Hello, WELCOME.
I have been working in the area of load testing and tuning with different applications like Core/Retail Banking Application, Net Banking Applications, E-commerce Application. In due course of time I got to work with all most 4 types of load simulation tools. As the basic thing we need to execute a load test, is a good load testing tool and understanding of the work load model that the AUT (Application Under Test) needs and is the tool able to simulate the actual work load . I would try to share the knowledge that I have got in due course of time through this.
As a load tester we have been executing the load tests with the traditional concurrent load model which is easily achievable by most of the load testing tools like HP Load Runner, IBM Rational Performance Tester, IBM Rational Robot etc.If you are testing an application where you know exactly the maximum number of users to your site then the concurrent model is the best suited for workload modeling but in case of e commerce application such as online stores where you donot know what will be the maximum load to your system in other words the application does not have any way to stop users from coming on to the site. There has been a shift in the load model i.e. the way users hit a site (online shopping or online banking etc) from the traditional concurrent model to arrival rate. I don’t mean to say that the concurrent model is a wrong approach. But to have an apple to apple comparison the arrival rate load model closely resembles to contemporary user load pattern to E-Commerce site than concurrent load model.
The best example that I can site is the two banking applications Retail Banking application and On line store like www.amazon.com. At any given point of time for a Retail banking Application The pattern in which users hit the Retail banking application is different than the way users come to Net Banking Application. Let’s understand the difference. For Retail banking one user means either a teller or a vault or a branch manager or to be more generic a fixed set of computer terminals to be used by Bank employees. In Retail application for a bank can restrict maximum number of users on the system. And if there is any Queuing or waiting happening due to extra load it is inform of the teller or Vaults desk. So this keeps the server isolated from unexpected load, at a given point of time the users will not increase beyond the max value here the concurrent model is the right apple.
On the other hand there is no way we can restrict the users who are accessing the internet banking application. As far as Net banking applications are concerned users have the privilege to hit the server any time. There is absolutely no way by which we can make the user to wait before it hits the server. And it is difficult to predict the maximum concurrent number of users at any given point of time. So, testing this application with a concurrent model we will not be the right apple to apple comparison.
Studies have stated that arrival rate (production data can give these statistics) work load modeling is a closer approach to the sites mainly dealing with E-Commerce Applications like online shopping, internet banking. Studies have found that the fashion in which users hit the server is not at a constant arrival rate. For Online applications since there is no way to restrict the user to come on to the site the queue starts either at Web-sever or at App-server.
