interface.go

/*
Copyright 2016 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 resourcelock

import (
	"k8s.io/kubernetes/pkg/api/unversioned"
	"k8s.io/kubernetes/pkg/client/record"
)

const (
	LeaderElectionRecordAnnotationKey = "control-plane.alpha.kubernetes.io/leader"
)

// LeaderElectionRecord is the record that is stored in the leader election annotation.
// This information should be used for observational purposes only and could be replaced
// with a random string (e.g. UUID) with only slight modification of this code.
// TODO(mikedanese): this should potentially be versioned
type LeaderElectionRecord struct {
	HolderIdentity       string           `json:"holderIdentity"`
	LeaseDurationSeconds int              `json:"leaseDurationSeconds"`
	AcquireTime          unversioned.Time `json:"acquireTime"`
	RenewTime            unversioned.Time `json:"renewTime"`
	LeaderTransitions    int              `json:"leaderTransitions"`
}

// ResourceLockConfig common data that exists across different
// resource locks
type ResourceLockConfig struct {
	Identity      string
	EventRecorder record.EventRecorder
}

// Interface offers a common interface for locking on arbitrary
// resources used in leader election.  The Interface is used
// to hide the details on specific implementations in order to allow
// them to change over time.  This interface is strictly for use
// by the leaderelection code.
type Interface interface {
	// Get returns the LeaderElectionRecord
	Get() (*LeaderElectionRecord, error)

	// Create attempts to create a LeaderElectionRecord
	Create(ler LeaderElectionRecord) error

	// Update will update and existing LeaderElectionRecord
	Update(ler LeaderElectionRecord) error

	// RecordEvent is used to record events
	RecordEvent(string)

	// Identity will return the locks Identity
	Identity() string

	// Describe is used to convert details on current resource lock
	// into a string
	Describe() string
}