istio.io/istio@v0.0.0-20240520182934-d79c90f27776/pilot/pkg/leaderelection/k8sleaderelection/metrics.go (about)

     1  /*
     2  Copyright 2018 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package k8sleaderelection
    18  
    19  import (
    20  	"sync"
    21  )
    22  
    23  // This file provides abstractions for setting the provider (e.g., prometheus)
    24  // of metrics.
    25  
    26  type leaderMetricsAdapter interface {
    27  	leaderOn(name string)
    28  	leaderOff(name string)
    29  }
    30  
    31  // GaugeMetric represents a single numerical value that can arbitrarily go up
    32  // and down.
    33  type SwitchMetric interface {
    34  	On(name string)
    35  	Off(name string)
    36  }
    37  
    38  type noopMetric struct{}
    39  
    40  func (noopMetric) On(name string)  {}
    41  func (noopMetric) Off(name string) {}
    42  
    43  // defaultLeaderMetrics expects the caller to lock before setting any metrics.
    44  type defaultLeaderMetrics struct {
    45  	// leader's value indicates if the current process is the owner of name lease
    46  	leader SwitchMetric
    47  }
    48  
    49  func (m *defaultLeaderMetrics) leaderOn(name string) {
    50  	if m == nil {
    51  		return
    52  	}
    53  	m.leader.On(name)
    54  }
    55  
    56  func (m *defaultLeaderMetrics) leaderOff(name string) {
    57  	if m == nil {
    58  		return
    59  	}
    60  	m.leader.Off(name)
    61  }
    62  
    63  type noMetrics struct{}
    64  
    65  func (noMetrics) leaderOn(name string)  {}
    66  func (noMetrics) leaderOff(name string) {}
    67  
    68  // MetricsProvider generates various metrics used by the leader election.
    69  type MetricsProvider interface {
    70  	NewLeaderMetric() SwitchMetric
    71  }
    72  
    73  type noopMetricsProvider struct{}
    74  
    75  func (noopMetricsProvider) NewLeaderMetric() SwitchMetric {
    76  	return noopMetric{}
    77  }
    78  
    79  var globalMetricsFactory = leaderMetricsFactory{
    80  	metricsProvider: noopMetricsProvider{},
    81  }
    82  
    83  type leaderMetricsFactory struct {
    84  	metricsProvider MetricsProvider
    85  
    86  	onlyOnce sync.Once
    87  }
    88  
    89  func (f *leaderMetricsFactory) setProvider(mp MetricsProvider) {
    90  	f.onlyOnce.Do(func() {
    91  		f.metricsProvider = mp
    92  	})
    93  }
    94  
    95  func (f *leaderMetricsFactory) newLeaderMetrics() leaderMetricsAdapter {
    96  	mp := f.metricsProvider
    97  	if mp == (noopMetricsProvider{}) {
    98  		return noMetrics{}
    99  	}
   100  	return &defaultLeaderMetrics{
   101  		leader: mp.NewLeaderMetric(),
   102  	}
   103  }
   104  
   105  // SetProvider sets the metrics provider for all subsequently created work
   106  // queues. Only the first call has an effect.
   107  func SetProvider(metricsProvider MetricsProvider) {
   108  	globalMetricsFactory.setProvider(metricsProvider)
   109  }