Golang dns.Client类代码示例

func TestDNS_ServiceLookup_TagPeriod(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"v1.master"},
			Port:    12345,
		},
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("v1.master.db.service.consul.", dns.TypeSRV)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	srvRec, ok := in.Answer[0].(*dns.SRV)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if srvRec.Port != 12345 {
		t.Fatalf("Bad: %#v", srvRec)
	}
	if srvRec.Target != "foo.node.dc1.consul." {
		t.Fatalf("Bad: %#v", srvRec)
	}

	aRec, ok := in.Extra[0].(*dns.A)
	if !ok {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.Hdr.Name != "foo.node.dc1.consul." {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.A.String() != "127.0.0.1" {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
}

func TestDNS_CaseInsensitiveNodeLookup(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "Foo",
		Address:    "127.0.0.1",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("fOO.node.dc1.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("empty lookup: %#v", in)
	}
}

func TestDNS_IsAlive(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	m := new(dns.Msg)
	m.SetQuestion("_test.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	txt, ok := in.Answer[0].(*dns.TXT)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if txt.Txt[0] != "ok" {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
}

func TestDNS_ServiceLookup_CNAME(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "google",
		Address:    "www.google.com",
		Service: &structs.NodeService{
			Service: "search",
			Port:    80,
		},
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("search.service.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 4 {
		t.Fatalf("Bad: %#v", in)
	}

	// Should have google CNAME
	cnRec, ok := in.Answer[0].(*dns.CNAME)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if cnRec.Target != "www.google.com." {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}

	// Check we recursively resolve
	for i := 1; i < 4; i++ {
		if _, ok := in.Answer[i].(*dns.A); !ok {
			t.Fatalf("Bad: %#v", in.Answer[i])
		}
	}
}

func TestDNS_NodeLookup_CNAME(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "google",
		Address:    "www.google.com",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("google.node.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	// Should have the CNAME record + a few A records
	if len(in.Answer) < 2 {
		t.Fatalf("Bad: %#v", in)
	}

	cnRec, ok := in.Answer[0].(*dns.CNAME)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if cnRec.Target != "www.google.com." {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if cnRec.Hdr.Ttl != 0 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
}

func TestDNS_NodeLookup_AAAA(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "bar",
		Address:    "::4242:4242",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("bar.node.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	aRec, ok := in.Answer[0].(*dns.AAAA)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aRec.AAAA.String() != "::4242:4242" {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aRec.Hdr.Ttl != 0 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
}

// Retrieve the MX records for miek.nl.
func ExampleMX() {
	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	c := new(dns.Client)
	m := new(dns.Msg)
	m.SetQuestion("miek.nl.", dns.TypeMX)
	m.RecursionDesired = true
	r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
	if err != nil {
		return
	}
	if r.Rcode != dns.RcodeSuccess {
		return
	}
	for _, a := range r.Answer {
		if mx, ok := a.(*dns.MX); ok {
			fmt.Printf("%s\n", mx.String())
		}
	}
}

func TestDNS_ReverseLookup_CustomDomain(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()
	srv.domain = dns.Fqdn("custom")

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo2",
		Address:    "127.0.0.2",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("2.0.0.127.in-addr.arpa.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	ptrRec, ok := in.Answer[0].(*dns.PTR)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if ptrRec.Ptr != "foo2.node.dc1.custom." {
		t.Fatalf("Bad: %#v", ptrRec)
	}
}

func TestDNS_Recurse(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	m := new(dns.Msg)
	m.SetQuestion("apple.com.", dns.TypeANY)

	c := new(dns.Client)
	c.Net = "tcp"
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) == 0 {
		t.Fatalf("Bad: %#v", in)
	}
	if in.Rcode != dns.RcodeSuccess {
		t.Fatalf("Bad: %#v", in)
	}
}

// Retrieve the DNSKEY records of a zone and convert them
// to DS records for SHA1, SHA256 and SHA384.
func ExampleDS(zone string) {
	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	c := new(dns.Client)
	m := new(dns.Msg)
	if zone == "" {
		zone = "miek.nl"
	}
	m.SetQuestion(dns.Fqdn(zone), dns.TypeDNSKEY)
	m.SetEdns0(4096, true)
	r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
	if err != nil {
		return
	}
	if r.Rcode != dns.RcodeSuccess {
		return
	}
	for _, k := range r.Answer {
		if key, ok := k.(*dns.DNSKEY); ok {
			for _, alg := range []uint8{dns.SHA1, dns.SHA256, dns.SHA384} {
				fmt.Printf("%s; %d\n", key.ToDS(alg).String(), key.Flags)
			}
		}
	}
}

//.........这里部分代码省略.........
		Datacenter: "dc1",
		Node:       "bar",
		Address:    "127.0.0.2",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID: "serf",
			Name:    "serf",
			Status:  structs.HealthCritical,
		},
	}
	if err := srv.agent.RPC("Catalog.Register", args2, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args3 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "bar",
		Address:    "127.0.0.2",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthCritical,
		},
	}
	if err := srv.agent.RPC("Catalog.Register", args3, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args4 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "baz",
		Address:    "127.0.0.3",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
	}
	if err := srv.agent.RPC("Catalog.Register", args4, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args5 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "quux",
		Address:    "127.0.0.4",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthWarning,
		},
	}
	if err := srv.agent.RPC("Catalog.Register", args5, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("db.service.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	// Only 4 and 5 are not failing, so we should get 2 answers
	if len(in.Answer) != 2 {
		t.Fatalf("Bad: %#v", in)
	}

