bugfix: fix nil pointer in vtgate on topo connection error (#13010)

* fix nil pointer in vtgate on topo connection error

Signed-off-by: Olga Shestopalova <[email protected]>

* add test

Signed-off-by: Olga Shestopalova <[email protected]>

* fix year

Signed-off-by: Olga Shestopalova <[email protected]>

---------

Signed-off-by: Olga Shestopalova <[email protected]>
Co-authored-by: Olga Shestopalova <[email protected]>

go/vt/discovery/keyspace_events_test.go

@@ -0,0 +1,100 @@
+/*
+Copyright 2023 The Vitess Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package discovery
+
+import (
+	"context"
+	"encoding/hex"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
+	vschemapb "vitess.io/vitess/go/vt/proto/vschema"
+	"vitess.io/vitess/go/vt/topo"
+	"vitess.io/vitess/go/vt/topo/faketopo"
+)
+
+func TestSrvKeyspaceWithNilNewKeyspace(t *testing.T) {
+	cell := "cell"
+	keyspace := "testks"
+	factory := faketopo.NewFakeTopoFactory()
+	factory.AddCell(cell)
+	ts := faketopo.NewFakeTopoServer(factory)
+	ts2 := &fakeTopoServer{}
+	hc := NewHealthCheck(context.Background(), 1*time.Millisecond, time.Hour, ts, cell, "")
+	kew := NewKeyspaceEventWatcher(context.Background(), ts2, hc, cell)
+	kss := &keyspaceState{
+		kew:      kew,
+		keyspace: keyspace,
+		shards:   make(map[string]*shardState),
+	}
+	kss.lastKeyspace = &topodatapb.SrvKeyspace{
+		ServedFrom: []*topodatapb.SrvKeyspace_ServedFrom{
+			{
+				TabletType: topodatapb.TabletType_PRIMARY,
+				Keyspace:   keyspace,
+			},
+		},
+	}
+	require.True(t, kss.onSrvKeyspace(nil, nil))
+}
+
+type fakeTopoServer struct {
+}
+
+// GetTopoServer returns the full topo.Server instance.
+func (f *fakeTopoServer) GetTopoServer() (*topo.Server, error) {
+	return nil, nil
+}
+
+// GetSrvKeyspaceNames returns the list of keyspaces served in
+// the provided cell.
+func (f *fakeTopoServer) GetSrvKeyspaceNames(ctx context.Context, cell string, staleOK bool) ([]string, error) {
+	return []string{"ks1"}, nil
+}
+
+// GetSrvKeyspace returns the SrvKeyspace for a cell/keyspace.
+func (f *fakeTopoServer) GetSrvKeyspace(ctx context.Context, cell, keyspace string) (*topodatapb.SrvKeyspace, error) {
+	zeroHexBytes, _ := hex.DecodeString("")
+	eightyHexBytes, _ := hex.DecodeString("80")
+	ks := &topodatapb.SrvKeyspace{
+		Partitions: []*topodatapb.SrvKeyspace_KeyspacePartition{
+			{
+				ServedType: topodatapb.TabletType_PRIMARY,
+				ShardReferences: []*topodatapb.ShardReference{
+					{Name: "-80", KeyRange: &topodatapb.KeyRange{Start: zeroHexBytes, End: eightyHexBytes}},
+					{Name: "80-", KeyRange: &topodatapb.KeyRange{Start: eightyHexBytes, End: zeroHexBytes}},
+				},
+			},
+		},
+	}
+	return ks, nil
+}
+
+func (f *fakeTopoServer) WatchSrvKeyspace(ctx context.Context, cell, keyspace string, callback func(*topodatapb.SrvKeyspace, error) bool) {
+	ks, err := f.GetSrvKeyspace(ctx, cell, keyspace)
+	callback(ks, err)
+}
+
+// WatchSrvVSchema starts watching the SrvVSchema object for
+// the provided cell.  It will call the callback when
+// a new value or an error occurs.
+func (f *fakeTopoServer) WatchSrvVSchema(ctx context.Context, cell string, callback func(*vschemapb.SrvVSchema, error) bool) {
+
+}

go/vt/topo/topoproto/srvkeyspace.go

@@ -46,6 +46,9 @@ func (sra ShardReferenceArray) Sort() { sort.Sort(sra) }
 // SrvKeyspaceGetPartition returns a Partition for the given tablet type,
 // or nil if it's not there.
 func SrvKeyspaceGetPartition(sk *topodatapb.SrvKeyspace, tabletType topodatapb.TabletType) *topodatapb.SrvKeyspace_KeyspacePartition {
+	if sk == nil {
+		return nil
+	}
 	for _, p := range sk.Partitions {
 		if p.ServedType == tabletType {
 			return p