allow tablet picker to exclude specified tablets from its candidate l…

…ist (#14224)

Signed-off-by: Priya Bibra <pbibra@slack-corp.com>

go/vt/discovery/tablet_picker.go

@@ -135,6 +135,8 @@ type TabletPicker struct {
 	inOrder       bool
 	cellPref      TabletPickerCellPreference
 	localCellInfo localCellInfo
+	// This map is keyed on the results of TabletAlias.String().
+	ignoreTablets map[string]struct{}
 }
 
 // NewTabletPicker returns a TabletPicker.
@@ -144,6 +146,7 @@ func NewTabletPicker(
 	cells []string,
 	localCell, keyspace, shard, tabletTypesStr string,
 	options TabletPickerOptions,
+	ignoreTablets ...*topodatapb.TabletAlias,
 ) (*TabletPicker, error) {
 	// Keep inOrder parsing here for backward compatability until TabletPickerTabletOrder is fully adopted.
 	if tabletTypesStr == "" {
@@ -219,7 +222,7 @@ func NewTabletPicker(
 		}
 	}
 
-	return &TabletPicker{
+	tp := &TabletPicker{
 		ts:            ts,
 		cells:         dedupeCells(cells),
 		localCellInfo: localCellInfo{localCell: localCell, cellsInAlias: aliasCellMap},
@@ -228,7 +231,15 @@ func NewTabletPicker(
 		tabletTypes:   tabletTypes,
 		inOrder:       inOrder,
 		cellPref:      cellPref,
-	}, nil
+		ignoreTablets: make(map[string]struct{}, len(ignoreTablets)),
+	}
+
+	for _, ignoreTablet := range ignoreTablets {
+		tp.ignoreTablets[ignoreTablet.String()] = struct{}{}
+	}
+
+	return tp, nil
+
 }
 
 // dedupeCells is used to remove duplicates in the cell list in case it is passed in
@@ -358,7 +369,9 @@ func (tp *TabletPicker) GetMatchingTablets(ctx context.Context) []*topo.TabletIn
 			log.Errorf("Error getting shard %s/%s: %v", tp.keyspace, tp.shard, err)
 			return nil
 		}
-		aliases = append(aliases, si.PrimaryAlias)
+		if _, ignore := tp.ignoreTablets[si.PrimaryAlias.String()]; !ignore {
+			aliases = append(aliases, si.PrimaryAlias)
+		}
 	} else {
 		actualCells := make([]string, 0)
 		for _, cell := range tp.cells {
@@ -394,7 +407,9 @@ func (tp *TabletPicker) GetMatchingTablets(ctx context.Context) []*topo.TabletIn
 				continue
 			}
 			for _, node := range sri.Nodes {
-				aliases = append(aliases, node.TabletAlias)
+				if _, ignore := tp.ignoreTablets[node.TabletAlias.String()]; !ignore {
+					aliases = append(aliases, node.TabletAlias)
+				}
 			}
 		}
 	}

go/vt/discovery/tablet_picker_test.go

@@ -391,6 +391,29 @@ func TestPickUsingCellAsAlias(t *testing.T) {
 	}
 }
 
+func TestPickWithIgnoreList(t *testing.T) {
+	ctx := utils.LeakCheckContext(t)
+
+	te := newPickerTestEnv(t, ctx, []string{"cell1", "cell2"})
+
+	want := addTablet(ctx, te, 101, topodatapb.TabletType_REPLICA, "cell1", true, true)
+	defer deleteTablet(t, te, want)
+
+	dontWant := addTablet(ctx, te, 102, topodatapb.TabletType_REPLICA, "cell1", true, true)
+	defer deleteTablet(t, te, dontWant)
+
+	// Specify the alias as the cell.
+	tp, err := NewTabletPicker(ctx, te.topoServ, []string{"cella"}, "cell1", te.keyspace, te.shard, "replica", TabletPickerOptions{}, dontWant.GetAlias())
+	require.NoError(t, err)
+
+	// Try it many times to be sure we don't ever pick from the ignore list.
+	for i := 0; i < 100; i++ {
+		tablet, err := tp.PickForStreaming(ctx)
+		require.NoError(t, err)
+		require.False(t, proto.Equal(dontWant, tablet), "Picked the tablet we shouldn't have: %v", dontWant)
+	}
+}
+
 func TestPickUsingCellAliasOnlySpecified(t *testing.T) {
 	ctx := utils.LeakCheckContextTimeout(t, 200*time.Millisecond)
 

go/vt/vtgate/vstream_manager.go

@@ -27,17 +27,17 @@ import (
 
 	"vitess.io/vitess/go/stats"
 	"vitess.io/vitess/go/vt/discovery"
-	querypb "vitess.io/vitess/go/vt/proto/query"
+	"vitess.io/vitess/go/vt/log"
 	"vitess.io/vitess/go/vt/servenv"
+	"vitess.io/vitess/go/vt/srvtopo"
 	"vitess.io/vitess/go/vt/topo"
+	"vitess.io/vitess/go/vt/vterrors"
 
-	"vitess.io/vitess/go/vt/log"
 	binlogdatapb "vitess.io/vitess/go/vt/proto/binlogdata"
+	querypb "vitess.io/vitess/go/vt/proto/query"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	vtgatepb "vitess.io/vitess/go/vt/proto/vtgate"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
-	"vitess.io/vitess/go/vt/srvtopo"
-	"vitess.io/vitess/go/vt/vterrors"
 )
 
