mirror of https://github.com/ethereum/go-ethereum
Péter Szilágyi
6 years ago
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9a000601c6
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434dd5bc00
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@ -0,0 +1,150 @@ |
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# BigCache [](https://travis-ci.org/allegro/bigcache) [](https://coveralls.io/github/allegro/bigcache?branch=master) [](https://godoc.org/github.com/allegro/bigcache) [](https://goreportcard.com/report/github.com/allegro/bigcache) |
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|
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Fast, concurrent, evicting in-memory cache written to keep big number of entries without impact on performance. |
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BigCache keeps entries on heap but omits GC for them. To achieve that operations on bytes arrays take place, |
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therefore entries (de)serialization in front of the cache will be needed in most use cases. |
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|
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## Usage |
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|
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### Simple initialization |
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|
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```go |
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import "github.com/allegro/bigcache" |
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cache, _ := bigcache.NewBigCache(bigcache.DefaultConfig(10 * time.Minute)) |
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cache.Set("my-unique-key", []byte("value")) |
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entry, _ := cache.Get("my-unique-key") |
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fmt.Println(string(entry)) |
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``` |
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|
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### Custom initialization |
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When cache load can be predicted in advance then it is better to use custom initialization because additional memory |
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allocation can be avoided in that way. |
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|
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```go |
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import ( |
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"log" |
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"github.com/allegro/bigcache" |
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) |
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config := bigcache.Config { |
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// number of shards (must be a power of 2) |
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Shards: 1024, |
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// time after which entry can be evicted |
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LifeWindow: 10 * time.Minute, |
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// rps * lifeWindow, used only in initial memory allocation |
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MaxEntriesInWindow: 1000 * 10 * 60, |
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// max entry size in bytes, used only in initial memory allocation |
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MaxEntrySize: 500, |
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// prints information about additional memory allocation |
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Verbose: true, |
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// cache will not allocate more memory than this limit, value in MB |
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// if value is reached then the oldest entries can be overridden for the new ones |
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// 0 value means no size limit |
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HardMaxCacheSize: 8192, |
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// callback fired when the oldest entry is removed because of its expiration time or no space left |
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// for the new entry, or because delete was called. A bitmask representing the reason will be returned. |
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// Default value is nil which means no callback and it prevents from unwrapping the oldest entry. |
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OnRemove: nil, |
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// OnRemoveWithReason is a callback fired when the oldest entry is removed because of its expiration time or no space left |
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// for the new entry, or because delete was called. A constant representing the reason will be passed through. |
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// Default value is nil which means no callback and it prevents from unwrapping the oldest entry. |
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// Ignored if OnRemove is specified. |
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OnRemoveWithReason: nil, |
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} |
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cache, initErr := bigcache.NewBigCache(config) |
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if initErr != nil { |
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log.Fatal(initErr) |
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} |
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cache.Set("my-unique-key", []byte("value")) |
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|
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if entry, err := cache.Get("my-unique-key"); err == nil { |
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fmt.Println(string(entry)) |
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} |
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``` |
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|
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## Benchmarks |
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|
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Three caches were compared: bigcache, [freecache](https://github.com/coocood/freecache) and map. |
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Benchmark tests were made using an i7-6700K with 32GB of RAM on Windows 10. |
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|
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### Writes and reads |
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|
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```bash |
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cd caches_bench; go test -bench=. -benchtime=10s ./... -timeout 30m |
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|
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BenchmarkMapSet-8 3000000 569 ns/op 202 B/op 3 allocs/op |
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BenchmarkConcurrentMapSet-8 1000000 1592 ns/op 347 B/op 8 allocs/op |
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BenchmarkFreeCacheSet-8 3000000 775 ns/op 355 B/op 2 allocs/op |
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BenchmarkBigCacheSet-8 3000000 640 ns/op 303 B/op 2 allocs/op |
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BenchmarkMapGet-8 5000000 407 ns/op 24 B/op 1 allocs/op |
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BenchmarkConcurrentMapGet-8 3000000 558 ns/op 24 B/op 2 allocs/op |
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BenchmarkFreeCacheGet-8 2000000 682 ns/op 136 B/op 2 allocs/op |
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BenchmarkBigCacheGet-8 3000000 512 ns/op 152 B/op 4 allocs/op |
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BenchmarkBigCacheSetParallel-8 10000000 225 ns/op 313 B/op 3 allocs/op |
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BenchmarkFreeCacheSetParallel-8 10000000 218 ns/op 341 B/op 3 allocs/op |
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BenchmarkConcurrentMapSetParallel-8 5000000 318 ns/op 200 B/op 6 allocs/op |
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BenchmarkBigCacheGetParallel-8 20000000 178 ns/op 152 B/op 4 allocs/op |
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BenchmarkFreeCacheGetParallel-8 20000000 295 ns/op 136 B/op 3 allocs/op |
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BenchmarkConcurrentMapGetParallel-8 10000000 237 ns/op 24 B/op 2 allocs/op |
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``` |
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|
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Writes and reads in bigcache are faster than in freecache. |
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Writes to map are the slowest. |
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|
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### GC pause time |
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|
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```bash |
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cd caches_bench; go run caches_gc_overhead_comparison.go |
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Number of entries: 20000000 |
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GC pause for bigcache: 5.8658ms |
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GC pause for freecache: 32.4341ms |
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GC pause for map: 52.9661ms |
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``` |
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Test shows how long are the GC pauses for caches filled with 20mln of entries. |
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Bigcache and freecache have very similar GC pause time. |
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It is clear that both reduce GC overhead in contrast to map |
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which GC pause time took more than 10 seconds. |
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|
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## How it works |
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|
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BigCache relies on optimization presented in 1.5 version of Go ([issue-9477](https://github.com/golang/go/issues/9477)). |
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This optimization states that if map without pointers in keys and values is used then GC will omit its content. |
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Therefore BigCache uses `map[uint64]uint32` where keys are hashed and values are offsets of entries. |
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|
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Entries are kept in bytes array, to omit GC again. |
