plugin/nomad: Support service filtering (#7724)

Signed-off-by: Olli Janatuinen <olli.janatuinen@gmail.com>

plugin/nomad/README.md

@@ -80,6 +80,7 @@ With only the plugin specified, the *nomad* plugin will default to `service.noma
 ~~~ txt
 nomad [ZONE] {
     address URL
+    filter FILTER
     token TOKEN
     ttl DURATION
 }
@@ -87,6 +88,8 @@ nomad [ZONE] {
 
 * `address` The address where a Nomad agent (server) is available. **URL** defaults to `http://127.0.0.1:4646`.
 
+* `filter` allows you to filter Nomad services. **FILTER** defaults to `""`. Uses [filtering](https://developer.hashicorp.com/nomad/api-docs#filtering) syntax.
+
 * `token` The SecretID of an ACL token to use to authenticate API requests with if the Nomad cluster has ACL enabled. **TOKEN** defaults to `""`.
 
 * `ttl` allows you to set a custom TTL for responses. **DURATION** defaults to `30 seconds`. The minimum TTL allowed is `0` seconds, and the maximum is capped at `3600` seconds. Setting TTL to 0 will prevent records from being cached. The unit for the value is seconds.

plugin/nomad/nomad.go

@@ -29,6 +29,7 @@ type Nomad struct {
 	Zone    string
 	clients []*api.Client
 	current int
+	filter  string
 }
 
 func (n *Nomad) Name() string {
@@ -103,7 +104,7 @@ func fetchServiceRegistrations(n Nomad, serviceName, namespace string) ([]*api.S
 	if err != nil {
 		return nil, nil, err
 	}
-	return nc.Services().Get(serviceName, (&api.QueryOptions{Namespace: namespace}))
+	return nc.Services().Get(serviceName, (&api.QueryOptions{Namespace: namespace, Filter: n.filter}))
 }
 
 func handleServiceLookupError(w dns.ResponseWriter, m *dns.Msg, ctx context.Context, namespace string) (int, error) {

plugin/nomad/setup.go

@@ -77,6 +77,12 @@ func parse(c *caddy.Controller, n *Nomad) error {
 				return c.Err("at least one address is required")
 			}
 			addresses = append(addresses, args...)
+		case "filter":
+			args := c.RemainingArgs()
+			if len(args) != 1 {
+				return c.Err("exactly one filter is required")
+			}
+			n.filter = args[0]
 		case "token":
 			args := c.RemainingArgs()
 			if len(args) != 1 {

plugin/nomad/setup_test.go

@@ -13,6 +13,7 @@ func TestSetupNomad(t *testing.T) {
 		name           string
 		config         string
 		shouldErr      bool
+		expectedFilter string
 		expectedTTL    uint32
 	}{
 		{
@@ -23,17 +24,20 @@ nomad service.nomad {
     token test-token
 }`,
 			shouldErr:      false,
+			expectedFilter: "",
 			expectedTTL:    uint32(defaultTTL),
 		},
 		{
-			name: "valid_config_custom_ttl",
+			name: "valid_config_custom_filter_and_ttl",
 			config: `
 nomad service.nomad {
     address http://127.0.0.1:4646
+	filter "Tags not contains candidate"
     token test-token
     ttl 60
 }`,
 			shouldErr:      false,
+			expectedFilter: "Tags not contains candidate",
 			expectedTTL:    60,
 		},
 		{
@@ -85,6 +89,7 @@ nomad service.nomad {
 				ttl:     uint32(defaultTTL),
 				clients: make([]*nomad.Client, 0),
 				current: -1,
+				filter:  "",
 			}
 
 			err := parse(c, n)