forked from allegro/bigcache
-
Notifications
You must be signed in to change notification settings - Fork 0
/
bigcache.go
176 lines (149 loc) · 4.65 KB
/
bigcache.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
package bigcache
import (
"fmt"
"time"
)
const (
minimumEntriesInShard = 10 // Minimum number of entries in single shard
)
// BigCache is fast, concurrent, evicting cache created to keep big number of entries without impact on performance.
// It keeps entries on heap but omits GC for them. To achieve that operations on bytes arrays take place,
// therefore entries (de)serialization in front of the cache will be needed in most use cases.
type BigCache struct {
shards []*cacheShard
lifeWindow uint64
clock clock
hash Hasher
config Config
shardMask uint64
maxShardSize uint32
}
// RemoveReason is a value used to signal to the user why a particular key was removed in the OnRemove callback.
type RemoveReason uint32
const (
// Expired means the key is past its LifeWindow.
Expired RemoveReason = iota
// NoSpace means the key is the oldest and the cache size was at its maximum when Set was called, or the
// entry exceeded the maximum shard size.
NoSpace
// Deleted means Delete was called and this key was removed as a result.
Deleted
)
// NewBigCache initialize new instance of BigCache
func NewBigCache(config Config) (*BigCache, error) {
return newBigCache(config, &systemClock{})
}
func newBigCache(config Config, clock clock) (*BigCache, error) {
if !isPowerOfTwo(config.Shards) {
return nil, fmt.Errorf("Shards number must be power of two")
}
if config.Hasher == nil {
config.Hasher = newDefaultHasher()
}
cache := &BigCache{
shards: make([]*cacheShard, config.Shards),
lifeWindow: uint64(config.LifeWindow.Seconds()),
clock: clock,
hash: config.Hasher,
config: config,
shardMask: uint64(config.Shards - 1),
maxShardSize: uint32(config.maximumShardSize()),
}
var onRemove func(wrappedEntry []byte, reason RemoveReason)
if config.OnRemove != nil {
onRemove = cache.providedOnRemove
} else if config.OnRemoveWithReason != nil {
onRemove = cache.providedOnRemoveWithReason
} else {
onRemove = cache.notProvidedOnRemove
}
for i := 0; i < config.Shards; i++ {
cache.shards[i] = initNewShard(config, onRemove, clock)
}
if config.CleanWindow > 0 {
go func() {
for t := range time.Tick(config.CleanWindow) {
cache.cleanUp(uint64(t.Unix()))
}
}()
}
return cache, nil
}
// Get reads entry for the key.
// It returns an EntryNotFoundError when
// no entry exists for the given key.
func (c *BigCache) Get(key string) ([]byte, error) {
hashedKey := c.hash.Sum64(key)
shard := c.getShard(hashedKey)
return shard.get(key, hashedKey)
}
// Set saves entry under the key
func (c *BigCache) Set(key string, entry []byte) error {
hashedKey := c.hash.Sum64(key)
shard := c.getShard(hashedKey)
return shard.set(key, hashedKey, entry)
}
// Delete removes the key
func (c *BigCache) Delete(key string) error {
hashedKey := c.hash.Sum64(key)
shard := c.getShard(hashedKey)
return shard.del(key, hashedKey)
}
// Reset empties all cache shards
func (c *BigCache) Reset() error {
for _, shard := range c.shards {
shard.reset(c.config)
}
return nil
}
// Len computes number of entries in cache
func (c *BigCache) Len() int {
var len int
for _, shard := range c.shards {
len += shard.len()
}
return len
}
// Stats returns cache's statistics
func (c *BigCache) Stats() Stats {
var s Stats
for _, shard := range c.shards {
tmp := shard.getStats()
s.Hits += tmp.Hits
s.Misses += tmp.Misses
s.DelHits += tmp.DelHits
s.DelMisses += tmp.DelMisses
s.Collisions += tmp.Collisions
}
return s
}
// Iterator returns iterator function to iterate over EntryInfo's from whole cache.
func (c *BigCache) Iterator() *EntryInfoIterator {
return newIterator(c)
}
func (c *BigCache) onEvict(oldestEntry []byte, currentTimestamp uint64, evict func(reason RemoveReason) error) bool {
oldestTimestamp := readTimestampFromEntry(oldestEntry)
if currentTimestamp-oldestTimestamp > c.lifeWindow {
evict(Expired)
return true
}
return false
}
func (c *BigCache) cleanUp(currentTimestamp uint64) {
for _, shard := range c.shards {
shard.cleanUp(currentTimestamp)
}
}
func (c *BigCache) getShard(hashedKey uint64) (shard *cacheShard) {
return c.shards[hashedKey&c.shardMask]
}
func (c *BigCache) providedOnRemove(wrappedEntry []byte, reason RemoveReason) {
c.config.OnRemove(readKeyFromEntry(wrappedEntry), readEntry(wrappedEntry))
}
func (c *BigCache) providedOnRemoveWithReason(wrappedEntry []byte, reason RemoveReason) {
if c.config.onRemoveFilter == 0 || (1<<uint(reason))&c.config.onRemoveFilter > 0 {
c.config.OnRemoveWithReason(readKeyFromEntry(wrappedEntry), readEntry(wrappedEntry), reason)
}
}
func (c *BigCache) notProvidedOnRemove(wrappedEntry []byte, reason RemoveReason) {
}