Multi test object VU distribution

During a load test, VUs are distributed between load agents and test objects (test cases and test case groups).

Rule of thumb

Each load agent will execute the test independently during a distributed load test. The VUs are distributed in the following order:

Before the test starts, the controller allocates the VUs between the load agents according to their mix weight.
During the test, each load agent will distribute its own VUs between test objects according to each test object's mix weight.
Controller-only test
Step 1 is skipped during a controller-only test where only the local agent runs the test.

Mix Weights

An item's mix weight is the relative frequency the item gets picked (in round-robin order) compared to other items in the mix. Consider the example of 3 test cases and their mix weights.

Test Case	Mix Weight
View Store	5
Search Store	2
Place Order	6
Return Item	4
Total	15

In this example, for every 15 VUs, 5 VUs will execute View Store, 2 will execute Search Store, 6 will execute Place Order, and 2 will execute Return Item.

To find the percentage of VUs that will execute a test case, divide the mix weight or the item by the total weight. So View Store will be executed by 5/15 = 33.33%

Disable item

To disable an item from being picked, set its mix weight to 0.

Rounding

If the total mix weight is not a factor of the total VUs, the VU distribution is rounded unpredictably. Therefore, it is recommended to make the total mix weight a factor of the total VUs.

Determining mix weights

Let's take a test that will have a maximum load of 1000 VUs between 4 test cases running across 3 load agents (named East, West, and Local). Below is an example of desired VU distributions between the test cases.

Test Case	Desired VUs	Percent
View Store	350	35
Search Store	475	47.5
Place Order	125	12.5
Return Item	50	5

Click the Configure VU distribution > By Load Agent - TC... button in the Mix Weights control to bring up the VU configuration dialog.

Distribute VUs between load agents

According to the rule of thumb, first, the 1000 VUs are distributed between load agents. Select the All Load Agents node and modify the Mix Weight column on the left in the dialog. The VU Distribution column shows the actual number of VUs that will be executed on the agent.

Load Agent	Mix Weight	Percent	Number of VUs
East	500	50	500
West	300	30	300
Local	200	20	200

Tip

When the sum of the mix weights equals the sum of VUs to distribute, then the individual mix weights equal the individual VU distribution.

Distribute VUs between test cases

Now that the VUs have been distributed between the load agents, the test case distribution can be configured on each agent individually.

East (500 VUs)

West (300 VUs)

Local (200 VUs)

Test Case	Agent Mix Weight	Percent	Number of VUs
View Store	150	30	150
Search Store	300	60	300
Place Order	25	5	25
Return Item	25	5	25
TOTAL			500 VUs

Test Case	Agent Mix Weight	Percent	Number of VUs
View Store	150	50	150
Search Store	150	50	150
Place Order	0	0	0
Return Item	0	0	0
TOTAL			300 VUs

Test Case	Agent Mix Weight	Percent	Number of VUs
View Store	50	25	50
Search Store	25	12.5	25
Place Order	100	50	100
Return Item	25	12.5	25
TOTAL			200 VUs

Select an agent node to modify the test case mix weights

East (500 VUs)	West (300 VUs)	Local (200 VUs)

Note

In the above example, the test cases Place Order and Return Item will not run on the West since their mix weights are 0 for that load agent.