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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 (
"time"
"github.com/dexon-foundation/dexon-consensus-core/core/types"
)
type negativeAck struct {
// owner is the ID of proposer itself, this is used when deciding
// a node to be restricted or not.
owner types.NodeID
numOfNodes int
// timeDelay and timeExpire are for nack timeout.
timeDelay time.Duration
timeExpire time.Duration
// restricteds stores nodes which has been restricted and the time it's
// restricted.
restricteds map[types.NodeID]time.Time
// lastVotes and lockedVotes store the votes for nack. lastVotes[nid1][nid2]
// and lockedVotes[nid1][nid2] both mean that nid2 votes nid1. The difference
// is lockedVotes works only when nid1 is restricted, so that the votes are
// needed to be locked.
lastVotes map[types.NodeID]map[types.NodeID]struct{}
lockedVotes map[types.NodeID]map[types.NodeID]struct{}
// timeDiffs is the cache for last time stamps. timeDiffs[nid1][nid2] means
// the last updated timestamps nid1 sees nid2.
timeDiffs map[types.NodeID]map[types.NodeID]map[types.NodeID]time.Time
}
// newNegativeAck creates a new negaticeAck instance.
func newNegativeAck(nid types.NodeID) *negativeAck {
n := &negativeAck{
owner: nid,
numOfNodes: 0,
restricteds: make(map[types.NodeID]time.Time),
lastVotes: make(map[types.NodeID]map[types.NodeID]struct{}),
lockedVotes: make(map[types.NodeID]map[types.NodeID]struct{}),
timeDiffs: make(map[types.NodeID]map[types.NodeID]map[types.NodeID]time.Time),
}
n.addNode(nid)
return n
}
// processNewVote is called when a new "vote" occurs, that is, a node
// sees that other 2f + 1 nodes think a node is slow. "nid" is the
// node which propesed the block which the timestamps votes and "h" is
// the node been voted to be nacked.
func (n *negativeAck) processNewVote(
nid types.NodeID,
h types.NodeID,
) []types.NodeID {
nackeds := []types.NodeID{}
if _, exist := n.restricteds[h]; exist {
n.lockedVotes[h][nid] = struct{}{}
if len(n.lockedVotes[h]) > 2*(n.numOfNodes-1)/3 {
nackeds = append(nackeds, h)
delete(n.restricteds, h)
}
} else {
if n.owner == nid {
n.restrict(h)
} else {
n.lastVotes[h][nid] = struct{}{}
if len(n.lastVotes[h]) > (n.numOfNodes-1)/3 {
n.restrict(h)
}
}
}
return nackeds
}
// processTimestamps process new timestamps of a block which is proposed by
// node nid, and returns the nodes being nacked.
func (n *negativeAck) processTimestamps(
nid types.NodeID,
ts map[types.NodeID]time.Time,
) []types.NodeID {
n.checkRestrictExpire()
nackeds := []types.NodeID{}
for h := range n.timeDiffs {
if n.timeDiffs[nid][h][h].Equal(ts[h]) {
votes := 0
for hh := range n.timeDiffs {
if ts[hh].Sub(n.timeDiffs[nid][h][hh]) >= n.timeDelay {
votes++
}
}
if votes > 2*((n.numOfNodes-1)/3) {
n.lastVotes[h][nid] = struct{}{}
nack := n.processNewVote(nid, h)
for _, i := range nack {
nackeds = append(nackeds, i)
}
} else {
delete(n.lastVotes[h], nid)
}
} else {
for hh := range n.timeDiffs {
n.timeDiffs[nid][h][hh] = ts[hh]
}
delete(n.lastVotes[h], nid)
}
}
return nackeds
}
func (n *negativeAck) checkRestrictExpire() {
expired := []types.NodeID{}
now := time.Now()
for h, t := range n.restricteds {
if now.Sub(t) >= n.timeExpire {
expired = append(expired, h)
}
}
for _, h := range expired {
delete(n.restricteds, h)
}
}
func (n *negativeAck) restrict(nid types.NodeID) {
if _, exist := n.restricteds[nid]; !exist {
n.restricteds[nid] = time.Now().UTC()
n.lockedVotes[nid] = map[types.NodeID]struct{}{}
for h := range n.lastVotes[nid] {
n.lockedVotes[nid][h] = struct{}{}
}
}
}
func (n *negativeAck) getRestrictedNodes() map[types.NodeID]struct{} {
n.checkRestrictExpire()
ret := map[types.NodeID]struct{}{}
for h := range n.restricteds {
ret[h] = struct{}{}
}
return ret
}
func (n *negativeAck) setTimeDelay(t time.Duration) {
n.timeDelay = t
}
func (n *negativeAck) setTimeExpire(t time.Duration) {
n.timeExpire = t
}
func (n *negativeAck) addNode(nid types.NodeID) {
n.numOfNodes++
n.lastVotes[nid] = make(map[types.NodeID]struct{})
n.lockedVotes[nid] = make(map[types.NodeID]struct{})
newTimeDiff := make(map[types.NodeID]map[types.NodeID]time.Time)
for h := range n.timeDiffs {
newTimeDiff2 := make(map[types.NodeID]time.Time)
for hh := range n.timeDiffs {
newTimeDiff2[hh] = time.Time{}
}
newTimeDiff[h] = newTimeDiff2
}
n.timeDiffs[nid] = newTimeDiff
for h := range n.timeDiffs {
n.timeDiffs[h][nid] = make(map[types.NodeID]time.Time)
}
}
func (n *negativeAck) deleteNode(nid types.NodeID) {
n.numOfNodes--
delete(n.timeDiffs, nid)
for h := range n.lastVotes {
delete(n.lastVotes[h], nid)
}
delete(n.lastVotes, nid)
delete(n.lockedVotes, nid)
for h := range n.timeDiffs {
delete(n.timeDiffs[h], nid)
for hh := range n.timeDiffs[h] {
delete(n.timeDiffs[h][hh], nid)
}
}
delete(n.restricteds, nid)
}
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