add support for being able to return more than one event in a single long poll request, since the client will poll no more often than every half-second. this could have caused a rather large backlog of events to deliver if chat was active.

WebContent/js/cah.longpoll.js

@@ -30,23 +30,26 @@ cah.longpoll.complete = function() {
   }
 };
 
-cah.longpoll.done = function(data) {
-  cah.log.debug("long poll done", data);
+cah.longpoll.done = function(data_list) {
+  cah.log.debug("long poll done", data_list);
 
-  if (data['error']) {
-    // TODO cancel any timers or whatever we may have, and disable interface
-    // this probably should be done in the appropriate error code handler because we may not
-    // want to always be that extreme.
-    if (cah.longpoll.ErrorCodeHandlers[data.error_code]) {
-      cah.longpoll.ErrorCodeHandlers[data.error_code](data);
+  for ( var index in data_list) {
+    var data = data_list[index];
+    if (data['error']) {
+      // TODO cancel any timers or whatever we may have, and disable interface
+      // this probably should be done in the appropriate error code handler because we may not
+      // want to always be that extreme.
+      if (cah.longpoll.ErrorCodeHandlers[data.error_code]) {
+        cah.longpoll.ErrorCodeHandlers[data.error_code](data);
+      } else {
+        cah.log.error(data.error_message);
+      }
     } else {
-      cah.log.error(data.error_message);
-    }
-  } else {
-    if (cah.longpoll.EventHandlers[data.event]) {
-      cah.longpoll.EventHandlers[data.event](data);
-    } else {
-      cah.log.error("Unhandled event " + data.event);
+      if (cah.longpoll.EventHandlers[data.event]) {
+        cah.longpoll.EventHandlers[data.event](data);
+      } else {
+        cah.log.error("Unhandled event " + data.event);
+      }
     }
   }
 
@@ -56,7 +59,6 @@ cah.longpoll.done = function(data) {
 
 cah.longpoll.error = function(jqXHR, textStatus, errorThrown) {
   // TODO deal with this somehow
-  debugger;
   cah.log.debug(textStatus);
   cah.longpoll.Backoff *= 2;
   cah.log

src/net/socialgamer/cah/CahServlet.java

@@ -2,6 +2,7 @@ package net.socialgamer.cah;
 
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.util.List;
 import java.util.Map;
 
 import javax.servlet.ServletException;
@@ -108,7 +109,23 @@ public abstract class CahServlet extends HttpServlet {
    *          Key-value data to return as the response.
    */
   protected void returnData(final PrintWriter writer, final Map<String, Object> data) {
-    writer.println(JSONValue.toJSONString(data));
+    returnObject(writer, data);
+  }
+
+  /**
+   * Return multiple response data to the client.
+   * 
+   * @param writer
+   *          Writer for the response.
+   * @param data_list
+   *          List of key-value data to return as the response.
+   */
+  protected void returnArray(final PrintWriter writer, final List<Map<String, Object>> data_list) {
+    returnObject(writer, data_list);
+  }
+
+  private void returnObject(final PrintWriter writer, final Object object) {
+    writer.println(JSONValue.toJSONString(object));
   }
 
   protected Injector getInjector() {

src/net/socialgamer/cah/LongPollServlet.java

@@ -2,7 +2,10 @@ package net.socialgamer.cah;
 
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import javax.servlet.ServletException;
@@ -35,12 +38,10 @@ public class LongPollServlet extends CahServlet {
   private static final double TIMEOUT_RANDOMNESS = 20 * 1000 * 1000;
 
   /**
-   * @see HttpServlet#HttpServlet()
+   * The maximum number of messages which will be returned to a client during a single poll
+   * operation.
    */
-  public LongPollServlet() {
-    super();
-    // TODO Auto-generated constructor stub
-  }
+  private static final int MAX_MESSAGES_PER_POLL = 5;
 
   /**
    * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
@@ -67,10 +68,14 @@ public class LongPollServlet extends CahServlet {
       }
     }
     if (user.hasQueuedMessages()) {
-      final QueuedMessage qm = user.getNextQueuedMessage();
+      final Collection<QueuedMessage> msgs = user.getNextQueuedMessages(MAX_MESSAGES_PER_POLL);
       // just in case...
-      if (qm != null) {
-        returnData(out, qm.getData());
+      if (msgs.size() > 0) {
+        final List<Map<String, Object>> data = new ArrayList<Map<String, Object>>(msgs.size());
+        for (final QueuedMessage qm : msgs) {
+          data.add(qm.getData());
+        }
+        returnArray(out, data);
         return;
       }
     }
@@ -78,6 +83,8 @@ public class LongPollServlet extends CahServlet {
     final Map<String, Object> data = new HashMap<String, Object>();
     data.put("event", "noop");
     data.put("timestamp", System.currentTimeMillis());
-    returnData(out, data);
+    final List<Map<String, Object>> data_list = new ArrayList<Map<String, Object>>(1);
+    data_list.add(data);
+    returnArray(out, data_list);
   }
 }

src/net/socialgamer/cah/data/User.java

@@ -1,5 +1,7 @@
 package net.socialgamer.cah.data;
 
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.concurrent.PriorityBlockingQueue;
 
 
@@ -61,6 +63,15 @@ public class User {
     }
   }
 
+  public Collection<QueuedMessage> getNextQueuedMessages(final int maxElements) {
+    final ArrayList<QueuedMessage> c = new ArrayList<QueuedMessage>(maxElements);
+    synchronized (queuedMessageSynchronization) {
+      queuedMessages.drainTo(c, maxElements);
+    }
+    c.trimToSize();
+    return c;
+  }
+
   public String getNickname() {
     return nickname;
   }