

@@ -86,6 +86,17 @@
         <url-pattern>/logout</url-pattern>
     </servlet-mapping>
 
+    <!-- Session Keep-Alive Servlet -->
+    <servlet>
+        <description>Session keep-alive servlet.</description>
+        <servlet-name>SessionKeepAlive</servlet-name>
+        <servlet-class>org.glyptodon.guacamole.net.basic.SessionKeepAlive</servlet-class>
+    </servlet>
+    <servlet-mapping>
+        <servlet-name>SessionKeepAlive</servlet-name>
+        <url-pattern>/keep-alive</url-pattern>
+    </servlet-mapping>
+
     <!-- Clipboard State Servlet -->
     <servlet>
         <description>Clipboard state servlet.</description>

guacamole/src/main/webapp/scripts/client-ui.js

@@ -195,10 +195,11 @@ GuacUI.Client = {
     },
 
     /* Constants */
-    
-    "KEYBOARD_AUTO_RESIZE_INTERVAL" : 30,  /* milliseconds */
-    "RECONNECT_PERIOD"              : 15,  /* seconds */
-    "TEXT_INPUT_PADDING"            : 128, /* characters */
+
+    "KEEP_ALIVE_INTERVAL"           : 60000, /* milliseconds */
+    "KEYBOARD_AUTO_RESIZE_INTERVAL" : 30,    /* milliseconds */
+    "RECONNECT_PERIOD"              : 15,    /* seconds */
+    "TEXT_INPUT_PADDING"            : 128,   /* characters */
     "TEXT_INPUT_PADDING_CODEPOINT"  : 0x200B,
 
     /* Main application area */
@@ -1014,6 +1015,11 @@ GuacUI.Client.connect = function() {
         connect_string += "&video=" + encodeURIComponent(mimetype);
     });
 
+    // Ping server every 10 seconds
+    var session_keep_alive = window.setInterval(function _session_keep_alive() {
+        GuacamoleService.KeepAlive.ping();
+    }, GuacUI.Client.KEEP_ALIVE_INTERVAL);
+
     // Show connection errors from tunnel
     tunnel.onerror = function(status) {
         var message = GuacUI.Client.tunnel_errors[status.code] || GuacUI.Client.tunnel_errors.DEFAULT;
@@ -1021,10 +1027,20 @@ GuacUI.Client.connect = function() {
             GuacUI.Client.tunnel_auto_reconnect[status.code] && GuacUI.Client.RECONNECT_PERIOD);
     };
 
-    // Notify of disconnections (if not already notified of something else)
     tunnel.onstatechange = function(state) {
-        if (state === Guacamole.Tunnel.State.CLOSED && !GuacUI.Client.visibleStatus)
-            GuacUI.Client.showStatus("Disconnected", "You have been disconnected. Reload the page to reconnect.");
+
+        // Handle disconnect
+        if (state === Guacamole.Tunnel.State.CLOSED) {
+
+            // No need for a keep-alive ping if the tunnel is closed
+            window.clearInterval(session_keep_alive);
+
+            // Notify of disconnections (if not already notified of something else)
+            if (!GuacUI.Client.visibleStatus)
+                GuacUI.Client.showStatus("Disconnected",
+                                         "You have been disconnected. Reload the page to reconnect.");
+        }
+
     };
 
     // Connect

guacamole/src/main/webapp/scripts/service.js

@@ -1438,3 +1438,26 @@ GuacamoleService.Clipboard = {
     }
     
 };
+
+/**
+ * Collection of service functions which deal with the session keep-alive. Each
+ * function makes an explicit HTTP query to the server. In the case of the
+ * keep-alive ping, no response is expected, and any received response is
+ * ignored.
+ */
+GuacamoleService.KeepAlive = {
+    
+    "ping" : function(parameters) {
+        
+        // Construct request URL
+        var ping_url = "keep-alive";
+        if (parameters) ping_url += "?" + parameters;
+        
+        // Send keep-alive "ping"
+        var xhr = new XMLHttpRequest();
+        xhr.open("GET", ping_url, true);
+        xhr.send(null);
+        
+    }
+    
+};