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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 validator to be restricted or not.
owner types.ValidatorID
numOfValidators int
// timeDelay and timeExpire are for nack timeout.
timeDelay time.Duration
timeExpire time.Duration
// restricteds stores validators which has been restricted and the time it's
// restricted.
restricteds map[types.ValidatorID]time.Time
// lastVotes and lockedVotes store the votes for nack. lastVotes[vid1][vid2]
// and lockedVotes[vid1][vid2] both mean that vid2 votes vid1. The difference
// is lockedVotes works only when vid1 is restricted, so that the votes are
// needed to be locked.
lastVotes map[types.ValidatorID]map[types.ValidatorID]struct{}
lockedVotes map[types.ValidatorID]map[types.ValidatorID]struct{}
// timeDiffs is the cache for last time stamps. timeDiffs[vid1][vid2] means
// the last updated timestamps vid1 sees vid2.
timeDiffs map[types.ValidatorID]map[types.ValidatorID]map[types.ValidatorID]time.Time
}
// newNegativeAck creates a new negaticeAck instance.
func newNegativeAck(vid types.ValidatorID) *negativeAck {
n := &negativeAck{
owner: vid,
numOfValidators: 0,
restricteds: make(map[types.ValidatorID]time.Time),
lastVotes: make(map[types.ValidatorID]map[types.ValidatorID]struct{}),
lockedVotes: make(map[types.ValidatorID]map[types.ValidatorID]struct{}),
timeDiffs: make(map[types.ValidatorID]map[types.ValidatorID]map[types.ValidatorID]time.Time),
}
n.addValidator(vid)
return n
}
// processNewVote is called when a new "vote" occurs, that is, a validator
// sees that other 2f + 1 validators think a validator is slow. "vid" is the
// validator which propesed the block which the timestamps votes and "h" is
// the validator been voted to be nacked.
func (n *negativeAck) processNewVote(
vid types.ValidatorID,
h types.ValidatorID,
) []types.ValidatorID {
nackeds := []types.ValidatorID{}
if _, exist := n.restricteds[h]; exist {
n.lockedVotes[h][vid] = struct{}{}
if len(n.lockedVotes[h]) > 2*(n.numOfValidators-1)/3 {
nackeds = append(nackeds, h)
delete(n.restricteds, h)
}
} else {
if n.owner == vid {
n.restrict(h)
} else {
n.lastVotes[h][vid] = struct{}{}
if len(n.lastVotes[h]) > (n.numOfValidators-1)/3 {
n.restrict(h)
}
}
}
return nackeds
}
// processTimestamps process new timestamps of a block which is proposed by
// validator vid, and returns the validators being nacked.
func (n *negativeAck) processTimestamps(
vid types.ValidatorID,
ts map[types.ValidatorID]time.Time,
) []types.ValidatorID {
n.checkRestrictExpire()
nackeds := []types.ValidatorID{}
for h := range n.timeDiffs {
if n.timeDiffs[vid][h][h].Equal(ts[h]) {
votes := 0
for hh := range n.timeDiffs {
if ts[hh].Sub(n.timeDiffs[vid][h][hh]) >= n.timeDelay {
votes++
}
}
if votes > 2*((n.numOfValidators-1)/3) {
n.lastVotes[h][vid] = struct{}{}
nack := n.processNewVote(vid, h)
for _, i := range nack {
nackeds = append(nackeds, i)
}
} else {
delete(n.lastVotes[h], vid)
}
} else {
for hh := range n.timeDiffs {
n.timeDiffs[vid][h][hh] = ts[hh]
}
delete(n.lastVotes[h], vid)
}
}
return nackeds
}
func (n *negativeAck) checkRestrictExpire() {
expired := []types.ValidatorID{}
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(vid types.ValidatorID) {
if _, exist := n.restricteds[vid]; !exist {
n.restricteds[vid] = time.Now().UTC()
n.lockedVotes[vid] = map[types.ValidatorID]struct{}{}
for h := range n.lastVotes[vid] {
n.lockedVotes[vid][h] = struct{}{}
}
}
}
func (n *negativeAck) getRestrictedValidators() map[types.ValidatorID]struct{} {
n.checkRestrictExpire()
ret := map[types.ValidatorID]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) addValidator(vid types.ValidatorID) {
n.numOfValidators++
n.lastVotes[vid] = make(map[types.ValidatorID]struct{})
n.lockedVotes[vid] = make(map[types.ValidatorID]struct{})
newTimeDiff := make(map[types.ValidatorID]map[types.ValidatorID]time.Time)
for h := range n.timeDiffs {
newTimeDiff2 := make(map[types.ValidatorID]time.Time)
for hh := range n.timeDiffs {
newTimeDiff2[hh] = time.Time{}
}
newTimeDiff[h] = newTimeDiff2
}
n.timeDiffs[vid] = newTimeDiff
for h := range n.timeDiffs {
n.timeDiffs[h][vid] = make(map[types.ValidatorID]time.Time)
}
}
func (n *negativeAck) deleteValidator(vid types.ValidatorID) {
n.numOfValidators--
delete(n.timeDiffs, vid)
for h := range n.lastVotes {
delete(n.lastVotes[h], vid)
}
delete(n.lastVotes, vid)
delete(n.lockedVotes, vid)
for h := range n.timeDiffs {
delete(n.timeDiffs[h], vid)
for hh := range n.timeDiffs[h] {
delete(n.timeDiffs[h][hh], vid)
}
}
delete(n.restricteds, vid)
}
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