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Bytes array size can grow to gigabytes without impact on performance |
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because GC will only see single pointer to it. |
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|
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## Bigcache vs Freecache |
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|
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Both caches provide the same core features but they reduce GC overhead in different ways. |
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Bigcache relies on `map[uint64]uint32`, freecache implements its own mapping built on |
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slices to reduce number of pointers. |
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|
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Results from benchmark tests are presented above. |
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One of the advantage of bigcache over freecache is that you don’t need to know |
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the size of the cache in advance, because when bigcache is full, |
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it can allocate additional memory for new entries instead of |
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overwriting existing ones as freecache does currently. |
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However hard max size in bigcache also can be set, check [HardMaxCacheSize](https://godoc.org/github.com/allegro/bigcache#Config). |
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|
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## HTTP Server |
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|
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This package also includes an easily deployable HTTP implementation of BigCache, which can be found in the [server](/server) package. |
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|
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## More |
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|
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Bigcache genesis is described in allegro.tech blog post: [writing a very fast cache service in Go](http://allegro.tech/2016/03/writing-fast-cache-service-in-go.html) |
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|
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## License |
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|
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BigCache is released under the Apache 2.0 license (see [LICENSE](LICENSE)) |
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@ -0,0 +1,202 @@ |
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package bigcache |
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|
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import ( |
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"fmt" |
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"time" |
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) |
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|
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const ( |
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minimumEntriesInShard = 10 // Minimum number of entries in single shard
|
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) |
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|
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// BigCache is fast, concurrent, evicting cache created to keep big number of entries without impact on performance.
|
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// It keeps entries on heap but omits GC for them. To achieve that, operations take place on byte arrays,
|
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// therefore entries (de)serialization in front of the cache will be needed in most use cases.
|
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type BigCache struct { |
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shards []*cacheShard |
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lifeWindow uint64 |
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clock clock |
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hash Hasher |
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config Config |
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shardMask uint64 |
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maxShardSize uint32 |
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close chan struct{} |
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} |
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|
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// RemoveReason is a value used to signal to the user why a particular key was removed in the OnRemove callback.
|
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type RemoveReason uint32 |
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|
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const ( |
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// Expired means the key is past its LifeWindow.
|
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Expired RemoveReason = iota |
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// NoSpace means the key is the oldest and the cache size was at its maximum when Set was called, or the
|
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// entry exceeded the maximum shard size.
|
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NoSpace |
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// Deleted means Delete was called and this key was removed as a result.
|
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Deleted |
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) |
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|
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// NewBigCache initialize new instance of BigCache
|
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func NewBigCache(config Config) (*BigCache, error) { |
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return newBigCache(config, &systemClock{}) |
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} |
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|
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func newBigCache(config Config, clock clock) (*BigCache, error) { |
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|
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if !isPowerOfTwo(config.Shards) { |
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return nil, fmt.Errorf("Shards number must be power of two") |
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} |
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|
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if config.Hasher == nil { |
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config.Hasher = newDefaultHasher() |
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} |
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|
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cache := &BigCache{ |
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shards: make([]*cacheShard, config.Shards), |
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lifeWindow: uint64(config.LifeWindow.Seconds()), |
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clock: clock, |
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hash: config.Hasher, |
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config: config, |
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shardMask: uint64(config.Shards - 1), |
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maxShardSize: uint32(config.maximumShardSize()), |
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close: make(chan struct{}), |
||||
} |
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|
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var onRemove func(wrappedEntry []byte, reason RemoveReason) |
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if config.OnRemove != nil { |
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onRemove = cache.providedOnRemove |
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} else if config.OnRemoveWithReason != nil { |
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onRemove = cache.providedOnRemoveWithReason |
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} else { |
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onRemove = cache.notProvidedOnRemove |
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} |
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|
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for i := 0; i < config.Shards; i++ { |
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cache.shards[i] = initNewShard(config, onRemove, clock) |
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} |
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|
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if config.CleanWindow > 0 { |
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go func() { |
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ticker := time.NewTicker(config.CleanWindow) |
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defer ticker.Stop() |
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for { |
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select { |
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case t := <-ticker.C: |
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cache.cleanUp(uint64(t.Unix())) |
||||
case <-cache.close: |
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return |
||||
} |
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} |
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}() |
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} |
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|
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return cache, nil |
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} |
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|
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// Close is used to signal a shutdown of the cache when you are done with it.
|
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// This allows the cleaning goroutines to exit and ensures references are not
|
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// kept to the cache preventing GC of the entire cache.
|
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func (c *BigCache) Close() error { |
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close(c.close) |
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return nil |
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} |
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|
||||
// 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) |
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shard := c.getShard(hashedKey) |
||||
return shard.get(key, hashedKey) |
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} |
||||
|
||||
// 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 |
||||
} |
||||
|
||||
// Capacity returns amount of bytes store in the cache.
