/*
Copyright 2021 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 metrics

import (
	"sync"

	"k8s.io/component-base/metrics"
	"k8s.io/component-base/metrics/legacyregistry"
)

// JobControllerSubsystem - subsystem name used for this controller.
const JobControllerSubsystem = "job_controller"

var (
	// JobSyncDurationSeconds tracks the latency of Job syncs. Possible label
	// values:
	//   completion_mode: Indexed, NonIndexed
	//   result:          success, error
	//   action:          reconciling, tracking, pods_created, pods_deleted
	JobSyncDurationSeconds = metrics.NewHistogramVec(
		&metrics.HistogramOpts{
			Subsystem:      JobControllerSubsystem,
			Name:           "job_sync_duration_seconds",
			Help:           "The time it took to sync a job",
			StabilityLevel: metrics.ALPHA,
			Buckets:        metrics.ExponentialBuckets(0.001, 2, 15),
		},
		[]string{"completion_mode", "result", "action"},
	)
	// JobSyncNum tracks the number of Job syncs. Possible label values:
	//   completion_mode: Indexed, NonIndexed
	//   result:          success, error
	//   action:          reconciling, tracking, pods_created, pods_deleted
	JobSyncNum = metrics.NewCounterVec(
		&metrics.CounterOpts{
			Subsystem:      JobControllerSubsystem,
			Name:           "job_sync_total",
			Help:           "The number of job syncs",
			StabilityLevel: metrics.ALPHA,
		},
		[]string{"completion_mode", "result", "action"},
	)
	// JobFinishedNum tracks the number of Jobs that finish. Possible label
	// values:
	//   completion_mode: Indexed, NonIndexed
	//   result:          failed, succeeded
	JobFinishedNum = metrics.NewCounterVec(
		&metrics.CounterOpts{
			Subsystem:      JobControllerSubsystem,
			Name:           "job_finished_total",
			Help:           "The number of finished job",
			StabilityLevel: metrics.ALPHA,
		},
		[]string{"completion_mode", "result"},
	)
)

// Possible values for the "action" label in the above metrics.
const (
	// JobSyncActionReconciling when the Job's pod creation/deletion expectations
	// are unsatisfied and the controller is waiting for issued Pod
	// creation/deletions to complete.
	JobSyncActionReconciling = "reconciling"
	// JobSyncActionTracking when the Job's pod creation/deletion expectations
	// are satisfied and the number of active Pods matches expectations (i.e. no
	// pod creation/deletions issued in this sync). This is expected to be the
	// action in most of the syncs.
	JobSyncActionTracking = "tracking"
	// JobSyncActionPodsCreated when the controller creates Pods. This can happen
	// when the number of active Pods is less than the wanted Job parallelism.
	JobSyncActionPodsCreated = "pods_created"
	// JobSyncActionPodsDeleted when the controller deletes Pods. This can happen
	// if a Job is suspended or if the number of active Pods is more than
	// parallelism.
	JobSyncActionPodsDeleted = "pods_deleted"
)

var registerMetrics sync.Once

// Register registers Job controller metrics.
func Register() {
	registerMetrics.Do(func() {
		legacyregistry.MustRegister(JobSyncDurationSeconds)
		legacyregistry.MustRegister(JobSyncNum)
		legacyregistry.MustRegister(JobFinishedNum)
	})
}
