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cached.go
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cached.go
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// MIT License
//
// Copyright (c) 2023 kache.io
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package provider
import (
"context"
"fmt"
"sync"
"time"
)
// Cached is the two-tiered cache provider, adding a caching layer on top of a `Provider“.
type Cached struct {
// inner is the tier-two cache (remote, network).
inner Provider
// outer is the tier-one cache (local, in-memory).
outer Provider
// name is the layered cache name.
name string
// ttl is the default TTL.
ttl time.Duration
mu sync.Mutex
}
// NewCached adds a caching layer on top of a cache `Provider` (typically a remote cache) and
// wraps it with a local in-memory cache. Items will always be stored in both caches. Fetches are
// only satified by the underlying remote cache, if the item does not exist in the local cache.
// The local cache will remove items, depending on the capacity constraints of the cache or the
// lifetime constraints of the cached item, respectively.
func NewCached(cache Provider, name string, ttl time.Duration, config InMemoryCacheConfig) (*Cached, error) {
config.Sanitize()
if config.MaxItemSize > config.MaxSize {
return nil, fmt.Errorf("max item size (%v) must not exceed overall cache size (%v)",
config.MaxItemSize, config.MaxSize)
}
l, err := NewInMemoryCache(InMemoryCacheConfig{
MaxSize: config.MaxSize,
MaxItemSize: config.MaxItemSize,
})
if err != nil {
return nil, err
}
cached := &Cached{
inner: cache,
outer: l,
ttl: ttl,
name: "layered-" + name,
}
return cached, nil
}
// Get retrieves an element based on a key, returning nil if the element
// does not exist.
func (c *Cached) Get(ctx context.Context, key string) []byte {
c.mu.Lock()
defer c.mu.Unlock()
val := c.outer.Get(ctx, key)
if val != nil {
return val
}
val = c.inner.Get(ctx, key)
if val != nil {
c.outer.Set(key, val, c.ttl)
}
return val
}
// Set adds an element to the cache.
func (c *Cached) Set(key string, value []byte, ttl time.Duration) {
c.inner.Set(key, value, ttl)
c.mu.Lock()
defer c.mu.Unlock()
c.outer.Set(key, value, ttl)
}
// Delete deletes an element in the cache.
func (c *Cached) Delete(ctx context.Context, key string) bool {
c.mu.Lock()
c.outer.Delete(ctx, key)
c.mu.Unlock()
return c.inner.Delete(ctx, key)
}
// Keys returns a slice of cache keys.
func (c *Cached) Keys(ctx context.Context, prefix string) []string {
return c.inner.Keys(ctx, prefix) // always satisfied by inner cache.
}
// Purge purges all keys matching the spedified pattern from the cache.
func (c *Cached) Purge(ctx context.Context, pattern string) error {
c.mu.Lock()
_ = c.outer.Purge(ctx, pattern)
c.mu.Unlock()
return c.inner.Purge(ctx, pattern)
}
// Flush deletes all elements from the cache.
func (c *Cached) Flush(ctx context.Context) error {
c.mu.Lock()
_ = c.outer.Flush(ctx)
c.mu.Unlock()
return c.inner.Flush(ctx)
}
// Size returns the number of entries currently stored in the Cache.
func (c *Cached) Size() int {
return len(c.inner.Keys(context.Background(), ""))
}