fix flaky test

Author: ndyakov

internal/pool/conn_state.go

@@ -320,7 +320,8 @@ func (sm *ConnStateMachine) notifyWaiters() {
 					processed = true
 					break
 				} else {
-					// State changed - re-add waiter to front of queue and retry
+					// State changed - re-add waiter to front of queue to maintain FIFO ordering
+					// This waiter was first in line and should retain priority
 					sm.waiters.PushFront(w)
 					sm.waiterCount.Add(1)
 					// Continue to next iteration to re-read state

internal/pool/conn_state_test.go

@@ -401,32 +401,16 @@ func TestConnStateMachine_FIFOOrdering(t *testing.T) {
 	var orderMu sync.Mutex
 	var wg sync.WaitGroup
 
-	// Use channels to ensure deterministic queueing order
-	// Each goroutine waits for the previous one to queue before it queues
-	queuedChannels := make([]chan struct{}, numGoroutines)
-	for i := 0; i < numGoroutines; i++ {
-		queuedChannels[i] = make(chan struct{})
-	}
-
-	// Launch goroutines that will all wait
+	// Launch goroutines one at a time, ensuring each is queued before launching the next
 	for i := 0; i < numGoroutines; i++ {
 		wg.Add(1)
+		expectedWaiters := int32(i + 1)
+
 		go func(id int) {
 			defer wg.Done()
 
-			// Wait for previous goroutine to queue (except for goroutine 0)
-			if id > 0 {
-				<-queuedChannels[id-1]
-			}
-
-			// Small delay to ensure the previous goroutine's AwaitAndTransition has been called
-			time.Sleep(5 * time.Millisecond)
-
 			ctx := context.Background()
 
-			// Signal that we're about to queue
-			close(queuedChannels[id])
-
 			// This should queue in FIFO order
 			_, err := sm.AwaitAndTransition(ctx, []ConnState{StateIdle}, StateInitializing)
 			if err != nil {
@@ -441,16 +425,30 @@ func TestConnStateMachine_FIFOOrdering(t *testing.T) {
 
 			t.Logf("Goroutine %d: executed (position %d)", id, len(executionOrder))
 
-			// Transition back to READY to allow next waiter
+			// Transition back to IDLE to allow next waiter
 			sm.Transition(StateIdle)
 		}(i)
+
+		// Wait until this goroutine has been queued before launching the next
+		// Poll the waiter count to ensure the goroutine is actually queued
+		timeout := time.After(100 * time.Millisecond)
+		for {
+			if sm.waiterCount.Load() >= expectedWaiters {
+				break
+			}
+			select {
+			case <-timeout:
+				t.Fatalf("Timeout waiting for goroutine %d to queue", i)
+			case <-time.After(1 * time.Millisecond):
+				// Continue polling
+			}
+		}
 	}
 
-	// Wait for all goroutines to queue up
-	<-queuedChannels[numGoroutines-1]
-	time.Sleep(50 * time.Millisecond)
+	// Give all goroutines time to fully settle in the queue
+	time.Sleep(10 * time.Millisecond)
 
-	// Transition to READY to start processing the queue
+	// Transition to IDLE to start processing the queue
 	sm.Transition(StateIdle)
 
 	wg.Wait()