Golang tracing.NewTracer函数代码示例

// TestTxnCoordSenderErrorWithIntent validates that if a transactional request
// returns an error but also indicates a Writing transaction, the coordinator
// tracks it just like a successful request.
func TestTxnCoordSenderErrorWithIntent(t *testing.T) {
	defer leaktest.AfterTest(t)
	stopper := stop.NewStopper()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	ts := NewTxnCoordSender(senderFn(func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
		txn := ba.Txn.Clone()
		txn.Writing = true
		pErr := roachpb.NewError(roachpb.NewTransactionRetryError())
		pErr.SetTxn(&txn)
		return nil, pErr
	}), clock, false, tracing.NewTracer(), stopper)
	defer stopper.Stop()

	var ba roachpb.BatchRequest
	key := roachpb.Key("test")
	ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.EndTransactionRequest{})
	ba.Txn = &roachpb.Transaction{Name: "test"}
	if _, pErr := ts.Send(context.Background(), ba); !testutils.IsPError(pErr, "retry txn") {
		t.Fatalf("unexpected error: %v", pErr)
	}

	defer teardownHeartbeats(ts)
	ts.Lock()
	defer ts.Unlock()
	if len(ts.txns) != 1 {
		t.Fatalf("expected transaction to be tracked")
	}
}

// TestMultiRangeScanWithMaxResults tests that commands which access multiple
// ranges with MaxResults parameter are carried out properly.
func TestMultiRangeScanWithMaxResults(t *testing.T) {
	defer leaktest.AfterTest(t)()
	testCases := []struct {
		splitKeys []roachpb.Key
		keys      []roachpb.Key
	}{
		{[]roachpb.Key{roachpb.Key("m")},
			[]roachpb.Key{roachpb.Key("a"), roachpb.Key("z")}},
		{[]roachpb.Key{roachpb.Key("h"), roachpb.Key("q")},
			[]roachpb.Key{roachpb.Key("b"), roachpb.Key("f"), roachpb.Key("k"),
				roachpb.Key("r"), roachpb.Key("w"), roachpb.Key("y")}},
	}

	for i, tc := range testCases {
		s, _, _ := serverutils.StartServer(t, base.TestServerArgs{})
		defer s.Stopper().Stop()
		ts := s.(*TestServer)
		retryOpts := base.DefaultRetryOptions()
		retryOpts.Closer = ts.stopper.ShouldDrain()
		ds := kv.NewDistSender(&kv.DistSenderContext{
			Clock:           s.Clock(),
			RPCContext:      s.RPCContext(),
			RPCRetryOptions: &retryOpts,
		}, ts.Gossip())
		tds := kv.NewTxnCoordSender(ds, ts.Clock(), ts.Ctx.Linearizable, tracing.NewTracer(),
			ts.stopper, kv.NewTxnMetrics(metric.NewRegistry()))

		for _, sk := range tc.splitKeys {
			if err := ts.node.ctx.DB.AdminSplit(sk); err != nil {
				t.Fatal(err)
			}
		}

		for _, k := range tc.keys {
			put := roachpb.NewPut(k, roachpb.MakeValueFromBytes(k))
			if _, err := client.SendWrapped(tds, nil, put); err != nil {
				t.Fatal(err)
			}
		}

		// Try every possible ScanRequest startKey.
		for start := 0; start < len(tc.keys); start++ {
			// Try every possible maxResults, from 1 to beyond the size of key array.
			for maxResults := 1; maxResults <= len(tc.keys)-start+1; maxResults++ {
				scan := roachpb.NewScan(tc.keys[start], tc.keys[len(tc.keys)-1].Next(),
					int64(maxResults))
				reply, err := client.SendWrapped(tds, nil, scan)
				if err != nil {
					t.Fatal(err)
				}
				rows := reply.(*roachpb.ScanResponse).Rows
				if start+maxResults <= len(tc.keys) && len(rows) != maxResults {
					t.Errorf("%d: start=%s: expected %d rows, but got %d", i, tc.keys[start], maxResults, len(rows))
				} else if start+maxResults == len(tc.keys)+1 && len(rows) != maxResults-1 {
					t.Errorf("%d: expected %d rows, but got %d", i, maxResults-1, len(rows))
				}
			}
		}
	}
}