|
||||
func (c *BigCache) Capacity() int { |
||||
var len int |
||||
for _, shard := range c.shards { |
||||
len += shard.capacity() |
||||
} |
||||
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) { |
||||
} |
||||
@ -0,0 +1,14 @@ |
||||
// +build !appengine
|
||||
|
||||
package bigcache |
||||
|
||||
import ( |
||||
"reflect" |
||||
"unsafe" |
||||
) |
||||
|
||||
func bytesToString(b []byte) string { |
||||
bytesHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b)) |
||||
strHeader := reflect.StringHeader{Data: bytesHeader.Data, Len: bytesHeader.Len} |
||||
return *(*string)(unsafe.Pointer(&strHeader)) |
||||
} |
||||
@ -0,0 +1,7 @@ |
||||
// +build appengine
|
||||
|
||||
package bigcache |
||||
|
||||
func bytesToString(b []byte) string { |
||||
return string(b) |
||||
} |
||||
@ -0,0 +1,14 @@ |
||||
package bigcache |
||||
|
||||
import "time" |
||||
|
||||
type clock interface { |
||||
epoch() int64 |
||||
} |
||||
|
||||
type systemClock struct { |
||||
} |
||||
|
||||
func (c systemClock) epoch() int64 { |
||||
return time.Now().Unix() |
||||
} |
||||
@ -0,0 +1,86 @@ |
||||
package bigcache |
||||
|
||||
import "time" |
||||
|
||||
// Config for BigCache
|
||||
type Config struct { |
||||
// Number of cache shards, value must be a power of two
|
||||
Shards int |
||||
// Time after which entry can be evicted
|
||||
LifeWindow time.Duration |
||||
// Interval between removing expired entries (clean up).
|
||||
// If set to <= 0 then no action is performed. Setting to < 1 second is counterproductive — bigcache has a one second resolution.
|
||||
CleanWindow time.Duration |
||||
// Max number of entries in life window. Used only to calculate initial size for cache shards.
|
||||
// When proper value is set then additional memory allocation does not occur.
|
||||
MaxEntriesInWindow int |
||||
// Max size of entry in bytes. Used only to calculate initial size for cache shards.
|
||||
MaxEntrySize int |
||||
// Verbose mode prints information about new memory allocation
|
||||
Verbose bool |
||||
// Hasher used to map between string keys and unsigned 64bit integers, by default fnv64 hashing is used.
|
||||
Hasher Hasher |
||||
// HardMaxCacheSize is a limit for cache size in MB. Cache will not allocate more memory than this limit.
|
||||
// It can protect application from consuming all available memory on machine, therefore from running OOM Killer.
|
||||
// Default value is 0 which means unlimited size. When the limit is higher than 0 and reached then
|
||||
// the oldest entries are overridden for the new ones.
|
||||
HardMaxCacheSize int |
||||
// OnRemove is a callback fired when the oldest entry is removed because of its expiration time or no space left
|
||||
// for the new entry, or because delete was called.
|
||||
// Default value is nil which means no callback and it prevents from unwrapping the oldest entry.
|
||||
OnRemove func(key string, entry []byte) |
||||
// OnRemoveWithReason is a callback fired when the oldest entry is removed because of its expiration time or no space left
|
||||
// for the new entry, or because delete was called. A constant representing the reason will be passed through.
|
||||
// Default value is nil which means no callback and it prevents from unwrapping the oldest entry.
|
||||
// Ignored if OnRemove is specified.
|
||||
OnRemoveWithReason func(key string, entry []byte, reason RemoveReason) |
||||
|
||||
onRemoveFilter int |
||||
|
||||
// Logger is a logging interface and used in combination with `Verbose`
|
||||
// Defaults to `DefaultLogger()`
|
||||
Logger Logger |
||||
} |
||||
|
||||
// DefaultConfig initializes config with default values.
|
||||
// When load for BigCache can be predicted in advance then it is better to use custom config.
|
||||
func DefaultConfig(eviction time.Duration) Config { |
||||
return Config{ |
||||
Shards: 1024, |
||||
LifeWindow: eviction, |
||||
CleanWindow: 0, |
||||
MaxEntriesInWindow: 1000 * 10 * 60, |
||||
MaxEntrySize: 500, |
||||
Verbose: true, |
||||
Hasher: newDefaultHasher(), |
||||
HardMaxCacheSize: 0, |
||||
Logger: DefaultLogger(), |
||||
} |
||||
} |
||||
|
||||
// initialShardSize computes initial shard size
|
||||
func (c Config) initialShardSize() int { |
||||
return max(c.MaxEntriesInWindow/c.Shards, minimumEntriesInShard) |
||||
} |
||||
|
||||
// maximumShardSize computes maximum shard size
|
||||
func (c Config) maximumShardSize() int { |
||||
maxShardSize := 0 |
||||
|
||||
if c.HardMaxCacheSize > 0 { |
||||
maxShardSize = convertMBToBytes(c.HardMaxCacheSize) / c.Shards |
||||
} |
||||
|
||||
return maxShardSize |
||||
} |
||||
|
||||
// OnRemoveFilterSet sets which remove reasons will trigger a call to OnRemoveWithReason.
|
||||
// Filtering out reasons prevents bigcache from unwrapping them, which saves cpu.
