github.com/bhojpur/cache@v0.0.4/pkg/engine/cache.go (about)

     1  package engine
     2  
     3  // Copyright (c) 2018 Bhojpur Consulting Private Limited, India. All rights reserved.
     4  
     5  // Permission is hereby granted, free of charge, to any person obtaining a copy
     6  // of this software and associated documentation files (the "Software"), to deal
     7  // in the Software without restriction, including without limitation the rights
     8  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     9  // copies of the Software, and to permit persons to whom the Software is
    10  // furnished to do so, subject to the following conditions:
    11  
    12  // The above copyright notice and this permission notice shall be included in
    13  // all copies or substantial portions of the Software.
    14  
    15  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    16  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    17  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    18  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    19  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    20  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    21  // THE SOFTWARE.
    22  
    23  // Cache is a generic interface type for a data structure that keeps recently used
    24  // objects in memory and evicts them when it becomes full.
    25  type Cache interface {
    26  	Get(key string) (interface{}, bool)
    27  	Set(key string, val interface{}) bool
    28  	ForEach(callback func(interface{}) bool)
    29  
    30  	Delete(key string)
    31  	Clear()
    32  
    33  	// Wait waits for all pending operations on the cache to settle. Since cache writes
    34  	// are asynchronous, a write may not be immediately accessible unless the user
    35  	// manually calls Wait.
    36  	Wait()
    37  
    38  	Len() int
    39  	Evictions() int64
    40  	UsedCapacity() int64
    41  	MaxCapacity() int64
    42  	SetCapacity(int64)
    43  }
    44  
    45  type cachedObject interface {
    46  	CachedSize(alloc bool) int64
    47  }
    48  
    49  // NewDefaultCacheImpl returns the default cache implementation for Vitess. The options in the
    50  // Config struct control the memory and entry limits for the cache, and the underlying cache
    51  // implementation.
    52  func NewDefaultCacheImpl(cfg *Config) Cache {
    53  	switch {
    54  	case cfg == nil:
    55  		return &nullCache{}
    56  
    57  	case cfg.LFU:
    58  		if cfg.MaxEntries == 0 || cfg.MaxMemoryUsage == 0 {
    59  			return &nullCache{}
    60  		}
    61  		return NewRistrettoCache(cfg.MaxEntries, cfg.MaxMemoryUsage, func(val interface{}) int64 {
    62  			return val.(cachedObject).CachedSize(true)
    63  		})
    64  
    65  	default:
    66  		if cfg.MaxEntries == 0 {
    67  			return &nullCache{}
    68  		}
    69  		return NewLRUCache(cfg.MaxEntries, func(_ interface{}) int64 {
    70  			return 1
    71  		})
    72  	}
    73  }
    74  
    75  // Config is the configuration options for a cache instance
    76  type Config struct {
    77  	// MaxEntries is the estimated amount of entries that the cache will hold at capacity
    78  	MaxEntries int64
    79  	// MaxMemoryUsage is the maximum amount of memory the cache can handle
    80  	MaxMemoryUsage int64
    81  	// LFU toggles whether to use a new cache implementation with a TinyLFU admission policy
    82  	LFU bool
    83  }
    84  
    85  // DefaultConfig is the default configuration for a cache instance in Vitess
    86  var DefaultConfig = &Config{
    87  	MaxEntries:     5000,
    88  	MaxMemoryUsage: 32 * 1024 * 1024,
    89  	LFU:            true,
    90  }