// TestSendToOneClient verifies that Send correctly sends a request
// to one server using the heartbeat RPC.
func TestSendToOneClient(t *testing.T) {
	defer leaktest.AfterTest(t)()

	stopper := stop.NewStopper()
	defer stopper.Stop()

	ctx := newNodeTestContext(nil, stopper)
	s, ln := newTestServer(t, ctx)
	registerBatch(t, s, 0)

	sp := tracing.NewTracer().StartSpan("node test")
	defer sp.Finish()

	opts := SendOptions{
		Ordering:        orderStable,
		SendNextTimeout: 1 * time.Second,
		Timeout:         10 * time.Second,
		Trace:           sp,
	}
	reply, err := sendBatch(opts, []net.Addr{ln.Addr()}, ctx)
	if err != nil {
		t.Fatal(err)
	}
	if reply == nil {
		t.Errorf("expected reply")
	}
}

// TestTxnCoordSenderSingleRoundtripTxn checks that a batch which completely
// holds the writing portion of a Txn (including EndTransaction) does not
// launch a heartbeat goroutine at all.
func TestTxnCoordSenderSingleRoundtripTxn(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper := stop.NewStopper()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	ts := NewTxnCoordSender(senderFn(func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
		br := ba.CreateReply()
		txnClone := ba.Txn.Clone()
		br.Txn = &txnClone
		br.Txn.Writing = true
		return br, nil
	}), clock, false, tracing.NewTracer(), stopper, NewTxnMetrics(metric.NewRegistry()))

	// Stop the stopper manually, prior to trying the transaction. This has the
	// effect of returning a NodeUnavailableError for any attempts at launching
	// a heartbeat goroutine.
	stopper.Stop()

	var ba roachpb.BatchRequest
	key := roachpb.Key("test")
	ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.EndTransactionRequest{})
	ba.Txn = &roachpb.Transaction{Name: "test"}
	_, pErr := ts.Send(context.Background(), ba)
	if pErr != nil {
		t.Fatal(pErr)
	}
}

// NewDistSender returns a batch.Sender instance which connects to the
// Cockroach cluster via the supplied gossip instance. Supplying a
// DistSenderContext or the fields within is optional. For omitted values, sane
// defaults will be used.
func NewDistSender(ctx *DistSenderContext, gossip *gossip.Gossip) *DistSender {
	if ctx == nil {
		ctx = &DistSenderContext{}
	}
	clock := ctx.Clock
	if clock == nil {
		clock = hlc.NewClock(hlc.UnixNano)
	}
	ds := &DistSender{
		clock:  clock,
		gossip: gossip,
	}
	if ctx.nodeDescriptor != nil {
		atomic.StorePointer(&ds.nodeDescriptor, unsafe.Pointer(ctx.nodeDescriptor))
	}
	rcSize := ctx.RangeDescriptorCacheSize
	if rcSize <= 0 {
		rcSize = defaultRangeDescriptorCacheSize
	}
	rdb := ctx.RangeDescriptorDB
	if rdb == nil {
		rdb = ds
	}
	ds.rangeCache = newRangeDescriptorCache(rdb, int(rcSize))
	lcSize := ctx.LeaderCacheSize
	if lcSize <= 0 {
		lcSize = defaultLeaderCacheSize
	}
	ds.leaderCache = newLeaderCache(int(lcSize))
	if ctx.RangeLookupMaxRanges <= 0 {
		ds.rangeLookupMaxRanges = defaultRangeLookupMaxRanges
	}
	if ctx.TransportFactory != nil {
		ds.transportFactory = ctx.TransportFactory
	}
	ds.rpcRetryOptions = base.DefaultRetryOptions()
	if ctx.RPCRetryOptions != nil {
		ds.rpcRetryOptions = *ctx.RPCRetryOptions
	}
	if ctx.RPCContext != nil {
		ds.rpcContext = ctx.RPCContext
		if ds.rpcRetryOptions.Closer == nil {
			ds.rpcRetryOptions.Closer = ds.rpcContext.Stopper.ShouldDrain()
		}
	}
	if ctx.Tracer != nil {
		ds.Tracer = ctx.Tracer
	} else {
		ds.Tracer = tracing.NewTracer()
	}
	if ctx.SendNextTimeout != 0 {
		ds.sendNextTimeout = ctx.SendNextTimeout
	} else {
		ds.sendNextTimeout = defaultSendNextTimeout
	}

