Add leader election for autodiscover

deploy/kubernetes/metricbeat-kubernetes.yaml

@@ -367,6 +367,12 @@ rules:
   - "/metrics"
   verbs:
   - get
+- apiGroups:
+    - coordination.k8s.io
+  resources:
+    - leases
+  verbs:
+    - '*'
 ---
 apiVersion: v1
 kind: ServiceAccount

deploy/kubernetes/metricbeat/metricbeat-role.yaml

@@ -33,3 +33,9 @@ rules:
   - "/metrics"
   verbs:
   - get
+- apiGroups:
+    - coordination.k8s.io
+  resources:
+    - leases
+  verbs:
+    - '*'

go.mod

@@ -167,7 +167,7 @@ require (
 	golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae
 	golang.org/x/text v0.3.2
 	golang.org/x/time v0.0.0-20191024005414-555d28b269f0
-	golang.org/x/tools v0.0.0-20200701041122-1837592efa10
+	golang.org/x/tools v0.0.0-20200731060945-b5fad4ed8dd6
 	google.golang.org/api v0.15.0
 	google.golang.org/genproto v0.0.0-20191230161307-f3c370f40bfb
 	google.golang.org/grpc v1.29.1

libbeat/autodiscover/providers/kubernetes/config.go

@@ -44,6 +44,9 @@ type Config struct {
 	// Scope can be either node or cluster.
 	Scope    string `config:"scope"`
 	Resource string `config:"resource"`
+	// Unique identifies if this provider enables its templates only when it is elected as leader in a k8s cluster
+	Unique     bool   `config:"unique"`
+	Identifier string `config:"identifier"`
 
 	Prefix    string                  `config:"prefix"`
 	Hints     *common.Config          `config:"hints"`
@@ -60,6 +63,8 @@ func defaultConfig() *Config {
 		Resource:       "pod",
 		CleanupTimeout: 60 * time.Second,
 		Prefix:         "co.elastic",
+		Unique:         false,
+		Identifier:     "",
 	}
 }
 
@@ -98,6 +103,9 @@ func (c *Config) Validate() error {
 	if c.Scope != "node" && c.Scope != "cluster" {
 		return fmt.Errorf("invalid `scope` configured. supported values are `node` and `cluster`")
 	}
+	if c.Unique && c.Scope != "cluster" {
+		logp.L().Warnf("can only set `unique` when scope is `cluster`")
+	}
 
 	return nil
 }

libbeat/autodiscover/providers/kubernetes/kubernetes.go

@@ -20,7 +20,14 @@
 package kubernetes
 
 import (
+	"context"
 	"fmt"
+	"time"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	k8s "k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/tools/leaderelection"
+	"k8s.io/client-go/tools/leaderelection/resourcelock"
 
 	"github.com/gofrs/uuid"
 	"github.com/pkg/errors"
@@ -31,6 +38,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/common/bus"
 	"github.com/elastic/beats/v7/libbeat/common/kubernetes"
 	"github.com/elastic/beats/v7/libbeat/common/kubernetes/k8skeystore"
+	"github.com/elastic/beats/v7/libbeat/conditions"
 	"github.com/elastic/beats/v7/libbeat/keystore"
 	"github.com/elastic/beats/v7/libbeat/logp"
 )
@@ -49,13 +57,15 @@ type Eventer interface {
 
 // Provider implements autodiscover provider for docker containers
 type Provider struct {
-	config    *Config
-	bus       bus.Bus
-	templates template.Mapper
-	builders  autodiscover.Builders
-	appenders autodiscover.Appenders
-	logger    *logp.Logger
-	eventer   Eventer
+	config               *Config
+	bus                  bus.Bus
+	templates            template.Mapper
+	builders             autodiscover.Builders
+	appenders            autodiscover.Appenders
+	logger               *logp.Logger
+	eventer              Eventer
+	leaderElection       leaderelection.LeaderElectionConfig
+	cancelLeaderElection context.CancelFunc
 }
 
 // AutodiscoverBuilder builds and returns an autodiscover provider
@@ -67,11 +77,17 @@ func AutodiscoverBuilder(bus bus.Bus, uuid uuid.UUID, c *common.Config, keystore
 	}
 
 	config := defaultConfig()
+	config.Identifier = uuid.String()
 	err := c.Unpack(&config)
 	if err != nil {
 		return nil, errWrap(err)
 	}
 
