added vendors

vendor/k8s.io/client-go/tools/leaderelection/leaderelection.go

@@ -0,0 +1,274 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package leaderelection implements leader election of a set of endpoints.
+// It uses an annotation in the endpoints object to store the record of the
+// election state.
+//
+// This implementation does not guarantee that only one client is acting as a
+// leader (a.k.a. fencing). A client observes timestamps captured locally to
+// infer the state of the leader election. Thus the implementation is tolerant
+// to arbitrary clock skew, but is not tolerant to arbitrary clock skew rate.
+//
+// However the level of tolerance to skew rate can be configured by setting
+// RenewDeadline and LeaseDuration appropriately. The tolerance expressed as a
+// maximum tolerated ratio of time passed on the fastest node to time passed on
+// the slowest node can be approximately achieved with a configuration that sets
+// the same ratio of LeaseDuration to RenewDeadline. For example if a user wanted
+// to tolerate some nodes progressing forward in time twice as fast as other nodes,
+// the user could set LeaseDuration to 60 seconds and RenewDeadline to 30 seconds.
+//
+// While not required, some method of clock synchronization between nodes in the
+// cluster is highly recommended. It's important to keep in mind when configuring
+// this client that the tolerance to skew rate varies inversely to master
+// availability.
+//
+// Larger clusters often have a more lenient SLA for API latency. This should be
+// taken into account when configuring the client. The rate of leader transitions
+// should be monitored and RetryPeriod and LeaseDuration should be increased
+// until the rate is stable and acceptably low. It's important to keep in mind
+// when configuring this client that the tolerance to API latency varies inversely
+// to master availability.
+//
+// DISCLAIMER: this is an alpha API. This library will likely change significantly
+// or even be removed entirely in subsequent releases. Depend on this API at
+// your own risk.
+package leaderelection
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	rl "k8s.io/client-go/tools/leaderelection/resourcelock"
+
+	"github.com/golang/glog"
+)
+
+const (
+	JitterFactor = 1.2
+)
+
+// NewLeaderElector creates a LeaderElector from a LeaderElectionConfig
+func NewLeaderElector(lec LeaderElectionConfig) (*LeaderElector, error) {
+	if lec.LeaseDuration <= lec.RenewDeadline {
+		return nil, fmt.Errorf("leaseDuration must be greater than renewDeadline")
+	}
+	if lec.RenewDeadline <= time.Duration(JitterFactor*float64(lec.RetryPeriod)) {
+		return nil, fmt.Errorf("renewDeadline must be greater than retryPeriod*JitterFactor")
+	}
+	if lec.Lock == nil {
+		return nil, fmt.Errorf("Lock must not be nil.")
+	}
+	return &LeaderElector{
+		config: lec,
+	}, nil
+}
+
+type LeaderElectionConfig struct {
+	// Lock is the resource that will be used for locking
+	Lock rl.Interface
+
+	// LeaseDuration is the duration that non-leader candidates will
+	// wait to force acquire leadership. This is measured against time of
+	// last observed ack.
+	LeaseDuration time.Duration
+	// RenewDeadline is the duration that the acting master will retry
+	// refreshing leadership before giving up.
+	RenewDeadline time.Duration
+	// RetryPeriod is the duration the LeaderElector clients should wait
+	// between tries of actions.
+	RetryPeriod time.Duration
+
+	// Callbacks are callbacks that are triggered during certain lifecycle
+	// events of the LeaderElector
+	Callbacks LeaderCallbacks
+}
+
+// LeaderCallbacks are callbacks that are triggered during certain
+// lifecycle events of the LeaderElector. These are invoked asynchronously.
+//
+// possible future callbacks:
+//  * OnChallenge()
+type LeaderCallbacks struct {
+	// OnStartedLeading is called when a LeaderElector client starts leading
+	OnStartedLeading func(stop <-chan struct{})
+	// OnStoppedLeading is called when a LeaderElector client stops leading
+	OnStoppedLeading func()
+	// OnNewLeader is called when the client observes a leader that is
+	// not the previously observed leader. This includes the first observed
+	// leader when the client starts.
+	OnNewLeader func(identity string)
+}
+
+// LeaderElector is a leader election client.
+//
+// possible future methods:
+//  * (le *LeaderElector) IsLeader()
+//  * (le *LeaderElector) GetLeader()
+type LeaderElector struct {
+	config LeaderElectionConfig
+	// internal bookkeeping
+	observedRecord rl.LeaderElectionRecord
+	observedTime   time.Time
+	// used to implement OnNewLeader(), may lag slightly from the
+	// value observedRecord.HolderIdentity if the transition has
+	// not yet been reported.
+	reportedLeader string
+}
+
+// Run starts the leader election loop
+func (le *LeaderElector) Run() {
+	defer func() {
+		runtime.HandleCrash()
+		le.config.Callbacks.OnStoppedLeading()
+	}()
+	le.acquire()
+	stop := make(chan struct{})
+	go le.config.Callbacks.OnStartedLeading(stop)
+	le.renew()
+	close(stop)
+}
+
+// RunOrDie starts a client with the provided config or panics if the config
+// fails to validate.