	return ds
}

// TestRetryableError verifies that Send returns a retryable error
// when it hits an RPC error.
func TestRetryableError(t *testing.T) {
	defer leaktest.AfterTest(t)()

	clientStopper := stop.NewStopper()
	defer clientStopper.Stop()
	clientContext := newNodeTestContext(nil, clientStopper)

	serverStopper := stop.NewStopper()
	serverContext := newNodeTestContext(nil, serverStopper)

	s, ln := newTestServer(t, serverContext)
	roachpb.RegisterInternalServer(s, Node(0))

	conn, err := clientContext.GRPCDial(ln.Addr().String())
	if err != nil {
		t.Fatal(err)
	}
	ctx := context.Background()
	waitForConnState := func(desiredState grpc.ConnectivityState) {
		clientState, err := conn.State()
		for clientState != desiredState {
			if err != nil {
				t.Fatal(err)
			}
			if clientState == grpc.Shutdown {
				t.Fatalf("%v has unexpectedly shut down", conn)
			}
			clientState, err = conn.WaitForStateChange(ctx, clientState)
		}
	}
	// Wait until the client becomes healthy and shut down the server.
	waitForConnState(grpc.Ready)
	serverStopper.Stop()
	// Wait until the client becomes unhealthy.
	waitForConnState(grpc.TransientFailure)

	sp := tracing.NewTracer().StartSpan("node test")
	defer sp.Finish()

	opts := SendOptions{
		Ordering:        orderStable,
		SendNextTimeout: 100 * time.Millisecond,
		Timeout:         100 * time.Millisecond,
		Trace:           sp,
	}
	if _, err := sendBatch(opts, []net.Addr{ln.Addr()}, clientContext); err != nil {
		retryErr, ok := err.(retry.Retryable)
		if !ok {
			t.Fatalf("Unexpected error type: %v", err)
		}
		if !retryErr.CanRetry() {
			t.Errorf("Expected retryable error: %v", retryErr)
		}
	} else {
		t.Fatalf("Unexpected success")
	}
}

// setupMetricsTest returns a TxnCoordSender and ManualClock pointing to a newly created
// LocalTestCluster. Also returns a cleanup function to be executed at the end of the
// test.
func setupMetricsTest(t *testing.T) (*hlc.ManualClock, *TxnCoordSender, func()) {
	s, testSender := createTestDB(t)
	reg := metric.NewRegistry()
	txnMetrics := NewTxnMetrics(reg)
	sender := NewTxnCoordSender(testSender.wrapped, s.Clock, false, tracing.NewTracer(), s.Stopper, txnMetrics)

	return s.Manual, sender, func() {
		teardownHeartbeats(sender)
		s.Stop()
	}
}

// setupMetricsTest returns a TxnCoordSender and ManualClock pointing to a newly created
// LocalTestCluster. Also returns a cleanup function to be executed at the end of the
// test.
func setupMetricsTest(t *testing.T) (*hlc.ManualClock, *TxnCoordSender, func()) {
	s, testSender := createTestDB(t)
	txnMetrics := MakeTxnMetrics()
	ctx := tracing.WithTracer(context.Background(), tracing.NewTracer())
	sender := NewTxnCoordSender(ctx, testSender.wrapped, s.Clock, false, s.Stopper, txnMetrics)

