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// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus-core library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus-core library. If not, see
// <http://www.gnu.org/licenses/>.
package core
import (
"errors"
"sync"
"github.com/dexon-foundation/dexon-consensus-core/core/crypto"
"github.com/dexon-foundation/dexon-consensus-core/core/types"
)
var (
// ErrRoundNotReady means we got nil config from governance contract.
ErrRoundNotReady = errors.New("round is not ready")
)
// NodeSetCache caches node set information from governance contract.
type NodeSetCache struct {
lock sync.RWMutex
gov Governance
rounds map[uint64]*types.NodeSet
keyPool map[types.NodeID]*struct {
pubKey crypto.PublicKey
refCnt int
}
}
// NewNodeSetCache constructs an NodeSetCache instance.
func NewNodeSetCache(gov Governance) *NodeSetCache {
return &NodeSetCache{
gov: gov,
rounds: make(map[uint64]*types.NodeSet),
keyPool: make(map[types.NodeID]*struct {
pubKey crypto.PublicKey
refCnt int
}),
}
}
// Exists checks if a node is in node set of that round.
func (cache *NodeSetCache) Exists(
round uint64, nodeID types.NodeID) (exists bool, err error) {
nIDs, exists := cache.get(round)
if !exists {
if nIDs, err = cache.update(round); err != nil {
return
}
}
_, exists = nIDs.IDs[nodeID]
return
}
// GetPublicKey return public key for that node:
func (cache *NodeSetCache) GetPublicKey(
nodeID types.NodeID) (key crypto.PublicKey, exists bool) {
cache.lock.RLock()
defer cache.lock.RUnlock()
rec, exists := cache.keyPool[nodeID]
if exists {
key = rec.pubKey
}
return
}
// GetNodeSet returns IDs of nodes set of this round as map.
func (cache *NodeSetCache) GetNodeSet(
round uint64) (nIDs *types.NodeSet, err error) {
IDs, exists := cache.get(round)
if !exists {
if IDs, err = cache.update(round); err != nil {
return
}
}
nIDs = IDs.Clone()
return
}
// update node set for that round.
//
// This cache would maintain 10 rounds before the updated round and purge
// rounds not in this range.
func (cache *NodeSetCache) update(
round uint64) (nIDs *types.NodeSet, err error) {
cache.lock.Lock()
defer cache.lock.Unlock()
// Get the requested round from governance contract.
keySet := cache.gov.GetNodeSet(round)
if keySet == nil {
// That round is not ready yet.
err = ErrRoundNotReady
return
}
// Cache new round.
nIDs = types.NewNodeSet()
for _, key := range keySet {
nID := types.NewNodeID(key)
nIDs.Add(nID)
if rec, exists := cache.keyPool[nID]; exists {
rec.refCnt++
} else {
cache.keyPool[nID] = &struct {
pubKey crypto.PublicKey
refCnt int
}{key, 1}
}
}
cache.rounds[round] = nIDs
// Purge older rounds.
for rID, nIDs := range cache.rounds {
if round-rID <= 5 {
continue
}
for nID := range nIDs.IDs {
rec := cache.keyPool[nID]
if rec.refCnt--; rec.refCnt == 0 {
delete(cache.keyPool, nID)
}
}
delete(cache.rounds, rID)
}
return
}
func (cache *NodeSetCache) get(
round uint64) (nIDs *types.NodeSet, exists bool) {
cache.lock.RLock()
defer cache.lock.RUnlock()
nIDs, exists = cache.rounds[round]
return
}
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