Sending ping event when starting long polling

src/EventStream.hs

@@ -103,6 +103,11 @@ field l b = l `mappend` b `mappend` nl
 -}
 flushAfter b = b `mappend` flush
 
+{-|
+    Send a comment with the string "ping" to the client.
+-}
+pingEvent = flushAfter $ field commentField (fromString "ping")
+
 
 {-|
     Converts a 'ServerEvent' to its wire representation as specified by the
@@ -123,19 +128,18 @@ eventSourceBuilder (ServerEvent n i d)= Just $ flushAfter $
 
 eventSourceEnum source builder timeoutAction finalizer = withInitialPing
   where
-    withInitialPing (Continue k) = k (Chunks [ping]) >>== go
+    withInitialPing (Continue k) = k (Chunks [pingEvent]) >>== go
     go (Continue k) = do
       liftIO $ timeoutAction 10
       event <- liftIO $ timeout 9000000 source
       case fmap builder event of
         Just (Just b)  -> k (Chunks [b]) >>== go
         Just Nothing -> k EOF
         Nothing -> do
-          k (Chunks [ping]) >>== go
+          k (Chunks [pingEvent]) >>== go
     go step = do
       liftIO finalizer
       returnI step
-    ping = flushAfter $ field commentField (fromString "ping")
 
 
 {-|
@@ -155,6 +159,7 @@ eventStream source builder finalizer = do
 -}
 eventResponse :: IO ServerEvent -> (ServerEvent -> Maybe Builder) -> IO () -> Snap ()
 eventResponse source builder finalizer = do
+    writeBuilder pingEvent
     event <- liftIO $ source `onException` finalizer
     case builder event of
       Just b  -> writeBuilder b

src/Main.hs

@@ -77,9 +77,8 @@ brokerInfo :: DB -> UString -> Snap ()
 brokerInfo db uuid = do
     result <- liftIO $ Conn.count db uuid
     case result of
-        Right count -> do
-            modifyResponse $ setContentType "application/json"
-            writeBS $ BS.pack $ "{\"brokerId\": " ++ (show uuid) ++ ", \"connections\": " ++ (show count) ++ "}"
+        Right count ->
+            sendJSON $ BS.pack $ "{\"brokerId\": " ++ (show uuid) ++ ", \"connections\": " ++ (show count) ++ "}"
         Left e -> do
             modifyResponse $ setResponseCode 500
             writeBS $ BS.pack $ "Database Connection Problem: " ++ (show e)
@@ -103,9 +102,8 @@ createSocket db uuid = do
           Left failure -> do
               logError (BS.pack $ show failure)
               showError 500 "Database Connection Error"
-          Right _ -> do
-              modifyResponse $ setContentType "application/json"
-              writeBS $ BS.pack ("{\"socket\": \"" ++ socketId ++ "\"}")
+          Right _ ->
+              sendJSON $ BS.pack ("{\"socket\": \"" ++ socketId ++ "\"}")
 
 
 postEvent :: DB -> Channel -> UString -> Snap ()
@@ -199,6 +197,12 @@ showError code msg = do
     finishWith r
 
 
+sendJSON :: ByteString -> Snap ()
+sendJSON json = do
+    modifyResponse $ setContentType "application/json"
+    writeBS json
+
+
 -- |Returns the transport method to use for this request
 getTransport :: Snap (IO ServerEvent -> IO () -> Snap ())
 getTransport = withRequest $ \request ->

static/eventsource.polyfill.js

@@ -29,6 +29,7 @@
 if ("EventSource" in window) return;
 
 var reTrim = /^(\s|\u00A0)+|(\s|\u00A0)+$/g;
+var onProgressSupport = navigator.userAgent.match(/Firefox/);
 
 var EventSource = function (url) {
   var eventsource = this,
@@ -62,7 +63,7 @@ var EventSource = function (url) {
 
       // we must make use of this on the server side unlesss we're using firefox - because they don't trigger
       // readychange until the server connection is closed
-      if (!navigator.userAgent.match(/Firefox/)) {
+      if (!onProgressSupport) {
         xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
       }
 
@@ -71,7 +72,7 @@ var EventSource = function (url) {
 
       xhr.timeout = 50000;
       xhr.onreadystatechange = function () {
-        if ((this.readyState == 3 || this.readyState == 4) && this.status == 200) {
+        if (((onProgressSupport && this.readyState == 3) || this.readyState == 4) && this.status == 200) {
           // on success
           if (eventsource.readyState == eventsource.CONNECTING) {
             eventsource.readyState = eventsource.OPEN;

templates/eshq.js.st

@@ -1,6 +1,12 @@
 (function() {
   var origin = "$origin$";
 
+	if (typeof(window.addEventListener) == "undefined") {
+		window.addEventListener = function(name, fn) {
+			window.attachEvent("on" + name, fn);
+		};
+	}
+
   var post = function(path, data, callback) {
     var xhr = new XMLHttpRequest();
     xhr.open('POST', path, true);