|
||||
func (c Config) OnRemoveFilterSet(reasons ...RemoveReason) Config { |
||||
c.onRemoveFilter = 0 |
||||
for i := range reasons { |
||||
c.onRemoveFilter |= 1 << uint(reasons[i]) |
||||
} |
||||
|
||||
return c |
||||
} |
||||
@ -0,0 +1,62 @@ |
||||
package bigcache |
||||
|
||||
import ( |
||||
"encoding/binary" |
||||
) |
||||
|
||||
const ( |
||||
timestampSizeInBytes = 8 // Number of bytes used for timestamp
|
||||
hashSizeInBytes = 8 // Number of bytes used for hash
|
||||
keySizeInBytes = 2 // Number of bytes used for size of entry key
|
||||
headersSizeInBytes = timestampSizeInBytes + hashSizeInBytes + keySizeInBytes // Number of bytes used for all headers
|
||||
) |
||||
|
||||
func wrapEntry(timestamp uint64, hash uint64, key string, entry []byte, buffer *[]byte) []byte { |
||||
keyLength := len(key) |
||||
blobLength := len(entry) + headersSizeInBytes + keyLength |
||||
|
||||
if blobLength > len(*buffer) { |
||||
*buffer = make([]byte, blobLength) |
||||
} |
||||
blob := *buffer |
||||
|
||||
binary.LittleEndian.PutUint64(blob, timestamp) |
||||
binary.LittleEndian.PutUint64(blob[timestampSizeInBytes:], hash) |
||||
binary.LittleEndian.PutUint16(blob[timestampSizeInBytes+hashSizeInBytes:], uint16(keyLength)) |
||||
copy(blob[headersSizeInBytes:], key) |
||||
copy(blob[headersSizeInBytes+keyLength:], entry) |
||||
|
||||
return blob[:blobLength] |
||||
} |
||||
|
||||
func readEntry(data []byte) []byte { |
||||
length := binary.LittleEndian.Uint16(data[timestampSizeInBytes+hashSizeInBytes:]) |
||||
|
||||
// copy on read
|
||||
dst := make([]byte, len(data)-int(headersSizeInBytes+length)) |
||||
copy(dst, data[headersSizeInBytes+length:]) |
||||
|
||||
return dst |
||||
} |
||||
|
||||
func readTimestampFromEntry(data []byte) uint64 { |
||||
return binary.LittleEndian.Uint64(data) |
||||
} |
||||
|
||||
func readKeyFromEntry(data []byte) string { |
||||
length := binary.LittleEndian.Uint16(data[timestampSizeInBytes+hashSizeInBytes:]) |
||||
|
||||
// copy on read
|
||||
dst := make([]byte, length) |
||||
copy(dst, data[headersSizeInBytes:headersSizeInBytes+length]) |
||||
|
||||
return bytesToString(dst) |
||||
} |
||||
|
||||
func readHashFromEntry(data []byte) uint64 { |
||||
return binary.LittleEndian.Uint64(data[timestampSizeInBytes:]) |
||||
} |
||||
|
||||
func resetKeyFromEntry(data []byte) { |
||||
binary.LittleEndian.PutUint64(data[timestampSizeInBytes:], 0) |
||||
} |
||||
@ -0,0 +1,17 @@ |
||||
package bigcache |
||||
|
||||
import "fmt" |
||||
|
||||
// EntryNotFoundError is an error type struct which is returned when entry was not found for provided key
|
||||
type EntryNotFoundError struct { |
||||
key string |
||||
} |
||||
|
||||
func notFound(key string) error { |
||||
return &EntryNotFoundError{key} |
||||
} |
||||
|
||||
// Error returned when entry does not exist.
|
||||
func (e EntryNotFoundError) Error() string { |
||||
return fmt.Sprintf("Entry %q not found", e.key) |
||||
} |
||||
@ -0,0 +1,28 @@ |
||||
package bigcache |
||||
|
||||
// newDefaultHasher returns a new 64-bit FNV-1a Hasher which makes no memory allocations.
|
||||
// Its Sum64 method will lay the value out in big-endian byte order.
|
||||
// See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
|
||||
func newDefaultHasher() Hasher { |
||||
return fnv64a{} |
||||
} |
||||
|
||||
type fnv64a struct{} |
||||
|
||||
const ( |
||||
// offset64 FNVa offset basis. See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash
|
||||
offset64 = 14695981039346656037 |
||||
// prime64 FNVa prime value. See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash
|
||||
prime64 = 1099511628211 |
||||
) |
||||
|
||||
// Sum64 gets the string and returns its uint64 hash value.
|
||||
func (f fnv64a) Sum64(key string) uint64 { |
||||
var hash uint64 = offset64 |
||||
for i := 0; i < len(key); i++ { |
||||
hash ^= uint64(key[i]) |
||||
hash *= prime64 |
||||
} |
||||
|
||||
return hash |
||||
} |
||||
@ -0,0 +1,8 @@ |
||||
package bigcache |
||||
|
||||
// Hasher is responsible for generating unsigned, 64 bit hash of provided string. Hasher should minimize collisions
|
||||
// (generating same hash for different strings) and while performance is also important fast functions are preferable (i.e.
|
||||
// you can use FarmHash family).
|
||||
type Hasher interface { |
||||
Sum64(string) uint64 |
||||
} |
||||
@ -0,0 +1,122 @@ |
||||
package bigcache |
||||
|
||||
import "sync" |
||||
|
||||
type iteratorError string |
||||
|
||||
func (e iteratorError) Error() string { |
||||
return string(e) |
||||
} |
||||
|
||||
// ErrInvalidIteratorState is reported when iterator is in invalid state
|
||||
const ErrInvalidIteratorState = iteratorError("Iterator is in invalid state. Use SetNext() to move to next position") |
||||
|
||||
// ErrCannotRetrieveEntry is reported when entry cannot be retrieved from underlying
|
||||
const ErrCannotRetrieveEntry = iteratorError("Could not retrieve entry from cache") |
||||
|
||||
var emptyEntryInfo = EntryInfo{} |
||||
|
||||
// EntryInfo holds informations about entry in the cache
|
||||
type EntryInfo struct { |
||||
timestamp uint64 |
||||
hash uint64 |
||||
key string |
||||
value []byte |
||||
} |
||||
|
||||
// Key returns entry's underlying key
|
||||
func (e EntryInfo) Key() string { |
||||
return e.key |
||||
} |
||||
|
||||
// Hash returns entry's hash value
|
||||
func (e EntryInfo) Hash() uint64 { |
||||
return e.hash |
||||
} |
||||
|
||||
// Timestamp returns entry's timestamp (time of insertion)
|
||||
func (e EntryInfo) Timestamp() uint64 { |
||||
return e.timestamp |
||||
} |
||||
|
||||
// Value returns entry's underlying value
|
||||
func (e EntryInfo) Value() []byte { |
||||
return e.value |
||||
} |
||||
|
||||
// EntryInfoIterator allows to iterate over entries in the cache
|
||||
type EntryInfoIterator struct { |
||||
mutex sync.Mutex |
||||
cache *BigCache |
||||
currentShard int |
||||
currentIndex int |
||||
elements []uint32 |
||||
elementsCount int |
||||
valid bool |
||||
} |
||||
|
||||
// SetNext moves to next element and returns true if it exists.
