knative.dev/pkg@v0.0.0-20260602142205-ac97e43f6622/apis/duck/cached.go (about)

     1  /*
     2  Copyright 2018 The Knative 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 duck
    18  
    19  import (
    20  	"context"
    21  	"sync"
    22  
    23  	"k8s.io/apimachinery/pkg/runtime/schema"
    24  	"k8s.io/client-go/tools/cache"
    25  )
    26  
    27  // CachedInformerFactory implements InformerFactory by delegating to another
    28  // InformerFactory, but memoizing the results.
    29  type CachedInformerFactory struct {
    30  	Delegate InformerFactory
    31  
    32  	m     sync.Mutex
    33  	cache map[schema.GroupVersionResource]*informerCache
    34  }
    35  
    36  // Check that CachedInformerFactory implements InformerFactory.
    37  var _ InformerFactory = (*CachedInformerFactory)(nil)
    38  
    39  // Get implements InformerFactory.
    40  func (cif *CachedInformerFactory) Get(ctx context.Context, gvr schema.GroupVersionResource) (cache.SharedIndexInformer, cache.GenericLister, error) {
    41  	cif.m.Lock()
    42  
    43  	if cif.cache == nil {
    44  		cif.cache = make(map[schema.GroupVersionResource]*informerCache)
    45  	}
    46  
    47  	ic, ok := cif.cache[gvr]
    48  	if !ok {
    49  		ic = &informerCache{}
    50  		ic.init = func() {
    51  			ic.Lock()
    52  			defer ic.Unlock()
    53  
    54  			// double-checked lock to ensure we call the Delegate
    55  			// only once even if multiple goroutines end up inside
    56  			// init() simultaneously
    57  			if ic.hasInformer() {
    58  				return
    59  			}
    60  
    61  			ic.inf, ic.lister, ic.err = cif.Delegate.Get(ctx, gvr)
    62  		}
    63  		cif.cache[gvr] = ic
    64  	}
    65  
    66  	// If this were done via "defer", then TestDifferentGVRs will fail.
    67  	cif.m.Unlock()
    68  
    69  	// The call to the delegate could be slow because it syncs informers, so do
    70  	// this outside of the main lock.
    71  	return ic.Get()
    72  }
    73  
    74  type informerCache struct {
    75  	sync.RWMutex
    76  
    77  	init func()
    78  
    79  	inf    cache.SharedIndexInformer
    80  	lister cache.GenericLister
    81  	err    error
    82  }
    83  
    84  // Get returns the cached informer. If it does not yet exist, we first try to
    85  // acquire one by executing the cache's init function.
    86  func (ic *informerCache) Get() (cache.SharedIndexInformer, cache.GenericLister, error) {
    87  	if !ic.initialized() {
    88  		ic.init()
    89  	}
    90  	return ic.inf, ic.lister, ic.err
    91  }
    92  
    93  func (ic *informerCache) initialized() bool {
    94  	ic.RLock()
    95  	defer ic.RUnlock()
    96  	return ic.hasInformer()
    97  }
    98  
    99  func (ic *informerCache) hasInformer() bool {
   100  	return ic.inf != nil && ic.lister != nil
   101  }