mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
100 lines
2.5 KiB
Go
100 lines
2.5 KiB
Go
// Copyright 2016 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package cache
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import (
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"sync"
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"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
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pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
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"github.com/golang/groupcache/lru"
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)
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var (
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DefaultMaxEntries = 2048
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ErrCompacted = rpctypes.ErrGRPCCompacted
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)
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type Cache interface {
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Add(req *pb.RangeRequest, resp *pb.RangeResponse)
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Get(req *pb.RangeRequest) (*pb.RangeResponse, error)
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Compact(revision int64)
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}
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// keyFunc returns the key of an request, which is used to look up in the cache for it's caching response.
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func keyFunc(req *pb.RangeRequest) string {
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// TODO: use marshalTo to reduce allocation
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b, err := req.Marshal()
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if err != nil {
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panic(err)
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}
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return string(b)
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}
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func NewCache(maxCacheEntries int) Cache {
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return &cache{
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lru: lru.New(maxCacheEntries),
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}
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}
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// cache implements Cache
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type cache struct {
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mu sync.RWMutex
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lru *lru.Cache
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compactedRev int64
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}
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// Add adds the response of a request to the cache if its revision is larger than the compacted revision of the cache.
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func (c *cache) Add(req *pb.RangeRequest, resp *pb.RangeResponse) {
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key := keyFunc(req)
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c.mu.Lock()
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defer c.mu.Unlock()
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if req.Revision > c.compactedRev {
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c.lru.Add(key, resp)
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}
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}
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// Get looks up the caching response for a given request.
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// Get is also responsible for lazy eviction when accessing compacted entries.
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func (c *cache) Get(req *pb.RangeRequest) (*pb.RangeResponse, error) {
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key := keyFunc(req)
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c.mu.Lock()
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defer c.mu.Unlock()
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if req.Revision > c.compactedRev {
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c.lru.Remove(key)
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return nil, ErrCompacted
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}
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if resp, ok := c.lru.Get(key); ok {
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return resp.(*pb.RangeResponse), nil
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}
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return nil, nil
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}
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// Compact invalidate all caching response before the given rev.
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// Replace with the invalidation is lazy. The actual removal happens when the entries is accessed.
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func (c *cache) Compact(revision int64) {
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c.mu.Lock()
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defer c.mu.Unlock()
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if revision > c.compactedRev {
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c.compactedRev = revision
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}
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}
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