// 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 test
import (
"errors"
"math"
"math/rand"
"time"
"github.com/dexon-foundation/dexon-consensus-core/blockdb"
"github.com/dexon-foundation/dexon-consensus-core/common"
"github.com/dexon-foundation/dexon-consensus-core/core/types"
)
// ErrParentNotAcked would be raised when some block doesn't
// ack its parent block.
var ErrParentNotAcked = errors.New("parent is not acked")
// validatorStatus is a state holder for each validator
// during generating blocks.
type validatorStatus struct {
blocks []*types.Block
lastAckingHeight map[types.ValidatorID]uint64
}
// getAckedBlockHash would randomly pick one block between
// last acked one to current head.
func (vs *validatorStatus) getAckedBlockHash(
ackedVID types.ValidatorID,
ackedValidator *validatorStatus,
randGen *rand.Rand) (
hash common.Hash, ok bool) {
baseAckingHeight, exists := vs.lastAckingHeight[ackedVID]
if exists {
// Do not ack the same block(height) twice.
baseAckingHeight++
}
totalBlockCount := uint64(len(ackedValidator.blocks))
if totalBlockCount <= baseAckingHeight {
// There is no new block to ack.
return
}
ackableRange := totalBlockCount - baseAckingHeight
height := uint64((randGen.Uint64() % ackableRange) + baseAckingHeight)
vs.lastAckingHeight[ackedVID] = height
hash = ackedValidator.blocks[height].Hash
ok = true
return
}
// validatorSetStatus is a state holder for all validators
// during generating blocks.
type validatorSetStatus struct {
status map[types.ValidatorID]*validatorStatus
validatorIDs []types.ValidatorID
randGen *rand.Rand
}
func newValidatorSetStatus(vIDs []types.ValidatorID) *validatorSetStatus {
status := make(map[types.ValidatorID]*validatorStatus)
for _, vID := range vIDs {
status[vID] = &validatorStatus{
blocks: []*types.Block{},
lastAckingHeight: make(map[types.ValidatorID]uint64),
}
}
return &validatorSetStatus{
status: status,
validatorIDs: vIDs,
randGen: rand.New(rand.NewSource(time.Now().UnixNano())),
}
}
// findIncompleteValidators is a helper to check which validator
// doesn't generate enough blocks.
func (vs *validatorSetStatus) findIncompleteValidators(
blockCount int) (vIDs []types.ValidatorID) {
for vID, status := range vs.status {
if len(status.blocks) < blockCount {
vIDs = append(vIDs, vID)
}
}
return
}
// prepareAcksForNewBlock collects acks for one block.
func (vs *validatorSetStatus) prepareAcksForNewBlock(
proposerID types.ValidatorID, ackingCount int) (
acks map[common.Hash]struct{}, err error) {
acks = make(map[common.Hash]struct{})
if len(vs.status[proposerID].blocks) == 0 {
// The 'Acks' filed of genesis blocks would always be empty.
return
}
// Pick validatorIDs to be acked.
ackingVIDs := map[types.ValidatorID]struct{}{
proposerID: struct{}{}, // Acking parent block is always required.
}
if ackingCount > 0 {
ackingCount-- // We would always include ack to parent block.
}
for _, i := range vs.randGen.Perm(len(vs.validatorIDs))[:ackingCount] {
ackingVIDs[vs.validatorIDs[i]] = struct{}{}
}
// Generate acks.
for vID := range ackingVIDs {
ack, ok := vs.status[proposerID].getAckedBlockHash(
vID, vs.status[vID], vs.randGen)
if !ok {
if vID == proposerID {
err = ErrParentNotAcked
}
continue
}
acks[ack] = struct{}{}
}
return
}
// proposeBlock propose new block and update validator status.
func (vs *validatorSetStatus) proposeBlock(
proposerID types.ValidatorID,
acks map[common.Hash]struct{}) *types.Block {
status := vs.status[proposerID]
hash := common.NewRandomHash()
parentHash := common.Hash{}
if len(status.blocks) > 0 {
parentHash = status.blocks[len(status.blocks)-1].Hash
}
newBlock := &types.Block{
ProposerID: proposerID,
ParentHash: parentHash,
Hash: hash,
Height: uint64(len(status.blocks)),
Acks: acks,
// TODO(mission.liao): Generate timestamp randomly.
}
status.blocks = append(status.blocks, newBlock)
return newBlock
}
// normalAckingCountGenerator would randomly pick acking count
// by a normal distribution.
func normalAckingCountGenerator(
validatorCount int, mean, deviation float64) func() int {
return func() int {
var expected float64
for {
expected = rand.NormFloat64()*deviation + mean
if expected >= 0 && expected <= float64(validatorCount) {
break
}
}
return int(math.Ceil(expected))
}
}
// generateValidatorPicker is a function generator, which would generate
// a function to randomly pick one validator ID from a slice of validator ID.
func generateValidatorPicker() func([]types.ValidatorID) types.ValidatorID {
privateRand := rand.New(rand.NewSource(time.Now().UnixNano()))
return func(vIDs []types.ValidatorID) types.ValidatorID {
return vIDs[privateRand.Intn(len(vIDs))]
}
}
// BlocksGenerator could generate blocks forming valid DAGs.
type BlocksGenerator struct {
validatorPicker func([]types.ValidatorID) types.ValidatorID
}
// NewBlocksGenerator constructs BlockGenerator.
func NewBlocksGenerator(validatorPicker func(
[]types.ValidatorID) types.ValidatorID) *BlocksGenerator {
if validatorPicker == nil {
validatorPicker = generateValidatorPicker()
}
return &BlocksGenerator{
validatorPicker: validatorPicker,
}
}
// Generate is the entry point to generate blocks. The caller is responsible
// to provide a function to generate count of acked block for each new block.
// The prototype of ackingCountGenerator is a function returning 'int'.
// For example, if you need to generate a group of blocks and each of them
// has maximum 2 acks.
// func () int { return 2 }
// The default ackingCountGenerator would randomly pick a number based on
// the validatorCount you provided with a normal distribution.
func (gen *BlocksGenerator) Generate(
validatorCount int,
blockCount int,
ackingCountGenerator func() int,
writer blockdb.Writer) (err error) {
if ackingCountGenerator == nil {
ackingCountGenerator = normalAckingCountGenerator(
validatorCount,
float64(validatorCount/2),
float64(validatorCount/4+1))
}
validators := []types.ValidatorID{}
for i := 0; i < validatorCount; i++ {
validators = append(
validators, types.ValidatorID{Hash: common.NewRandomHash()})
}
status := newValidatorSetStatus(validators)
// We would record the smallest height of block that could be acked
// from each validator's point-of-view.
toAck := make(map[types.ValidatorID]map[types.ValidatorID]uint64)
for _, vID := range validators {
toAck[vID] = make(map[types.ValidatorID]uint64)
}
for {
// Find validators that doesn't propose enough blocks and
// pick one from them randomly.
notYet := status.findIncompleteValidators(blockCount)
if len(notYet) == 0 {
break
}
// Propose a new block.
var (
proposerID = gen.validatorPicker(notYet)
acks map[common.Hash]struct{}
)
acks, err = status.prepareAcksForNewBlock(
proposerID, ackingCountGenerator())
if err != nil {
return
}
newBlock := status.proposeBlock(proposerID, acks)
// Persist block to db.
err = writer.Put(*newBlock)
if err != nil {
return
}
}
return
}
