Server push and Comet (Rails user group Hamburg 2009-06-10)

Server Push
or „How to initiate client side changes from the server
without polling every second or so“

Donnerstag, 11. Juni 2009

Websocket


HTML5


var myWebSocket = new(quot;ws://www.websocket.orgquot;);
myWebSocket.onmessage = function(evt)
{ alert( quot;Received Message: quot; + evt.data); };


Can you use it?


IE6 (released 2001) market share May 09:

~15%


No!


Then what?


Juggernaut


needs ﬂash


no thanks


Comet


general technique, no implementation


longer connections


server and client side components


server side


traditionally (think Apache):
one thread per connection


Comet servers
reduce server-side resources per connection

• Reduce overhead per thread
• use event libraries
• use microthreads (e.g. Erlang)


client side


asynchronous request


hold it!


drop connection after receiving something useful


then reinitiate connection


still request/reponse


BUT

data ﬂow occurs on the server‘s schedule

close approximation of the server → client ﬂow


Implementations


Bayeux


standard protocol


many servers use it

Cometd
ErlyComet
GlassFish
Jetty
Orbited
Persevere
...


many client libs use it

Dojo (inventor)
jQuery
GWT
...


combine any server and js lib


Jabber


JS libs available


mature Server


scales


can hold ten thousands connections on a single server


proprietary solutions


RMDS2Web Server

500.000 concurrent users on single Dell-server

quot;most scalable real-time push web systemquot;

commercial


APE (Ajax Push Engine)

quot;Real time data streamingquot;

open source client and server
proprietary protocol (NOT Bayeux)


Who is doing it?


Facebook
Meebo (Chat)
...


That is all!


Reminder:

Rails-Konferenz call for papers deadline:

1st of July

Server push and Comet (Rails user group Hamburg 2009-06-10)

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