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If implemented, will provide users with a way to cache index files. This addresses issues where the index file is loaded and unmarshalled in concurrent reconciliation resulting in a heavy memory footprint. The caching strategy used is cache aside, and the cache is a k/v store with expiration. The cache number of entries and ttl for entries are configurable. The cache is optional and is disabled by default Signed-off-by: Soule BA <soule@weave.works>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,234 @@ | ||
| /* | ||
| Copyright 2022 The Flux authors | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
|
|
||
| package cache | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "runtime" | ||
| "sync" | ||
| "time" | ||
| ) | ||
|
|
||
| // NOTE: this is heavily based on patrickmn/go-cache: | ||
| // https://github.com/patrickmn/go-cache | ||
|
|
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| // Cache is a thread-safe in-memory key/value store. | ||
| type Cache struct { | ||
| *cache | ||
| } | ||
|
|
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| // Item is an item stored in the cache. | ||
| type Item struct { | ||
| Object interface{} | ||
| Expiration int64 | ||
| } | ||
|
|
||
| type cache struct { | ||
| // Items holds the elements in the cache. | ||
| Items map[string]Item | ||
| // Maximum number of items the cache can hold. | ||
| MaxItems int | ||
| mu sync.RWMutex | ||
| janitor *janitor | ||
| } | ||
|
|
||
| // ItemCount returns the number of items in the cache. | ||
| // This may include items that have expired, but have not yet been cleaned up. | ||
| func (c *cache) ItemCount() int { | ||
| c.mu.RLock() | ||
| n := len(c.Items) | ||
| c.mu.RUnlock() | ||
| return n | ||
| } | ||
|
|
||
| func (c *cache) set(key string, value interface{}, expiration time.Duration) { | ||
| var e int64 | ||
| if expiration > 0 { | ||
| e = time.Now().Add(expiration).UnixNano() | ||
| } | ||
|
|
||
| c.Items[key] = Item{ | ||
| Object: value, | ||
| Expiration: e, | ||
| } | ||
| } | ||
|
|
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| // Set adds an item to the cache, replacing any existing item. | ||
| // If expiration is zero, the item never expires. | ||
| // If the cache is full, Set will return an error. | ||
| func (c *cache) Set(key string, value interface{}, expiration time.Duration) error { | ||
| c.mu.Lock() | ||
| _, found := c.Items[key] | ||
| if found { | ||
| c.set(key, value, expiration) | ||
| c.mu.Unlock() | ||
| return nil | ||
| } | ||
|
|
||
| if c.MaxItems > 0 && len(c.Items) < c.MaxItems { | ||
| c.set(key, value, expiration) | ||
| c.mu.Unlock() | ||
| return nil | ||
| } | ||
|
|
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| c.mu.Unlock() | ||
| return fmt.Errorf("Cache is full") | ||
| } | ||
|
|
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| func (c *cache) Add(key string, value interface{}, expiration time.Duration) error { | ||
| c.mu.Lock() | ||
| _, found := c.Items[key] | ||
| if found { | ||
| c.mu.Unlock() | ||
| return fmt.Errorf("Item %s already exists", key) | ||
| } | ||
|
|
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| if c.MaxItems > 0 && len(c.Items) < c.MaxItems { | ||
| c.set(key, value, expiration) | ||
| c.mu.Unlock() | ||
| return nil | ||
| } | ||
|
|
||
| c.mu.Unlock() | ||
| return fmt.Errorf("Cache is full") | ||
| } | ||
|
|
||
| func (c *cache) Get(key string) (interface{}, bool) { | ||
| c.mu.RLock() | ||
| item, found := c.Items[key] | ||
| if !found { | ||
| c.mu.RUnlock() | ||
| return nil, false | ||
| } | ||
| if item.Expiration > 0 { | ||
| if item.Expiration < time.Now().UnixNano() { | ||
| c.mu.RUnlock() | ||
| return nil, false | ||
| } | ||
| } | ||
| c.mu.RUnlock() | ||
| return item.Object, true | ||
| } | ||
|
|
||
| func (c *cache) Delete(key string) { | ||
| c.mu.Lock() | ||
| delete(c.Items, key) | ||
| c.mu.Unlock() | ||
| } | ||
|
|
||
| func (c *cache) Clear() { | ||
| c.mu.Lock() | ||
| c.Items = make(map[string]Item) | ||
| c.mu.Unlock() | ||
| } | ||
|
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| func (c *cache) HasExpired(key string) bool { | ||
| c.mu.RLock() | ||
| item, ok := c.Items[key] | ||
| if !ok { | ||
| c.mu.RUnlock() | ||
| return true | ||
| } | ||
| if item.Expiration > 0 { | ||
| if item.Expiration < time.Now().UnixNano() { | ||
| c.mu.RUnlock() | ||
| return true | ||
| } | ||
| } | ||
| c.mu.RUnlock() | ||
| return false | ||
| } | ||
|
|
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| func (c *cache) SetExpiration(key string, expiration time.Duration) { | ||
| c.mu.Lock() | ||
| item, ok := c.Items[key] | ||
| if !ok { | ||
| c.mu.Unlock() | ||
| return | ||
| } | ||
| item.Expiration = time.Now().Add(expiration).UnixNano() | ||
| c.mu.Unlock() | ||
| } | ||
|
|
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| func (c *cache) GetExpiration(key string) time.Duration { | ||
| c.mu.RLock() | ||
| item, ok := c.Items[key] | ||
| if !ok { | ||
| c.mu.RUnlock() | ||
| return 0 | ||
| } | ||
| if item.Expiration > 0 { | ||
| if item.Expiration < time.Now().UnixNano() { | ||
| c.mu.RUnlock() | ||
| return 0 | ||
| } | ||
| } | ||
| c.mu.RUnlock() | ||
| return time.Duration(item.Expiration - time.Now().UnixNano()) | ||
| } | ||
|
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| func (c *cache) DeleteExpired() { | ||
| c.mu.Lock() | ||
| for k, v := range c.Items { | ||
| if v.Expiration > 0 && v.Expiration < time.Now().UnixNano() { | ||
| delete(c.Items, k) | ||
| } | ||
| } | ||
| c.mu.Unlock() | ||
| } | ||
|
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| type janitor struct { | ||
| Interval time.Duration | ||
| stop chan bool | ||
| } | ||
|
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| func (j *janitor) Run(c *cache) { | ||
| ticker := time.NewTicker(j.Interval) | ||
| for { | ||
| select { | ||
| case <-ticker.C: | ||
| c.DeleteExpired() | ||
| case <-j.stop: | ||
| ticker.Stop() | ||
| return | ||
| } | ||
| } | ||
| } | ||
|
|
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| func stopJanitor(c *Cache) { | ||
| c.janitor.stop <- true | ||
| } | ||
|
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| func New(maxItems int, interval time.Duration) *Cache { | ||
| c := &cache{ | ||
| Items: make(map[string]Item), | ||
| MaxItems: maxItems, | ||
| janitor: &janitor{ | ||
| Interval: interval, | ||
| stop: make(chan bool), | ||
| }, | ||
| } | ||
|
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| C := &Cache{c} | ||
|
|
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| if interval > 0 { | ||
| go c.janitor.Run(c) | ||
| runtime.SetFinalizer(C, stopJanitor) | ||
| } | ||
|
|
||
| return C | ||
| } |
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