Golang gossip.MakeNodeIDKey函數代碼示例

// TestNodeJoin verifies a new node is able to join a bootstrapped
// cluster consisting of one node.
func TestNodeJoin(t *testing.T) {
	defer leaktest.AfterTest(t)
	engineStopper := stop.NewStopper()
	defer engineStopper.Stop()
	e := engine.NewInMem(roachpb.Attributes{}, 1<<20, engineStopper)
	stopper := stop.NewStopper()
	_, err := BootstrapCluster("cluster-1", []engine.Engine{e}, stopper)
	if err != nil {
		t.Fatal(err)
	}
	stopper.Stop()

	// Set an aggressive gossip interval to make sure information is exchanged tout de suite.
	testContext.GossipInterval = gossip.TestInterval
	// Start the bootstrap node.
	engines1 := []engine.Engine{e}
	addr1 := util.CreateTestAddr("tcp")
	server1, node1, stopper1 := createAndStartTestNode(addr1, engines1, addr1, t)
	defer stopper1.Stop()

	// Create a new node.
	engines2 := []engine.Engine{engine.NewInMem(roachpb.Attributes{}, 1<<20, engineStopper)}
	server2, node2, stopper2 := createAndStartTestNode(util.CreateTestAddr("tcp"), engines2, server1.Addr(), t)
	defer stopper2.Stop()

	// Verify new node is able to bootstrap its store.
	if err := util.IsTrueWithin(func() bool { return node2.lSender.GetStoreCount() == 1 }, 50*time.Millisecond); err != nil {
		t.Fatal(err)
	}

	// Verify node1 sees node2 via gossip and vice versa.
	node1Key := gossip.MakeNodeIDKey(node1.Descriptor.NodeID)
	node2Key := gossip.MakeNodeIDKey(node2.Descriptor.NodeID)
	if err := util.IsTrueWithin(func() bool {
		nodeDesc1 := &roachpb.NodeDescriptor{}
		if err := node1.ctx.Gossip.GetInfoProto(node2Key, nodeDesc1); err != nil {
			return false
		}
		if addr2 := nodeDesc1.Address.AddressField; addr2 != server2.Addr().String() {
			t.Errorf("addr2 gossip %s doesn't match addr2 address %s", addr2, server2.Addr().String())
		}
		nodeDesc2 := &roachpb.NodeDescriptor{}
		if err := node2.ctx.Gossip.GetInfoProto(node1Key, nodeDesc2); err != nil {
			return false
		}
		if addr1 := nodeDesc2.Address.AddressField; addr1 != server1.Addr().String() {
			t.Errorf("addr1 gossip %s doesn't match addr1 address %s", addr1, server1.Addr().String())
		}
		return true
	}, 50*time.Millisecond); err != nil {
		t.Error(err)
	}
}

// TestNodeJoin verifies a new node is able to join a bootstrapped
// cluster consisting of one node.
func TestNodeJoin(t *testing.T) {
	defer leaktest.AfterTest(t)()
	engineStopper := stop.NewStopper()
	defer engineStopper.Stop()
	e := engine.NewInMem(roachpb.Attributes{}, 1<<20, engineStopper)
	if _, err := bootstrapCluster([]engine.Engine{e}, kv.NewTxnMetrics(metric.NewRegistry())); err != nil {
		t.Fatal(err)
	}

	// Start the bootstrap node.
	engines1 := []engine.Engine{e}
	addr1 := util.CreateTestAddr("tcp")
	_, server1Addr, node1, stopper1 := createAndStartTestNode(addr1, engines1, addr1, t)
	defer stopper1.Stop()

	// Create a new node.
	engines2 := []engine.Engine{engine.NewInMem(roachpb.Attributes{}, 1<<20, engineStopper)}
	addr2 := util.CreateTestAddr("tcp")
	_, server2Addr, node2, stopper2 := createAndStartTestNode(addr2, engines2, server1Addr, t)
	defer stopper2.Stop()

	// Verify new node is able to bootstrap its store.
	util.SucceedsSoon(t, func() error {
		if sc := node2.stores.GetStoreCount(); sc != 1 {
			return util.Errorf("GetStoreCount() expected 1; got %d", sc)
		}
		return nil
	})

