The VU Activity Chart shows the activity of every VU associated with the load test. It allows visualizing the VU activity and how it relates to other VUs actions. Specifically, it shows which test case and iteration each VU was executing, on which load generator it was emulated and what other VUs were running simultaneously. Because this information is depicted on the timeline, it helps isolate performance issues by seeing how load patterns and test case concurrences correlate with slower test iterations. You can further drill down every test iteration to display a waterfall chart corresponding to this iteration, which displays activity detailed on the level of individual pages and requests.

Info: The VU Activity Chart is available only after running the load test.

An example of a VU Activity chart is provided above: 

  • The vertical axle shows VUs (a). 
  • VUs 1-250 were emulated on a controller (b); VUs 251-500 were emulated on the agent (c).
  • Horizontal axle (d) is the timeline. The test duration was a little longer than one hour.
  • During the first 22 minutes, the controller and the agent ramped up VUs to the full capacity of 250 VUs each (e). 
  • To zoom-in to a specific VUs/Iterations range, select an appropriate rectangular area (f). 
  • Each VU is depicted by a set of horizontal bars, representing a single test iteration. 
  • The length of a bar indicates how long it took to complete the iteration. Breaks between the bars (g) represent delays after the test cases.
  • The bars are color-coded. Each test case is assigned two unique colors. One of them is used for even iterations (h), and another one is used for odd iterations (i) (alternate coloring). For example, VU 251 and 256 (j) executed the same test case. Also, areas 1, 2, and 3 display how VUs executed the first three iterations at different times.
  • To display details of each test iteration, mouse over its bar. The tooltip (k) will display the following information:
    • VU number
    • Iteration number
    • Iteration start and end time
    • Iteration duration
    • Iteration duration w/o think time.
    • Agent Name
    • Test case name

Generating Test Iteration Waterfall

  • To display a waterfall of an iteration, Dbl-Click its horizontal bar, or right-click (l) and select View Waterfall.
  • You can compare the waterfalls of two iterations. After selecting the first waterfall, navigate back to VU Activity view and Ctrl+Dbl-Click the second iteration bar, or right-click it (l) and select Compare Waterfalls.

Other Commands:

  • To zoom-out, right-click (m), and select Un-Zoom.
  • For additional context menu commands, right-click and select Copy Image, Save Image, or Print Graph Image.

Large activity

As the activity iterations grow to large numbers, the activity control may slow down. Starting from v5.7, when the number of iterations is high, StresStimulus will only display the first 1000 iterations. To change the number of iterations to display, enter the number in the Max iterations textbox and click the Refresh button. 

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