Don't run any reparent commands if the host is empty

go/vt/vttablet/tabletmanager/rpc_replication.go

@@ -697,6 +697,10 @@ func (tm *TabletManager) setReplicationSourceLocked(ctx context.Context, parentA
 	}
 	host := parent.Tablet.MysqlHostname
 	port := parent.Tablet.MysqlPort
+	// If host is empty, then we shouldn't even attempt the reparent. That tablet has already shutdown.
+	if host == "" {
+		return vterrors.New(vtrpc.Code_FAILED_PRECONDITION, "Shard primary has empty mysql hostname")
+	}
 	if status.SourceHost != host || status.SourcePort != port {
 		// This handles both changing the address and starting replication.
 		if err := tm.MysqlDaemon.SetReplicationSource(ctx, host, port, wasReplicating, shouldbeReplicating); err != nil {

go/vt/wrangler/testlib/fake_tablet.go

@@ -245,7 +245,7 @@ func (ft *FakeTablet) StartActionLoop(t *testing.T, wr *wrangler.Wrangler) {
 // StopActionLoop will stop the Action Loop for the given FakeTablet
 func (ft *FakeTablet) StopActionLoop(t *testing.T) {
 	if ft.TM == nil {
-		t.Fatalf("TM for %v is not running", ft.Tablet.Alias)
+		return
 	}
 	if ft.StartHTTPServer {
 		ft.HTTPListener.Close()

go/vt/wrangler/testlib/reparent_utils_test.go

@@ -22,6 +22,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+
 	"vitess.io/vitess/go/vt/vtctl/reparentutil/reparenttestutil"
 
 	"vitess.io/vitess/go/vt/discovery"
@@ -183,62 +185,97 @@ func TestReparentTablet(t *testing.T) {
 	checkSemiSyncEnabled(t, false, true, replica)
 }
 
-// TestSetReplicationSourceRelayLogError tests that SetReplicationSource works as intended when we receive a relay log error while starting replication.
-func TestSetReplicationSourceRelayLogError(t *testing.T) {
+// TestSetReplicationSource tests that SetReplicationSource works as intended under various circumstances.
+func TestSetReplicationSource(t *testing.T) {
 	ctx := context.Background()
 	ts := memorytopo.NewServer("cell1", "cell2")
 	wr := wrangler.New(logutil.NewConsoleLogger(), ts, tmclient.NewTabletManagerClient())
 
 	// create shard and tablets
-	if _, err := ts.GetOrCreateShard(ctx, "test_keyspace", "0"); err != nil {
-		t.Fatalf("CreateShard failed: %v", err)
-	}
+	_, err := ts.GetOrCreateShard(ctx, "test_keyspace", "0")
+	require.NoError(t, err, "CreateShard failed")
+
 	primary := NewFakeTablet(t, wr, "cell1", 1, topodatapb.TabletType_PRIMARY, nil)
-	replica := NewFakeTablet(t, wr, "cell1", 2, topodatapb.TabletType_REPLICA, nil)
 	reparenttestutil.SetKeyspaceDurability(context.Background(), t, ts, "test_keyspace", "semi_sync")
 
 	// mark the primary inside the shard
-	if _, err := ts.UpdateShardFields(ctx, "test_keyspace", "0", func(si *topo.ShardInfo) error {
+	_, err = ts.UpdateShardFields(ctx, "test_keyspace", "0", func(si *topo.ShardInfo) error {
 		si.PrimaryAlias = primary.Tablet.Alias
 		return nil
-	}); err != nil {
-		t.Fatalf("UpdateShardFields failed: %v", err)
-	}
+	})
+	require.NoError(t, err, "UpdateShardFields failed")
 
 	// primary action loop (to initialize host and port)
 	primary.StartActionLoop(t, wr)
 	defer primary.StopActionLoop(t)
 