	// Verify node1 sees node2 via gossip and vice versa.
	node1Key := gossip.MakeNodeIDKey(node1.Descriptor.NodeID)
	node2Key := gossip.MakeNodeIDKey(node2.Descriptor.NodeID)
	util.SucceedsSoon(t, func() error {
		var nodeDesc1 roachpb.NodeDescriptor
		if err := node1.ctx.Gossip.GetInfoProto(node2Key, &nodeDesc1); err != nil {
			return err
		}
		if addr2Str, server2AddrStr := nodeDesc1.Address.String(), server2Addr.String(); addr2Str != server2AddrStr {
			return util.Errorf("addr2 gossip %s doesn't match addr2 address %s", addr2Str, server2AddrStr)
		}
		var nodeDesc2 roachpb.NodeDescriptor
		if err := node2.ctx.Gossip.GetInfoProto(node1Key, &nodeDesc2); err != nil {
			return err
		}
		if addr1Str, server1AddrStr := nodeDesc2.Address.String(), server1Addr.String(); addr1Str != server1AddrStr {
			return util.Errorf("addr1 gossip %s doesn't match addr1 address %s", addr1Str, server1AddrStr)
		}
		return nil
	})
}

// createTestStoreWithEngine creates a test store using the given engine and clock.
// The caller is responsible for closing the store on exit.
func createTestStoreWithEngine(t *testing.T, eng engine.Engine, clock *hlc.Clock,
	bootstrap bool, sCtx *storage.StoreContext) (*storage.Store, *stop.Stopper) {
	stopper := stop.NewStopper()
	rpcContext := rpc.NewContext(&base.Context{}, clock, stopper)
	if sCtx == nil {
		// make a copy
		ctx := storage.TestStoreContext
		sCtx = &ctx
	}
	nodeDesc := &proto.NodeDescriptor{NodeID: 1}
	sCtx.Gossip = gossip.New(rpcContext, gossip.TestInterval, gossip.TestBootstrap)
	localSender := kv.NewLocalSender()
	rpcSend := func(_ rpc.Options, _ string, _ []net.Addr,
		getArgs func(addr net.Addr) gogoproto.Message, getReply func() gogoproto.Message,
		_ *rpc.Context) ([]gogoproto.Message, error) {
		call := proto.Call{
			Args:  getArgs(nil /* net.Addr */).(proto.Request),
			Reply: getReply().(proto.Response),
		}
		localSender.Send(context.Background(), call)
		return []gogoproto.Message{call.Reply}, call.Reply.Header().GoError()
	}

	// Mostly makes sure that we don't see a warning per request.
	{
		if err := sCtx.Gossip.AddInfoProto(gossip.MakeNodeIDKey(nodeDesc.NodeID), nodeDesc, time.Hour); err != nil {
			t.Fatal(err)
		}
		if err := sCtx.Gossip.SetNodeDescriptor(nodeDesc); err != nil {
			t.Fatal(err)
		}
	}
	distSender := kv.NewDistSender(&kv.DistSenderContext{
		Clock:             clock,
		RPCSend:           rpcSend,     // defined above
		RangeDescriptorDB: localSender, // for descriptor lookup
	}, sCtx.Gossip)

	sender := kv.NewTxnCoordSender(distSender, clock, false, nil, stopper)
	sCtx.Clock = clock
	sCtx.DB = client.NewDB(sender)
	sCtx.Transport = multiraft.NewLocalRPCTransport(stopper)
	// TODO(bdarnell): arrange to have the transport closed.
	store := storage.NewStore(*sCtx, eng, nodeDesc)
	if bootstrap {
		if err := store.Bootstrap(proto.StoreIdent{NodeID: 1, StoreID: 1}, stopper); err != nil {
			t.Fatal(err)
		}
	}
	localSender.AddStore(store)
	if bootstrap {
		if err := store.BootstrapRange(sql.GetInitialSystemValues()); err != nil {
			t.Fatal(err)
		}
	}
	if err := store.Start(stopper); err != nil {
		t.Fatal(err)
	}
	return store, stopper
}

func makeTestGossip(t *testing.T) (*gossip.Gossip, func()) {
	n := simulation.NewNetwork(1, "tcp", gossip.TestInterval)
	g := n.Nodes[0].Gossip
	permConfig := &config.PermConfig{
		Read:  []string{""},
		Write: []string{""},
	}