+func RunOrDie(lec LeaderElectionConfig) {
+	le, err := NewLeaderElector(lec)
+	if err != nil {
+		panic(err)
+	}
+	le.Run()
+}
+
+// GetLeader returns the identity of the last observed leader or returns the empty string if
+// no leader has yet been observed.
+func (le *LeaderElector) GetLeader() string {
+	return le.observedRecord.HolderIdentity
+}
+
+// IsLeader returns true if the last observed leader was this client else returns false.
+func (le *LeaderElector) IsLeader() bool {
+	return le.observedRecord.HolderIdentity == le.config.Lock.Identity()
+}
+
+// acquire loops calling tryAcquireOrRenew and returns immediately when tryAcquireOrRenew succeeds.
+func (le *LeaderElector) acquire() {
+	stop := make(chan struct{})
+	desc := le.config.Lock.Describe()
+	glog.Infof("attempting to acquire leader lease  %v...", desc)
+	wait.JitterUntil(func() {
+		succeeded := le.tryAcquireOrRenew()
+		le.maybeReportTransition()
+		if !succeeded {
+			glog.V(4).Infof("failed to acquire lease %v", desc)
+			return
+		}
+		le.config.Lock.RecordEvent("became leader")
+		glog.Infof("successfully acquired lease %v", desc)
+		close(stop)
+	}, le.config.RetryPeriod, JitterFactor, true, stop)
+}
+
+// renew loops calling tryAcquireOrRenew and returns immediately when tryAcquireOrRenew fails.
+func (le *LeaderElector) renew() {
+	stop := make(chan struct{})
+	wait.Until(func() {
+		err := wait.Poll(le.config.RetryPeriod, le.config.RenewDeadline, func() (bool, error) {
+			return le.tryAcquireOrRenew(), nil
+		})
+		le.maybeReportTransition()
+		desc := le.config.Lock.Describe()
+		if err == nil {
+			glog.V(4).Infof("successfully renewed lease %v", desc)
+			return
+		}
+		le.config.Lock.RecordEvent("stopped leading")
+		glog.Infof("failed to renew lease %v: %v", desc, err)
+		close(stop)
+	}, 0, stop)
+}
+
+// tryAcquireOrRenew tries to acquire a leader lease if it is not already acquired,
+// else it tries to renew the lease if it has already been acquired. Returns true
+// on success else returns false.
+func (le *LeaderElector) tryAcquireOrRenew() bool {
+	now := metav1.Now()
+	leaderElectionRecord := rl.LeaderElectionRecord{
+		HolderIdentity:       le.config.Lock.Identity(),
+		LeaseDurationSeconds: int(le.config.LeaseDuration / time.Second),
+		RenewTime:            now,
+		AcquireTime:          now,
+	}
+
+	// 1. obtain or create the ElectionRecord
+	oldLeaderElectionRecord, err := le.config.Lock.Get()
+	if err != nil {
+		if !errors.IsNotFound(err) {
+			glog.Errorf("error retrieving resource lock %v: %v", le.config.Lock.Describe(), err)
+			return false
+		}
+		if err = le.config.Lock.Create(leaderElectionRecord); err != nil {
+			glog.Errorf("error initially creating leader election record: %v", err)
+			return false
+		}
+		le.observedRecord = leaderElectionRecord
+		le.observedTime = time.Now()
+		return true
+	}
+
+	// 2. Record obtained, check the Identity & Time
+	if !reflect.DeepEqual(le.observedRecord, *oldLeaderElectionRecord) {
+		le.observedRecord = *oldLeaderElectionRecord
+		le.observedTime = time.Now()
+	}
+	if le.observedTime.Add(le.config.LeaseDuration).After(now.Time) &&
+		oldLeaderElectionRecord.HolderIdentity != le.config.Lock.Identity() {
+		glog.V(4).Infof("lock is held by %v and has not yet expired", oldLeaderElectionRecord.HolderIdentity)
+		return false
+	}
+
+	// 3. We're going to try to update. The leaderElectionRecord is set to it's default
+	// here. Let's correct it before updating.
+	if oldLeaderElectionRecord.HolderIdentity == le.config.Lock.Identity() {
+		leaderElectionRecord.AcquireTime = oldLeaderElectionRecord.AcquireTime
+		leaderElectionRecord.LeaderTransitions = oldLeaderElectionRecord.LeaderTransitions
+	} else {
+		leaderElectionRecord.LeaderTransitions = oldLeaderElectionRecord.LeaderTransitions + 1
+	}
+
+	// update the lock itself
+	if err = le.config.Lock.Update(leaderElectionRecord); err != nil {
+		glog.Errorf("Failed to update lock: %v", err)
+		return false
+	}
+	le.observedRecord = leaderElectionRecord
+	le.observedTime = time.Now()
+	return true
+}
+
+func (l *LeaderElector) maybeReportTransition() {
+	if l.observedRecord.HolderIdentity == l.reportedLeader {
+		return
+	}
+	l.reportedLeader = l.observedRecord.HolderIdentity
+	if l.config.Callbacks.OnNewLeader != nil {
+		go l.config.Callbacks.OnNewLeader(l.reportedLeader)
+	}
+}