fix(flamegraph): Dispatch candidates using goroutine

CHANGELOG.md

@@ -41,7 +41,7 @@
 - Remove module frame in python ([#496](https://github.com/getsentry/vroom/pull/496))
 - Handle js profile normalization for react+android profiles ([#499](https://github.com/getsentry/vroom/pull/499))
 - Fix metrics example list ([#505](https://github.com/getsentry/vroom/pull/505))
-- Increase readjob channel size  ([#512](https://github.com/getsentry/vroom/pull/512))
+- Increase readjob channel size ([#512](https://github.com/getsentry/vroom/pull/512))
 
 **Internal**:
 
@@ -102,6 +102,7 @@
 - Lift Intervals struct to utils ([#498](https://github.com/getsentry/vroom/pull/498))
 - Fix flakey test for profile examples ([#504](https://github.com/getsentry/vroom/pull/504))
 - Instrument flamegraph generation with spans ([#510](https://github.com/getsentry/vroom/pull/510)), ([#511](https://github.com/getsentry/vroom/pull/511))
+- Dispatch candidates using goroutine ([#513](https://github.com/getsentry/vroom/pull/513))
 
 ## 23.12.0
 

internal/flamegraph/flamegraph.go

@@ -483,37 +483,41 @@ func GetFlamegraphFromCandidates(
 	results := make(chan storageutil.ReadJobResult, numCandidates)
 	defer close(results)
 
-	dispatchSpan := span.StartChild("dispatch candidates")
-	dispatchSpan.SetData("transaction_candidates", len(transactionProfileCandidates))
-	dispatchSpan.SetData("continuous_candidates", len(continuousProfileCandidates))
-
-	for _, candidate := range transactionProfileCandidates {
-		jobs <- profile.ReadJob{
-			Ctx:            ctx,
-			OrganizationID: organizationID,
-			ProjectID:      candidate.ProjectID,
-			ProfileID:      candidate.ProfileID,
-			Storage:        storage,
-			Result:         results,
+	// We dispatch the read jobs within a goroutine so we can start reading the results
+	// immediately and NOT block until all the candidates have been dispatched.
+	go func() {
+		dispatchSpan := span.StartChild("dispatch candidates")
+		dispatchSpan.SetData("transaction_candidates", len(transactionProfileCandidates))
+		dispatchSpan.SetData("continuous_candidates", len(continuousProfileCandidates))
+
+		for _, candidate := range transactionProfileCandidates {
+			jobs <- profile.ReadJob{
+				Ctx:            ctx,
+				OrganizationID: organizationID,
+				ProjectID:      candidate.ProjectID,
+				ProfileID:      candidate.ProfileID,
+				Storage:        storage,
+				Result:         results,
+			}
 		}
-	}
 
-	for _, candidate := range continuousProfileCandidates {
-		jobs <- chunk.ReadJob{
-			Ctx:            ctx,
-			OrganizationID: organizationID,
-			ProjectID:      candidate.ProjectID,
-			ProfilerID:     candidate.ProfilerID,
-			ChunkID:        candidate.ChunkID,
-			TransactionID:  candidate.TransactionID,
-			ThreadID:       candidate.ThreadID,
-			Start:          candidate.Start,
-			End:            candidate.End,
-			Storage:        storage,
-			Result:         results,
+		for _, candidate := range continuousProfileCandidates {
+			jobs <- chunk.ReadJob{
+				Ctx:            ctx,
+				OrganizationID: organizationID,
+				ProjectID:      candidate.ProjectID,
+				ProfilerID:     candidate.ProfilerID,
+				ChunkID:        candidate.ChunkID,
+				TransactionID:  candidate.TransactionID,
+				ThreadID:       candidate.ThreadID,
+				Start:          candidate.Start,
+				End:            candidate.End,
+				Storage:        storage,
+				Result:         results,
+			}
 		}
-	}
-	dispatchSpan.Finish()
+		dispatchSpan.Finish()
+	}()
 
 	var flamegraphTree []*nodetree.Node