|
||||
func (it *EntryInfoIterator) SetNext() bool { |
||||
it.mutex.Lock() |
||||
|
||||
it.valid = false |
||||
it.currentIndex++ |
||||
|
||||
if it.elementsCount > it.currentIndex { |
||||
it.valid = true |
||||
it.mutex.Unlock() |
||||
return true |
||||
} |
||||
|
||||
for i := it.currentShard + 1; i < it.cache.config.Shards; i++ { |
||||
it.elements, it.elementsCount = it.cache.shards[i].copyKeys() |
||||
|
||||
// Non empty shard - stick with it
|
||||
if it.elementsCount > 0 { |
||||
it.currentIndex = 0 |
||||
it.currentShard = i |
||||
it.valid = true |
||||
it.mutex.Unlock() |
||||
return true |
||||
} |
||||
} |
||||
it.mutex.Unlock() |
||||
return false |
||||
} |
||||
|
||||
func newIterator(cache *BigCache) *EntryInfoIterator { |
||||
elements, count := cache.shards[0].copyKeys() |
||||
|
||||
return &EntryInfoIterator{ |
||||
cache: cache, |
||||
currentShard: 0, |
||||
currentIndex: -1, |
||||
elements: elements, |
||||
elementsCount: count, |
||||
} |
||||
} |
||||
|
||||
// Value returns current value from the iterator
|
||||
func (it *EntryInfoIterator) Value() (EntryInfo, error) { |
||||
it.mutex.Lock() |
||||
|
||||
if !it.valid { |
||||
it.mutex.Unlock() |
||||
return emptyEntryInfo, ErrInvalidIteratorState |
||||
} |
||||
|
||||
entry, err := it.cache.shards[it.currentShard].getEntry(int(it.elements[it.currentIndex])) |
||||
|
||||
if err != nil { |
||||
it.mutex.Unlock() |
||||
return emptyEntryInfo, ErrCannotRetrieveEntry |
||||
} |
||||
it.mutex.Unlock() |
||||
|
||||
return EntryInfo{ |
||||
timestamp: readTimestampFromEntry(entry), |
||||
hash: readHashFromEntry(entry), |
||||
key: readKeyFromEntry(entry), |
||||
value: readEntry(entry), |
||||
}, nil |
||||
} |
||||
@ -0,0 +1,30 @@ |
||||
package bigcache |
||||
|
||||
import ( |
||||
"log" |
||||
"os" |
||||
) |
||||
|
||||
// Logger is invoked when `Config.Verbose=true`
|
||||
type Logger interface { |
||||
Printf(format string, v ...interface{}) |
||||
} |
||||
|
||||
// this is a safeguard, breaking on compile time in case
|
||||
// `log.Logger` does not adhere to our `Logger` interface.
|
||||
// see https://golang.org/doc/faq#guarantee_satisfies_interface
|
||||
var _ Logger = &log.Logger{} |
||||
|
||||
// DefaultLogger returns a `Logger` implementation
|
||||
// backed by stdlib's log
|
||||
func DefaultLogger() *log.Logger { |
||||
return log.New(os.Stdout, "", log.LstdFlags) |
||||
} |
||||
|
||||
func newLogger(custom Logger) Logger { |
||||
if custom != nil { |
||||
return custom |
||||
} |
||||
|
||||
return DefaultLogger() |
||||
} |
||||
@ -0,0 +1,210 @@ |
||||
package queue |
||||
|
||||
import ( |
||||
"encoding/binary" |
||||
"log" |
||||
"time" |
||||
) |
||||
|
||||
const ( |
||||
// Number of bytes used to keep information about entry size
|
||||
headerEntrySize = 4 |
||||
// Bytes before left margin are not used. Zero index means element does not exist in queue, useful while reading slice from index
|
||||
leftMarginIndex = 1 |
||||
// Minimum empty blob size in bytes. Empty blob fills space between tail and head in additional memory allocation.
|
||||
// It keeps entries indexes unchanged
|
||||
minimumEmptyBlobSize = 32 + headerEntrySize |
||||
) |
||||
|
||||
// BytesQueue is a non-thread safe queue type of fifo based on bytes array.
|
||||
// For every push operation index of entry is returned. It can be used to read the entry later
|
||||
type BytesQueue struct { |
||||
array []byte |
||||
capacity int |
||||
maxCapacity int |
||||
head int |
||||
tail int |
||||
count int |
||||
rightMargin int |
||||
headerBuffer []byte |
||||
verbose bool |
||||
initialCapacity int |
||||
} |
||||
|
||||
type queueError struct { |
||||
message string |
||||
} |
||||
|
||||
// NewBytesQueue initialize new bytes queue.