	configMap, err := config.NewPrefixConfigMap([]*config.PrefixConfig{
		{proto.KeyMin, nil, permConfig},
	})
	if err != nil {
		t.Fatalf("failed to make prefix config map, err: %s", err.Error())
	}
	if err := g.AddInfo(gossip.KeySentinel, "cluster1", time.Hour); err != nil {
		t.Fatal(err)
	}
	if err := g.AddInfo(gossip.KeyConfigPermission, configMap, time.Hour); err != nil {
		t.Fatal(err)
	}
	if err := g.AddInfo(gossip.KeyFirstRangeDescriptor, testRangeDescriptor, time.Hour); err != nil {
		t.Fatal(err)
	}
	nodeIDKey := gossip.MakeNodeIDKey(1)
	if err := g.AddInfo(nodeIDKey, &proto.NodeDescriptor{
		NodeID:  1,
		Address: util.MakeUnresolvedAddr(testAddress.Network(), testAddress.String()),
		Attrs:   proto.Attributes{Attrs: []string{"attr1", "attr2"}},
	}, time.Hour); err != nil {
		t.Fatal(err)
	}
	return g, n.Stop
}

// TestSendRPCRetry verifies that sendRPC failed on first address but succeed on
// second address, the second reply should be successfully returned back.
func TestSendRPCRetry(t *testing.T) {
	defer leaktest.AfterTest(t)
	g, s := makeTestGossip(t)
	defer s()
	if err := g.SetNodeDescriptor(&proto.NodeDescriptor{NodeID: 1}); err != nil {
		t.Fatal(err)
	}
	// Fill RangeDescriptor with 2 replicas
	var descriptor = proto.RangeDescriptor{
		RaftID:   1,
		StartKey: proto.Key("a"),
		EndKey:   proto.Key("z"),
	}
	for i := 1; i <= 2; i++ {
		addr := util.MakeUnresolvedAddr("tcp", fmt.Sprintf("node%d", i))
		nd := &proto.NodeDescriptor{
			NodeID: proto.NodeID(i),
			Address: proto.Addr{
				Network: addr.Network(),
				Address: addr.String(),
			},
		}
		if err := g.AddInfo(gossip.MakeNodeIDKey(proto.NodeID(i)), nd, time.Hour); err != nil {
			t.Fatal(err)
		}

		descriptor.Replicas = append(descriptor.Replicas, proto.Replica{
			NodeID:  proto.NodeID(i),
			StoreID: proto.StoreID(i),
		})
	}
	// Define our rpcSend stub which returns success on the second address.
	var testFn rpcSendFn = func(_ rpc.Options, method string, addrs []net.Addr, getArgs func(addr net.Addr) interface{}, getReply func() interface{}, _ *rpc.Context) ([]interface{}, error) {
		if method == "Node.Scan" {
			// reply from first address failed
			_ = getReply()
			// reply from second address succeed
			reply := getReply()
			reply.(*proto.ScanResponse).Rows = append([]proto.KeyValue{}, proto.KeyValue{Key: proto.Key("b"), Value: proto.Value{}})
			return []interface{}{reply}, nil
		}
		return nil, util.Errorf("Not expected method %v", method)
	}
	ctx := &DistSenderContext{
		rpcSend: testFn,
		rangeDescriptorDB: mockRangeDescriptorDB(func(_ proto.Key, _ lookupOptions) ([]proto.RangeDescriptor, error) {
			return []proto.RangeDescriptor{descriptor}, nil
		}),
	}
	ds := NewDistSender(ctx, g)
	call := proto.ScanCall(proto.Key("a"), proto.Key("d"), 1)
	sr := call.Reply.(*proto.ScanResponse)
	ds.Send(context.Background(), call)
	if err := sr.GoError(); err != nil {
		t.Fatal(err)
	}
	if l := len(sr.Rows); l != 1 {
		t.Fatalf("expected 1 row; got %d", l)
	}
}

// TestSendRPCRetry verifies that sendRPC failed on first address but succeed on
// second address, the second reply should be successfully returned back.
func TestSendRPCRetry(t *testing.T) {
	defer leaktest.AfterTest(t)
	g, s := makeTestGossip(t)
	defer s()
	g.SetNodeID(1)
	if err := g.SetNodeDescriptor(&roachpb.NodeDescriptor{NodeID: 1}); err != nil {
		t.Fatal(err)
	}
	// Fill RangeDescriptor with 2 replicas
	var descriptor = roachpb.RangeDescriptor{
		RangeID:  1,
		StartKey: roachpb.RKey("a"),
		EndKey:   roachpb.RKey("z"),
	}
	for i := 1; i <= 2; i++ {
		addr := util.MakeUnresolvedAddr("tcp", fmt.Sprintf("node%d", i))
		nd := &roachpb.NodeDescriptor{
			NodeID:  roachpb.NodeID(i),
			Address: util.MakeUnresolvedAddr(addr.Network(), addr.String()),
		}
		if err := g.AddInfoProto(gossip.MakeNodeIDKey(roachpb.NodeID(i)), nd, time.Hour); err != nil {
			t.Fatal(err)
		}

