I'm using Twisted to write a web server. One of the tasks that this server performs takes a long time (~5 minutes). I would like to be able to efficiently notify the client that this task has completed.
I have looked into using Comet/long polling, but for the life of me I can't get the browser to render the data when it receives it.
To prototype this mechanism, I wrote the following:
clock.py
from twisted.internet import reactor, task
from twisted.web.static import File
from twisted.web.server import Site
from twisted.web import server
from twisted.web.resource import Resource
import time
class Clock(Resource):
def __init__(self):
self.presence=[]
loopingCall = task.LoopingCall(self.__print_time)
loopingCall.start(1, False)
Resource.__init__(self)
def render_GET(self, request):
print "request from",request.getClientIP()
request.write(time.ctime())
self.presence.append(request)
return server.NOT_DONE_YET
def __print_time(self):
print "tick"
for p in self.presence:
print "pushing data to",p.getClientIP()
p.write(time.ctime())
root = Resource()
clock = ClockPage()
index = File("index.html")
root.putChild("index.html",index)
root.putChild("clock",clock)
factory = Site(root)
reactor.listenTCP(8080, factory)
reactor.run()
index.html
<html>
<head>
</head>
<body>
<div id="data">Hello</div>
<script type="text/javascript">
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function(){
if(xhttp.readyState == 4 && xhttp.status == 200){
alert(xhttp.responseText);
document.getElementById("data").innerHTML=xhttp.responseText;
}
};
xhttp.open("GET","clock",true);
xhttp.send(null);
</script>
</body>
</html>
What I've been doing on the server side is calling request.write with the time, every second.
On the client side, all I do is open a XMLHTTPRequest to the appropriate resource and dump the responseText directly into a div whenever .readyState == 4 and .status == 200.
The problem is: the div never gets overwritten and the alert is never called.
I keep reading about using multipart/x-mixed-replace, but I'm not really sure how to use it. Any pointers to tutorials or documentation on implementing this sort of thing in twisted would be greatly appreciated.
