forked from cockroachdb/cockroach
/
leader_cache.go
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/
leader_cache.go
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// Copyright 2015 The Cockroach Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License. See the AUTHORS file
// for names of contributors.
//
// Author: Tobias Schottdorf (tobias.schottdorf@gmail.com)
package kv
import (
"sync"
"github.com/cockroachdb/cockroach/roachpb"
"github.com/cockroachdb/cockroach/util/cache"
)
// A leaderCache is a cache used to keep track of the leader
// replica of Raft consensus groups.
type leaderCache struct {
mu sync.Mutex
cache *cache.UnorderedCache
}
// newLeaderCache creates a new leaderCache of the given size.
// The underlying cache internally uses a hash map, so lookups
// are cheap.
func newLeaderCache(size int) *leaderCache {
return &leaderCache{
cache: cache.NewUnorderedCache(cache.Config{
Policy: cache.CacheLRU,
ShouldEvict: func(s int, key, value interface{}) bool {
return s > size
},
}),
}
}
// Lookup consults the cache for the replica cached as the leader of
// the given Raft consensus group.
func (lc *leaderCache) Lookup(group roachpb.RangeID) roachpb.ReplicaDescriptor {
lc.mu.Lock()
defer lc.mu.Unlock()
v, ok := lc.cache.Get(group)
if !ok || v == nil {
return roachpb.ReplicaDescriptor{}
}
return *(v.(*roachpb.ReplicaDescriptor))
}
// Update invalidates the cached leader for the given Raft group.
// If a replica is passed in, it is inserted into the cache.
// A StoreID of 0 (empty replica) means evict.
func (lc *leaderCache) Update(group roachpb.RangeID, r roachpb.ReplicaDescriptor) {
lc.mu.Lock()
defer lc.mu.Unlock()
lc.cache.Del(group)
if r.StoreID != 0 {
lc.cache.Add(group, &r)
}
}