		descriptor.Replicas = append(descriptor.Replicas, roachpb.ReplicaDescriptor{
			NodeID:  roachpb.NodeID(i),
			StoreID: roachpb.StoreID(i),
		})
	}
	// Define our rpcSend stub which returns success on the second address.
	var testFn rpcSendFn = func(_ rpc.Options, method string, addrs []net.Addr, getArgs func(addr net.Addr) proto.Message, getReply func() proto.Message, _ *rpc.Context) ([]proto.Message, error) {
		if method == "Node.Batch" {
			// reply from first address failed
			_ = getReply()
			// reply from second address succeed
			batchReply := getReply().(*roachpb.BatchResponse)
			reply := &roachpb.ScanResponse{}
			batchReply.Add(reply)
			reply.Rows = append([]roachpb.KeyValue{}, roachpb.KeyValue{Key: roachpb.Key("b"), Value: roachpb.Value{}})
			return []proto.Message{batchReply}, nil
		}
		return nil, util.Errorf("unexpected method %v", method)
	}
	ctx := &DistSenderContext{
		RPCSend: testFn,
		RangeDescriptorDB: mockRangeDescriptorDB(func(_ roachpb.RKey, _, _ bool) ([]roachpb.RangeDescriptor, *roachpb.Error) {
			return []roachpb.RangeDescriptor{descriptor}, nil
		}),
	}
	ds := NewDistSender(ctx, g)
	scan := roachpb.NewScan(roachpb.Key("a"), roachpb.Key("d"), 1)
	sr, err := client.SendWrapped(ds, nil, scan)
	if err != nil {
		t.Fatal(err)
	}
	if l := len(sr.(*roachpb.ScanResponse).Rows); l != 1 {
		t.Fatalf("expected 1 row; got %d", l)
	}
}

// GossipNode gossips the node's address, which is necessary before
// any messages can be sent to it. Normally done automatically by
// AddNode.
func (rttc *raftTransportTestContext) GossipNode(nodeID roachpb.NodeID, addr net.Addr) {
	if err := rttc.gossip.AddInfoProto(gossip.MakeNodeIDKey(nodeID),
		&roachpb.NodeDescriptor{
			Address: util.MakeUnresolvedAddr(addr.Network(), addr.String()),
		},
		time.Hour); err != nil {
		rttc.t.Fatal(err)
	}
}

// isNetworkConnected returns true if the network is fully connected
// with no partitions (i.e. every node knows every other node's
// network address).
func (n *Network) isNetworkConnected() bool {
	for _, leftNode := range n.Nodes {
		for _, rightNode := range n.Nodes {
			if _, err := leftNode.Gossip.GetInfo(gossip.MakeNodeIDKey(rightNode.Gossip.GetNodeID())); err != nil {
				return false
			}
		}
	}
	return true
}

// TestSendRPCRetry verifies that sendRPC failed on first address but succeed on
// second address, the second reply should be successfully returned back.
func TestSendRPCRetry(t *testing.T) {
	defer leaktest.AfterTest(t)
	g, s := makeTestGossip(t)
	defer s()
	g.SetNodeID(1)
	if err := g.SetNodeDescriptor(&roachpb.NodeDescriptor{NodeID: 1}); err != nil {
		t.Fatal(err)
	}
	// Fill RangeDescriptor with 2 replicas
	var descriptor = roachpb.RangeDescriptor{
		RangeID:  1,
		StartKey: roachpb.RKey("a"),
		EndKey:   roachpb.RKey("z"),
	}
	for i := 1; i <= 2; i++ {
		addr := util.MakeUnresolvedAddr("tcp", fmt.Sprintf("node%d", i))
		nd := &roachpb.NodeDescriptor{
			NodeID:  roachpb.NodeID(i),
			Address: util.MakeUnresolvedAddr(addr.Network(), addr.String()),
		}
		if err := g.AddInfoProto(gossip.MakeNodeIDKey(roachpb.NodeID(i)), nd, time.Hour); err != nil {
			t.Fatal(err)
		}

