fixup! Fix active VU reporting by arrival-rate executors

lib/executor/constant_arrival_rate.go

@@ -264,6 +264,10 @@ func (car ConstantArrivalRate) Run(parentCtx context.Context, out chan<- metrics
 	}()
 
 	returnVU := func(u lib.InitializedVU) {
+		// Return the VU without decreasing the global active VU counter, which
+		// is done in the goroutine started by activeVUPool.AddVU, whenever the
+		// VU finishes running an iteration. This results in a more accurate
+		// report of VUs that are _actually_ active.
 		car.executionState.ReturnVU(u, false)
 		activeVUsWg.Done()
 	}

lib/executor/ramping_arrival_rate.go

@@ -382,6 +382,10 @@ func (varr RampingArrivalRate) Run(parentCtx context.Context, out chan<- metrics
 	}()
 
 	returnVU := func(u lib.InitializedVU) {
+		// Return the VU without decreasing the global active VU counter, which
+		// is done in the goroutine started by activeVUPool.AddVU, whenever the
+		// VU finishes running an iteration. This results in a more accurate
+		// report of VUs that are _actually_ active.
 		varr.executionState.ReturnVU(u, false)
 		activeVUsWg.Done()
 	}
@@ -522,8 +526,10 @@ func (p *activeVUPool) Running() uint64 {
 	return atomic.LoadUint64(&p.running)
 }
 
-// AddVU adds the active VU to the pool of VUs for handling the incoming requests.
-// When a new request is accepted the runfn function is executed.
+// AddVU adds the active VU to the pool of VUs for handling the incoming
+// requests. When a new request is accepted the runfn function is executed. This
+// is also when we change the global active VUs counter, since it results in a
+// more accurate report of VUs that are _actually_ active.
 func (p *activeVUPool) AddVU(ctx context.Context, avu lib.ActiveVU, runfn func(context.Context, lib.ActiveVU) bool) {
 	p.wg.Add(1)
 	ch := make(chan struct{})