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Support using MX records for DNS discovery (#10099)
It's currently possible to use blackbox_exporter to probe MX records themselves. However it's not possible to do an end-to-end test, like is possible with SRV records. This makes it possible to use MX records as a source of hostnames in the same way as SRV records. Signed-off-by: David Leadbeater <dgl@dgl.cx>
This commit is contained in:
David Leadbeater
GitHub
parent
a7f19b5775
commit
d677ec489e
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@ -40,6 +40,8 @@ const (
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dnsSrvRecordPrefix = model.MetaLabelPrefix + "dns_srv_record_"
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dnsSrvRecordTargetLabel = dnsSrvRecordPrefix + "target"
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dnsSrvRecordPortLabel = dnsSrvRecordPrefix + "port"
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dnsMxRecordPrefix = model.MetaLabelPrefix + "dns_mx_record_"
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dnsMxRecordTargetLabel = dnsMxRecordPrefix + "target"
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// Constants for instrumentation.
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namespace = "prometheus"
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@ -100,7 +102,7 @@ func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
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}
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switch strings.ToUpper(c.Type) {
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case "SRV":
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case "A", "AAAA":
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case "A", "AAAA", "MX":
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if c.Port == 0 {
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return errors.New("a port is required in DNS-SD configs for all record types except SRV")
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}
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@ -136,6 +138,8 @@ func NewDiscovery(conf SDConfig, logger log.Logger) *Discovery {
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qtype = dns.TypeAAAA
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case "SRV":
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qtype = dns.TypeSRV
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case "MX":
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qtype = dns.TypeMX
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}
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d := &Discovery{
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names: conf.Names,
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@ -195,7 +199,7 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
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}
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for _, record := range response.Answer {
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var target, dnsSrvRecordTarget, dnsSrvRecordPort model.LabelValue
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var target, dnsSrvRecordTarget, dnsSrvRecordPort, dnsMxRecordTarget model.LabelValue
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switch addr := record.(type) {
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case *dns.SRV:
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@ -206,6 +210,13 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
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addr.Target = strings.TrimRight(addr.Target, ".")
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target = hostPort(addr.Target, int(addr.Port))
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case *dns.MX:
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dnsMxRecordTarget = model.LabelValue(addr.Mx)
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// Remove the final dot from rooted DNS names to make them look more usual.
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addr.Mx = strings.TrimRight(addr.Mx, ".")
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target = hostPort(addr.Mx, d.port)
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case *dns.A:
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target = hostPort(addr.A.String(), d.port)
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case *dns.AAAA:
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@ -222,6 +233,7 @@ func (d *Discovery) refreshOne(ctx context.Context, name string, ch chan<- *targ
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dnsNameLabel: model.LabelValue(name),
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dnsSrvRecordTargetLabel: dnsSrvRecordTarget,
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dnsSrvRecordPortLabel: dnsSrvRecordPort,
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dnsMxRecordTargetLabel: dnsMxRecordTarget,
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})
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}
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@ -80,6 +80,7 @@ func TestDNS(t *testing.T) {
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"__meta_dns_name": "web.example.com.",
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"__meta_dns_srv_record_target": "",
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"__meta_dns_srv_record_port": "",
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"__meta_dns_mx_record_target": "",
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},
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},
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},
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@ -110,6 +111,7 @@ func TestDNS(t *testing.T) {
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"__meta_dns_name": "web.example.com.",
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"__meta_dns_srv_record_target": "",
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"__meta_dns_srv_record_port": "",
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"__meta_dns_mx_record_target": "",
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},
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},
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},
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@ -140,12 +142,14 @@ func TestDNS(t *testing.T) {
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"__meta_dns_name": "_mysql._tcp.db.example.com.",
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"__meta_dns_srv_record_target": "db1.example.com.",
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"__meta_dns_srv_record_port": "3306",
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"__meta_dns_mx_record_target": "",
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},
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{
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"__address__": "db2.example.com:3306",
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"__meta_dns_name": "_mysql._tcp.db.example.com.",
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"__meta_dns_srv_record_target": "db2.example.com.",
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"__meta_dns_srv_record_port": "3306",
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"__meta_dns_mx_record_target": "",
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},
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},
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},
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@ -175,6 +179,7 @@ func TestDNS(t *testing.T) {
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"__meta_dns_name": "_mysql._tcp.db.example.com.",
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"__meta_dns_srv_record_target": "db1.example.com.",
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"__meta_dns_srv_record_port": "3306",
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"__meta_dns_mx_record_target": "",
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},
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},
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},
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@ -195,6 +200,45 @@ func TestDNS(t *testing.T) {
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},
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},
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},
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{
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name: "MX record query",
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config: SDConfig{
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Names: []string{"example.com."},
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Type: "MX",
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Port: 25,
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RefreshInterval: model.Duration(time.Minute),
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},
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lookup: func(name string, qtype uint16, logger log.Logger) (*dns.Msg, error) {
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return &dns.Msg{
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Answer: []dns.RR{
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&dns.MX{Preference: 0, Mx: "smtp1.example.com."},
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&dns.MX{Preference: 10, Mx: "smtp2.example.com."},
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},
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},
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nil
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},
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expected: []*targetgroup.Group{
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{
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Source: "example.com.",
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Targets: []model.LabelSet{
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{
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"__address__": "smtp1.example.com:25",
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"__meta_dns_name": "example.com.",
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"__meta_dns_srv_record_target": "",
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"__meta_dns_srv_record_port": "",
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"__meta_dns_mx_record_target": "smtp1.example.com.",
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},
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{
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"__address__": "smtp2.example.com:25",
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"__meta_dns_name": "example.com.",
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"__meta_dns_srv_record_target": "",
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"__meta_dns_srv_record_port": "",
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"__meta_dns_mx_record_target": "smtp2.example.com.",
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},
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},
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},
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},
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},
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}
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for _, tc := range testCases {
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@ -961,8 +961,8 @@ A DNS-based service discovery configuration allows specifying a set of DNS
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domain names which are periodically queried to discover a list of targets. The
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DNS servers to be contacted are read from `/etc/resolv.conf`.
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This service discovery method only supports basic DNS A, AAAA and SRV record
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queries, but not the advanced DNS-SD approach specified in
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This service discovery method only supports basic DNS A, AAAA, MX and SRV
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record queries, but not the advanced DNS-SD approach specified in
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[RFC6763](https://tools.ietf.org/html/rfc6763).
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The following meta labels are available on targets during [relabeling](#relabel_config):
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@ -970,13 +970,14 @@ The following meta labels are available on targets during [relabeling](#relabel_
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* `__meta_dns_name`: the record name that produced the discovered target.
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* `__meta_dns_srv_record_target`: the target field of the SRV record
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* `__meta_dns_srv_record_port`: the port field of the SRV record
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* `__meta_dns_mx_record_target`: the target field of the MX record
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```yaml
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# A list of DNS domain names to be queried.
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names:
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[ - <string> ]
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# The type of DNS query to perform. One of SRV, A, or AAAA.
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# The type of DNS query to perform. One of SRV, A, AAAA or MX.
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[ type: <string> | default = 'SRV' ]
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# The port number used if the query type is not SRV.
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