-	// replica loop
-	// We have to set the settings as replicating. Otherwise,
-	// the replication manager intervenes and tries to fix replication,
-	// which ends up making this test unpredictable.
-	replica.FakeMysqlDaemon.Replicating = true
-	replica.FakeMysqlDaemon.IOThreadRunning = true
-	replica.FakeMysqlDaemon.SetReplicationSourceInputs = append(replica.FakeMysqlDaemon.SetReplicationSourceInputs, topoproto.MysqlAddr(primary.Tablet))
-	replica.FakeMysqlDaemon.ExpectedExecuteSuperQueryList = []string{
-		// These 3 statements come from tablet startup
-		"STOP SLAVE",
-		"FAKE SET MASTER",
-		"START SLAVE",
-		// We stop and reset the replication parameters because of relay log issues.
-		"STOP SLAVE",
-		"RESET SLAVE",
-		"START SLAVE",
-	}
-	replica.StartActionLoop(t, wr)
-	defer replica.StopActionLoop(t)
-
-	// Set the correct error message that indicates we have received a relay log error.
-	replica.FakeMysqlDaemon.SetReplicationSourceError = errors.New("ERROR 1201 (HY000): Could not initialize master info structure; more error messages can be found in the MySQL error log")
-	// run ReparentTablet
-	if err := wr.SetReplicationSource(ctx, replica.Tablet); err != nil {
-		t.Fatalf("SetReplicationSource failed: %v", err)
-	}
-
-	// check what was run
-	if err := replica.FakeMysqlDaemon.CheckSuperQueryList(); err != nil {
-		t.Fatalf("replica.FakeMysqlDaemon.CheckSuperQueryList failed: %v", err)
-	}
-	checkSemiSyncEnabled(t, false, true, replica)
+	// test when we receive a relay log error while starting replication
+	t.Run("Relay log error", func(t *testing.T) {
+		replica := NewFakeTablet(t, wr, "cell1", 2, topodatapb.TabletType_REPLICA, nil)
+		// replica loop
+		// We have to set the settings as replicating. Otherwise,
+		// the replication manager intervenes and tries to fix replication,
+		// which ends up making this test unpredictable.
+		replica.FakeMysqlDaemon.Replicating = true
+		replica.FakeMysqlDaemon.IOThreadRunning = true
+		replica.FakeMysqlDaemon.SetReplicationSourceInputs = append(replica.FakeMysqlDaemon.SetReplicationSourceInputs, topoproto.MysqlAddr(primary.Tablet))
+		replica.FakeMysqlDaemon.ExpectedExecuteSuperQueryList = []string{
+			// These 3 statements come from tablet startup
+			"STOP SLAVE",
+			"FAKE SET MASTER",
+			"START SLAVE",
+			// We stop and reset the replication parameters because of relay log issues.
+			"STOP SLAVE",
+			"RESET SLAVE",
+			"START SLAVE",
+		}
+		replica.StartActionLoop(t, wr)
+		defer replica.StopActionLoop(t)
+
+		// Set the correct error message that indicates we have received a relay log error.
+		replica.FakeMysqlDaemon.SetReplicationSourceError = errors.New("ERROR 1201 (HY000): Could not initialize master info structure; more error messages can be found in the MySQL error log")
+		// run ReparentTablet
+		err = wr.SetReplicationSource(ctx, replica.Tablet)
+		require.NoError(t, err, "SetReplicationSource failed")
+
+		// check what was run
+		err = replica.FakeMysqlDaemon.CheckSuperQueryList()
+		require.NoError(t, err, "CheckSuperQueryList failed")
+		checkSemiSyncEnabled(t, false, true, replica)
+	})
+
+	// test setting an empty hostname because of primary shutdown
+	t.Run("Primary tablet already shutdown", func(t *testing.T) {
+		replica := NewFakeTablet(t, wr, "cell1", 3, topodatapb.TabletType_REPLICA, nil)
+		// replica loop
+		replica.FakeMysqlDaemon.Replicating = true
+		replica.FakeMysqlDaemon.IOThreadRunning = true
+		replica.FakeMysqlDaemon.SetReplicationSourceInputs = append(replica.FakeMysqlDaemon.SetReplicationSourceInputs, topoproto.MysqlAddr(primary.Tablet))
+		replica.FakeMysqlDaemon.ExpectedExecuteSuperQueryList = []string{
+			// These 3 statements come from tablet startup
+			"STOP SLAVE",
+			"FAKE SET MASTER",
+			"START SLAVE",
+			// For the SetReplicationSource call, we shouldn't get any queries at all!
+		}
+		replica.StartActionLoop(t, wr)
+		defer replica.StopActionLoop(t)
+
+		// stop the primary
+		primary.StopActionLoop(t)
+		// update the primary topo record
+		wr.TopoServer().UpdateTabletFields(ctx, primary.Tablet.Alias, func(tablet *topodatapb.Tablet) error {
+			tablet.MysqlHostname = ""
+			return nil
+		})
+
+		// run SetReplicationSource
+		err = wr.SetReplicationSource(ctx, replica.Tablet)
+		require.ErrorContains(t, err, "Shard primary has empty mysql hostname")
+
+		// check what was run
+		err = replica.FakeMysqlDaemon.CheckSuperQueryList()
+		require.NoError(t, err, "CheckSuperQueryList failed")
+		checkSemiSyncEnabled(t, false, true, replica)
+	})
 }