|
||||
// Initial capacity is used in bytes array allocation
|
||||
// When verbose flag is set then information about memory allocation are printed
|
||||
func NewBytesQueue(initialCapacity int, maxCapacity int, verbose bool) *BytesQueue { |
||||
return &BytesQueue{ |
||||
array: make([]byte, initialCapacity), |
||||
capacity: initialCapacity, |
||||
maxCapacity: maxCapacity, |
||||
headerBuffer: make([]byte, headerEntrySize), |
||||
tail: leftMarginIndex, |
||||
head: leftMarginIndex, |
||||
rightMargin: leftMarginIndex, |
||||
verbose: verbose, |
||||
initialCapacity: initialCapacity, |
||||
} |
||||
} |
||||
|
||||
// Reset removes all entries from queue
|
||||
func (q *BytesQueue) Reset() { |
||||
// Just reset indexes
|
||||
q.tail = leftMarginIndex |
||||
q.head = leftMarginIndex |
||||
q.rightMargin = leftMarginIndex |
||||
q.count = 0 |
||||
} |
||||
|
||||
// Push copies entry at the end of queue and moves tail pointer. Allocates more space if needed.
|
||||
// Returns index for pushed data or error if maximum size queue limit is reached.
|
||||
func (q *BytesQueue) Push(data []byte) (int, error) { |
||||
dataLen := len(data) |
||||
|
||||
if q.availableSpaceAfterTail() < dataLen+headerEntrySize { |
||||
if q.availableSpaceBeforeHead() >= dataLen+headerEntrySize { |
||||
q.tail = leftMarginIndex |
||||
} else if q.capacity+headerEntrySize+dataLen >= q.maxCapacity && q.maxCapacity > 0 { |
||||
return -1, &queueError{"Full queue. Maximum size limit reached."} |
||||
} else { |
||||
q.allocateAdditionalMemory(dataLen + headerEntrySize) |
||||
} |
||||
} |
||||
|
||||
index := q.tail |
||||
|
||||
q.push(data, dataLen) |
||||
|
||||
return index, nil |
||||
} |
||||
|
||||
func (q *BytesQueue) allocateAdditionalMemory(minimum int) { |
||||
start := time.Now() |
||||
if q.capacity < minimum { |
||||
q.capacity += minimum |
||||
} |
||||
q.capacity = q.capacity * 2 |
||||
if q.capacity > q.maxCapacity && q.maxCapacity > 0 { |
||||
q.capacity = q.maxCapacity |
||||
} |
||||
|
||||
oldArray := q.array |
||||
q.array = make([]byte, q.capacity) |
||||
|
||||
if leftMarginIndex != q.rightMargin { |
||||
copy(q.array, oldArray[:q.rightMargin]) |
||||
|
||||
if q.tail < q.head { |
||||
emptyBlobLen := q.head - q.tail - headerEntrySize |
||||
q.push(make([]byte, emptyBlobLen), emptyBlobLen) |
||||
q.head = leftMarginIndex |
||||
q.tail = q.rightMargin |
||||
} |
||||
} |
||||
|
||||
if q.verbose { |
||||
log.Printf("Allocated new queue in %s; Capacity: %d \n", time.Since(start), q.capacity) |
||||
} |
||||
} |
||||
|
||||
func (q *BytesQueue) push(data []byte, len int) { |
||||
binary.LittleEndian.PutUint32(q.headerBuffer, uint32(len)) |
||||
q.copy(q.headerBuffer, headerEntrySize) |
||||
|
||||
q.copy(data, len) |
||||
|
||||
if q.tail > q.head { |
||||
q.rightMargin = q.tail |
||||
} |
||||
|
||||
q.count++ |
||||
} |
||||
|
||||
func (q *BytesQueue) copy(data []byte, len int) { |
||||
q.tail += copy(q.array[q.tail:], data[:len]) |
||||
} |
||||
|
||||
// Pop reads the oldest entry from queue and moves head pointer to the next one
|
||||
func (q *BytesQueue) Pop() ([]byte, error) { |
||||
data, size, err := q.peek(q.head) |
||||
if err != nil { |
||||
return nil, err |
||||
} |
||||
|
||||
q.head += headerEntrySize + size |
||||
q.count-- |
||||
|
||||
if q.head == q.rightMargin { |
||||
q.head = leftMarginIndex |
||||
if q.tail == q.rightMargin { |
||||
q.tail = leftMarginIndex |
||||
} |
||||
q.rightMargin = q.tail |
||||
} |
||||
|
||||
return data, nil |
||||
} |
||||
|
||||
// Peek reads the oldest entry from list without moving head pointer
|
||||
func (q *BytesQueue) Peek() ([]byte, error) { |
||||
data, _, err := q.peek(q.head) |
||||
return data, err |
||||
} |
||||
|
||||
// Get reads entry from index
|
||||
func (q *BytesQueue) Get(index int) ([]byte, error) { |
||||
data, _, err := q.peek(index) |
||||
return data, err |
||||
} |
||||
|
||||
// Capacity returns number of allocated bytes for queue
|
||||
func (q *BytesQueue) Capacity() int { |
||||
return q.capacity |
||||
} |
||||
|
||||
// Len returns number of entries kept in queue
|
||||
func (q *BytesQueue) Len() int { |
||||
return q.count |
||||
} |
||||
|
||||
// Error returns error message
|
||||
func (e *queueError) Error() string { |
||||
return e.message |
||||
} |
