Enable clear/purge for failed digests

go/util/caching.go

 package util
 
 import (
         "encoding/json"
         "reflect"
         "sync"
 
         "github.com/golang/groupcache/lru"
 )
 
 // Generic LRUCache interface.
 type LRUCache interface {
         // Add adds a key-value pair to the cache.
         Add(key, value interface{}) bool
 
         // Get returns a key value for the given cache. If ok is true
         // the fetch was succesfull.
         Get(key interface{}) (value interface{}, ok bool)
 
         // Len returns the current size of the cache.
         Len() int
 
         // Remove removes a key value pair from the cache.
         Remove(key interface{})
+
+        // Keys returns all the keys in the LRUCache.
+        Keys() []interface{}
 }
 
 // LRUCodec converts serializes/deserializes an instance of a type to/from
 // byte arrays. Encode and Decode have to be the inverse of each other.
 type LRUCodec interface {
         // Encode serializes the given value to a byte array (inverse of Decode).
         Encode(interface{}) ([]byte, error)
 
         // Decode deserializes the byte array to an instance of the type that
         // was passed to Encode in a prior call.
         Decode([]byte) (interface{}, error)
 }
 
 type MemLRUCache struct {
         cache *lru.Cache
+        keys  map[string]bool
         mutex sync.RWMutex
 }
 
 func NewMemLRUCache(maxEntries int) *MemLRUCache {
-        return &MemLRUCache{
+        ret := &MemLRUCache{
                 cache: lru.New(maxEntries),
+                keys:  map[string]bool{},
         }
+
+        ret.cache.OnEvicted = func(key lru.Key, value interface{}) {
+                delete(ret.keys, getStringKey(key))
+        }
+
+        return ret
+}
+
+func getStringKey(key interface{}) string {
+        k := ""
+        switch key := key.(type) {
+        case string:
+                k = key
+        case []byte:
+                if key != nil {
+                        k = string(key)
+                }
+        }
+        return k
 }
 
 func (m *MemLRUCache) Add(key, value interface{}) bool {
         m.mutex.Lock()
         defer m.mutex.Unlock()
         m.cache.Add(key, value)
+        m.keys[getStringKey(key)] = true
         return true
 }
 
 func (m *MemLRUCache) Get(key interface{}) (value interface{}, ok bool) {
         m.mutex.RLock()
         m.mutex.RUnlock()
         return m.cache.Get(key)
 }
 
 func (m *MemLRUCache) Len() int {
         m.mutex.RLock()
         m.mutex.RUnlock()
         return m.cache.Len()
 }
 
 func (m *MemLRUCache) Remove(key interface{}) {
         m.mutex.Lock()
         defer m.mutex.Unlock()
+        m.cache.Remove(key)
+        delete(m.keys, getStringKey(key))
+}
+
+func (m *MemLRUCache) Keys() []interface{} {

[jcgregorio, 2015/10/13 18:40:24]

Needs unit tests.

[stephana, 2015/10/14 14:26:30]

Done. I factored out tests from redisutils to be a generic unit test for the
LRUCache interface. 

+        m.mutex.RLock()
+        m.mutex.RUnlock()

[jcgregorio, 2015/10/13 18:40:24]

defer m.mutex.RUnlock()

[stephana, 2015/10/14 14:26:30]

Good catch. Fixed.

+        ret := make([]interface{}, 0, len(m.keys))
+        for k := range m.keys {
+                ret = append(ret, k)
+        }
+        return ret
 }
 
 type jsonCodec struct {
         targetType reflect.Type
         isSlice    bool
 }
 
 // JSONCodec implements the LRUCodec interface by serializing and
 // deserializing instances of the underlying type of 'instance'.
 // Generally it's assumed that 'instance' is a struct, a pointer to
@@ skipping 20 matching lines @@
         ret := reflect.New(j.targetType).Interface()
         err := json.Unmarshal(byteData, ret)
         if err != nil {
                 return nil, err
         } else if j.isSlice {
                 return reflect.ValueOf(ret).Elem().Interface(), nil
         }
 
         return ret, nil
 }