		descriptor.Replicas = append(descriptor.Replicas, roachpb.ReplicaDescriptor{
			NodeID:  roachpb.NodeID(i),
			StoreID: roachpb.StoreID(i),
		})
	}
	var testFn rpcSendFn = func(_ SendOptions, _ ReplicaSlice,
		args roachpb.BatchRequest, _ *rpc.Context) (proto.Message, error) {
		batchReply := &roachpb.BatchResponse{}
		reply := &roachpb.ScanResponse{}
		batchReply.Add(reply)
		reply.Rows = append([]roachpb.KeyValue{}, roachpb.KeyValue{Key: roachpb.Key("b"), Value: roachpb.Value{}})
		return batchReply, nil
	}
	ctx := &DistSenderContext{
		RPCSend: testFn,
		RangeDescriptorDB: mockRangeDescriptorDB(func(_ roachpb.RKey, _, _ bool) ([]roachpb.RangeDescriptor, *roachpb.Error) {
			return []roachpb.RangeDescriptor{descriptor}, nil
		}),
	}
	ds := NewDistSender(ctx, g)
	scan := roachpb.NewScan(roachpb.Key("a"), roachpb.Key("d"), 1)
	sr, err := client.SendWrapped(ds, nil, scan)
	if err != nil {
		t.Fatal(err)
	}
	if l := len(sr.(*roachpb.ScanResponse).Rows); l != 1 {
		t.Fatalf("expected 1 row; got %d", l)
	}
}

func TestOwnNodeCertain(t *testing.T) {
	defer leaktest.AfterTest(t)()
	g, s := makeTestGossip(t)
	defer s()
	const expNodeID = 42
	nd := &roachpb.NodeDescriptor{
		NodeID:  expNodeID,
		Address: util.MakeUnresolvedAddr("tcp", "foobar:1234"),
	}
	g.ResetNodeID(nd.NodeID)
	if err := g.SetNodeDescriptor(nd); err != nil {
		t.Fatal(err)
	}
	if err := g.AddInfoProto(gossip.MakeNodeIDKey(expNodeID), nd, time.Hour); err != nil {
		t.Fatal(err)
	}

	act := make(map[roachpb.NodeID]roachpb.Timestamp)
	var testFn rpcSendFn = func(_ SendOptions, _ ReplicaSlice,
		ba roachpb.BatchRequest, _ *rpc.Context) (*roachpb.BatchResponse, error) {
		for k, v := range ba.Txn.ObservedTimestamps {
			act[k] = v
		}
		return ba.CreateReply(), nil
	}

	ctx := &DistSenderContext{
		RPCSend: testFn,
		RangeDescriptorDB: mockRangeDescriptorDB(func(_ roachpb.RKey, _, _ bool) ([]roachpb.RangeDescriptor, *roachpb.Error) {
			return []roachpb.RangeDescriptor{testRangeDescriptor}, nil
		}),
	}
	expTS := roachpb.ZeroTimestamp.Add(1, 2)
	ds := NewDistSender(ctx, g)
	v := roachpb.MakeValueFromString("value")
	put := roachpb.NewPut(roachpb.Key("a"), v)
	if _, err := client.SendWrappedWith(ds, nil, roachpb.Header{
		// MaxTimestamp is set very high so that all uncertainty updates have
		// effect.
		Txn: &roachpb.Transaction{OrigTimestamp: expTS, MaxTimestamp: roachpb.MaxTimestamp},
	}, put); err != nil {
		t.Fatalf("put encountered error: %s", err)
	}
	exp := map[roachpb.NodeID]roachpb.Timestamp{
		expNodeID: expTS,
	}
	if !reflect.DeepEqual(exp, act) {
		t.Fatalf("wanted %v, got %v", exp, act)
	}

