text: /*
  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 workqueue
  
  import (
  	"sync"
  	"time"
  )
  
  // This file provides abstractions for setting the provider (e.g., prometheus)
  // of metrics.
  
  type queueMetrics interface {
  	add(item t)
  	get(item t)
  	done(item t)
  }
  
  // GaugeMetric represents a single numerical value that can arbitrarily go up
  // and down.
  type GaugeMetric interface {
  	Inc()
  	Dec()
  }
  
  // CounterMetric represents a single numerical value that only ever
  // goes up.
  type CounterMetric interface {
  	Inc()
  }
  
  // SummaryMetric captures individual observations.
  type SummaryMetric interface {
  	Observe(float64)
  }
  
  type noopMetric struct{}
  
  func (noopMetric) Inc()            {}
  func (noopMetric) Dec()            {}
  func (noopMetric) Observe(float64) {}
  
  type defaultQueueMetrics struct {
  	// current depth of a workqueue
  	depth GaugeMetric
  	// total number of adds handled by a workqueue
  	adds CounterMetric
  	// how long an item stays in a workqueue
  	latency SummaryMetric
  	// how long processing an item from a workqueue takes
  	workDuration         SummaryMetric
  	addTimes             map[t]time.Time
  	processingStartTimes map[t]time.Time
  }
  
  func (m *defaultQueueMetrics) add(item t) {
  	if m == nil {
  		return
  	}
  
  	m.adds.Inc()
  	m.depth.Inc()
  	if _, exists := m.addTimes[item]; !exists {
  		m.addTimes[item] = time.Now()
  	}
  }
  
  func (m *defaultQueueMetrics) get(item t) {
  	if m == nil {
  		return
  	}
  
  	m.depth.Dec()
  	m.processingStartTimes[item] = time.Now()
  	if startTime, exists := m.addTimes[item]; exists {
  		m.latency.Observe(sinceInMicroseconds(startTime))
  		delete(m.addTimes, item)
  	}
  }
  
  func (m *defaultQueueMetrics) done(item t) {
  	if m == nil {
  		return
  	}
  
  	if startTime, exists := m.processingStartTimes[item]; exists {
  		m.workDuration.Observe(sinceInMicroseconds(startTime))
  		delete(m.processingStartTimes, item)
  	}
  }
  
  // Gets the time since the specified start in microseconds.
  func sinceInMicroseconds(start time.Time) float64 {
  	return float64(time.Since(start).Nanoseconds() / time.Microsecond.Nanoseconds())
  }
  
  type retryMetrics interface {
  	retry()
  }
  
  type defaultRetryMetrics struct {
  	retries CounterMetric
  }
  
  func (m *defaultRetryMetrics) retry() {
  	if m == nil {
  		return
  	}
  
  	m.retries.Inc()
  }
  
  // MetricsProvider generates various metrics used by the queue.
  type MetricsProvider interface {
  	NewDepthMetric(name string) GaugeMetric
  	NewAddsMetric(name string) CounterMetric
  	NewLatencyMetric(name string) SummaryMetric
  	NewWorkDurationMetric(name string) SummaryMetric
  	NewRetriesMetric(name string) CounterMetric
  }
  
  type noopMetricsProvider struct{}
  
  func (_ noopMetricsProvider) NewDepthMetric(name string) GaugeMetric {
  	return noopMetric{}
  }
  
  func (_ noopMetricsProvider) NewAddsMetric(name string) CounterMetric {
  	return noopMetric{}
  }
  
  func (_ noopMetricsProvider) NewLatencyMetric(name string) SummaryMetric {
  	return noopMetric{}
  }
  
  func (_ noopMetricsProvider) NewWorkDurationMetric(name string) SummaryMetric {
  	return noopMetric{}
  }
  
  func (_ noopMetricsProvider) NewRetriesMetric(name string) CounterMetric {
  	return noopMetric{}
  }
  
  var metricsFactory = struct {
  	metricsProvider MetricsProvider
  	setProviders    sync.Once
  }{
  	metricsProvider: noopMetricsProvider{},
  }
  
  func newQueueMetrics(name string) queueMetrics {
  	var ret *defaultQueueMetrics
  	if len(name) == 0 {
  		return ret
  	}
  	return &defaultQueueMetrics{
  		depth:                metricsFactory.metricsProvider.NewDepthMetric(name),
  		adds:                 metricsFactory.metricsProvider.NewAddsMetric(name),
  		latency:              metricsFactory.metricsProvider.NewLatencyMetric(name),
  		workDuration:         metricsFactory.metricsProvider.NewWorkDurationMetric(name),
  		addTimes:             map[t]time.Time{},
  		processingStartTimes: map[t]time.Time{},
  	}
  }
  
  func newRetryMetrics(name string) retryMetrics {
  	var ret *defaultRetryMetrics
  	if len(name) == 0 {
  		return ret
  	}
  	return &defaultRetryMetrics{
  		retries: metricsFactory.metricsProvider.NewRetriesMetric(name),
  	}
  }
  
  // SetProvider sets the metrics provider of the metricsFactory.
  func SetProvider(metricsProvider MetricsProvider) {
  	metricsFactory.setProviders.Do(func() {
  		metricsFactory.metricsProvider = metricsProvider
  	})
  }
  