aboutsummaryrefslogtreecommitdiffstats
path: root/core/blocklattice.go
blob: 4dc43a4501d38bb7f3d9ecd56904d86bde041be3 (plain) (blame)
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
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
// 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 (
    "fmt"

    "github.com/dexon-foundation/dexon-consensus-core/common"
    "github.com/dexon-foundation/dexon-consensus-core/core/types"
)

// Errors for sanity check error.
var (
    ErrAckingBlockNotExists    = fmt.Errorf("acking block not exists")
    ErrInvalidParentChain      = fmt.Errorf("invalid parent chain")
    ErrDuplicatedAckOnOneChain = fmt.Errorf("duplicated ack on one chain")
    ErrChainStatusCorrupt      = fmt.Errorf("chain status corrupt")
)

// blockLattice is a module for storing blocklattice.
type blockLattice struct {
    // lattice stores chains' blocks and other info.
    chains []*chainStatus

    // blockByHash stores blocks, indexed by block hash.
    blockByHash map[common.Hash]*types.Block

    // shardID caches which shard I belongs to.
    shardID uint32
}

type chainStatus struct {
    // ID keeps the chainID of this chain status.
    ID uint32

    // blocks stores blocks proposed for this chain, sorted by height.
    blocks []*types.Block

    // minHeight keeps minimum height in blocks.
    minHeight uint64

    // nextAck stores the height of next height that should be acked, i.e. last
    // acked height + 1. Initialized to 0.
    // being acked. For example, rb.chains[vid1].nextAck[vid2] - 1 is the last
    // acked height by vid2 acking vid1.
    nextAck []uint64

    // nextOutput is the next output height of block, default to 0.
    nextOutput uint64
}

func (s *chainStatus) getBlockByHeight(height uint64) (b *types.Block) {
    if height < s.minHeight {
        return
    }
    idx := int(height - s.minHeight)
    if idx >= len(s.blocks) {
        return
    }
    b = s.blocks[idx]
    return
}

func (s *chainStatus) addBlock(b *types.Block) error {
    if len(s.blocks) > 0 {
        // Make sure the height of incoming block should be
        // plus one to current latest blocks if exists.
        if s.blocks[len(s.blocks)-1].Position.Height != b.Position.Height-1 {
            return ErrChainStatusCorrupt
        }
    } else {
        if b.Position.Height != 0 {
            return ErrChainStatusCorrupt
        }
    }
    s.blocks = append(s.blocks, b)
    return nil
}

func (s *chainStatus) calcPurgeHeight() (safe uint64, ok bool) {
    // blocks with height less than min(nextOutput, nextAck...)
    // are safe to be purged.
    safe = s.nextOutput
    for _, ackedHeight := range s.nextAck {
        if safe > ackedHeight {
            safe = ackedHeight
        }
    }
    // Both 'nextOutput' and 'nextAck' represents some block to be
    // outputed/acked. To find a block already outputed/acked, the height
    // needs to be minus 1.
    if safe == 0 {
        // Avoid underflow.
        return
    }
    safe--
    if safe < s.minHeight {
        return
    }
    ok = true
    return
}

// purge blocks if they are safe to be deleted from working set.
func (s *chainStatus) purge() (purged common.Hashes) {
    safe, ok := s.calcPurgeHeight()
    if !ok {
        return
    }
    newMinIndex := safe - s.minHeight + 1
    for _, b := range s.blocks[:newMinIndex] {
        purged = append(purged, b.Hash)
    }
    s.blocks = s.blocks[newMinIndex:]
    s.minHeight = safe + 1
    return
}

// nextPosition returns a valid position for new block in this chain.
func (s *chainStatus) nextPosition(shardID uint32) types.Position {
    return types.Position{
        ShardID: shardID,
        ChainID: s.ID,
        Height:  s.minHeight + uint64(len(s.blocks)),
    }
}

// newBlockLattice creates a new blockLattice struct.
func newBlockLattice(shardID, chainNum uint32) (bl *blockLattice) {
    bl = &blockLattice{
        shardID:     shardID,
        chains:      make([]*chainStatus, chainNum),
        blockByHash: make(map[common.Hash]*types.Block),
    }
    for i := range bl.chains {
        bl.chains[i] = &chainStatus{
            ID:      uint32(i),
            blocks:  []*types.Block{},
            nextAck: make([]uint64, chainNum),
        }
    }
    return
}

func (bl *blockLattice) sanityCheck(b *types.Block) error {
    // Check if the chain id is valid.
    if b.Position.ChainID >= uint32(len(bl.chains)) {
        return ErrInvalidChainID
    }

    // TODO(mission): Check if its proposer is in validator set somewhere,
    //                blocklattice doesn't have to know about node set.

    // Check if it forks
    if bInLattice := bl.chains[b.Position.ChainID].getBlockByHeight(
        b.Position.Height); bInLattice != nil {

        if b.Hash != bInLattice.Hash {
            return ErrForkBlock
        }
        return ErrAlreadyInLattice
    }
    // TODO(mission): check if fork by loading blocks from DB if the block
    //                doesn't exists because forking is serious.