	return s.Manual, sender, func() {
		teardownHeartbeats(sender)
		s.Stop()
	}
}

// createTestNode creates an rpc server using the specified address,
// gossip instance, KV database and a node using the specified slice
// of engines. The server, clock and node are returned. If gossipBS is
// not nil, the gossip bootstrap address is set to gossipBS.
func createTestNode(addr net.Addr, engines []engine.Engine, gossipBS net.Addr, t *testing.T) (
	*grpc.Server, net.Addr, *hlc.Clock, *Node, *stop.Stopper) {
	ctx := storage.StoreContext{}

	stopper := stop.NewStopper()
	ctx.Clock = hlc.NewClock(hlc.UnixNano)
	nodeRPCContext := rpc.NewContext(nodeTestBaseContext, ctx.Clock, stopper)
	ctx.ScanInterval = 10 * time.Hour
	ctx.ConsistencyCheckInterval = 10 * time.Hour
	grpcServer := rpc.NewServer(nodeRPCContext)
	serverCtx := makeTestContext()
	g := gossip.New(
		context.Background(),
		nodeRPCContext,
		grpcServer,
		serverCtx.GossipBootstrapResolvers,
		stopper,
		metric.NewRegistry())
	ln, err := netutil.ListenAndServeGRPC(stopper, grpcServer, addr)
	if err != nil {
		t.Fatal(err)
	}
	if gossipBS != nil {
		// Handle possibility of a :0 port specification.
		if gossipBS.Network() == addr.Network() && gossipBS.String() == addr.String() {
			gossipBS = ln.Addr()
		}
		r, err := resolver.NewResolverFromAddress(gossipBS)
		if err != nil {
			t.Fatalf("bad gossip address %s: %s", gossipBS, err)
		}
		g.SetResolvers([]resolver.Resolver{r})
		g.Start(ln.Addr())
	}
	ctx.Gossip = g
	retryOpts := base.DefaultRetryOptions()
	retryOpts.Closer = stopper.ShouldQuiesce()
	distSender := kv.NewDistSender(&kv.DistSenderConfig{
		Clock:           ctx.Clock,
		RPCContext:      nodeRPCContext,
		RPCRetryOptions: &retryOpts,
	}, g)
	ctx.Ctx = tracing.WithTracer(context.Background(), tracing.NewTracer())
	sender := kv.NewTxnCoordSender(ctx.Ctx, distSender, ctx.Clock, false, stopper,
		kv.MakeTxnMetrics())
	ctx.DB = client.NewDB(sender)
	ctx.Transport = storage.NewDummyRaftTransport()
	node := NewNode(ctx, status.NewMetricsRecorder(ctx.Clock), metric.NewRegistry(), stopper,
		kv.MakeTxnMetrics(), sql.MakeEventLogger(nil))
	roachpb.RegisterInternalServer(grpcServer, node)
	return grpcServer, ln.Addr(), ctx.Clock, node, stopper
}

