Gatling: Concurrent execution within a scenario

I am trying to test the loading time of a home page. The sequence of HTTP requests made by browser when loading the home page is like A -> B -> [C, D, E]

Which is to say

B executes after A's response is received and
C, D, E starts concurrently after B's response is received.

I tried the below approach to simulate this:

Approach 1

Have one scenario each for A, B, C, D, E. All of the scenarios are configured with say 50 users. I tried this:

A.inject().andThen(B.inject.andThen(C.inject(), D.inject(), E.inject()))

The problem with this is that, B starts only after all users of A has stopped. This does not simulate the home page loading accurately because I expect a user who has finished A to start with B without waiting for other users.

Approach 2

I created a single scenario with all the http requests.

exec(A).exec(B).exec(C).exec(D).exec(E)

This would mean that for example, D executes only after C's response is received. This is not right.

What is the best way to solve the problem?

Solution

That's not how Gatling works, nor do your actual web clients.

You should have 1 single scenario with users performing request A, then request B, then requests C, D and E concurrently using resources.

val scn = scenario("foo")
  .exec(requestA)
  .exec(requestB
    .resources(requestC, requestD, requestE)
  )