> Work Load
- WorkLoad is nothing but a model based on your future forecast.
- The distribution of load across the identified scenario.
- Different workloads are created to study the behavior of the system.
> Work Load Modelling
- WorkLoad Modelling identifies one or more workload profiles to be simulated against the tested application.
- The workload model attempt to approximate real life usage scenario and includes different user types and characteristics.
- Workload model depends on the parameters like transaction per sec (TPS) , pacing, think time and response time. According to queueing theory, a discipline in mathematics Little's theorem.
👉Little's Law 👈
Little's law helps to design an accurate workload model to achieve the performance testing goal.
Average number of users in the system =Throughput*Total execution time
N=TPS * (RT+TT+PT)
N (No. of Users) = Number of active users as defined in the load test scenario.
TPS (Transaction Per Second) = It is the number of transactions processed per sec; it can be used as the arrival rate (λ). Throughput can also be used as TPS.
TPH (Transaction Per Hour)= It is the number of transactions processed per hour.(If you have TPH-Transaction Per Hour value, divide it by 3600 to convert in to TPS).
RT (Response Time) = Average response time is the amount of time a request spent in the system.
TT (Think Time) = Think time is the user pause between the transactions.
PT ( Pacing/ Session Pacing)= Pacing is the time duration provided to put delay between the two iterations.
Example :
1. Calculating no of users using Little's law:
Suppose we have an application with order place workflow. Client has given a requirement that they want to achieve 3600 order in an hour with think time of 20 seconds and pacing of 5 seconds. Assume that script take 20 seconds to execute without think time and pacing. Calculate no of virtual users to achieve the desired output.
Formula for calculation number of users :
N=TPS * (RT+TT+PT)
TPS = (TPH/3600)
TPS = 3600/3600 = 1
RT= 20
TT= 20
Pacing = 5
N = 1 * (20+20+5)
N = 1 * 45
N = 45
Total no of virtual users is 45.
2. Calculating pacing/session using Little's law:
An e-commerce website has 600 customers load during normal hours and receives average 5000 orders per hour.
- One business functionality : Product Order
- Test scripts contains these below transactions : 12 transaction
- Home Page
- Login
- Search Product
- Select Product
- Product Details
- Add to Cart
- Review Cart Item
- Checkout
- Select Delivery Address
- Order Summary
- Payment Page
- Logout
Formula for calculating Pacing :
N=TPS * (RT+TT+PT)
TPS = (TPH/3600)
TPS = 5000/3600 = 1.38
N=600
RT=?
TT=?
Pacing=?
=>600=1.38 * (RT +TT +Pacing)
=>600/1.38=(RT +TT +Pacing)
=>434.78 =(RT +TT +Pacing)
Execute the script for 1 iteration without TT.
The script took 24 seconds.
=>434.78 = 24 +TT + Pacing
=>434.78-24 = TT + Pacing
=> 410.78 =TT + Pacing
Assume TT as per content & user activities. (Browse the application manually and record the TT for each transaction ** Use developer tool** )
12 transaction = 110 seconds
=> 410.78 =110+ Pacing
=> 410.78-110 = Pacing
=> 300.78 = Pacing
Pacing will be 300.78 sec.