	ips := make(map[string]bool)
	for _, resp := range in.Answer {
		aRec := resp.(*dns.A)
		ips[aRec.A.String()] = true
	}

	if !ips["127.0.0.3"] {
		t.Fatalf("Bad: %#v should contain 127.0.0.3 (state healthy)", in)
	}
	if !ips["127.0.0.4"] {
		t.Fatalf("Bad: %#v should contain 127.0.0.4 (state warning)", in)
	}
}

func TestDNS_ServiceLookup_TTL(t *testing.T) {
	config := &DNSConfig{
		ServiceTTL: map[string]time.Duration{
			"db": 10 * time.Second,
			"*":  5 * time.Second,
		},
		AllowStale: true,
		MaxStale:   time.Second,
	}

	dir, srv := makeDNSServerConfig(t, config)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node with 2 services
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args = &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
		Service: &structs.NodeService{
			Service: "api",
			Port:    2222,
		},
	}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("db.service.consul.", dns.TypeSRV)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	srvRec, ok := in.Answer[0].(*dns.SRV)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if srvRec.Hdr.Ttl != 10 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}

	aRec, ok := in.Extra[0].(*dns.A)
	if !ok {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.Hdr.Ttl != 10 {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}

	m = new(dns.Msg)
	m.SetQuestion("api.service.consul.", dns.TypeSRV)
	in, _, err = c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	srvRec, ok = in.Answer[0].(*dns.SRV)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if srvRec.Hdr.Ttl != 5 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}

	aRec, ok = in.Extra[0].(*dns.A)
	if !ok {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.Hdr.Ttl != 5 {
//.........这里部分代码省略.........

func TestDNS_NodeLookup_TTL(t *testing.T) {
	config := &DNSConfig{
		NodeTTL:    10 * time.Second,
		AllowStale: true,
		MaxStale:   time.Second,
	}

	dir, srv := makeDNSServerConfig(t, config)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("foo.node.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	aRec, ok := in.Answer[0].(*dns.A)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aRec.A.String() != "127.0.0.1" {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aRec.Hdr.Ttl != 10 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}

	// Register node with IPv6
	args = &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "bar",
		Address:    "::4242:4242",
	}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	// Check an IPv6 record
	m = new(dns.Msg)
	m.SetQuestion("bar.node.consul.", dns.TypeANY)

	in, _, err = c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	aaaaRec, ok := in.Answer[0].(*dns.AAAA)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aaaaRec.AAAA.String() != "::4242:4242" {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if aaaaRec.Hdr.Ttl != 10 {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}

	// Register node with CNAME
	args = &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "google",
		Address:    "www.google.com",
	}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m = new(dns.Msg)
	m.SetQuestion("google.node.consul.", dns.TypeANY)

	in, _, err = c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
//.........这里部分代码省略.........

func TestDNS_ServiceLookup_Randomize(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register nodes
	for i := 0; i < 3*maxServiceResponses; i++ {
		args := &structs.RegisterRequest{
			Datacenter: "dc1",
			Node:       fmt.Sprintf("foo%d", i),
			Address:    fmt.Sprintf("127.0.0.%d", i+1),
			Service: &structs.NodeService{
				Service: "web",
				Port:    8000,
			},
		}

		var out struct{}
		if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
			t.Fatalf("err: %v", err)
		}
	}

	// Ensure the response is randomized each time.
	loops := 5
	uniques := map[string]struct{}{}
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	for i := 0; i < loops; i++ {
		m := new(dns.Msg)
		m.SetQuestion("web.service.consul.", dns.TypeANY)

		c := new(dns.Client)
		in, _, err := c.Exchange(m, addr.String())
		if err != nil {
			t.Fatalf("err: %v", err)
		}

		// Response length should be truncated
		// We should get an A record for each response
		if len(in.Answer) != maxServiceResponses {
			t.Fatalf("Bad: %#v", len(in.Answer))
		}

		// Collect all the names
		var names []string
		for _, rec := range in.Answer {
			switch v := rec.(type) {
			case *dns.SRV:
				names = append(names, v.Target)
			case *dns.A:
				names = append(names, v.A.String())
			}
		}
		nameS := strings.Join(names, "|")

		// Tally the results
		uniques[nameS] = struct{}{}
	}

	// Give some wiggle room. Since the responses are randomized and there
	// is a finite number of combinations, requiring 0 duplicates every
	// test run eventually gives us failures.
	if len(uniques) < (loops - 1) {
		t.Fatalf("unique response ratio too low: %d/%d\n%v",
			len(uniques), loops, uniques)
	}
}

func TestDNS_ServiceLookup_OnlyPassing(t *testing.T) {
	dir, srv := makeDNSServerConfig(t, &DNSConfig{OnlyPassing: true})
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register nodes
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthPassing,
		},
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args2 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "bar",
		Address:    "127.0.0.2",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthWarning,
		},
	}

	if err := srv.agent.RPC("Catalog.Register", args2, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args3 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "baz",
		Address:    "127.0.0.3",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthCritical,
		},
	}

	if err := srv.agent.RPC("Catalog.Register", args3, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	args4 := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "quux",
		Address:    "127.0.0.4",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"master"},
			Port:    12345,
		},
		Check: &structs.HealthCheck{
			CheckID:   "db",
			Name:      "db",
			ServiceID: "db",
			Status:    structs.HealthUnknown,
		},
	}

	if err := srv.agent.RPC("Catalog.Register", args4, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("db.service.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
//.........这里部分代码省略.........