NetScaler Web 2.0 Push technology scales Comet or Reverse Ajax applications that depend on long running idle client connections. It offloads server load by handling all the client connections on the NetScaler and publishing a REST API for the server application to send periodic updates.

1. Web 2.0 Push Technical overview Netscaler Product Group

2. Web 2.0 - Server Push or Reverse Ajax Reverse Ajax is the ability to push data from a web or app server to the browser, without user interaction "Publish-Subscribe" model Clients subscribe to information channels/feed Servers push “new” information out to the subscribers Many different names and techniques HTTP Server Push HTTP Streaming COMET (Server Push + Long Polling) Long Polling BOSH (Bidirectional-streams Over Synchronous HTTP ) © The Coding Machine

3. Client Update: Three Common Techniques Server Push Client Pull

4. Server Client Client Req Req_1 t Quiet period Quiet period (y) Query finishes Req_2 Quiet period Quiet period (y) Query finishes Chunk_1 (data) Chunk_0 (data) Chunk_2 (data) Req_3 Server Push – Two Common Techniques Long Polling Streaming Server Time Connection resource tied up on Server Connection resource tied up on Server t + y t + 2y

5. NetScaler Web 2.0 Push: Offloading Connection Management Benefits Improves server utilization by 10x Improves application responsiveness Cuts data center energy and cooling costs Availability Available in NetScaler 9.x – (March 2009) Available in Platinum and Enterprise edition Requires custom script development to adapt a given application to work with our Push technology to enable tagging data streams as “Server Push-able” Millions of clients Few servers

7. Parks millions of persistent client connections

8. Enables configuration driven approach to identifying a client connection and server push setup – aka label

9. Offloads client connection management from servers

10. Reuses server connections thus improving server utilization and “push”es data to client based on returned label

12. NetScaler Web 2.0 Push Building Blocks Connection Labeling Protocol Receive and terminate connections; decrypt and analyze every request Setup transaction label over multiplexed HTTP connections Push Switching Protocol NetScaler accepts asynchronous out of band label updates over few TCP connections NetScaler demultiplexes label and dispatches updates over persistent client connections

13. NetScaler Web 2.0 Push : An Example Setup Server Push messages are sent to NetScaler over a few pooled connections Client-VIP 10.217.6.86:80 Push-VIP 10.217.6.87:80 Server 10.217.6.53:80 Client 10.216.134.59

14. PUSH_VIP: IP-Prt NS_HDR GET RES DEFERABLE = Yes, Label = L1 msg0 msg1 msg2 POST /client/L1 POST /client/L1 POST /client/L1 data0 data1 final NetScaler Web 2.0 Push: HTTP Streaming Support NetScaler AppServer Client Messaging Bus V I P Labeling protocol Transaction Labeled. TCP connection can be optionally closed GET RES-HDR Quiet period. NS holding onto client connection. P U S H - V I P Quiet period. Waiting for next update. Chunk_0 (data) Quiet period. NS holding onto client connection. Quiet period. Waiting for next update. Chunk_1 (data) LastChunk (data)

15. Request from NetScaler to Server Request from Client (Browser) to NetScaler VIP Response from NetScaler VIP to Client (Browser) Response from Server to NetScaler Connection Labeling Protocol Client to Server Server to Client

16. NetScaler Push Updates Update from Server to Push VIP using REST API Update forwarded to Client by NetScaler Status Ack from NetScaler to Server in XML

17. Application code change for NetScaler Web 2.0 Push def longpoll_update(np, pushvs, label): holdtime = 10 + random.randint(0,5) time.sleep(holdtime) data = mesg % (label, holdtime) np.push_post_update(pushvs, label, data, True) def process_request(): pushvs = os.environ.get('HTTP_NSPUSHVSERVER', '') if pushvs == '': print "Content-Type: text/html" print "" print "NetScaler PUSH functionality not enabled. " sys.exit() np = nspush.NsPushMgr() label = np.push_label_client() #daemonize this process, so the parent exits # and the long poll will send update later daemon.createDaemon() longpoll_update(np, pushvs, label) if __name__ == '__main__': process_request() class NsPushMgr: def push_label_client(self): label = str(int(time.time())) print "NSDEFERRABLE: YES" print "NSSERVERLABEL: ", label print "Content-Type: text/html" print "" return label def push_post_update(self, pushvip, label, data, msg_end): pushvip = re.sub('_', ':', pushvip) if msg_end is True: uri = '/CLIENT/V10/' + label + '?MSG_END=1' else: uri = '/CLIENT/V10/' + label + '?MSG_END=0' conn = httplib.HTTPConnection(pushvip) conn.request('POST', uri, data, {}) resp = conn.getresponse() conn.close() poll.py nspush.py