+	if config.Unique {
+		// enrich the config with Unique templates before building Mapper
+		initUniqueTemplate(config)
+	}
+
 	client, err := kubernetes.GetKubernetesClient(config.KubeConfig)
 	if err != nil {
 		return nil, errWrap(err)
@@ -118,6 +134,10 @@ func AutodiscoverBuilder(bus bus.Bus, uuid uuid.UUID, c *common.Config, keystore
 		return nil, errWrap(err)
 	}
 
+	if p.config.Unique {
+		p.initLeaderElectionConfig(client, uuid.String())
+	}
+
 	return p, nil
 }
 
@@ -126,11 +146,33 @@ func (p *Provider) Start() {
 	if err := p.eventer.Start(); err != nil {
 		p.logger.Errorf("Error starting kubernetes autodiscover provider: %s", err)
 	}
+
+	if p.config.Unique {
+		ctx, cancel := context.WithCancel(context.Background())
+		p.cancelLeaderElection = cancel
+		p.StartLeaderElector(ctx, p.leaderElection)
+	}
+}
+
+// StartLeaderElector starts a Leader Elector in the background with the provided config
+func (p *Provider) StartLeaderElector(ctx context.Context, lec leaderelection.LeaderElectionConfig) {
+	le, err := leaderelection.NewLeaderElector(lec)
+	if err != nil {
+		p.logger.Errorf("leader election lock GAINED, id %v", err)
+	}
+	if lec.WatchDog != nil {
+		lec.WatchDog.SetLeaderElection(le)
+	}
+	p.logger.Debugf("Starting Leader Elector")
+	go le.Run(ctx)
 }
 
 // Stop signals the stop channel to force the watch loop routine to stop.
 func (p *Provider) Stop() {
 	p.eventer.Stop()
+	if p.cancelLeaderElection != nil {
+		p.cancelLeaderElection()
+	}
 }
 
 // String returns a description of kubernetes autodiscover provider.
@@ -154,3 +196,78 @@ func (p *Provider) publish(event bus.Event) {
 	p.appenders.Append(event)
 	p.bus.Publish(event)
 }
+
+func (p *Provider) startLeading(uuid string, eventID string) {
+	event := bus.Event{
+		"start":    true,
+		"provider": uuid,
+		"id":       eventID,
+		"unique":   "true",
+	}
+	if config := p.templates.GetConfig(event); config != nil {
+		event["config"] = config
+	}
+	p.bus.Publish(event)
+}
+
+func (p *Provider) stopLeading(uuid string, eventID string) {
+	event := bus.Event{
+		"stop":     true,
+		"provider": uuid,
+		"id":       eventID,
+		"unique":   "true",
+	}
+	if config := p.templates.GetConfig(event); config != nil {
+		event["config"] = config
+	}
+	p.bus.Publish(event)
+}
+
+func (p *Provider) initLeaderElectionConfig(client k8s.Interface, uuid string) {
+	id := "beats-leader-" + p.config.Node
+	if p.config.Identifier != "" {
+		id = id + "-" + p.config.Identifier
+	}
+	lease := metav1.ObjectMeta{
+		Name:      "beats-cluster-leader",
+		Namespace: "default",
+	}
+	metaUID := lease.GetObjectMeta().GetUID()
+	p.leaderElection = leaderelection.LeaderElectionConfig{
+		Lock: &resourcelock.LeaseLock{
+			LeaseMeta: lease,
+			Client:    client.CoordinationV1(),
+			LockConfig: resourcelock.ResourceLockConfig{
+				Identity: id,
+			},
+		},
+		ReleaseOnCancel: true,
+		LeaseDuration:   15 * time.Second,
+		RenewDeadline:   10 * time.Second,
+		RetryPeriod:     2 * time.Second,
+		Callbacks: leaderelection.LeaderCallbacks{
+			OnStartedLeading: func(ctx context.Context) {
+				p.logger.Debugf("leader election lock GAINED, id %v", id)
+				eventID := fmt.Sprintf("%v-%v", metaUID, time.Now().UnixNano())
+				p.startLeading(uuid, eventID)
+			},
+			OnStoppedLeading: func() {
+				p.logger.Debugf("leader election lock LOST, id %v", id)
+				eventID := fmt.Sprintf("%v-%v", metaUID, time.Now().UnixNano())
+				p.stopLeading(uuid, eventID)
+			},
+		},
+	}
+}
+
+func initUniqueTemplate(config *Config) {
+	m := make(map[string]interface{})
+	m["unique"] = "true"
+	fields := &conditions.Fields{}
+	fields.Unpack(m)
+	for _, template := range config.Templates {
+		template.ConditionConfig = &conditions.Config{
+			Contains: fields,
+		}
+	}
+}