1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus 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 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 library. If not, see
// <http://www.gnu.org/licenses/>.
package core
import (
"errors"
"time"
"github.com/dexon-foundation/dexon-consensus/core/types"
)
// consensusTimestamp calculates a block's finalization timestamp. Notice that
// the Finalization timestamps are increasing (but not strictly increasing).
// Instance functions:
// - processBlocks(blocks []*types.Block) error
// called with blocks output from total ordering
// - appendConfig(round uint64, config *types.Config) error
// called when a new config is known
// - synced() bool
// called in sync mode
type consensusTimestamp struct {
timestampsOfChains []time.Time
// Stores number of chains for rounds.
numChainsOfRounds []uint32
numChainsBase uint64
// dMoment represents the genesis time.
dMoment time.Time
// lastTimestamp is the previous assigned consensus timestamp.
lastTimestamp time.Time
}
var (
// ErrTimestampNotIncrease for timestamp is not strictly increasing on one
// chain.
ErrTimestampNotIncrease = errors.New("timestamp is not increasing")
// ErrNoRoundConfig for no round config found.
ErrNoRoundConfig = errors.New("no round config found")
// ErrConsensusTimestampRewind for rewinding timestamp.
ErrConsensusTimestampRewind = errors.New("consensus timestamp rewind")
)
// newConsensusTimestamp creates consensus timestamp instance.
func newConsensusTimestamp(
dMoment time.Time, round uint64, numChains uint32) *consensusTimestamp {
ts := make([]time.Time, numChains)
for i := range ts {
ts[i] = dMoment
}
return &consensusTimestamp{
numChainsOfRounds: []uint32{numChains},
numChainsBase: round,
dMoment: dMoment,
timestampsOfChains: ts,
}
}
// appendConfig appends a configuration for upcoming round. When you append
// a config for round R, next time you can only append the config for round R+1.
func (ct *consensusTimestamp) appendConfig(
round uint64, config *types.Config) error {
if round != uint64(len(ct.numChainsOfRounds))+ct.numChainsBase {
return ErrRoundNotIncreasing
}
// This segment is to handle the corner case for config checking logic in
// processBlock method.
if len(ct.numChainsOfRounds) == 1 {
if ct.numChainsOfRounds[0] > config.NumChains {
ct.resizeTimetamps(ct.numChainsOfRounds[0])
} else {
ct.resizeTimetamps(config.NumChains)
}
}
ct.numChainsOfRounds = append(ct.numChainsOfRounds, config.NumChains)
return nil
}
func (ct *consensusTimestamp) resizeTimetamps(numChain uint32) {
l := uint32(len(ct.timestampsOfChains))
if numChain > l {
for i := l; i < numChain; i++ {
ct.timestampsOfChains = append(ct.timestampsOfChains, ct.dMoment)
}
} else if numChain < l {
ct.timestampsOfChains = ct.timestampsOfChains[:numChain]
}
}
// ProcessBlocks is the entry function.
func (ct *consensusTimestamp) processBlocks(blocks []*types.Block) (err error) {
for _, block := range blocks {
// Rounds might interleave within rounds if no configuration change
// occurs. And it is limited to one round, that is, round r can only
// interleave with r-1 and r+1.
round := block.Position.Round
if ct.numChainsBase == round || ct.numChainsBase+1 == round {
// Normal case, no need to modify timestampsOfChains.
} else if ct.numChainsBase+2 == round {
// Resize timestampsOfChains if block from r+2 comes, because the interleave
// of rounds must be less than 1. Resize the size to
// max(numChainsOfRounds[r+1], numChainsOfRounds[r+2]).
if len(ct.numChainsOfRounds) < 2 {
return ErrNoRoundConfig
}
ct.numChainsBase++
ct.numChainsOfRounds = ct.numChainsOfRounds[1:]
if ct.numChainsOfRounds[0] > ct.numChainsOfRounds[1] {
ct.resizeTimetamps(ct.numChainsOfRounds[0])
} else {
ct.resizeTimetamps(ct.numChainsOfRounds[1])
}
} else {
// Error if round < base or round > base + 2.
return ErrInvalidRoundID
}
ts := ct.timestampsOfChains[:ct.numChainsOfRounds[round-ct.numChainsBase]]
if block.Finalization.Timestamp, err = getMedianTime(ts); err != nil {
return
}
if block.Timestamp.Before(ct.timestampsOfChains[block.Position.ChainID]) {
return ErrTimestampNotIncrease
}
ct.timestampsOfChains[block.Position.ChainID] = block.Timestamp
// If the finalization timestamp is before the last timestamp, set it to
// the last one. Notice that the finalization timestamps are increasing but
// not strictly increasing.
if block.Finalization.Timestamp.Before(ct.lastTimestamp) {
block.Finalization.Timestamp = ct.lastTimestamp
} else {
ct.lastTimestamp = block.Finalization.Timestamp
}
}
return
}
func (ct *consensusTimestamp) isSynced() bool {
numChain := ct.numChainsOfRounds[0]
for i := uint32(0); i < numChain; i++ {
if ct.timestampsOfChains[i].Equal(ct.dMoment) {
return false
}
}
return true
}
|