// TestTxnCoordSenderErrorWithIntent validates that if a transactional request
// returns an error but also indicates a Writing transaction, the coordinator
// tracks it just like a successful request.
func TestTxnCoordSenderErrorWithIntent(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper := stop.NewStopper()
	defer stopper.Stop()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	testCases := []struct {
		roachpb.Error
		errMsg string
	}{
		{*roachpb.NewError(roachpb.NewTransactionRetryError()), "retry txn"},
		{*roachpb.NewError(roachpb.NewTransactionPushError(roachpb.Transaction{
			TxnMeta: enginepb.TxnMeta{
				ID: uuid.NewV4(),
			}})), "failed to push"},
		{*roachpb.NewErrorf("testError"), "testError"},
	}
	for i, test := range testCases {
		func() {
			senderFunc := func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
				txn := ba.Txn.Clone()
				txn.Writing = true
				pErr := &roachpb.Error{}
				*pErr = test.Error
				pErr.SetTxn(&txn)
				return nil, pErr
			}
			ctx := tracing.WithTracer(context.Background(), tracing.NewTracer())
			ts := NewTxnCoordSender(ctx, senderFn(senderFunc), clock, false, stopper, MakeTxnMetrics())

			var ba roachpb.BatchRequest
			key := roachpb.Key("test")
			ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
			ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
			ba.Add(&roachpb.EndTransactionRequest{})
			ba.Txn = &roachpb.Transaction{Name: "test"}
			_, pErr := ts.Send(context.Background(), ba)
			if !testutils.IsPError(pErr, test.errMsg) {
				t.Errorf("%d: error did not match %s: %v", i, test.errMsg, pErr)
			}

			defer teardownHeartbeats(ts)
			ts.Lock()
			defer ts.Unlock()
			if len(ts.txns) != 1 {
				t.Errorf("%d: expected transaction to be tracked", i)
			}
		}()
	}
}

// setupMetricsTest returns a TxnCoordSender and ManualClock pointing to a newly created
// LocalTestCluster. Also returns a cleanup function to be executed at the end of the
// test.
func setupMetricsTest(t *testing.T) (*hlc.ManualClock, *TxnCoordSender, func()) {
	s := createTestDB(t)
	reg := metric.NewRegistry()
	txnMetrics := NewTxnMetrics(reg)
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	sender := NewTxnCoordSender(s.distSender, clock, false, tracing.NewTracer(), s.Stopper, txnMetrics)

	return manual, sender, func() {
		teardownHeartbeats(sender)
		s.Stop()
	}
}

// NewDistSender returns a batch.Sender instance which connects to the
// Cockroach cluster via the supplied gossip instance. Supplying a
// DistSenderContext or the fields within is optional. For omitted values, sane
// defaults will be used.
func NewDistSender(ctx *DistSenderContext, gossip *gossip.Gossip) *DistSender {
	if ctx == nil {
		ctx = &DistSenderContext{}
	}
	clock := ctx.Clock
	if clock == nil {
		clock = hlc.NewClock(hlc.UnixNano)
	}
	ds := &DistSender{
		clock:  clock,
		gossip: gossip,
	}
	if ctx.nodeDescriptor != nil {
		atomic.StorePointer(&ds.nodeDescriptor, unsafe.Pointer(ctx.nodeDescriptor))
	}
	rcSize := ctx.RangeDescriptorCacheSize
	if rcSize <= 0 {
		rcSize = defaultRangeDescriptorCacheSize
	}
	rdb := ctx.RangeDescriptorDB
	if rdb == nil {
		rdb = ds
	}
	ds.rangeCache = newRangeDescriptorCache(rdb, int(rcSize))
	lcSize := ctx.LeaderCacheSize
	if lcSize <= 0 {
		lcSize = defaultLeaderCacheSize
	}
	ds.leaderCache = newLeaderCache(int(lcSize))
	if ctx.RangeLookupMaxRanges <= 0 {
		ds.rangeLookupMaxRanges = defaultRangeLookupMaxRanges
	}
	ds.rpcSend = send
	if ctx.RPCSend != nil {
		ds.rpcSend = ctx.RPCSend
	}
	if ctx.RPCContext != nil {
		ds.rpcContext = ctx.RPCContext
	}
	ds.rpcRetryOptions = defaultRPCRetryOptions
	if ctx.RPCRetryOptions != nil {
		ds.rpcRetryOptions = *ctx.RPCRetryOptions
	}
	if ctx.Tracer != nil {
		ds.Tracer = ctx.Tracer
	} else {
		ds.Tracer = tracing.NewTracer()
	}

