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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
}
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