Add RFC-2782 style SRV lookups
This commit is contained in:
Gavin M. Roy
parent
2e56d505c0
commit
97b8960bd8
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@ -266,18 +266,33 @@ PARSE:
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goto INVALID
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}
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// Extract the service
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service := labels[n-2]
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// Support RFC 2782 style syntax
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if n == 3 && strings.HasPrefix(labels[n-2], "_") && strings.HasPrefix(labels[n-3], "_") {
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// Support "." in the label, re-join all the parts
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tag := ""
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if n >= 3 {
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tag = strings.Join(labels[:n-2], ".")
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// Grab the tag since we make nuke it if it's tcp
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tag := labels[n-2][1:]
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// Treat _name._tcp.service.consul as a default, no need to filter on that tag
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if tag == "tcp" {
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tag = ""
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}
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// _name._tag.service.consul
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d.serviceLookup(network, datacenter, labels[n-3][1:], tag, req, resp)
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// Consul 0.3 and prior format for SRV queries
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} else {
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// Support "." in the label, re-join all the parts
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tag := ""
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if n >= 3 {
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tag = strings.Join(labels[:n-2], ".")
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}
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// tag[.tag].name.service.consul
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d.serviceLookup(network, datacenter, labels[n-2], tag, req, resp)
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}
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// Handle lookup with and without tag
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d.serviceLookup(network, datacenter, service, tag, req, resp)
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case "node":
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if len(labels) == 1 {
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goto INVALID
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@ -1120,3 +1120,137 @@ func TestDNS_ServiceLookup_TTL(t *testing.T) {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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}
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func TestDNS_ServiceLookup_SRV_RFC(t *testing.T) {
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dir, srv := makeDNSServer(t)
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defer os.RemoveAll(dir)
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defer srv.agent.Shutdown()
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testutil.WaitForLeader(t, srv.agent.RPC, "dc1")
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// Register node
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args := &structs.RegisterRequest{
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Datacenter: "dc1",
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Node: "foo",
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Address: "127.0.0.1",
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Service: &structs.NodeService{
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Service: "db",
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Tags: []string{"master"},
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Port: 12345,
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},
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}
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var out struct{}
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if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
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t.Fatalf("err: %v", err)
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}
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m := new(dns.Msg)
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m.SetQuestion("_db._master.service.consul.", dns.TypeSRV)
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c := new(dns.Client)
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addr, _ := srv.agent.config.ClientListener(srv.agent.config.Ports.DNS)
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in, _, err := c.Exchange(m, addr.String())
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if err != nil {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 1 {
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t.Fatalf("Bad: %#v", in)
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}
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srvRec, ok := in.Answer[0].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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if srvRec.Port != 12345 {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Target != "foo.node.dc1.consul." {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Hdr.Ttl != 0 {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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aRec, ok := in.Extra[0].(*dns.A)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.Hdr.Name != "foo.node.dc1.consul." {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.A.String() != "127.0.0.1" {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.Hdr.Ttl != 0 {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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}
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func TestDNS_ServiceLookup_SRV_RFC_TCP_Default(t *testing.T) {
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dir, srv := makeDNSServer(t)
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defer os.RemoveAll(dir)
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defer srv.agent.Shutdown()
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testutil.WaitForLeader(t, srv.agent.RPC, "dc1")
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// Register node
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args := &structs.RegisterRequest{
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Datacenter: "dc1",
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Node: "foo",
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Address: "127.0.0.1",
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Service: &structs.NodeService{
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Service: "db",
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Tags: []string{"master"},
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Port: 12345,
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},
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}
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var out struct{}
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if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
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t.Fatalf("err: %v", err)
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}
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m := new(dns.Msg)
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m.SetQuestion("_db._tcp.service.consul.", dns.TypeSRV)
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c := new(dns.Client)
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addr, _ := srv.agent.config.ClientListener(srv.agent.config.Ports.DNS)
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in, _, err := c.Exchange(m, addr.String())
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if err != nil {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 1 {
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t.Fatalf("Bad: %#v", in)
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}
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srvRec, ok := in.Answer[0].(*dns.SRV)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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if srvRec.Port != 12345 {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Target != "foo.node.dc1.consul." {
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t.Fatalf("Bad: %#v", srvRec)
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}
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if srvRec.Hdr.Ttl != 0 {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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aRec, ok := in.Extra[0].(*dns.A)
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if !ok {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.Hdr.Name != "foo.node.dc1.consul." {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.A.String() != "127.0.0.1" {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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if aRec.Hdr.Ttl != 0 {
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t.Fatalf("Bad: %#v", in.Extra[0])
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}
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}
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@ -73,9 +73,14 @@ the node.
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## Service Lookups
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A service lookup is the alternate type of query. It is used to query for service
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providers. The format of a service lookup is like the following:
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providers and supports two mode of lookup, a strict RCF style lookup and the
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standard lookup.
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<tag>.<service>.service.<datacenter>.<domain>
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### Standard Style Lookup
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The format of a standard service lookup is like the following:
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[tag.]<service>.service[.datacenter][.domain]
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As with node lookups, the `datacenter` is optional, as is the `tag`. If no tag is
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provided, then no filtering is done on tag. So, if we want to find any redis service
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@ -114,6 +119,46 @@ SRV records.
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;; ADDITIONAL SECTION:
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foobar.node.dc1.consul. 0 IN A 10.1.10.12
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### RFC-2782 Style Lookup
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The format for RFC style lookups uses the following format:
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_<service>._<protocol>.service[.datacenter][.domain]
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Per [RFC-2782](https://www.ietf.org/rfc/rfc2782.txt), SRV queries should use
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underscores (_) as a prefix to the `service` and `protocol` values in a query to
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prevent DNS collisions. The `protocol` value can be any of the tags for a
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service or if the service has no tags, the value "tcp" should be used. If "tcp"
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is specified as the protocol, the query will not perform any tag filtering.
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Other than the query format and default "tcp" protocol/tag value, the behavior
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of the RFC style lookup is the same as the standard style of lookup.
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Using the RCF style lookup, If you registered the service "rabbitmq" on port
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5672 and tagged it with "amqp" you would query the SRV record as
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"_rabbitmq._amqp.service.consul" as illustrated in the example below:
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$ dig @127.0.0.1 -p 8600 consul.service.consul SRV
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; <<>> DiG 9.8.3-P1 <<>> @127.0.0.1 -p 8600 _rabbitmq._amqp.service.consul ANY
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52838
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;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
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;; WARNING: recursion requested but not available
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;; QUESTION SECTION:
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;_rabbitmq._amqp.service.consul. IN SRV
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;; ANSWER SECTION:
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_rabbitmq._amqp.service.consul. 0 IN SRV 1 1 5672 rabbitmq.node1.dc1.consul.
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;; ADDITIONAL SECTION:
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rabbitmq.node1.dc1.consul. 0 IN A 10.1.11.20
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### UDP Based DNS Queries
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When the DNS query is performed using UDP, Consul will truncate the results
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without setting the truncate bit. This is to prevent a redundant lookup over
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TCP which generate additional load. If the lookup is done over TCP, the results
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@ -125,4 +170,3 @@ By default, all DNS results served by Consul set a 0 TTL value. This disables
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caching of DNS results. However, there are many situations in which caching is
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desirable for performance and scalability. This is discussed more in the guide
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for [DNS Caching](/docs/guides/dns-cache.html).
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