Add websocket fallback

NchanSubscriber.js

@@ -76,6 +76,14 @@ var ughbind = (Function.prototype.bind
 );
 
 var sharedSubscriberTable={};
+var conn = 0;    // counter to save total connection made by one type of connector.
+var maxConn = 3;  // Switch to different protocol if it is reached to conn reached to maxConn.
+var priorityIndex = 0; // Counter to switch to another protocol type.
+var connError = false;   // This helps to differentiate the errors and timeout of connection.
+var disconnectError = false;
+var time = 5000;  // Hold time after iterating through every connection type.
+var timeFactor = 1.3; // Increase hold time by timefactor.
+var maxWaitTime = 120000;   // Put cap on hold time upto 2 mins.
 
 "use strict"; 
 function NchanSubscriber(url, opt) {
@@ -98,6 +106,18 @@ function NchanSubscriber(url, opt) {
   }
   this.desiredTransport = opt.subscriber;
 
+  if(opt.maxTry) {
+    maxConn = opt.maxTry;
+  }
+  if(opt.holdTime) {
+    time = opt.holdTime;
+  }
+  if(opt.timeFactor) {
+    timeFactor = opt.timeFactor;
+  }
+  if(opt.maxWaitTime) {
+    maxWaitTime = opt.maxWaitTime;
+  }
   if(opt.shared) {
     if (!("localStorage" in global)) {
       throw "localStorage unavailable for use in shared NchanSubscriber";
@@ -420,9 +440,12 @@ function NchanSubscriber(url, opt) {
 Emitter(NchanSubscriber.prototype);
 
 NchanSubscriber.prototype.initializeTransport = function(possibleTransports) {
-  if(possibleTransports) {
-    this.desiredTransport = possibleTransports;
-  }
+  // This is commented out because the original client is not sending any data.
+  // We are reinitializing our client to unable the websocket fallback. 
+  // this.desiredTransport contains all the mentioned type of connection protocols.
+  // if(possibleTransports) {
+  //   this.desiredTransport = possibleTransports;
+  // }
   if(this.shared && this.shared.role == "slave") {
     this.transport = new this.SubscriberClass["__slave"](ughbind(this.emit, this)); //try it
   }
@@ -438,12 +461,9 @@ NchanSubscriber.prototype.initializeTransport = function(possibleTransports) {
     }, this);
 
     var i;
-    if(this.desiredTransport) {
-      for(i=0; i<this.desiredTransport.length; i++) {
-        if(tryInitializeTransport(this.desiredTransport[i])) {
-          break;
+    if(possibleTransports) {
+        if(tryInitializeTransport(possibleTransports)) {
         }
-      }
     }
     else {
       for(i in this.SubscriberClass) {
@@ -532,16 +552,41 @@ NchanSubscriber.prototype.start = function() {
     }
   }
   else {
-    if(!this.transport) {
-      this.initializeTransport();
+    // First it will select one protocol and try to establish connection upto maxConn type.
+    // If it fails alll the time then it will switch to next protocol.
+    // If all the configured protocols fail to establish connection then client will go on hold state.
+    // It will wait upto holdtime and then it will again try to make connection using configured protocols.
+    if (!connError && disconnectError) {
+      conn = 0;
+    }
+    connError = false;
+    disconnectError = false;
+    if (conn<maxConn){
+     if(!this.transport) {
+        this.initializeTransport(this.desiredTransport[priorityIndex]);
+      }
+      conn++;
+      this.transport.listen(this.url, this.lastMessageId);
+      this.running = true;
+      delete this.starting;
+    }else{
+      conn = 0
+      priorityIndex++;
+      this.transport = null
+      if (priorityIndex<this.desiredTransport.length){
+        this.initializeTransport(this.desiredTransport[priorityIndex]);
+        this.transport.listen(this.url, this.lastMessageId);
+        this.running = true;
+        delete this.starting;
+      }else{
+        priorityIndex = 0;
+        setTimeout(this.start.bind(this), time);
+        time = Math.min(time * timeFactor, maxWaitTime);
+      }
     }
-    this.transport.listen(this.url, this.lastMessageId);
-    this.running = true;
-    delete this.starting;
   }
   return this;
 };
-
 NchanSubscriber.prototype.stop = function() {
   if(!this.running)
     throw "Can't stop NchanSubscriber, it's not running.";
@@ -636,11 +681,13 @@ NchanSubscriber.prototype.SubscriberClass = {
 
       l.onerror = ughbind(function(evt) {
         //console.log("error", evt);
+        connError = true;
         this.emit('error', evt, l);
         delete this.listener;
       }, this);
 
       l.onclose = ughbind(function(evt) {
+        disconnectError = true;
         this.emit('__disconnect', evt);
         delete this.listener;
       }, this);
@@ -744,18 +791,22 @@ NchanSubscriber.prototype.SubscriberClass = {
           this.reqStartTime = new Date().getTime();
           this.req = nanoajax.ajax({url: this.url, headers: this.headers}, requestCallback);
         }
-        else if((code == 0 && response_text == "Error" && req.readyState == 4) || (code === null && response_text != "Abort")) {
-          //console.log("abort!!!");
+        else if(code == 408) {
+          this.reqStartTime = new Date().getTime();
+          this.req = nanoajax.ajax({url: this.url, headers: this.headers}, requestCallback);
+        }
+        else if((code == 0 && response_text == "Error" && req.readyState == 4) || (code === null && response_text != "Abort")) {     
           this.emit("__disconnect", code || 0, response_text);
           delete this.req;
         }
         else if(code !== null) {
           //HTTP error
+          connError = true;
           this.emit("error", code, response_text);
           delete this.req;
         }
         else {
-          //don't care about abortions 
+          //don't care about abortions
           delete this.req;
           this.emit("__disconnect");
           //console.log("abort!");