release-21.2: rangefeed: fix panic due to rangefeed stopper race

pkg/kv/kvserver/rangefeed/processor.go

@@ -198,15 +198,16 @@ type CatchUpIteratorConstructor func() *CatchUpIterator
 // calling its Close method when it is finished. If the iterator is nil then
 // no initialization scan will be performed and the resolved timestamp will
 // immediately be considered initialized.
-func (p *Processor) Start(stopper *stop.Stopper, rtsIterFunc IntentScannerConstructor) {
+func (p *Processor) Start(stopper *stop.Stopper, rtsIterFunc IntentScannerConstructor) error {
 	ctx := p.AnnotateCtx(context.Background())
 	if err := stopper.RunAsyncTask(ctx, "rangefeed.Processor", func(ctx context.Context) {
 		p.run(ctx, p.RangeID, rtsIterFunc, stopper)
 	}); err != nil {
-		pErr := roachpb.NewError(err)
-		p.reg.DisconnectWithErr(all, pErr)
+		p.reg.DisconnectWithErr(all, roachpb.NewError(err))
 		close(p.stoppedC)
+		return err
 	}
+	return nil
 }
 
 // run is called from Start and runs the rangefeed.

pkg/kv/kvserver/rangefeed/processor_test.go

@@ -134,8 +134,9 @@ func rangeFeedCheckpoint(span roachpb.Span, ts hlc.Timestamp) *roachpb.RangeFeed
 const testProcessorEventCCap = 16
 
 func newTestProcessorWithTxnPusher(
-	rtsIter storage.SimpleMVCCIterator, txnPusher TxnPusher,
+	t *testing.T, rtsIter storage.SimpleMVCCIterator, txnPusher TxnPusher,
 ) (*Processor, *stop.Stopper) {
+	t.Helper()
 	stopper := stop.NewStopper()
 
 	var pushTxnInterval, pushTxnAge time.Duration = 0, 0 // disable
@@ -154,7 +155,7 @@ func newTestProcessorWithTxnPusher(
 		EventChanCap:         testProcessorEventCCap,
 		CheckStreamsInterval: 10 * time.Millisecond,
 	})
-	p.Start(stopper, makeIntentScannerConstructor(rtsIter))
+	require.NoError(t, p.Start(stopper, makeIntentScannerConstructor(rtsIter)))
 	return p, stopper
 }
 
@@ -165,13 +166,16 @@ func makeIntentScannerConstructor(rtsIter storage.SimpleMVCCIterator) IntentScan
 	return func() IntentScanner { return NewLegacyIntentScanner(rtsIter) }
 }
 
-func newTestProcessor(rtsIter storage.SimpleMVCCIterator) (*Processor, *stop.Stopper) {
-	return newTestProcessorWithTxnPusher(rtsIter, nil /* pusher */)
+func newTestProcessor(
+	t *testing.T, rtsIter storage.SimpleMVCCIterator,
+) (*Processor, *stop.Stopper) {
+	t.Helper()
+	return newTestProcessorWithTxnPusher(t, rtsIter, nil /* pusher */)
 }
 
 func TestProcessorBasic(t *testing.T) {
 	defer leaktest.AfterTest(t)()
-	p, stopper := newTestProcessor(nil /* rtsIter */)
+	p, stopper := newTestProcessor(t, nil /* rtsIter */)
 	defer stopper.Stop(context.Background())
 
 	// Test processor without registrations.
@@ -434,13 +438,13 @@ func TestNilProcessor(t *testing.T) {
 	// to call on a nil Processor.
 	stopper := stop.NewStopper()
 	defer stopper.Stop(context.Background())
-	require.Panics(t, func() { p.Start(stopper, nil) })
+	require.Panics(t, func() { _ = p.Start(stopper, nil) })
 	require.Panics(t, func() { p.Register(roachpb.RSpan{}, hlc.Timestamp{}, nil, false, nil, nil) })
 }
 
 func TestProcessorSlowConsumer(t *testing.T) {
 	defer leaktest.AfterTest(t)()
-	p, stopper := newTestProcessor(nil /* rtsIter */)
+	p, stopper := newTestProcessor(t, nil /* rtsIter */)
 	defer stopper.Stop(context.Background())
 
 	// Add a registration.
@@ -566,7 +570,7 @@ func TestProcessorInitializeResolvedTimestamp(t *testing.T) {
 	}, nil)
 	rtsIter.block = make(chan struct{})
 
-	p, stopper := newTestProcessor(rtsIter)
+	p, stopper := newTestProcessor(t, rtsIter)
 	defer stopper.Stop(context.Background())
 
 	// The resolved timestamp should not be initialized.
@@ -728,7 +732,7 @@ func TestProcessorTxnPushAttempt(t *testing.T) {
 		return nil
 	})
 
-	p, stopper := newTestProcessorWithTxnPusher(nil /* rtsIter */, &tp)
+	p, stopper := newTestProcessorWithTxnPusher(t, nil /* rtsIter */, &tp)
 	defer stopper.Stop(context.Background())
 
 	// Add a few intents and move the closed timestamp forward.
@@ -818,7 +822,7 @@ func TestProcessorConcurrentStop(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	const trials = 10
 	for i := 0; i < trials; i++ {
-		p, stopper := newTestProcessor(nil /* rtsIter */)
+		p, stopper := newTestProcessor(t, nil /* rtsIter */)
 
 		var wg sync.WaitGroup
 		wg.Add(6)
@@ -864,7 +868,7 @@ func TestProcessorConcurrentStop(t *testing.T) {
 // observes only operations that are consumed after it has registered.
 func TestProcessorRegistrationObservesOnlyNewEvents(t *testing.T) {
 	defer leaktest.AfterTest(t)()
-	p, stopper := newTestProcessor(nil /* rtsIter */)
+	p, stopper := newTestProcessor(t, nil /* rtsIter */)
 	defer stopper.Stop(context.Background())
 
 	firstC := make(chan int64)

pkg/kv/kvserver/replica_rangefeed.go

@@ -411,7 +411,15 @@ func (r *Replica) registerWithRangefeedRaftMuLocked(
 		return rangefeed.NewLegacyIntentScanner(iter)
 	}
 
-	p.Start(r.store.Stopper(), rtsIter)
+	// NB: This only errors if the stopper is stopping, and we have to return here
+	// in that case. We do check ShouldQuiesce() below, but that's not sufficient
+	// because the stopper has two states: stopping and quiescing. If this errors
+	// due to stopping, but before it enters the quiescing state, then the select
+	// below will fall through to the panic.
+	if err := p.Start(r.store.Stopper(), rtsIter); err != nil {
+		errC <- roachpb.NewError(err)
+		return nil
+	}
 
 	// Register with the processor *before* we attach its reference to the
 	// Replica struct. This ensures that the registration is in place before