Missing HTTP requests after being redirected

This is the result of a simulation run with .users(1000).ramp(40):

What is the reason for 218? I expected 500. When I run a simulation with .users(10).ramp(10) I get 10 OK on each line, as expected.

What might be happening here?

I am using gatling-charts-highcharts-1.4.0-20121120.113804-42-bundle.

What does your simulation look like?
What is request 2?

The only explaination I can come with is that your application doesn’t handle status codes properly (quite a common mistake):

  • Under load, request 2 doesn’t always return a proper 30X for redirecting, but a nice “A technical error happened” with a 200 status, so Gatling doesn’t issue any redirect
  • The only check configured on request 2 is the default one (status in 200-210) or one checking that the status is 200. Both are true, so Gatling counts those requests as OK

If that’s indeed what happens, you should either fix your app so that it returns proper status codes, or add some checks to ensure that the landing page after request 2 is the expected one.