fix: resolve Test_batcherFlush/RetriesOnTransientFailure flake (#24112)

fixes https://github.com/coder/internal/issues/1452

enterprise/coderd/connectionlog/connectionlog.go

@@ -468,9 +468,10 @@ func (b *DBBatcher) retryLoop() {
 func (b *DBBatcher) retryBatch(params database.BatchUpsertConnectionLogsParams) {
 	count := len(params.ID)
 	for attempt := range maxRetries {
-		t := time.NewTimer(retryInterval)
+		t := b.clock.NewTimer(retryInterval, "connectionLogBatcher", "retryBackoff")
 		select {
 		case <-b.ctx.Done():
+			t.Stop()
 			b.shutdownBatch(params)
 			return
 		case <-t.C:

enterprise/coderd/connectionlog/connectionlog_internal_test.go

@@ -355,15 +355,20 @@ func Test_batcherFlush(t *testing.T) {
 		store := dbmock.NewMockStore(ctrl)
 		clock := quartz.NewMock(t)
 
-		scheduledTrap := clock.Trap().TimerReset("connectionLogBatcher", "scheduledFlush")
-		defer scheduledTrap.Close()
+		// Trap the capacity flush (fires when batch reaches maxBatchSize).
+		capacityTrap := clock.Trap().TimerReset("connectionLogBatcher", "capacityFlush")
+		defer capacityTrap.Close()
 
-		b := NewDBBatcher(ctx, store, log, WithClock(clock), WithBatchSize(100))
+		// Trap the retry backoff timer created by retryBatch.
+		retryTrap := clock.Trap().NewTimer("connectionLogBatcher", "retryBackoff")
+		defer retryTrap.Close()
+
+		// Batch size of 1: consuming the item triggers an immediate
+		// capacity flush, avoiding the timer/itemCh select race.
+		b := NewDBBatcher(ctx, store, log, WithClock(clock), WithBatchSize(1))
 
 		evt := fakeConnectEvent(uuid.New(), "agent1", uuid.New())
 
-		// First call (synchronous in flush) fails, then the
-		// retry worker retries after the backoff and succeeds.
 		gomock.InOrder(
 			store.EXPECT().
 				BatchUpsertConnectionLogs(gomock.Any(), gomock.Any()).
@@ -380,14 +385,15 @@ func Test_batcherFlush(t *testing.T) {
 
 		require.NoError(t, b.Upsert(ctx, evt))
 
-		// Trigger a scheduled flush while the batcher is still
-		// running. The synchronous write fails and queues to
-		// retryCh. The retry worker picks it up after a real-
-		// time 1s delay and succeeds.
-		clock.Advance(defaultFlushInterval).MustWait(ctx)
-		scheduledTrap.MustWait(ctx).MustRelease(ctx)
+		// Item consumed → capacity flush fires → transient error →
+		// batch queued to retryCh → timer reset trapped.
+		capacityTrap.MustWait(ctx).MustRelease(ctx)
+
+		// Retry worker creates a timer — trap it, release, advance.
+		retryCall := retryTrap.MustWait(ctx)
+		retryCall.MustRelease(ctx)
+		clock.Advance(retryInterval).MustWait(ctx)
 
-		// Wait for the retry to complete (real-time 1s delay).
 		require.NoError(t, b.Close())
 	})
 
@@ -400,10 +406,10 @@ func Test_batcherFlush(t *testing.T) {
 		store := dbmock.NewMockStore(ctrl)
 		clock := quartz.NewMock(t)
 
-		scheduledTrap := clock.Trap().TimerReset("connectionLogBatcher", "scheduledFlush")
-		defer scheduledTrap.Close()
+		capacityTrap := clock.Trap().TimerReset("connectionLogBatcher", "capacityFlush")
+		defer capacityTrap.Close()
 
-		b := NewDBBatcher(ctx, store, log, WithClock(clock), WithBatchSize(100))
+		b := NewDBBatcher(ctx, store, log, WithClock(clock), WithBatchSize(1))
 
 		evt := fakeConnectEvent(uuid.New(), "agent1", uuid.New())
 
@@ -428,10 +434,9 @@ func Test_batcherFlush(t *testing.T) {
 			}).
 			AnyTimes()
 
-		// Send event and trigger flush — fails, queues.
+		// Send event — capacity flush triggers immediately.
 		require.NoError(t, b.Upsert(ctx, evt))
-		clock.Advance(defaultFlushInterval).MustWait(ctx)
-		scheduledTrap.MustWait(ctx).MustRelease(ctx)
+		capacityTrap.MustWait(ctx).MustRelease(ctx)
 
 		// Close triggers shutdown. The retry worker drains
 		// retryCh and writes the batch via writeBatch.