}

// getNodeDescriptor returns ds.nodeDescriptor, but makes an attempt to load
// it from the Gossip network if a nil value is found.
// We must jump through hoops here to get the node descriptor because it's not available
// until after the node has joined the gossip network and been allowed to initialize
// its stores.
func (ds *DistSender) getNodeDescriptor() *proto.NodeDescriptor {
	if desc := atomic.LoadPointer(&ds.nodeDescriptor); desc != nil {
		return (*proto.NodeDescriptor)(desc)
	}

	ownNodeID := ds.gossip.GetNodeID()
	if ownNodeID > 0 {
		nodeDesc := &proto.NodeDescriptor{}
		if err := ds.gossip.GetInfoProto(gossip.MakeNodeIDKey(ownNodeID), nodeDesc); err == nil {
			atomic.StorePointer(&ds.nodeDescriptor, unsafe.Pointer(nodeDesc))
			return nodeDesc
		}
	}
	log.Infof("unable to determine this node's attributes for replica " +
		"selection; node is most likely bootstrapping")
	return nil
}

func TestOwnNodeCertain(t *testing.T) {
	defer leaktest.AfterTest(t)
	g, s := makeTestGossip(t)
	defer s()
	const expNodeID = 42
	nd := &roachpb.NodeDescriptor{
		NodeID:  expNodeID,
		Address: util.MakeUnresolvedAddr("tcp", "foobar:1234"),
	}
	g.SetNodeID(nd.NodeID)
	if err := g.SetNodeDescriptor(nd); err != nil {
		t.Fatal(err)
	}
	if err := g.AddInfoProto(gossip.MakeNodeIDKey(expNodeID), nd, time.Hour); err != nil {
		t.Fatal(err)
	}

	var act roachpb.NodeList
	var testFn rpcSendFn = func(_ rpc.Options, _ string, _ []net.Addr, getArgs func(addr net.Addr) proto.Message, _ func() proto.Message, _ *rpc.Context) ([]proto.Message, error) {
		ba := getArgs(nil).(*roachpb.BatchRequest)
		for _, nodeID := range ba.Txn.CertainNodes.Nodes {
			act.Add(roachpb.NodeID(nodeID))
		}
		return []proto.Message{ba.CreateReply()}, nil
	}

	ctx := &DistSenderContext{
		RPCSend: testFn,
		RangeDescriptorDB: mockRangeDescriptorDB(func(_ roachpb.RKey, _, _ bool) ([]roachpb.RangeDescriptor, *roachpb.Error) {
			return []roachpb.RangeDescriptor{testRangeDescriptor}, nil
		}),
	}
	ds := NewDistSender(ctx, g)
	v := roachpb.MakeValueFromString("value")
	put := roachpb.NewPut(roachpb.Key("a"), v)
	if _, err := client.SendWrappedWith(ds, nil, roachpb.Header{
		Txn: &roachpb.Transaction{},
	}, put); err != nil {
		t.Fatalf("put encountered error: %s", err)
	}
	if expNodes := []roachpb.NodeID{expNodeID}; !reflect.DeepEqual(act.Nodes, expNodes) {
		t.Fatalf("got %v, expected %v", act.Nodes, expNodes)
	}

}

func makeTestGossip(t *testing.T) (*gossip.Gossip, func()) {
	n := simulation.NewNetwork(1)
	g := n.Nodes[0].Gossip

	if err := g.AddInfo(gossip.KeySentinel, nil, time.Hour); err != nil {
		t.Fatal(err)
	}
	if err := g.AddInfoProto(gossip.KeyFirstRangeDescriptor, &testRangeDescriptor, time.Hour); err != nil {
		t.Fatal(err)
	}
	nodeIDKey := gossip.MakeNodeIDKey(1)
	if err := g.AddInfoProto(nodeIDKey, &roachpb.NodeDescriptor{
		NodeID:  1,
		Address: util.MakeUnresolvedAddr(testAddress.Network(), testAddress.String()),
		Attrs:   roachpb.Attributes{Attrs: []string{"attr1", "attr2"}},
	}, time.Hour); err != nil {
		t.Fatal(err)
	}
	return g, n.Stop
}

// getNodeDescriptor returns ds.nodeDescriptor, but makes an attempt to load
// it from the Gossip network if a nil value is found.
// We must jump through hoops here to get the node descriptor because it's not available
// until after the node has joined the gossip network and been allowed to initialize
// its stores.
func (ds *DistSender) getNodeDescriptor() *roachpb.NodeDescriptor {
	if desc := atomic.LoadPointer(&ds.nodeDescriptor); desc != nil {
		return (*roachpb.NodeDescriptor)(desc)
	}
	if ds.gossip == nil {
		return nil
	}

	ownNodeID := ds.gossip.GetNodeID()
	if ownNodeID > 0 {
		// TODO(tschottdorf): Consider instead adding the NodeID of the
		// coordinator to the header, so we can get this from incoming
		// requests. Just in case we want to mostly eliminate gossip here.
		nodeDesc := &roachpb.NodeDescriptor{}
		if err := ds.gossip.GetInfoProto(gossip.MakeNodeIDKey(ownNodeID), nodeDesc); err == nil {
			atomic.StorePointer(&ds.nodeDescriptor, unsafe.Pointer(nodeDesc))
			return nodeDesc
		}
	}
	log.Infof("unable to determine this node's attributes for replica " +
		"selection; node is most likely bootstrapping")
	return nil
}