    // Check if it acks older blocks.
    acksByChainID := make(map[uint32]struct{}, len(bl.chains))
    for _, hash := range b.Acks {
        if bAck, exist := bl.blockByHash[hash]; exist {
            if bAck.Position.Height <
                bl.chains[bAck.Position.ChainID].nextAck[b.Position.ChainID] {
                return ErrDoubleAck
            }
            // Check if ack two blocks on the same chain. This would need
            // to check after we replace map with slice for acks.
            if _, acked := acksByChainID[bAck.Position.ChainID]; acked {
                return ErrDuplicatedAckOnOneChain
            }
            acksByChainID[bAck.Position.ChainID] = struct{}{}
        } else {
            // This error has the same checking effect as areAllAcksInLattice.
            return ErrAckingBlockNotExists
        }
    }

    // Check non-genesis blocks if it acks its parent.
    if b.Position.Height > 0 {
        if !b.IsAcking(b.ParentHash) {
            return ErrNotAckParent
        }
        bParent := bl.blockByHash[b.ParentHash]
        if bParent.Position.ChainID != b.Position.ChainID {
            return ErrInvalidParentChain
        }
        if bParent.Position.Height != b.Position.Height-1 {
            return ErrInvalidBlockHeight
        }
        // Check if its timestamp is valid.
        if !b.Timestamp.After(bParent.Timestamp) {
            return ErrInvalidTimestamp
        }
    }
    return nil
}

// areAllAcksReceived checks if all ack blocks of a block are all in lattice,
// blockLattice would make sure all blocks not acked by some chain would be kept
// in working set.
func (bl *blockLattice) areAllAcksInLattice(b *types.Block) bool {
    for _, h := range b.Acks {
        bAck, exist := bl.blockByHash[h]
        if !exist {
            return false
        }
        if bAckInLattice := bl.chains[bAck.Position.ChainID].getBlockByHeight(
            bAck.Position.Height); bAckInLattice != nil {

            if bAckInLattice.Hash != bAck.Hash {
                panic("areAllAcksInLattice: blockLattice.chains has corrupted")
            }
        } else {
            return false
        }
    }
    return true
}

// addBlock processes block, it does sanity check, inserts block into
// lattice and deletes blocks which will not be used.
func (bl *blockLattice) addBlock(
    block *types.Block) (deliverable []*types.Block, err error) {

    var (
        bAck    *types.Block
        updated bool
    )
    // If a block does not pass sanity check, report error.
    if err = bl.sanityCheck(block); err != nil {
        return
    }
    if err = bl.chains[block.Position.ChainID].addBlock(block); err != nil {
        return
    }
    bl.blockByHash[block.Hash] = block
    // Update nextAcks.
    for _, ack := range block.Acks {
        bAck = bl.blockByHash[ack]
        bl.chains[bAck.Position.ChainID].nextAck[block.Position.ChainID] =
            bAck.Position.Height + 1
    }
    // Extract blocks that deliverable to total ordering.
    // A block is deliverable to total ordering iff:
    //  - All its acking blocks are delivered to total ordering.
    for {
        updated = false
        for _, status := range bl.chains {
            tip := status.getBlockByHeight(status.nextOutput)
            if tip == nil {
                continue
            }
            allAckingBlockDelivered := true
            for _, ack := range tip.Acks {
                bAck, exists := bl.blockByHash[ack]
                if !exists {
                    continue
                }
                if bl.chains[bAck.Position.ChainID].nextOutput >
                    bAck.Position.Height {

                    continue
                }
                // This acked block exists and not delivered yet.
                allAckingBlockDelivered = false
            }
            if allAckingBlockDelivered {
                deliverable = append(deliverable, tip)
                status.nextOutput++
                updated = true
            }
        }
        if !updated {
            break
        }
    }

    // Delete old blocks in "chains" and "blocks" to release memory space.
    //
    // A block is safe to be deleted iff:
    //  - It's delivered to total ordering
    //  - All chains (including its proposing chain) acks some block with
    //    higher height in its proposing chain.
    //
    // This works because blocks of height below this minimum are not going to be
    // acked anymore, the ackings of these blocks are illegal.
    for _, status := range bl.chains {
        for _, h := range status.purge() {
            delete(bl.blockByHash, h)
        }
    }
    return
}

// prepareBlock helps to setup fields of block based on its ProposerID,
// including:
//  - Set 'Acks' and 'Timestamps' for the highest block of each validator not
//    acked by this proposer before.
//  - Set 'ParentHash' and 'Height' from parent block, if we can't find a
//    parent, these fields would be setup like a genesis block.
func (bl *blockLattice) prepareBlock(block *types.Block) {
    // Reset fields to make sure we got these information from parent block.
    block.Position.Height = 0
    block.ParentHash = common.Hash{}
    acks := common.Hashes{}
    for chainID := range bl.chains {
        // find height of the latest block for that validator.
        var (
            curBlock   *types.Block
            nextHeight = bl.chains[chainID].nextAck[block.Position.ChainID]
        )
        for {
            tmpBlock := bl.chains[chainID].getBlockByHeight(nextHeight)
            if tmpBlock == nil {
                break
            }
            curBlock = tmpBlock
            nextHeight++
        }
        if curBlock == nil {
            continue
        }
        acks = append(acks, curBlock.Hash)
        if uint32(chainID) == block.Position.ChainID {
            block.ParentHash = curBlock.Hash
            block.Position.Height = curBlock.Position.Height + 1
        }
    }
    block.Acks = common.NewSortedHashes(acks)
    return
}

// TODO(mission): make more abstraction for this method.
// nextHeight returns the next height for the chain.
func (bl *blockLattice) nextPosition(chainID uint32) types.Position {
    return bl.chains[chainID].nextPosition(bl.shardID)
}