112 lines
2.2 KiB
Go
112 lines
2.2 KiB
Go
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package cache
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import (
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"sync"
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"time"
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)
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var zeroTTL = time.Duration(0)
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// MemoryTTL holds the required variables to compose an in memory cache system
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// which also provides expiring key mechanism
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type MemoryTTL struct {
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// Mutex is used for handling the concurrent
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// read/write requests for cache
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sync.Mutex
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// cache holds the cache data
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cache *MemoryNoTS
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// setAts holds the time that related item's set at
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setAts map[string]time.Time
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// ttl is a duration for a cache key to expire
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ttl time.Duration
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// gcInterval is a duration for garbage collection
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gcInterval time.Duration
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}
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// NewMemoryWithTTL creates an inmemory cache system
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// Which everytime will return the true values about a cache hit
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// and never will leak memory
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// ttl is used for expiration of a key from cache
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func NewMemoryWithTTL(ttl time.Duration) *MemoryTTL {
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return &MemoryTTL{
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cache: NewMemoryNoTS(),
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setAts: map[string]time.Time{},
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ttl: ttl,
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}
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}
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// StartGC starts the garbage collection process in a go routine
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func (r *MemoryTTL) StartGC(gcInterval time.Duration) {
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r.gcInterval = gcInterval
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go func() {
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for _ = range time.Tick(gcInterval) {
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for key := range r.cache.items {
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if !r.isValid(key) {
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r.Delete(key)
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}
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}
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}
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}()
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}
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// Get returns a value of a given key if it exists
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// and valid for the time being
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func (r *MemoryTTL) Get(key string) (interface{}, error) {
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r.Lock()
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defer r.Unlock()
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if !r.isValid(key) {
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r.delete(key)
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return nil, ErrNotFound
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}
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value, err := r.cache.Get(key)
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if err != nil {
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return nil, err
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}
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return value, nil
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}
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// Set will persist a value to the cache or
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// override existing one with the new one
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func (r *MemoryTTL) Set(key string, value interface{}) error {
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r.Lock()
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defer r.Unlock()
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r.cache.Set(key, value)
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r.setAts[key] = time.Now()
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return nil
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}
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// Delete deletes a given key if exists
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func (r *MemoryTTL) Delete(key string) error {
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r.Lock()
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defer r.Unlock()
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r.delete(key)
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return nil
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}
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func (r *MemoryTTL) delete(key string) {
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r.cache.Delete(key)
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delete(r.setAts, key)
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}
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func (r *MemoryTTL) isValid(key string) bool {
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setAt, ok := r.setAts[key]
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if !ok {
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return false
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}
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if r.ttl == zeroTTL {
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return true
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}
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return setAt.Add(r.ttl).After(time.Now())
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}
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