 // vstreamManager manages vstream requests.
@@ -53,6 +53,10 @@ type vstreamManager struct {
 // maxSkewTimeoutSeconds is the maximum allowed skew between two streams when the MinimizeSkew flag is set
 const maxSkewTimeoutSeconds = 10 * 60
 
+// tabletPickerContextTimeout is the timeout for the child context used to select candidate tablets
+// for a vstream
+const tabletPickerContextTimeout = 90 * time.Second
+
 // vstream contains the metadata for one VStream request.
 type vstream struct {
 	// mu protects parts of vgtid, the semantics of a send, and journaler.
@@ -124,6 +128,7 @@ type journalEvent struct {
 
 func newVStreamManager(resolver *srvtopo.Resolver, serv srvtopo.Server, cell string) *vstreamManager {
 	exporter := servenv.NewExporter(cell, "VStreamManager")
+
 	return &vstreamManager{
 		resolver: resolver,
 		toposerv: serv,
@@ -473,6 +478,7 @@ func (vs *vstream) streamFromTablet(ctx context.Context, sgtid *binlogdatapb.Sha
 	// journalDone is assigned a channel when a journal event is encountered.
 	// It will be closed when all journal events converge.
 	var journalDone chan struct{}
+	ignoreTablets := make([]*topodatapb.TabletAlias, 0)
 
 	errCount := 0
 	for {
@@ -490,12 +496,19 @@ func (vs *vstream) streamFromTablet(ctx context.Context, sgtid *binlogdatapb.Sha
 		var eventss [][]*binlogdatapb.VEvent
 		var err error
 		cells := vs.getCells()
-		tp, err := discovery.NewTabletPicker(ctx, vs.ts, cells, vs.vsm.cell, sgtid.Keyspace, sgtid.Shard, vs.tabletType.String(), vs.tabletPickerOptions)
+
+		tp, err := discovery.NewTabletPicker(ctx, vs.ts, cells, vs.vsm.cell, sgtid.Keyspace, sgtid.Shard, vs.tabletType.String(), vs.tabletPickerOptions, ignoreTablets...)
 		if err != nil {
 			log.Errorf(err.Error())
 			return err
 		}
-		tablet, err := tp.PickForStreaming(ctx)
+
+		// Create a child context with a stricter timeout when picking a tablet.
+		// This will prevent hanging in the case no tablets are found.
+		tpCtx, tpCancel := context.WithTimeout(ctx, tabletPickerContextTimeout)
+		defer tpCancel()
+
+		tablet, err := tp.PickForStreaming(tpCtx)
 		if err != nil {
 			log.Errorf(err.Error())
 			return err
@@ -670,11 +683,18 @@ func (vs *vstream) streamFromTablet(ctx context.Context, sgtid *binlogdatapb.Sha
 			// Unreachable.
 			err = vterrors.Errorf(vtrpcpb.Code_UNKNOWN, "vstream ended unexpectedly")
 		}
-		if vterrors.Code(err) != vtrpcpb.Code_FAILED_PRECONDITION && vterrors.Code(err) != vtrpcpb.Code_UNAVAILABLE {
+
+		retry, ignoreTablet := vs.shouldRetry(err)
+		if !retry {
 			log.Errorf("vstream for %s/%s error: %v", sgtid.Keyspace, sgtid.Shard, err)
 			return err
 		}
+		if ignoreTablet {
+			ignoreTablets = append(ignoreTablets, tablet.GetAlias())
+		}
+
 		errCount++
+		// Retry, at most, 3 times if the error can be retried.
 		if errCount >= 3 {
 			log.Errorf("vstream for %s/%s had three consecutive failures: %v", sgtid.Keyspace, sgtid.Shard, err)
 			return err
@@ -683,6 +703,30 @@ func (vs *vstream) streamFromTablet(ctx context.Context, sgtid *binlogdatapb.Sha
 	}
 }
 
+// shouldRetry determines whether we should exit immediately or retry the vstream.
+// The first return value determines if the error can be retried, while the second
+// indicates whether the tablet with which the error occurred should be ommitted
+// from the candidate list of tablets to choose from on the retry.
+//
+// An error should be retried if it is expected to be transient.
+// A tablet should be ignored upon retry if it's likely another tablet will not
+// produce the same error.
+func (vs *vstream) shouldRetry(err error) (bool, bool) {
+	errCode := vterrors.Code(err)
+
+	if errCode == vtrpcpb.Code_FAILED_PRECONDITION || errCode == vtrpcpb.Code_UNAVAILABLE {
+		return true, false
+	}
+
+	// If there is a GTIDSet Mismatch on the tablet, omit it from the candidate
+	// list in the TabletPicker on retry.
+	if errCode == vtrpcpb.Code_INVALID_ARGUMENT && strings.Contains(err.Error(), "GTIDSet Mismatch") {
+		return true, true
+	}
+
+	return false, false
+}
+
 // sendAll sends a group of events together while holding the lock.
 func (vs *vstream) sendAll(ctx context.Context, sgtid *binlogdatapb.ShardGtid, eventss [][]*binlogdatapb.VEvent) error {
 	vs.mu.Lock()