Address feedback from PR review

cmd/run.go

@@ -85,10 +85,11 @@ func (c *cmdRun) run(cmd *cobra.Command, args []string) (err error) {
 	}
 
 	defer func() {
-		emitEvent(&event.Event{
+		waitExitDone := emitEvent(&event.Event{
 			Type: event.Exit,
 			Data: &event.ExitData{Error: err},
-		})()
+		})
+		waitExitDone()
 		c.gs.Events.UnsubscribeAll()
 	}()
 
@@ -179,10 +180,6 @@ func (c *cmdRun) run(cmd *cobra.Command, args []string) (err error) {
 		}()
 	}
 
-	// TODO: Subscribe all initialization processes (outputs, VUs and executors)
-	// to the Init event. This would allow running them concurrently, and they
-	// could be synchronized by waiting for the event processing to complete.
-	// This could later be expanded to also initialize browser processes.
 	waitInitDone := emitEvent(&event.Event{Type: event.Init})
 
 	// Create and start the outputs. We do it quite early to get any output URLs
@@ -334,13 +331,15 @@ func (c *cmdRun) run(cmd *cobra.Command, args []string) (err error) {
 
 	waitInitDone()
 
-	emitEvent(&event.Event{Type: event.TestStart})()
+	waitTestStartDone := emitEvent(&event.Event{Type: event.TestStart})
+	waitTestStartDone()
 
 	// Start the test! However, we won't immediately return if there was an
 	// error, we still have things to do.
 	err = execScheduler.Run(globalCtx, runCtx, samples)
 
-	defer emitEvent(&event.Event{Type: event.TestEnd})()
+	waitTestEndDone := emitEvent(&event.Event{Type: event.TestEnd})
+	defer waitTestEndDone()
 
 	// Init has passed successfully, so unless disabled, make sure we send a
 	// usage report after the context is done.

js/modules/modules.go

@@ -44,6 +44,10 @@ type VU interface {
 
 	// Events allows subscribing to global k6 execution events, such as Init and
 	// Exit, and to local (per-VU) events, such as IterStart and IterEnd.
+	// NOTE: This API is EXPERIMENTAL and may be changed, renamed or
+	// completely removed in a later k6 release.
+	// FIXME: Subscribing to global events shouldn't be part of this VU (local)
+	// interface.
 	Events() common.Events
 
 	// InitEnv returns common.InitEnvironment instance if present
@@ -59,9 +63,6 @@ type VU interface {
 	// on the event loop *at a later point in time*. See the documentation for
 	// `EventLoop.RegisterCallback()` in the `k6/js/eventloop` Go module for
 	// the very important details on its usage and restrictions.
-	//
-	// Notice: This API is EXPERIMENTAL and may be changed, renamed or
-	// completely removed in a later k6 release.
 	RegisterCallback() (enqueueCallback func(func() error))
 
 	// sealing field will help probably with pointing users that they just need to embed this in their Instance

js/runner.go

@@ -773,18 +773,16 @@ func (u *ActiveVU) RunOnce() error {
 		ScenarioName: u.scenarioName,
 	}
 
-	emitEvent := func(evt *event.Event) func() {
+	emitAndWaitEvent := func(evt *event.Event) {
 		waitDone := u.moduleVUImpl.events.local.Emit(evt)
-		return func() {
-			waitCtx, waitCancel := context.WithTimeout(u.RunContext, 30*time.Minute)
-			defer waitCancel()
-			if werr := waitDone(waitCtx); werr != nil {
-				u.state.Logger.WithError(werr).Warn()
-			}
+		waitCtx, waitCancel := context.WithTimeout(u.RunContext, 30*time.Minute)
+		defer waitCancel()
+		if werr := waitDone(waitCtx); werr != nil {
+			u.state.Logger.WithError(werr).Warn()
 		}
 	}
 
-	emitEvent(&event.Event{Type: event.IterStart, Data: eventIterData})()
+	emitAndWaitEvent(&event.Event{Type: event.IterStart, Data: eventIterData})
 
 	// Call the exported function.
 	_, isFullIteration, totalTime, err := u.runFn(ctx, true, fn, cancel, u.setupData)
@@ -799,7 +797,7 @@ func (u *ActiveVU) RunOnce() error {
 		eventIterData.Error = err
 	}
 
-	emitEvent(&event.Event{Type: event.IterEnd, Data: eventIterData})()
+	emitAndWaitEvent(&event.Event{Type: event.IterEnd, Data: eventIterData})
 
 	// If MinIterationDuration is specified and the iteration wasn't canceled
 	// and was less than it, sleep for the remainder