Web 2.0 Push Technical overviewNetscaler Product Group

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/feedServers push “new” information out to the subscribers

Many different names and techniquesHTTP Server PushHTTP StreamingCOMET (Server Push + Long Polling)Long PollingBOSH (Bidirectional-streams Over Synchronous HTTP ) © The Coding Machine

Client Update: Three Common Techniques

Server PushClient Pull

Server Push – Two Common Techniques

ServerLong Polling

Req_1

Query finishes

Quiet period (y)

Query finishes

Req_2

Req_3

Client Server

Quiet period (y)

Streaming

t

t + y

t + 2y

Req

Chunk_1 (data)

Chunk_0 (data)

Quiet period

Client

Quiet period

Chunk_2 (data)

Time

Connection resource tied up

on Server

Connection resource tied up

on Server

NetScaler Web 2.0 Push: Offloading Connection Management

BenefitsImproves server utilization by 10xImproves application responsivenessCuts data center energy and cooling costs

AvailabilityAvailable in NetScaler 9.x – (March 2009)Available in Platinum and Enterprise editionRequires 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

NetScaler Web 2.0 Push: Asynchronous Connection Mgmt

• NetScaler acts as a full proxy between subscribers (persistent clients) and publishers (push servers)

• Parks millions of persistent client connections

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

• Offloads client connection management from servers

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

• Enables all existing policy, availability and security services across asynchronous interaction

NetScaler Web 2.0 Push Message Flow

Step 1: Connection Setup

Step 2: Client Identification

Step 3: Connection Labeling

Step 4: Server Push

NetScaler Web 2.0 Push Building Blocks

Connection Labeling ProtocolReceive and terminate connections;

decrypt and analyze every request Setup transaction label over multiplexed

HTTP connections

Push Switching ProtocolNetScaler accepts asynchronous out of

band label updates over few TCP connections

NetScaler demultiplexes label and dispatches updates over persistent client connections

NetScaler Web 2.0 Push : An Example Setup

Server10.217.6.53:80

Push-VIP10.217.6.87:80

Client10.216.134.59

Client-VIP10.217.6.86:80

Server Push messages are sent to NetScaler over a few pooled connections

NetScaler Web 2.0 Push: HTTP Streaming Support

PUSH-VIP

LastChunk (data)

msg0

RES

DEFERABLE = Yes, Label = L1RES-HDR

GET

POST /client/L1 data0

Chunk_0 (data)

POST /client/L1 data1

Chunk_1 (data)

VIP

POST /client/L1 final

AppServer Messaging BusClient NetScaler PUSH_VIP: IP-Prt

NS_HDRGET Labeling protocolTransaction Labeled. TCP connection can be optionally closed

Quiet period. NS holding onto client connection.

Quiet period. NS holding onto client connection.

msg1

msg2

Quiet period. Waiting for next update.

Quiet period. Waiting for next update.

Request from Client (Browser) to NetScaler VIP Request from NetScaler to Server

Response from NetScaler VIP to Client (Browser)Response from Server to NetScaler

Connection Labeling ProtocolClient to Server

Server to Client

NetScaler Push UpdatesUpdate from Server to Push VIP using

REST API

Update forwarded to Client by NetScaler

Status Ack from NetScaler to Server in XML

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