	return ds
}

// TestRetryableError verifies that Send returns a retryable error
// when it hits an RPC error.
func TestRetryableError(t *testing.T) {
	defer leaktest.AfterTest(t)()

	clientStopper := stop.NewStopper()
	defer clientStopper.Stop()
	clientContext := newNodeTestContext(nil, clientStopper)
	clientContext.HeartbeatTimeout = 10 * clientContext.HeartbeatInterval

	serverStopper := stop.NewStopper()
	serverContext := newNodeTestContext(nil, serverStopper)

	s, ln := newTestServer(t, serverContext)
	registerBatch(t, s, 0)

	c := rpc.NewClient(ln.Addr(), clientContext)
	// Wait until the client becomes healthy and shut down the server.
	<-c.Healthy()
	serverStopper.Stop()
	// Wait until the client becomes unhealthy.
	func() {
		for r := retry.Start(retry.Options{}); r.Next(); {
			select {
			case <-c.Healthy():
			case <-time.After(1 * time.Nanosecond):
				return
			}
		}
	}()

	sp := tracing.NewTracer().StartSpan("node test")
	defer sp.Finish()

	opts := SendOptions{
		Ordering:        orderStable,
		SendNextTimeout: 100 * time.Millisecond,
		Timeout:         100 * time.Millisecond,
		Trace:           sp,
	}
	if _, err := sendBatch(opts, []net.Addr{ln.Addr()}, clientContext); err != nil {
		retryErr, ok := err.(retry.Retryable)
		if !ok {
			t.Fatalf("Unexpected error type: %v", err)
		}
		if !retryErr.CanRetry() {
			t.Errorf("Expected retryable error: %v", retryErr)
		}
	} else {
		t.Fatalf("Unexpected success")
	}
}

// createTestNode creates an rpc server using the specified address,
// gossip instance, KV database and a node using the specified slice
// of engines. The server, clock and node are returned. If gossipBS is
// not nil, the gossip bootstrap address is set to gossipBS.
func createTestNode(addr net.Addr, engines []engine.Engine, gossipBS net.Addr, t *testing.T) (
	*rpc.Server, net.Addr, *hlc.Clock, *Node, *stop.Stopper) {
	ctx := storage.StoreContext{}

	stopper := stop.NewStopper()
	ctx.Clock = hlc.NewClock(hlc.UnixNano)
	nodeRPCContext := rpc.NewContext(nodeTestBaseContext, ctx.Clock, stopper)
	ctx.ScanInterval = 10 * time.Hour
	rpcServer := rpc.NewServer(nodeRPCContext)
	grpcServer := grpc.NewServer()
	tlsConfig, err := nodeRPCContext.GetServerTLSConfig()
	if err != nil {
		t.Fatal(err)
	}
	ln, err := util.ListenAndServe(stopper, grpcutil.GRPCHandlerFunc(grpcServer, rpcServer), addr, tlsConfig)
	if err != nil {
		t.Fatal(err)
	}
	g := gossip.New(nodeRPCContext, testContext.GossipBootstrapResolvers, stopper)
	if gossipBS != nil {
		// Handle possibility of a :0 port specification.
		if gossipBS.Network() == addr.Network() && gossipBS.String() == addr.String() {
			gossipBS = ln.Addr()
		}
		r, err := resolver.NewResolverFromAddress(gossipBS)
		if err != nil {
			t.Fatalf("bad gossip address %s: %s", gossipBS, err)
		}
		g.SetResolvers([]resolver.Resolver{r})
		g.Start(grpcServer, ln.Addr())
	}
	ctx.Gossip = g
	retryOpts := kv.GetDefaultDistSenderRetryOptions()
	retryOpts.Closer = stopper.ShouldDrain()
	distSender := kv.NewDistSender(&kv.DistSenderContext{
		Clock:           ctx.Clock,
		RPCContext:      nodeRPCContext,
		RPCRetryOptions: &retryOpts,
	}, g)
	tracer := tracing.NewTracer()
	sender := kv.NewTxnCoordSender(distSender, ctx.Clock, false, tracer, stopper)
	ctx.DB = client.NewDB(sender)
	// TODO(bdarnell): arrange to have the transport closed.
	// (or attach LocalRPCTransport.Close to the stopper)
	ctx.Transport = storage.NewLocalRPCTransport(stopper)
	ctx.EventFeed = util.NewFeed(stopper)
	ctx.Tracer = tracer
	node := NewNode(ctx, metric.NewRegistry(), stopper, nil)
	return rpcServer, ln.Addr(), ctx.Clock, node, stopper
}

