discovery/kubernetes: select between discovery role

This adds `role` field to the Kubernetes SD config, which indicates
which type of Kubernetes SD should be run.
This no longer allows discovering pods and nodes with the same SD
configuration for example.

config/config.go

@@ -792,6 +792,7 @@ func (c *MarathonSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) erro
 // KubernetesSDConfig is the configuration for Kubernetes service discovery.
 type KubernetesSDConfig struct {
 	APIServers      []URL          `yaml:"api_servers"`
+	Role            string         `yaml:"role"`
 	InCluster       bool           `yaml:"in_cluster,omitempty"`
 	BasicAuth       *BasicAuth     `yaml:"basic_auth,omitempty"`
 	BearerToken     string         `yaml:"bearer_token,omitempty"`
@@ -804,6 +805,29 @@ type KubernetesSDConfig struct {
 	XXX map[string]interface{} `yaml:",inline"`
 }
 
+type KubernetesRole string
+
+const (
+	KubernetesRoleNode      = "node"
+	KubernetesRolePod       = "pod"
+	KubernetesRoleContainer = "container"
+	KubernetesRoleService   = "service"
+	KubernetesRoleEndpoint  = "endpoint"
+	KubernetesRoleAPIServer = "apiserver"
+)
+
+func (c *KubernetesRole) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	if err := unmarshal((*string)(c)); err != nil {
+		return err
+	}
+	switch *c {
+	case KubernetesRoleNode, KubernetesRolePod, KubernetesRoleContainer, KubernetesRoleService, KubernetesRoleEndpoint, KubernetesRoleAPIServer:
+		return nil
+	default:
+		return fmt.Errorf("Unknown Kubernetes SD role %q", c)
+	}
+}
+
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
 func (c *KubernetesSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	*c = DefaultKubernetesSDConfig
@@ -815,6 +839,9 @@ func (c *KubernetesSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 	if err := checkOverflow(c.XXX, "kubernetes_sd_config"); err != nil {
 		return err
 	}
+	if c.Role == "" {
+		return fmt.Errorf("role missing (one of: container, pod, service, endpoint, node, apiserver)")
+	}
 	if len(c.APIServers) == 0 {
 		return fmt.Errorf("Kubernetes SD configuration requires at least one Kubernetes API server")
 	}
@@ -824,7 +851,6 @@ func (c *KubernetesSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 	if c.BasicAuth != nil && (len(c.BearerToken) > 0 || len(c.BearerTokenFile) > 0) {
 		return fmt.Errorf("at most one of basic_auth, bearer_token & bearer_token_file must be configured")
 	}
-
 	return nil
 }
 

config/config_test.go

@@ -223,6 +223,7 @@ var expectedConf = &Config{
 			KubernetesSDConfigs: []*KubernetesSDConfig{
 				{
 					APIServers: []URL{kubernetesSDHostURL()},
+					Role:       KubernetesRoleEndpoint,
 					BasicAuth: &BasicAuth{
 						Username: "myusername",
 						Password: "mypassword",

config/testdata/conf.good.yml

@@ -109,7 +109,8 @@ scrape_configs:
 - job_name: service-kubernetes
 
   kubernetes_sd_configs:
-  - api_servers:
+  - role: endpoint 
+    api_servers:
     - 'https://localhost:1234'
 
     basic_auth:

config/testdata/kubernetes_bearertoken.bad.yml

@@ -2,7 +2,8 @@ scrape_configs:
   - job_name: prometheus
 
     kubernetes_sd_configs:
-    - api_servers:
+    - role: node
+      api_servers:
       - 'https://localhost:1234'
 
       bearer_token: 1234

config/testdata/kubernetes_bearertoken_basicauth.bad.yml

@@ -2,7 +2,8 @@ scrape_configs:
   - job_name: prometheus
 
     kubernetes_sd_configs:
-    - api_servers:
+    - role: pod
+      api_servers:
       - 'https://localhost:1234'
 
       bearer_token: 1234

retrieval/discovery/kubernetes/discovery.go

@@ -127,52 +127,35 @@ func (kd *Discovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	log.Debugf("Kubernetes Discovery.Run beginning")
 	defer close(ch)
 
-	var wg sync.WaitGroup
-
-	pd := &podDiscovery{
-		retryInterval: time.Duration(kd.Conf.RetryInterval),
-		kd:            kd,
-	}
-	wg.Add(1)
-	go func() {
+	switch kd.Conf.Role {
+	case config.KubernetesRolePod, config.KubernetesRoleContainer:
+		pd := &podDiscovery{
+			retryInterval: time.Duration(kd.Conf.RetryInterval),
+			kd:            kd,
+		}
 		pd.run(ctx, ch)
-		wg.Done()
-	}()
-
-	nd := &nodeDiscovery{
-		retryInterval: time.Duration(kd.Conf.RetryInterval),
-		kd:            kd,
-	}
-	wg.Add(1)
-	go func() {
+	case config.KubernetesRoleNode:
+		nd := &nodeDiscovery{
+			retryInterval: time.Duration(kd.Conf.RetryInterval),
+			kd:            kd,
+		}
 		nd.run(ctx, ch)
-		wg.Done()
-	}()
-
-	sd := &serviceDiscovery{
-		retryInterval: time.Duration(kd.Conf.RetryInterval),
-		kd:            kd,
-	}
-	wg.Add(1)
-	go func() {
+	case config.KubernetesRoleService, config.KubernetesRoleEndpoint:
+		sd := &serviceDiscovery{
+			retryInterval: time.Duration(kd.Conf.RetryInterval),
+			kd:            kd,
+		}
 		sd.run(ctx, ch)
-		wg.Done()
-	}()
-
-	// Send an initial full view.
-	// TODO(fabxc): this does not include all available services and service
-	// endpoints yet. Service endpoints were also missing in the previous Sources() method.
-	var all []*config.TargetGroup
-
-	all = append(all, kd.updateAPIServersTargetGroup())
-
-	select {
-	case ch <- all:
-	case <-ctx.Done():
+	case config.KubernetesRoleAPIServer:
+		select {
+		case ch <- []*config.TargetGroup{kd.updateAPIServersTargetGroup()}:
+		case <-ctx.Done():
+			return
+		}
+	default:
+		log.Errorf("unknown Kubernetes discovery kind %q", kd.Conf.Role)
 		return
 	}
-
-	wg.Wait()
 }
 
 func (kd *Discovery) queryAPIServerPath(path string) (*http.Response, error) {