A stock trading system was taken as a case study where real time market updates as well as online refresh of transaction data requires implementation of push technologies. This evaluation was intended for coming up with the best possible solution in terms of speed, initial loading, dependencies required to be installed and memory utilization across browsers. The technology evaluated must work across platforms and across browsers. The below mentioned approaches are tested on IE, Firefox, Chrome and Opera.
This document describes the evaluation methodologies and results for the various data push technologies on the internet. Data pushing refers that the client receives data updates in an asynchronous manner at server's discretion, generally after expressing interest in a certain type of information (subscription). In other words, the client becomes a passive part of the system, receiving updated information as soon as it is available on the server by just subscribing to it only once during a session.
The following data push technologies were evaluated
- Java Applet
- Flex component (SWF file)
- Light Streamer
A server developed in .NET which generated random price for a script and sent data via TCP/IP was used for evaluation of both java applet and flex based techniques.
The symbols were stored in the hash table from where the server fetched the symbol, generated the random tick and sent the data to the client on a TCP socket continuously.
A Java Applet was developed in which a socket connection was opened that read data from TCP/IP socket and updated that data within applet. The corresponding .jar file was included in the HTML page.
A Flex application was developed in which a socket connection was opened, that read data from TCP/IP and updated that data in Flex supported mx:Datagrid [Flex Control].The application was compiled into an swf file. The swf file was included in the HTML page.
Light streamer runs on any platform compatible with Java std edition 1.4.2 or greater . Java SE 6 is recommended for best performance. Light streamer server should be set up on same machine as web server .Light streamer is able to update the information shown on an HTML page without having to reload it, and above all, without having to add anything" extraneous", such as a Java applet or plug-ins of any kind.
The .NET Server sends the data to the Light streamer server through a socket connection.
The Light streamer server pushes the data to the html page through http connection using an adapter, the adapter resides with the light streamer server and contains the details of request reply ports and notify port. The html page is enabled with java script , configured with the adapter to receive data from the light streamer server. Every time new data available in the light streamer server is pushed to the html page through the adapter.
(Light Streamer is tested with free version called Moderato)
- Data updates were observed faster in flash as compared to java applet for the same no of symbols.
- The User Interface was updated faster in case of flex component as compared to Java applet.
- The CPU utilization was directly proportional to the number of scrips and ticks/sec.
- The figures below are derived using 50 symbols and 10 ticks/sec
Flash Player 9 or above
No plugin required
Plug In Size
Files at webserver
.jar file should reside on webserver
.swf file and crossdomain.xml should reside on webserver
One Light Streamer java adapter should be on Web Server
The max no of ticks that can be handled are 92 ticks/sec at a CPU utilization of 50%.
From the above table Flex component approach 2 seems to be the most obvious choice.
Light streamer doesn’t require any plug-in on the client side but require an additional light streamer server module on the server side which means an additional point of failure. The commercial version of Light Streamer would incur additional costs.
Java applets perform poor as compared to Flex and pose security issues concerning certificates. In Java applet approach 2 HTML page continuously requests Java Applet for data hence this is not purely a push technology. The .jar file should reside on webserver.
Other alternatives available are HTML5 sockets but those are yet to be widely accepted and are not supported on IE browsers. Silverlight has support for sockets but Microsoft is soon going to stop the support of the same in favour of HTML5 , further Silverlight calls for a heavy plugin and is not widely installed. Also Silverlight will pose some cross platform issues and hence are not considered in this evaluation.