How to use Timers in Jmeter

By default, JMeter sends the request without pausing between each request. In that case, JMeter could overwhelm your test server by making too many requests in a short amount of times.
Let imagine that you send thousands request to a web serverunder test in a few seconds. This is what happens!
Timers allow JMeter to delay between each request which a thread makes. Timer can solve the server overload problem.
Also, in real life visitors do not arrive at a website all at the same time, but at different time intervals. So Timer will help mimic the real time behavior.
Following are some common types of timer in JMeter

Constant Timer:

          Constant timer delays each user request for the same amount of time.

Gaussian Random Timer:

         Gaussian random timer delays each user request for a random amount of time.

          Parameters:

Attribute
Description
Name
Descriptive name for this timer that is shown in the tree
Deviations (milliseconds)
A parameter of Gaussian Distribution Function
Constant Delay Offset (milliseconds)
Additional value in milliseconds

          So the total delay is described as below figure:

Uniform Random Timer:

          Uniform random timer delays each user request for a random amount of time.

          Parameters:

Attribute
Description
Name
Descriptive name for this timer that is shown in the tree
Random Delay Maximum
Maximum random number of milliseconds to delay.
Constant Delay Offset (milliseconds)
Additional value in milliseconds
         The total delay is the sum of the random value and the offset value.

BeanShell Timer

          The BeanShell Timer can be used to generate a delay time between each user request.

BSF Timer

          The BSF Timer can be used to generate a delay between each user request using a BSF scripting language.

JSR223 Timer

          The JSR223 Timer can be used to generate a delay between each user request using a JSR223 scripting language

Practical Demonstration of Timer Settings

In this example, you will use Constant Timer to set fixed delay between user requests to google.com.
Let start with a simple test script
  1. JMeter creates one user request to http://www.google.com 100 times
  2. Delay between each user request is 5000 ms
Here is the roadmap of this practical example:

Pre-condition:

We re-use the Step 1 and Step 2 in tutorial JMeter Performance Testing.

Step 1) Add Thread Group

Right click on the Test Plan and add a new thread group: Add-> Threads (Users) ->Thread Group
In Thread Group control panel, enter Thread Properties as following
This setting lets JMeter create one user request to http://www.google.com in 100 times

Step 2) Add JMeter elements

  • Add HTTP request default
  • Add HTTP request

 

Step 3) Add Constant Timer

Right click Thread Group -> Timer -> Constant Timer
Configuring Thread Delay of 5000 milliseconds

Step 4) Add View Results in Table

View Results in Table displays the test result in table format.
Right click Add -> Listener -> View Result in Table
View Results in Table displays as below figure

Step 5) Run your test

When you ready to run test, click Run button on the menu bar, or short key Ctrl+R
This is the result of this test
You can analyze the result as following:
The End Time of one sample is calculated as following:
For example, in the above figure, let analyze the Sample 2
  • Start time is 22:05:01.866
  • Sample Time of Sample 2 is 172 ms
  • Constant Timer : 5000 ms (as configured)
  • End Time of this sample is = 22:05:01.866 + 172 + 5000 = 22:05:07.038
So the Sample 3 should start at  the time is 22:05:07.039 ( As shown in the above figure)
The delay of each sample is 5000 ms
If you change the Constant Timer is zero, you will see the result is changed
Let analyze the Sample 1
  • Start time is 22:17:39.141
  • Sample Time of Sample 2 is 370 ms
  • Constant Timer : 0 ms (as configured)
  • End Time of this sample is = 22:17:39.141+ 370 + 0 = 22:17:39.511
So the Sample 2 should start at  the time is 22:17:39.512 (Shown in the above figure)

Troubleshooting:

If you face the issue while running the above scenario ... do the following
  1. Check whether you are connecting to internet via a proxy. If yes, remove the proxy.
  2. Open a new instance of JMeter
  3. Open the TimerTestPlan.jmx in Jmeter
  4. Double Click on Thread Group -> View Result in Table
  5. Run the Test
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