如何在Gatling中实现尖峰测试并完成用户负载回落？

Hey there! I totally get where you're coming from—when you're new to Gatling, figuring out how to simulate a realistic spike test (where traffic surges then settles back to baseline) can feel tricky. Let's break down how to add that load回落 step to your existing setup.

The Core Idea #

Gatling's injection steps run in sequence, so you just need to add a step that reduces the number of concurrent users back to your initial 100 after the peak. The easiest way to do this is using rampUsers() with a negative number, which tells Gatling to gradually remove users over a specified duration.

Updated Test Configuration #

Here's how to modify your existing code to include the load回落:

setUp(
  scn.inject(
    atOnceUsers(100), // Start with your baseline 100 users
    nothingFor(20 minutes), // Hold steady at 100 users for 20 mins
    rampUsers(900) over (60 seconds), // Spike up to 1000 total users over 60 seconds
    nothingFor(5 minutes), // Optional: Keep the peak load for a few minutes if needed
    rampUsers(-900) over (2 minutes) // Gradually remove 900 users over 2 minutes, back to 100
  )
).protocols(httpProtocol)

Key Details to Note #

• Negative rampUsers: Using -900 tells Gatling to reduce the concurrent user count by 900, which brings you back to your initial 100 users. Adjust the duration (here, 2 minutes) to match how quickly you want the load to settle—shorter durations mean a steeper drop-off.
• Optional Peak Hold: The nothingFor(5 minutes) step lets you keep the peak load steady before dropping it. You can remove this if you want to start the drop immediately after the spike.
• Scenario Lifecycle: Make sure your scenario (scn) is configured to run continuously (e.g., with a loop) if you want users to stay active during the steady state. If your scenario is a one-time execution, users will exit on their own, and you might need to adjust your injection strategy to maintain baseline users instead.

Alternative Approach (Using User Per Second) #

If you prefer more granular control over the rate of user addition/removal, you can use rampUsersPerSec() instead. For example:

setUp(
  scn.inject(
    atOnceUsers(100),
    nothingFor(20 minutes),
    rampUsersPerSec(15) over (60 seconds), // Add 15 users/sec for 60s = 900 total new users
    nothingFor(5 minutes),
    rampUsersPerSec(-7.5) over (2 minutes) // Remove 7.5 users/sec for 2 mins = 900 total removed
  )
).protocols(httpProtocol)

This works similarly but lets you tune the exact rate of load change, which can be useful for simulating more gradual real-world traffic shifts.

You don't need to split this into two separate scenarios—one scenario with sequential injection steps is all you need to get the full spike-and-settle behavior you're after.

内容的提问来源于stack exchange，提问作者jknutt1568