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package bigcache
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import "time"
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// Config for BigCache
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type Config struct {
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// Number of cache shards, value must be a power of two
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Shards int
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// Time after which entry can be evicted
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LifeWindow time.Duration
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// Interval between removing expired entries (clean up).
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// If set to <= 0 then no action is performed. Setting to < 1 second is counterproductive — bigcache has a one second resolution.
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CleanWindow time.Duration
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// Max number of entries in life window. Used only to calculate initial size for cache shards.
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// When proper value is set then additional memory allocation does not occur.
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MaxEntriesInWindow int
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// Max size of entry in bytes. Used only to calculate initial size for cache shards.
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MaxEntrySize int
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// StatsEnabled if true calculate the number of times a cached resource was requested.
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StatsEnabled bool
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// Verbose mode prints information about new memory allocation
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Verbose bool
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// Hasher used to map between string keys and unsigned 64bit integers, by default fnv64 hashing is used.
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Hasher Hasher
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// HardMaxCacheSize is a limit for BytesQueue size in MB.
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// It can protect application from consuming all available memory on machine, therefore from running OOM Killer.
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// Default value is 0 which means unlimited size. When the limit is higher than 0 and reached then
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// the oldest entries are overridden for the new ones. The max memory consumption will be bigger than
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// HardMaxCacheSize due to Shards' s additional memory. Every Shard consumes additional memory for map of keys
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// and statistics (map[uint64]uint32) the size of this map is equal to number of entries in
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// cache ~ 2×(64+32)×n bits + overhead or map itself.
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HardMaxCacheSize int
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// OnRemove 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.
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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 OnRemoveWithMetadata is specified.
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OnRemove func(key string, entry []byte)
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// OnRemoveWithMetadata 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 structure representing details about that specific entry.
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// Default value is nil which means no callback and it prevents from unwrapping the oldest entry.
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OnRemoveWithMetadata func(key string, entry []byte, keyMetadata Metadata)
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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 func(key string, entry []byte, reason RemoveReason)
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onRemoveFilter int
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// Logger is a logging interface and used in combination with `Verbose`
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// Defaults to `DefaultLogger()`
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Logger Logger
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}
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// DefaultConfig initializes config with default values.
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// When load for BigCache can be predicted in advance then it is better to use custom config.
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func DefaultConfig(eviction time.Duration) Config {
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return Config{
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Shards: 1024,
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LifeWindow: eviction,
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CleanWindow: 1 * time.Second,
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MaxEntriesInWindow: 1000 * 10 * 60,
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MaxEntrySize: 500,
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StatsEnabled: false,
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Verbose: true,
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Hasher: newDefaultHasher(),
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HardMaxCacheSize: 0,
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Logger: DefaultLogger(),
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}
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}
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// initialShardSize computes initial shard size
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func (c Config) initialShardSize() int {
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return max(c.MaxEntriesInWindow/c.Shards, minimumEntriesInShard)
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}
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// maximumShardSizeInBytes computes maximum shard size in bytes
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func (c Config) maximumShardSizeInBytes() int {
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maxShardSize := 0
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if c.HardMaxCacheSize > 0 {
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maxShardSize = convertMBToBytes(c.HardMaxCacheSize) / c.Shards
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}
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return maxShardSize
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}
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// OnRemoveFilterSet sets which remove reasons will trigger a call to OnRemoveWithReason.
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// Filtering out reasons prevents bigcache from unwrapping them, which saves cpu.
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func (c Config) OnRemoveFilterSet(reasons ...RemoveReason) Config {
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c.onRemoveFilter = 0
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for i := range reasons {
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c.onRemoveFilter |= 1 << uint(reasons[i])
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}
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return c
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}
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