Kubernetes SD improvements

* Support multiple masters with retries against each master as required.
* Scrape masters' metrics.
* Add role meta label for node/service/master to make it easier for relabeling.

config/config.go

@@ -605,7 +605,7 @@ type MarathonSDConfig struct {
 
 // KubernetesSDConfig is the configuration for Kubernetes service discovery.
 type KubernetesSDConfig struct {
-	Server          string   `yaml:"server"`
+	Masters         []URL    `yaml:"masters"`
 	KubeletPort     int      `yaml:"kubelet_port,omitempty"`
 	InCluster       bool     `yaml:"in_cluster,omitempty"`
 	BearerTokenFile string   `yaml:"bearer_token_file,omitempty"`
@@ -641,12 +641,8 @@ func (c *KubernetesSDConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 	if err != nil {
 		return err
 	}
-	if strings.TrimSpace(c.Server) == "" {
-		return fmt.Errorf("Kubernetes SD configuration requires a server address")
-	}
-	// Make sure server ends in trailing slash - simpler URL building later
-	if !strings.HasSuffix(c.Server, "/") {
-		c.Server += "/"
+	if len(c.Masters) == 0 {
+		return fmt.Errorf("Kubernetes SD configuration requires at least one Kubernetes master")
 	}
 
 	return checkOverflow(c.XXX, "kubernetes_sd_config")

config/config_test.go

@@ -16,6 +16,7 @@ package config
 import (
 	"encoding/json"
 	"io/ioutil"
+	"net/url"
 	"reflect"
 	"strings"
 	"testing"
@@ -196,7 +197,7 @@ var expectedConf = &Config{
 
 			KubernetesSDConfigs: []*KubernetesSDConfig{
 				{
-					Server:         "https://localhost:1234/",
+					Masters:        []URL{kubernetesSDHostURL()},
 					Username:       "myusername",
 					Password:       "mypassword",
 					KubeletPort:    10255,
@@ -332,3 +333,8 @@ func TestEmptyGlobalBlock(t *testing.T) {
 		t.Fatalf("want %v, got %v", exp, c)
 	}
 }
+
+func kubernetesSDHostURL() URL {
+	tURL, _ := url.Parse("https://localhost:1234")
+	return URL{URL: tURL}
+}

config/testdata/conf.good.yml

@@ -103,6 +103,7 @@ scrape_configs:
 - job_name: service-kubernetes
 
   kubernetes_sd_configs:
-  - server: 'https://localhost:1234'
+  - masters:
+    - 'https://localhost:1234'
     username: 'myusername'
     password: 'mypassword'

documentation/examples/prometheus-kubernetes.yml

@@ -8,14 +8,18 @@ global:
 scrape_configs:
 - job_name: 'kubernetes'
 
+  ca_cert: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
+  bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
+
   kubernetes_sd_configs:
-  - server: 'https://kubernetes.default.svc'
+  - masters:
+    - 'https://kubernetes.default.svc'
     in_cluster: true
 
   relabel_configs:
-  - source_labels: [__meta_kubernetes_node, __meta_kubernetes_service_annotation_prometheus_io_scrape]
+  - source_labels: [__meta_kubernetes_role, __meta_kubernetes_service_annotation_prometheus_io_scrape]
     action: keep
-    regex: ^(?:.+;|;true)$
+    regex: ^(?:(?:master|node);.*|.*;true)$
   - source_labels: [__meta_kubernetes_service_annotation_prometheus_io_scheme]
     action: replace
     target_label: __scheme__

retrieval/discovery/kubernetes/discovery.go

@@ -53,12 +53,16 @@ const (
 	serviceAnnotationPrefix = metaLabelPrefix + "service_annotation_"
 	// nodesTargetGroupName is the name given to the target group for nodes.
 	nodesTargetGroupName = "nodes"
+	// mastersTargetGroupName is the name given to the target group for masters.
+	mastersTargetGroupName = "masters"
+	// roleLabel is the name for the label containing a target's role.
+	roleLabel = metaLabelPrefix + "role"
 
 	serviceAccountToken  = "/var/run/secrets/kubernetes.io/serviceaccount/token"
 	serviceAccountCACert = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
 
 	apiVersion          = "v1"
-	apiPrefix           = "api/" + apiVersion
+	apiPrefix           = "/api/" + apiVersion
 	nodesURL            = apiPrefix + "/nodes"
 	servicesURL         = apiPrefix + "/services"
 	endpointsURL        = apiPrefix + "/endpoints"
@@ -70,6 +74,8 @@ type Discovery struct {
 	client *http.Client
 	Conf   *config.KubernetesSDConfig
 
