91 lines
2.7 KiB
Go
91 lines
2.7 KiB
Go
package ccache
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type Configuration struct {
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maxItems uint64
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buckets int
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itemsToPrune int
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deleteBuffer int
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promoteBuffer int
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getsPerPromote int32
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tracking bool
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}
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func Configure() *Configuration {
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return &Configuration{
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buckets: 16,
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itemsToPrune: 500,
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deleteBuffer: 1024,
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getsPerPromote: 3,
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promoteBuffer: 1024,
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maxItems: 5000,
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tracking: false,
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}
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}
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// The max number of items to store in the cache
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// [5000]
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func (c *Configuration) MaxItems(max uint64) *Configuration {
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c.maxItems = max
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return c
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}
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// Keys are hashed into % bucket count to provide greater concurrency (every set
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// requires a write lock on the bucket). Must be a power of 2 (1, 2, 4, 8, 16, ...)
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// [16]
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func (c *Configuration) Buckets(count uint32) *Configuration {
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if count == 0 || ((count&(^count+1)) == count) == false {
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count = 16
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}
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c.buckets = int(count)
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return c
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}
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// The number of items to prune when memory is low
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// [500]
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func (c *Configuration) ItemsToPrune(count uint32) *Configuration {
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c.itemsToPrune = int(count)
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return c
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}
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// The size of the queue for items which should be promoted. If the queue fills
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// up, promotions are skipped
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// [1024]
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func (c *Configuration) PromoteBuffer(size uint32) *Configuration {
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c.promoteBuffer = int(size)
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return c
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}
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// The size of the queue for items which should be deleted. If the queue fills
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// up, calls to Delete() will block
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func (c *Configuration) DeleteBuffer(size uint32) *Configuration {
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c.deleteBuffer = int(size)
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return c
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}
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// Give a large cache with a high read / write ratio, it's usually unecessary
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// to promote an item on every Get. GetsPerPromote specifies the number of Gets
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// a key must have before being promoted
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// [3]
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func (c *Configuration) GetsPerPromote(count int32) *Configuration {
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c.getsPerPromote = count
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return c
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}
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// Typically, a cache is agnostic about how cached values are use. This is fine
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// for a typical cache usage, where you fetch an item from the cache, do something
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// (write it out to) and nothing else.
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// However, if callers are going to keep a reference to a cached item for a long
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// time, things get messy. Specifically, the cache can evict the item, while
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// references still exist. Technically, this isn't an issue. However, if you reload
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// the item back into the cache, you end up with 2 objects representing the same
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// data. This is a waste of space and could lead to weird behavior (the type an
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// identity map is meant to solve).
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// By turning tracking on and using the cache's TrackingGet, the cache
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// won't evict items which you haven't called Release() on. It's a simple reference
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// counter.
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func (c *Configuration) Track() *Configuration {
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c.tracking = true
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return c
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}
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