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Merge pull request #614 from josephschorr/cache-interface
Move the cache implementation behind an interface
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| package cache | ||
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| // Config for caching. | ||
| // See: https://github.com/dgraph-io/ristretto#Config | ||
| type Config struct { | ||
| // NumCounters determines the number of counters (keys) to keep that hold | ||
| // access frequency information. It's generally a good idea to have more | ||
| // counters than the max cache capacity, as this will improve eviction | ||
| // accuracy and subsequent hit ratios. | ||
| // | ||
| // For example, if you expect your cache to hold 1,000,000 items when full, | ||
| // NumCounters should be 10,000,000 (10x). Each counter takes up roughly | ||
| // 3 bytes (4 bits for each counter * 4 copies plus about a byte per | ||
| // counter for the bloom filter). Note that the number of counters is | ||
| // internally rounded up to the nearest power of 2, so the space usage | ||
| // may be a little larger than 3 bytes * NumCounters. | ||
| NumCounters int64 | ||
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| // MaxCost can be considered as the cache capacity, in whatever units you | ||
| // choose to use. | ||
| // | ||
| // For example, if you want the cache to have a max capacity of 100MB, you | ||
| // would set MaxCost to 100,000,000 and pass an item's number of bytes as | ||
| // the `cost` parameter for calls to Set. If new items are accepted, the | ||
| // eviction process will take care of making room for the new item and not | ||
| // overflowing the MaxCost value. | ||
| MaxCost int64 | ||
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| // BufferItems determines the size of Get buffers. | ||
| // | ||
| // Unless you have a rare use case, using `64` as the BufferItems value | ||
| // results in good performance. | ||
| BufferItems int64 | ||
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| // Metrics determines whether cache statistics are kept during the cache's | ||
| // lifetime. There *is* some overhead to keeping statistics, so you should | ||
| // only set this flag to true when testing or throughput performance isn't a | ||
| // major factor. | ||
| Metrics bool | ||
| } | ||
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| // Cache defines an interface for a generic cache. | ||
| type Cache interface { | ||
| // Get returns the value for the given key in the cache, if it exists. | ||
| Get(key interface{}) (interface{}, bool) | ||
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| // Set sets a value for the key in the cache, with the given cost. | ||
| Set(key interface{}, entry interface{}, cost int64) bool | ||
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| // Wait waits for the cache to process and apply updates. | ||
| Wait() | ||
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| // Close closes the cache's background workers (if any). | ||
| Close() | ||
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| // GetMetrics returns the metrics block for the cache. | ||
| GetMetrics() Metrics | ||
| } | ||
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| // Metrics defines metrics exported by the cache. | ||
| type Metrics interface { | ||
| // Hits is the number of cache hits. | ||
| Hits() uint64 | ||
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| // Misses is the number of cache misses. | ||
| Misses() uint64 | ||
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| // CostAdded returns the total cost of added items. | ||
| CostAdded() uint64 | ||
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| // CostEvicted returns the total cost of evicted items. | ||
| CostEvicted() uint64 | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| //go:build !wasm | ||
| // +build !wasm | ||
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| package cache | ||
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| import ( | ||
| "github.com/dgraph-io/ristretto" | ||
| ) | ||
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| // NewCache creates a new ristretto cache from the given config. | ||
| func NewCache(config *Config) (Cache, error) { | ||
| cache, err := ristretto.NewCache(&ristretto.Config{ | ||
| NumCounters: config.NumCounters, | ||
| MaxCost: config.MaxCost, | ||
| BufferItems: config.BufferItems, | ||
| Metrics: config.Metrics, | ||
| }) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return wrapped{cache}, nil | ||
| } | ||
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| type wrapped struct { | ||
| *ristretto.Cache | ||
| } | ||
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| func (w wrapped) GetMetrics() Metrics { | ||
| return w.Cache.Metrics | ||
| } | ||
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| var _ Cache = &wrapped{} |
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