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72 lines
2.7 KiB
Markdown
72 lines
2.7 KiB
Markdown
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## TTLCache - an in-memory cache with expiration
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TTLCache is a simple key/value cache in golang with the following functions:
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1. Thread-safe
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2. Individual expiring time or global expiring time, you can choose
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3. Auto-Extending expiration on `Get` -or- DNS style TTL, see `SkipTtlExtensionOnHit(bool)`
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4. Fast and memory efficient
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5. Can trigger callback on key expiration
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6. Cleanup resources by calling `Close()` at end of lifecycle.
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Note (issue #25): by default, due to historic reasons, the TTL will be reset on each cache hit and you need to explicitly configure the cache to use a TTL that will not get extended.
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[](https://travis-ci.org/ReneKroon/ttlcache)
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#### Usage
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```go
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import (
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"time"
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"fmt"
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"github.com/ReneKroon/ttlcache"
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)
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func main () {
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newItemCallback := func(key string, value interface{}) {
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fmt.Printf("New key(%s) added\n", key)
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}
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checkExpirationCallback := func(key string, value interface{}) bool {
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if key == "key1" {
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// if the key equals "key1", the value
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// will not be allowed to expire
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return false
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}
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// all other values are allowed to expire
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return true
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}
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expirationCallback := func(key string, value interface{}) {
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fmt.Printf("This key(%s) has expired\n", key)
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}
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cache := ttlcache.NewCache()
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defer cache.Close()
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cache.SetTTL(time.Duration(10 * time.Second))
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cache.SetExpirationCallback(expirationCallback)
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cache.Set("key", "value")
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cache.SetWithTTL("keyWithTTL", "value", 10 * time.Second)
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value, exists := cache.Get("key")
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count := cache.Count()
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result := cache.Remove("key")
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}
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```
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#### TTLCache - Some design considerations
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1. The complexity of the current cache is already quite high. Therefore i will not add 'convenience' features like an interface to supply a function to get missing keys.
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2. The locking should be done only in the functions of the Cache struct. Else data races can occur or recursive locks are needed, which are both unwanted.
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3. I prefer correct functionality over fast tests. It's ok for new tests to take seconds to proof something.
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#### Original Project
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TTLCache was forked from [wunderlist/ttlcache](https://github.com/wunderlist/ttlcache) to add extra functions not avaiable in the original scope.
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The main differences are:
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1. A item can store any kind of object, previously, only strings could be saved
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2. Optionally, you can add callbacks too: check if a value should expire, be notified if a value expires, and be notified when new values are added to the cache
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3. The expiration can be either global or per item
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4. Can exist items without expiration time
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5. Expirations and callbacks are realtime. Don't have a pooling time to check anymore, now it's done with a heap.
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