||||
|
||||
func (q *BytesQueue) peek(index int) ([]byte, int, error) { |
||||
|
||||
if q.count == 0 { |
||||
return nil, 0, &queueError{"Empty queue"} |
||||
} |
||||
|
||||
if index <= 0 { |
||||
return nil, 0, &queueError{"Index must be grater than zero. Invalid index."} |
||||
} |
||||
|
||||
if index+headerEntrySize >= len(q.array) { |
||||
return nil, 0, &queueError{"Index out of range"} |
||||
} |
||||
|
||||
blockSize := int(binary.LittleEndian.Uint32(q.array[index : index+headerEntrySize])) |
||||
return q.array[index+headerEntrySize : index+headerEntrySize+blockSize], blockSize, nil |
||||
} |
||||
|
||||
func (q *BytesQueue) availableSpaceAfterTail() int { |
||||
if q.tail >= q.head { |
||||
return q.capacity - q.tail |
||||
} |
||||
return q.head - q.tail - minimumEmptyBlobSize |
||||
} |
||||
|
||||
func (q *BytesQueue) availableSpaceBeforeHead() int { |
||||
if q.tail >= q.head { |
||||
return q.head - leftMarginIndex - minimumEmptyBlobSize |
||||
} |
||||
return q.head - q.tail - minimumEmptyBlobSize |
||||
} |
||||
@ -0,0 +1,236 @@ |
||||
package bigcache |
||||
|
||||
import ( |
||||
"fmt" |
||||
"sync" |
||||
"sync/atomic" |
||||
|
||||
"github.com/allegro/bigcache/queue" |
||||
) |
||||
|
||||
type onRemoveCallback func(wrappedEntry []byte, reason RemoveReason) |
||||
|
||||
type cacheShard struct { |
||||
hashmap map[uint64]uint32 |
||||
entries queue.BytesQueue |
||||
lock sync.RWMutex |
||||
entryBuffer []byte |
||||
onRemove onRemoveCallback |
||||
|
||||
isVerbose bool |
||||
logger Logger |
||||
clock clock |
||||
lifeWindow uint64 |
||||
|
||||
stats Stats |
||||
} |
||||
|
||||
func (s *cacheShard) get(key string, hashedKey uint64) ([]byte, error) { |
||||
s.lock.RLock() |
||||
itemIndex := s.hashmap[hashedKey] |
||||
|
||||
if itemIndex == 0 { |
||||
s.lock.RUnlock() |
||||
s.miss() |
||||
return nil, notFound(key) |
||||
} |
||||
|
||||
wrappedEntry, err := s.entries.Get(int(itemIndex)) |
||||
if err != nil { |
||||
s.lock.RUnlock() |
||||
s.miss() |
||||
return nil, err |
||||
} |
||||
if entryKey := readKeyFromEntry(wrappedEntry); key != entryKey { |
||||
if s.isVerbose { |
||||
s.logger.Printf("Collision detected. Both %q and %q have the same hash %x", key, entryKey, hashedKey) |
||||
} |
||||
s.lock.RUnlock() |
||||
s.collision() |
||||
return nil, notFound(key) |
||||
} |
||||
s.lock.RUnlock() |
||||
s.hit() |
||||
return readEntry(wrappedEntry), nil |
||||
} |
||||
|
||||
func (s *cacheShard) set(key string, hashedKey uint64, entry []byte) error { |
||||
currentTimestamp := uint64(s.clock.epoch()) |
||||
|
||||
s.lock.Lock() |
||||
|
||||
if previousIndex := s.hashmap[hashedKey]; previousIndex != 0 { |
||||
if previousEntry, err := s.entries.Get(int(previousIndex)); err == nil { |
||||
resetKeyFromEntry(previousEntry) |
||||
} |
||||
} |
||||
|
||||
if oldestEntry, err := s.entries.Peek(); err == nil { |
||||
s.onEvict(oldestEntry, currentTimestamp, s.removeOldestEntry) |
||||
} |
||||
|
||||
w := wrapEntry(currentTimestamp, hashedKey, key, entry, &s.entryBuffer) |
||||
|
||||
for { |
||||
if index, err := s.entries.Push(w); err == nil { |
||||
s.hashmap[hashedKey] = uint32(index) |
||||
s.lock.Unlock() |
||||
return nil |
||||
} |
||||
if s.removeOldestEntry(NoSpace) != nil { |
||||
s.lock.Unlock() |
||||
return fmt.Errorf("entry is bigger than max shard size") |
||||
} |
||||
} |
||||
} |
||||
|
||||
func (s *cacheShard) del(key string, hashedKey uint64) error { |
||||
s.lock.RLock() |
||||
itemIndex := s.hashmap[hashedKey] |
||||
|
||||
if itemIndex == 0 { |
||||
s.lock.RUnlock() |
||||
s.delmiss() |
||||
return notFound(key) |
||||
} |
||||
|
||||
wrappedEntry, err := s.entries.Get(int(itemIndex)) |
||||
if err != nil { |
||||
s.lock.RUnlock() |
||||
s.delmiss() |
||||
return err |
||||
} |
||||
s.lock.RUnlock() |
||||
|
||||
s.lock.Lock() |
||||
{ |
||||
delete(s.hashmap, hashedKey) |
||||
s.onRemove(wrappedEntry, Deleted) |
||||
resetKeyFromEntry(wrappedEntry) |
||||
} |
||||
s.lock.Unlock() |
||||
|
||||
s.delhit() |
||||
return nil |
||||
} |
||||
|
||||
func (s *cacheShard) onEvict(oldestEntry []byte, currentTimestamp uint64, evict func(reason RemoveReason) error) bool { |
||||
oldestTimestamp := readTimestampFromEntry(oldestEntry) |
||||
if currentTimestamp-oldestTimestamp > s.lifeWindow { |
||||
