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// Package lrucache implements LRU (Least Recently Used) node |
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package lrucache |
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import ( |
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"encoding/json" |
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"github.com/arazmj/gerdu/cache" |
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"github.com/arazmj/gerdu/dlinklist" |
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"github.com/arazmj/gerdu/metrics" |
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"github.com/hashicorp/raft" |
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"github.com/inhies/go-bytesize" |
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"io" |
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"sync" |
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) |
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//LRUCache data structure |
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type LRUCache struct { |
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sync.RWMutex |
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cache.UnImplementedCache |
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node map[string]*dlinklist.Node |
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linklist *dlinklist.DLinkedList |
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capacity bytesize.ByteSize |
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size bytesize.ByteSize |
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} |
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// NewCache LRUCache constructor |
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func NewCache(capacity bytesize.ByteSize) *LRUCache { |
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l := &LRUCache{ |
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RWMutex: sync.RWMutex{}, |
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node: map[string]*dlinklist.Node{}, |
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linklist: dlinklist.NewLinkedList(), |
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capacity: capacity, |
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size: 0, |
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} |
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return l |
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} |
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// Get returns the value for the key |
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func (c *LRUCache) Get(key string) (value string, ok bool) { |
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defer c.Unlock() |
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c.Lock() |
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if value, ok := c.node[key]; ok { |
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metrics.Hits.Inc() |
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node := value |
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c.linklist.RemoveNode(node) |
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c.linklist.AddNode(node) |
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return node.Value, true |
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} |
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metrics.Miss.Inc() |
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return "", false |
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} |
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// applyPut updates or insert a new entry, evicts the old entry |
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// if node size is larger than capacity |
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func (c *LRUCache) Put(key string, value string) (created bool) { |
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defer c.Unlock() |
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c.Lock() |
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if v, ok := c.node[key]; ok { |
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node := v |
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c.linklist.RemoveNode(node) |
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c.linklist.AddNode(node) |
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node.Value = value |
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created = false |
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} else { |
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node := &dlinklist.Node{Key: key, Value: value} |
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c.linklist.AddNode(node) |
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c.node[key] = node |
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metrics.Adds.Inc() |
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c.size += bytesize.ByteSize(len(value)) |
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for c.size > c.capacity { |
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metrics.Deletes.Inc() |
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tail := c.linklist.PopTail() |
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c.size -= bytesize.ByteSize(len(tail.Value)) |
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delete(c.node, tail.Key) |
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} |
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created = true |
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} |
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return created |
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} |
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//applyDelete the key from the node |
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func (c *LRUCache) Delete(key string) (ok bool) { |
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if node, ok := c.node[key]; ok { |
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metrics.Deletes.Inc() |
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c.linklist.RemoveNode(node) |
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delete(c.node, key) |
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} else { |
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return false |
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} |
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return true |
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} |
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func (c *LRUCache) Snapshot() (raft.FSMSnapshot, error) { |
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c.RLock() |
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defer c.RUnlock() |
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o := make(map[string]string) |
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for k, v := range c.node { |
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o[k] = v.Value |
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} |
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return &fsmSnapshot{store: o}, nil |
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} |
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func (c *LRUCache) Restore(closer io.ReadCloser) error { |
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o := make(map[string]string) |
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if err := json.NewDecoder(closer).Decode(&o); err != nil { |
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return err |
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} |
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// Set the state from the snapshot, no lock required according to |
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// Hashicorp docs. |
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for k, v := range o { |
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c.Put(k, v) |
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} |
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return nil |
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} |
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type fsmSnapshot struct { |
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store map[string]string |
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} |
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func (f *fsmSnapshot) Persist(sink raft.SnapshotSink) error { |
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err := func() error { |
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// Encode data. |
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b, err := json.Marshal(f.store) |
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if err != nil { |
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return err |
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} |
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// Write data to sink. |
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if _, err := sink.Write(b); err != nil { |
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return err |
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} |
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// Close the sink. |
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return sink.Close() |
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}() |
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if err != nil { |
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sink.Cancel() |
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} |
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return err |
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} |
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func (f *fsmSnapshot) Release() {} |
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arazmj /
gerdu
