Merge pull request #13219 from djcode/main

Discovery: Add support for NS records to DNS Discovery

discovery/dns/dns.go

@@ -42,6 +42,8 @@ const (
 	dnsSrvRecordPortLabel   = dnsSrvRecordPrefix + "port"
 	dnsMxRecordPrefix       = model.MetaLabelPrefix + "dns_mx_record_"
 	dnsMxRecordTargetLabel  = dnsMxRecordPrefix + "target"
+	dnsNsRecordPrefix       = model.MetaLabelPrefix + "dns_ns_record_"
+	dnsNsRecordTargetLabel  = dnsNsRecordPrefix + "target"
 
 	// Constants for instrumentation.
 	namespace = "prometheus"
@@ -102,7 +104,7 @@ func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	}
 	switch strings.ToUpper(c.Type) {
 	case "SRV":
-	case "A", "AAAA", "MX":
+	case "A", "AAAA", "MX", "NS":
 		if c.Port == 0 {
 			return errors.New("a port is required in DNS-SD configs for all record types except SRV")
 		}
@@ -140,6 +142,8 @@ func NewDiscovery(conf SDConfig, logger log.Logger) *Discovery {
 		qtype = dns.TypeSRV
 	case "MX":
 		qtype = dns.TypeMX
+	case "NS":
+		qtype = dns.TypeNS
 	}
 	d := &Discovery{
 		names:    conf.Names,
@@ -199,7 +203,7 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
 	}
 
 	for _, record := range response.Answer {
-		var target, dnsSrvRecordTarget, dnsSrvRecordPort, dnsMxRecordTarget model.LabelValue
+		var target, dnsSrvRecordTarget, dnsSrvRecordPort, dnsMxRecordTarget, dnsNsRecordTarget model.LabelValue
 
 		switch addr := record.(type) {
 		case *dns.SRV:
@@ -217,6 +221,13 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
 			addr.Mx = strings.TrimRight(addr.Mx, ".")
 
 			target = hostPort(addr.Mx, d.port)
+		case *dns.NS:
+			dnsNsRecordTarget = model.LabelValue(addr.Ns)
+
+			// Remove the final dot from rooted DNS names to make them look more usual.
+			addr.Ns = strings.TrimRight(addr.Ns, ".")
+
+			target = hostPort(addr.Ns, d.port)
 		case *dns.A:
 			target = hostPort(addr.A.String(), d.port)
 		case *dns.AAAA:
@@ -234,6 +245,7 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
 			dnsSrvRecordTargetLabel: dnsSrvRecordTarget,
 			dnsSrvRecordPortLabel:   dnsSrvRecordPort,
 			dnsMxRecordTargetLabel:  dnsMxRecordTarget,
+			dnsNsRecordTargetLabel:  dnsNsRecordTarget,
 		})
 	}
 

discovery/dns/dns_test.go

@@ -81,6 +81,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "",
 							"__meta_dns_srv_record_port":   "",
 							"__meta_dns_mx_record_target":  "",
+							"__meta_dns_ns_record_target":  "",
 						},
 					},
 				},
@@ -112,6 +113,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "",
 							"__meta_dns_srv_record_port":   "",
 							"__meta_dns_mx_record_target":  "",
+							"__meta_dns_ns_record_target":  "",
 						},
 					},
 				},
@@ -143,6 +145,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "db1.example.com.",
 							"__meta_dns_srv_record_port":   "3306",
 							"__meta_dns_mx_record_target":  "",
+							"__meta_dns_ns_record_target":  "",
 						},
 						{
 							"__address__":                  "db2.example.com:3306",
@@ -150,6 +153,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "db2.example.com.",
 							"__meta_dns_srv_record_port":   "3306",
 							"__meta_dns_mx_record_target":  "",
+							"__meta_dns_ns_record_target":  "",
 						},
 					},
 				},
@@ -180,6 +184,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "db1.example.com.",
 							"__meta_dns_srv_record_port":   "3306",
 							"__meta_dns_mx_record_target":  "",
+							"__meta_dns_ns_record_target":  "",
 						},
 					},
 				},
@@ -227,6 +232,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "",
 							"__meta_dns_srv_record_port":   "",
 							"__meta_dns_mx_record_target":  "smtp1.example.com.",
+							"__meta_dns_ns_record_target":  "",
 						},
 						{
 							"__address__":                  "smtp2.example.com:25",
@@ -234,6 +240,7 @@ func TestDNS(t *testing.T) {
 							"__meta_dns_srv_record_target": "",
 							"__meta_dns_srv_record_port":   "",
 							"__meta_dns_mx_record_target":  "smtp2.example.com.",
+							"__meta_dns_ns_record_target":  "",
 						},
 					},
 				},

docs/configuration/configuration.md

@@ -1126,7 +1126,7 @@ A DNS-based service discovery configuration allows specifying a set of DNS
 domain names which are periodically queried to discover a list of targets. The
 DNS servers to be contacted are read from `/etc/resolv.conf`.
 
-This service discovery method only supports basic DNS A, AAAA, MX and SRV
+This service discovery method only supports basic DNS A, AAAA, MX, NS and SRV
 record queries, but not the advanced DNS-SD approach specified in
 [RFC6763](https://tools.ietf.org/html/rfc6763).
 
@@ -1136,13 +1136,14 @@ The following meta labels are available on targets during [relabeling](#relabel_
 * `__meta_dns_srv_record_target`: the target field of the SRV record
 * `__meta_dns_srv_record_port`: the port field of the SRV record
 * `__meta_dns_mx_record_target`: the target field of the MX record
+* `__meta_dns_ns_record_target`: the target field of the NS record
 
 ```yaml
 # A list of DNS domain names to be queried.
 names:
   [ - <string> ]
 
-# The type of DNS query to perform. One of SRV, A, AAAA or MX.
+# The type of DNS query to perform. One of SRV, A, AAAA, MX or NS.
 [ type: <string> | default = 'SRV' ]
 
 # The port number used if the query type is not SRV.