+	masters                  []config.URL
+	mastersMu                sync.RWMutex
 	nodesResourceVersion     string
 	servicesResourceVersion  string
 	endpointsResourceVersion string
@@ -88,6 +94,7 @@ func (kd *Discovery) Initialize() error {
 		return err
 	}
 
+	kd.masters = kd.Conf.Masters
 	kd.client = client
 	kd.nodes = map[string]*Node{}
 	kd.services = map[string]map[string]*Service{}
@@ -98,7 +105,12 @@ func (kd *Discovery) Initialize() error {
 
 // Sources implements the TargetProvider interface.
 func (kd *Discovery) Sources() []string {
-	res, err := kd.client.Get(kd.Conf.Server + nodesURL)
+	sourceNames := make([]string, 0, len(kd.masters))
+	for _, master := range kd.masters {
+		sourceNames = append(sourceNames, mastersTargetGroupName+":"+master.Host)
+	}
+
+	res, err := kd.queryMasterPath(nodesURL)
 	if err != nil {
 		// If we can't list nodes then we can't watch them. Assume this is a misconfiguration
 		// & log & return empty.
@@ -120,15 +132,13 @@ func (kd *Discovery) Sources() []string {
 	kd.nodesMu.Lock()
 	defer kd.nodesMu.Unlock()
 
-	sourceNames := make([]string, 0, len(nodes.Items))
-
 	kd.nodesResourceVersion = nodes.ResourceVersion
 	for idx, node := range nodes.Items {
 		sourceNames = append(sourceNames, nodesTargetGroupName+":"+node.ObjectMeta.Name)
 		kd.nodes[node.ObjectMeta.Name] = &nodes.Items[idx]
 	}
 
-	res, err = kd.client.Get(kd.Conf.Server + servicesURL)
+	res, err = kd.queryMasterPath(servicesURL)
 	if err != nil {
 		// If we can't list services then we can't watch them. Assume this is a misconfiguration
 		// & log & return empty.
@@ -166,6 +176,12 @@ func (kd *Discovery) Sources() []string {
 func (kd *Discovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
 
+	select {
+	case ch <- kd.updateMastersTargetGroup():
+	case <-done:
+		return
+	}
+
 	select {
 	case ch <- kd.updateNodesTargetGroup():
 	case <-done:
@@ -215,11 +231,78 @@ func (kd *Discovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	}
 }
 
+func (kd *Discovery) queryMasterPath(path string) (*http.Response, error) {
+	req, err := http.NewRequest("GET", path, nil)
+	if err != nil {
+		return nil, err
+	}
+	return kd.queryMasterReq(req)
+}
+
+func (kd *Discovery) queryMasterReq(req *http.Request) (*http.Response, error) {
+	// Lock in case we need to rotate masters to request.
+	kd.mastersMu.Lock()
+	defer kd.mastersMu.Unlock()
+	for i := 0; i < len(kd.masters); i++ {
+		cloneReq := *req
+		cloneReq.URL.Host = kd.masters[0].Host
+		cloneReq.URL.Scheme = kd.masters[0].Scheme
+		res, err := kd.client.Do(&cloneReq)
+		if err == nil {
+			return res, nil
+		}
+		kd.rotateMasters()
+	}
+	return nil, fmt.Errorf("Unable to query any masters")
+}
+
+func (kd *Discovery) rotateMasters() {
+	if len(kd.masters) > 1 {
+		kd.masters = append(kd.masters[1:], kd.masters[0])
+	}
+}
+
+func (kd *Discovery) updateMastersTargetGroup() *config.TargetGroup {
+	tg := &config.TargetGroup{
+		Source: mastersTargetGroupName,
+		Labels: model.LabelSet{
+			roleLabel: model.LabelValue("master"),
+		},
+	}
+
+	for _, master := range kd.masters {
+		masterAddress := master.Host
+		_, _, err := net.SplitHostPort(masterAddress)
+		// If error then no port is specified - use default for scheme.
+		if err != nil {
+			switch master.Scheme {
+			case "http":
+				masterAddress = net.JoinHostPort(masterAddress, "80")
+			case "https":
+				masterAddress = net.JoinHostPort(masterAddress, "443")
+			}
+		}
+
+		t := model.LabelSet{
+			model.AddressLabel: model.LabelValue(masterAddress),
+			model.SchemeLabel:  model.LabelValue(master.Scheme),
+		}
+		tg.Targets = append(tg.Targets, t)
+	}
+
+	return tg
+}
+
 func (kd *Discovery) updateNodesTargetGroup() *config.TargetGroup {
 	kd.nodesMu.Lock()
 	defer kd.nodesMu.Unlock()
 