// Start starts the test cluster by bootstrapping an in-memory store
// (defaults to maximum of 50M). The server is started, launching the
// node RPC server and all HTTP endpoints. Use the value of
// TestServer.Addr after Start() for client connections. Use Stop()
// to shutdown the server after the test completes.
func (ltc *LocalTestCluster) Start(t util.Tester, baseCtx *base.Context, initSender InitSenderFn) {
	nodeID := roachpb.NodeID(1)
	nodeDesc := &roachpb.NodeDescriptor{NodeID: nodeID}
	tracer := tracing.NewTracer()
	ltc.tester = t
	ltc.Manual = hlc.NewManualClock(0)
	ltc.Clock = hlc.NewClock(ltc.Manual.UnixNano)
	ltc.Stopper = stop.NewStopper()
	rpcContext := rpc.NewContext(baseCtx, ltc.Clock, ltc.Stopper)
	server := rpc.NewServer(rpcContext) // never started
	ltc.Gossip = gossip.New(
		context.Background(), rpcContext, server, nil, ltc.Stopper, metric.NewRegistry())
	ltc.Eng = engine.NewInMem(roachpb.Attributes{}, 50<<20, ltc.Stopper)

	ltc.Stores = storage.NewStores(ltc.Clock)

	ltc.Sender = initSender(nodeDesc, tracer, ltc.Clock, ltc.Latency, ltc.Stores, ltc.Stopper,
		ltc.Gossip)
	if ltc.DBContext == nil {
		dbCtx := client.DefaultDBContext()
		ltc.DBContext = &dbCtx
	}
	ltc.DB = client.NewDBWithContext(ltc.Sender, *ltc.DBContext)
	transport := storage.NewDummyRaftTransport()
	ctx := storage.TestStoreContext()
	if ltc.RangeRetryOptions != nil {
		ctx.RangeRetryOptions = *ltc.RangeRetryOptions
	}
	ctx.Ctx = tracing.WithTracer(context.Background(), tracer)
	ctx.Clock = ltc.Clock
	ctx.DB = ltc.DB
	ctx.Gossip = ltc.Gossip
	ctx.Transport = transport
	ltc.Store = storage.NewStore(ctx, ltc.Eng, nodeDesc)
	if err := ltc.Store.Bootstrap(roachpb.StoreIdent{NodeID: nodeID, StoreID: 1}, ltc.Stopper); err != nil {
		t.Fatalf("unable to start local test cluster: %s", err)
	}
	ltc.Stores.AddStore(ltc.Store)
	if err := ltc.Store.BootstrapRange(nil); err != nil {
		t.Fatalf("unable to start local test cluster: %s", err)
	}
	if err := ltc.Store.Start(context.Background(), ltc.Stopper); err != nil {
		t.Fatalf("unable to start local test cluster: %s", err)
	}
	ltc.Gossip.SetNodeID(nodeDesc.NodeID)
	if err := ltc.Gossip.SetNodeDescriptor(nodeDesc); err != nil {
		t.Fatalf("unable to set node descriptor: %s", err)
	}
}