1 files changed, 96 insertions, 0 deletions
diff --git a/src/com/vaadin/terminal/gwt/server/GAEApplicationServlet.java b/src/com/vaadin/terminal/gwt/server/GAEApplicationServlet.java
new file mode 100644
index 0000000000..13d01cfb49
--- /dev/null
+++ b/src/com/vaadin/terminal/gwt/server/GAEApplicationServlet.java
@@ -0,0 +1,96 @@
+package com.vaadin.terminal.gwt.server;
+
+import java.io.IOException;
+import java.util.Date;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+import com.google.appengine.api.memcache.Expiration;
+import com.google.appengine.api.memcache.MemcacheService;
+import com.google.appengine.api.memcache.MemcacheServiceFactory;
+import com.google.apphosting.api.DeadlineExceededException;
+import com.vaadin.ui.Window;
+
+public class GAEApplicationServlet extends ApplicationServlet {
+
+    private static final long serialVersionUID = 2179597952818898526L;
+
+    private static final String MUTEX_BASE = "vaadin.gae.mutex.";
+    // Note: currently interpreting Retry-After as ms, not sec
+    private static final int RETRY_AFTER_MILLISECONDS = 100;
+    private static final int KEEP_MUTEX_MILLISECONDS = 100;
+
+    @Override
+    protected void service(HttpServletRequest request,
+            HttpServletResponse response) throws ServletException, IOException {
+
+        boolean locked = false;
+        MemcacheService memcache = null;
+        String mutex = null;
+        try {
+            RequestType requestType = getRequestType(request);
+            if (requestType == RequestType.UIDL) {
+                memcache = MemcacheServiceFactory.getMemcacheService();
+                mutex = MUTEX_BASE + request.getSession().getId();
+                // try to get lock
+                locked = memcache.put(mutex, 1, Expiration.byDeltaSeconds(40),
+                        MemcacheService.SetPolicy.ADD_ONLY_IF_NOT_PRESENT);
+                if (!locked) {
+                    // could not obtain lock, tell client to retry
+                    request.setAttribute("noSerialize", new Object());
+                    response
+                            .setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
+                    // Note: currently interpreting Retry-After as ms, not sec
+                    response.setHeader("Retry-After", ""
+                            + RETRY_AFTER_MILLISECONDS);
+                    return;
+                }
+
+            }
+
+            super.service(request, response);
+
+            if (request.getAttribute("noSerialize") == null) {
+                // Explicitly touch session so it is re-serialized.
+                HttpSession session = request.getSession(false);
+                if (session != null) {
+                    session
+                            .setAttribute("sessionUpdated", new Date()
+                                    .getTime());
+                }
+            }
+
+        } catch (DeadlineExceededException e) {
+            System.err.println("DeadlineExceeded for "
+                    + request.getSession().getId());
+            // TODO i18n?
+            criticalNotification(
+                    request,
+                    response,
+                    "Deadline Exceeded",
+                    "I'm sorry, but the operation took too long to complete. We'll try reloading to see where we're at, please take note of any unsaved data...",
+                    "", null);
+        } finally {
+            // "Next, please!"
+            if (locked) {
+                memcache.delete(mutex, KEEP_MUTEX_MILLISECONDS);
+            }
+
+        }
+    }
+
+    protected boolean handleURI(CommunicationManager applicationManager,
+            Window window, HttpServletRequest request,
+            HttpServletResponse response) throws IOException {
+
+        if (super.handleURI(applicationManager, window, request, response)) {
+            request.setAttribute("noSerialize", new Object());
+            return true;
+        }
+        return false;
+    }
+
+}