-	tg := &config.TargetGroup{Source: nodesTargetGroupName}
+	tg := &config.TargetGroup{
+		Source: nodesTargetGroupName,
+		Labels: model.LabelSet{
+			roleLabel: model.LabelValue("node"),
+		},
+	}
 
 	// Now let's loop through the nodes & add them to the target group with appropriate labels.
 	for nodeName, node := range kd.nodes {
@@ -256,7 +339,7 @@ func (kd *Discovery) updateNode(node *Node, eventType EventType) {
 // watchNodes watches nodes as they come & go.
 func (kd *Discovery) watchNodes(events chan interface{}, done <-chan struct{}, retryInterval time.Duration) {
 	until(func() {
-		req, err := http.NewRequest("GET", kd.Conf.Server+nodesURL, nil)
+		req, err := http.NewRequest("GET", nodesURL, nil)
 		if err != nil {
 			log.Errorf("Failed to watch nodes: %s", err)
 			return
@@ -265,7 +348,7 @@ func (kd *Discovery) watchNodes(events chan interface{}, done <-chan struct{}, r
 		values.Add("watch", "true")
 		values.Add("resourceVersion", kd.nodesResourceVersion)
 		req.URL.RawQuery = values.Encode()
-		res, err := kd.client.Do(req)
+		res, err := kd.queryMasterReq(req)
 		if err != nil {
 			log.Errorf("Failed to watch nodes: %s", err)
 			return
@@ -296,7 +379,7 @@ func (kd *Discovery) watchNodes(events chan interface{}, done <-chan struct{}, r
 // watchServices watches services as they come & go.
 func (kd *Discovery) watchServices(events chan interface{}, done <-chan struct{}, retryInterval time.Duration) {
 	until(func() {
-		req, err := http.NewRequest("GET", kd.Conf.Server+servicesURL, nil)
+		req, err := http.NewRequest("GET", servicesURL, nil)
 		if err != nil {
 			log.Errorf("Failed to watch services: %s", err)
 			return
@@ -306,7 +389,7 @@ func (kd *Discovery) watchServices(events chan interface{}, done <-chan struct{}
 		values.Add("resourceVersion", kd.servicesResourceVersion)
 		req.URL.RawQuery = values.Encode()
 
-		res, err := kd.client.Do(req)
+		res, err := kd.queryMasterReq(req)
 		if err != nil {
 			log.Errorf("Failed to watch services: %s", err)
 			return
@@ -376,7 +459,7 @@ func (kd *Discovery) addService(service *Service) *config.TargetGroup {
 	namespace[service.ObjectMeta.Name] = service
 	endpointURL := fmt.Sprintf(serviceEndpointsURL, service.ObjectMeta.Namespace, service.ObjectMeta.Name)
 
-	res, err := kd.client.Get(kd.Conf.Server + endpointURL)
+	res, err := kd.queryMasterPath(endpointURL)
 	if err != nil {
 		log.Errorf("Error getting service endpoints: %s", err)
 		return nil
@@ -401,6 +484,7 @@ func (kd *Discovery) updateServiceTargetGroup(service *Service, eps *Endpoints)
 		Labels: model.LabelSet{
 			serviceNamespaceLabel: model.LabelValue(service.ObjectMeta.Namespace),
 			serviceNameLabel:      model.LabelValue(service.ObjectMeta.Name),
+			roleLabel:             model.LabelValue("service"),
 		},
 	}
 
@@ -437,7 +521,7 @@ func (kd *Discovery) updateServiceTargetGroup(service *Service, eps *Endpoints)
 // watchServiceEndpoints watches service endpoints as they come & go.
 func (kd *Discovery) watchServiceEndpoints(events chan interface{}, done <-chan struct{}, retryInterval time.Duration) {
 	until(func() {
-		req, err := http.NewRequest("GET", kd.Conf.Server+endpointsURL, nil)
+		req, err := http.NewRequest("GET", endpointsURL, nil)
 		if err != nil {
 			log.Errorf("Failed to watch service endpoints: %s", err)
 			return
@@ -447,7 +531,7 @@ func (kd *Discovery) watchServiceEndpoints(events chan interface{}, done <-chan
 		values.Add("resourceVersion", kd.servicesResourceVersion)
 		req.URL.RawQuery = values.Encode()
 
-		res, err := kd.client.Do(req)
+		res, err := kd.queryMasterReq(req)
 		if err != nil {
 			log.Errorf("Failed to watch service endpoints: %s", err)
 			return