Websocket integration with Rest API : sample application -I

Websocket is an independent TCP based protocol. Web socket establishes a persistent connection between client and server, both can send data at  any time.

Server side implementation responsible for keeping large number of connections open, with high concurrency and low performance cost.Mostly based on non blocking  IO or threading. 

In this blog, we will go though Tornado, a Python implementation  for web socket connections.

In this example , we create a websocket server which keeps pinging a rest api at fixed interval and it will push the response whoever is connected with.

from tornado import websocket, web, ioloop, gen

import json

import urllib

import urllib2

import threading

cl = []

class IndexHandler(web.RequestHandler):

    def get(self):

        self.render("index.html")

class SocketHandler(websocket.WebSocketHandler):

    def check_origin(self, origin):

        return True

    def doWork(self):

        print "in  f()..."

        url = 'http://localhost:8080/rest/v1/echo/11?'

        username = 'admin'

        password = 'admin'

        p = urllib2.HTTPPasswordMgrWithDefaultRealm()

        p.add_password(None, url, username, password)

        handler = urllib2.HTTPBasicAuthHandler(p)

        opener = urllib2.build_opener(handler)

        urllib2.install_opener(opener)

        value = urllib2.urlopen(url).read()

       

        data = json.dumps(value)

        for c in cl:

            c.write_message(data)

        # call doWork() again in 230 seconds

        threading.Timer(230, self.doWork).start()

    def open(self):

        if self not in cl:

            cl.append(self)

        print "in  self()..."

        self.f();

        

    def on_close(self):

        if self in cl:

            cl.remove(self)

            

    def synchronous_fetch():

        print "Doing stuff..."

        url = 'http://localhost:8080/rest/v1/pingserver'

        http_client = HTTPClient()

        response = http_client.fetch(url)

        return response.body

    

class ApiHandler(web.RequestHandler):

#approach II

    @web.asynchronous

    def get(self, *args):

        self.finish()

        url = 'http://localhost:8080/rest/v1/pingserver'

        value = urllib2.urlopen(url).read()

        id = self.get_argument("id")

        value=response

        data = {"id": id, "value" : value}

        data = json.dumps(data)

        for c in cl:

            c.write_message(data)

    @web.asynchronous

    def post(self):

        pass

app = web.Application([

    (r'/', IndexHandler),

    (r'/ws', SocketHandler),

    (r'/api', ApiHandler),

    (r'/(favicon.ico)', web.StaticFileHandler, {'path': '../'}),

    (r'/(web_socket_rest_api.png)', web.StaticFileHandler, {'path': './'}),

])

if __name__ == '__main__':

    app.listen(8888)

    ioloop.IOLoop.instance().start()