evict(Expired) |
||||
return true |
||||
} |
||||
return false |
||||
} |
||||
|
||||
func (s *cacheShard) cleanUp(currentTimestamp uint64) { |
||||
s.lock.Lock() |
||||
for { |
||||
if oldestEntry, err := s.entries.Peek(); err != nil { |
||||
break |
||||
} else if evicted := s.onEvict(oldestEntry, currentTimestamp, s.removeOldestEntry); !evicted { |
||||
break |
||||
} |
||||
} |
||||
s.lock.Unlock() |
||||
} |
||||
|
||||
func (s *cacheShard) getOldestEntry() ([]byte, error) { |
||||
return s.entries.Peek() |
||||
} |
||||
|
||||
func (s *cacheShard) getEntry(index int) ([]byte, error) { |
||||
return s.entries.Get(index) |
||||
} |
||||
|
||||
func (s *cacheShard) copyKeys() (keys []uint32, next int) { |
||||
keys = make([]uint32, len(s.hashmap)) |
||||
|
||||
s.lock.RLock() |
||||
|
||||
for _, index := range s.hashmap { |
||||
keys[next] = index |
||||
next++ |
||||
} |
||||
|
||||
s.lock.RUnlock() |
||||
return keys, next |
||||
} |
||||
|
||||
func (s *cacheShard) removeOldestEntry(reason RemoveReason) error { |
||||
oldest, err := s.entries.Pop() |
||||
if err == nil { |
||||
hash := readHashFromEntry(oldest) |
||||
delete(s.hashmap, hash) |
||||
s.onRemove(oldest, reason) |
||||
return nil |
||||
} |
||||
return err |
||||
} |
||||
|
||||
func (s *cacheShard) reset(config Config) { |
||||
s.lock.Lock() |
||||
s.hashmap = make(map[uint64]uint32, config.initialShardSize()) |
||||
s.entryBuffer = make([]byte, config.MaxEntrySize+headersSizeInBytes) |
||||
s.entries.Reset() |
||||
s.lock.Unlock() |
||||
} |
||||
|
||||
func (s *cacheShard) len() int { |
||||
s.lock.RLock() |
||||
res := len(s.hashmap) |
||||
s.lock.RUnlock() |
||||
return res |
||||
} |
||||
|
||||
func (s *cacheShard) capacity() int { |
||||
s.lock.RLock() |
||||
res := s.entries.Capacity() |
||||
s.lock.RUnlock() |
||||
return res |
||||
} |
||||
|
||||
func (s *cacheShard) getStats() Stats { |
||||
var stats = Stats{ |
||||
Hits: atomic.LoadInt64(&s.stats.Hits), |
||||
Misses: atomic.LoadInt64(&s.stats.Misses), |
||||
DelHits: atomic.LoadInt64(&s.stats.DelHits), |
||||
DelMisses: atomic.LoadInt64(&s.stats.DelMisses), |
||||
Collisions: atomic.LoadInt64(&s.stats.Collisions), |
||||
} |
||||
return stats |
||||
} |
||||
|
||||
func (s *cacheShard) hit() { |
||||
atomic.AddInt64(&s.stats.Hits, 1) |
||||
} |
||||
|
||||
func (s *cacheShard) miss() { |
||||
atomic.AddInt64(&s.stats.Misses, 1) |
||||
} |
||||
|
||||
func (s *cacheShard) delhit() { |
||||
atomic.AddInt64(&s.stats.DelHits, 1) |
||||
} |
||||
|
||||
func (s *cacheShard) delmiss() { |
||||
atomic.AddInt64(&s.stats.DelMisses, 1) |
||||
} |
||||
|
||||
func (s *cacheShard) collision() { |
||||
atomic.AddInt64(&s.stats.Collisions, 1) |
||||
} |
||||
|
||||
func initNewShard(config Config, callback onRemoveCallback, clock clock) *cacheShard { |
||||
return &cacheShard{ |
||||
hashmap: make(map[uint64]uint32, config.initialShardSize()), |
||||
entries: *queue.NewBytesQueue(config.initialShardSize()*config.MaxEntrySize, config.maximumShardSize(), config.Verbose), |
||||
entryBuffer: make([]byte, config.MaxEntrySize+headersSizeInBytes), |
||||
onRemove: callback, |
||||
|
||||
isVerbose: config.Verbose, |
||||
logger: newLogger(config.Logger), |
||||
clock: clock, |
||||
lifeWindow: uint64(config.LifeWindow.Seconds()), |
||||
} |
||||
} |
||||
@ -0,0 +1,15 @@ |
||||
package bigcache |
||||
|
||||
// Stats stores cache statistics
|
||||
type Stats struct { |
||||
// Hits is a number of successfully found keys
|
||||
Hits int64 `json:"hits"` |
||||
// Misses is a number of not found keys
|
||||
Misses int64 `json:"misses"` |
||||
// DelHits is a number of successfully deleted keys
|
||||
DelHits int64 `json:"delete_hits"` |
||||
// DelMisses is a number of not deleted keys
|
||||
DelMisses int64 `json:"delete_misses"` |
||||
// Collisions is a number of happened key-collisions
|
||||
Collisions int64 `json:"collisions"` |
||||
} |
||||
@ -0,0 +1,16 @@ |
||||
package bigcache |
||||
|
||||
func max(a, b int) int { |
||||
if a > b { |
||||
return a |
||||
} |
||||
return b |
||||
} |
||||
|
||||
func convertMBToBytes(value int) int { |
||||
return value * 1024 * 1024 |
||||
} |
||||
|
||||
func isPowerOfTwo(number int) bool { |
||||
return (number & (number - 1)) == 0 |
||||
} |
||||
Loading…
Reference in new issue