//.........這裏部分代碼省略.........
		},
		// Inconsistent Get without matching attributes but leader (node 3). Should just
		// go random as the leader does not matter.
		{
			args:       &roachpb.GetRequest{},
			attrs:      []string{},
			order:      rpc.OrderRandom,
			expReplica: []int32{1, 2, 3, 4, 5},
			leader:     2,
		},
	}

	descriptor := roachpb.RangeDescriptor{
		StartKey: roachpb.RKeyMin,
		EndKey:   roachpb.RKeyMax,
		RangeID:  rangeID,
		Replicas: nil,
	}

	// Stub to be changed in each test case.
	var verifyCall func(rpc.Options, []net.Addr) error

	var testFn rpcSendFn = func(opts rpc.Options, method string,
		addrs []net.Addr, getArgs func(addr net.Addr) proto.Message,
		getReply func() proto.Message, _ *rpc.Context) ([]proto.Message, error) {
		if err := verifyCall(opts, addrs); err != nil {
			return nil, err
		}
		return []proto.Message{getArgs(addrs[0]).(*roachpb.BatchRequest).CreateReply()}, nil
	}

	ctx := &DistSenderContext{
		RPCSend: testFn,
		RangeDescriptorDB: mockRangeDescriptorDB(func(roachpb.RKey, bool, bool) ([]roachpb.RangeDescriptor, *roachpb.Error) {
			return []roachpb.RangeDescriptor{descriptor}, nil
		}),
	}

	ds := NewDistSender(ctx, g)

	for n, tc := range testCases {
		verifyCall = makeVerifier(tc.order, tc.expReplica)
		descriptor.Replicas = nil // could do this once above, but more convenient here
		for i := int32(1); i <= 5; i++ {
			addr := util.MakeUnresolvedAddr("tcp", fmt.Sprintf("node%d", i))
			addrToNode[addr.String()] = i
			nd := &roachpb.NodeDescriptor{
				NodeID:  roachpb.NodeID(i),
				Address: util.MakeUnresolvedAddr(addr.Network(), addr.String()),
				Attrs: roachpb.Attributes{
					Attrs: nodeAttrs[i],
				},
			}
			if err := g.AddInfoProto(gossip.MakeNodeIDKey(roachpb.NodeID(i)), nd, time.Hour); err != nil {
				t.Fatal(err)
			}
			descriptor.Replicas = append(descriptor.Replicas, roachpb.ReplicaDescriptor{
				NodeID:  roachpb.NodeID(i),
				StoreID: roachpb.StoreID(i),
			})
		}

		{
			// The local node needs to get its attributes during sendRPC.
			nd := &roachpb.NodeDescriptor{
				NodeID: 6,
				Attrs: roachpb.Attributes{
					Attrs: tc.attrs,
				},
			}
			g.SetNodeID(nd.NodeID)
			if err := g.SetNodeDescriptor(nd); err != nil {
				t.Fatal(err)
			}
		}

		ds.leaderCache.Update(roachpb.RangeID(rangeID), roachpb.ReplicaDescriptor{})
		if tc.leader > 0 {
			ds.leaderCache.Update(roachpb.RangeID(rangeID), descriptor.Replicas[tc.leader-1])
		}

		args := tc.args
		args.Header().Key = roachpb.Key("a")
		if roachpb.IsRange(args) {
			args.Header().EndKey = roachpb.Key("b")
		}
		consistency := roachpb.CONSISTENT
		if !tc.consistent {
			consistency = roachpb.INCONSISTENT
		}
		// Kill the cached NodeDescriptor, enforcing a lookup from Gossip.
		ds.nodeDescriptor = nil
		if _, err := client.SendWrappedWith(ds, nil, roachpb.Header{
			RangeID:         rangeID, // Not used in this test, but why not.
			ReadConsistency: consistency,
		}, args); err != nil {
			t.Errorf("%d: %s", n, err)
		}
	}
}