path: root/core/lattice.go

// 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 (
    "fmt"
    "sync"
    "time"

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

// Errors for sanity check error.
var (
    ErrRetrySanityCheckLater = fmt.Errorf("retry sanity check later")
)

// Lattice represents a unit to produce a global ordering from multiple chains.
type Lattice struct {
    lock       sync.RWMutex
    authModule *Authenticator
    app        Application
    debug      Debug
    pool       blockPool
    retryAdd   bool
    data       *latticeData
    toModule   *totalOrdering
    ctModule   *consensusTimestamp
    logger     common.Logger
}

// NewLattice constructs an Lattice instance.
func NewLattice(
    dMoment time.Time,
    round uint64,
    cfg *types.Config,
    authModule *Authenticator,
    app Application,
    debug Debug,
    db blockdb.BlockDatabase,
    logger common.Logger) *Lattice {

    // Create genesis latticeDataConfig.
    return &Lattice{
        authModule: authModule,
        app:        app,
        debug:      debug,
        pool:       newBlockPool(cfg.NumChains),
        data:       newLatticeData(db, dMoment, round, cfg),
        toModule:   newTotalOrdering(dMoment, cfg),
        ctModule:   newConsensusTimestamp(dMoment, round, cfg.NumChains),
        logger:     logger,
    }
}

// PrepareBlock setups block's fields based on current status.
func (l *Lattice) PrepareBlock(
    b *types.Block, proposeTime time.Time) (err error) {

    l.lock.RLock()
    defer l.lock.RUnlock()

    b.Timestamp = proposeTime
    if err = l.data.prepareBlock(b); err != nil {
        return
    }
    l.logger.Debug("Calling Application.PreparePayload", "position", &b.Position)
    if b.Payload, err = l.app.PreparePayload(b.Position); err != nil {
        return
    }
    l.logger.Debug("Calling Application.PrepareWitness",
        "height", b.Witness.Height)
    if b.Witness, err = l.app.PrepareWitness(b.Witness.Height); err != nil {
        return
    }
    if err = l.authModule.SignBlock(b); err != nil {
        return
    }
    return
}

// PrepareEmptyBlock setups block's fields based on current lattice status.
func (l *Lattice) PrepareEmptyBlock(b *types.Block) (err error) {
    l.lock.RLock()
    defer l.lock.RUnlock()
    l.data.prepareEmptyBlock(b)
    if b.Hash, err = hashBlock(b); err != nil {
        return
    }
    return
}

// SanityCheck checks the validity of a block.
//
// If any acking block of this block does not exist, Lattice caches this block
// and retries when Lattice.ProcessBlock is called.
func (l *Lattice) SanityCheck(b *types.Block) (err error) {
    if b.IsEmpty() {
        // Only need to verify block's hash.
        var hash common.Hash
        if hash, err = hashBlock(b); err != nil {
            return
        }
        if b.Hash != hash {
            return ErrInvalidBlock
        }
    } else {
        // Verify block's signature.
        if err = l.authModule.VerifyBlock(b); err != nil {
            return
        }
    }
    // Make sure acks are sorted.
    for i := range b.Acks {
        if i == 0 {
            continue
        }
        if !b.Acks[i-1].Less(b.Acks[i]) {
            err = ErrAcksNotSorted
            return
        }
    }
    if err = func() (err error) {
        l.lock.RLock()
        defer l.lock.RUnlock()
        if err = l.data.sanityCheck(b); err != nil {
            if _, ok := err.(*ErrAckingBlockNotExists); ok {
                err = ErrRetrySanityCheckLater
            }
            l.logger.Error("Sanity Check failed", "error", err)
            return
        }
        return
    }(); err != nil {
        return
    }
    return
}

// addBlockToLattice adds a block into lattice, and delivers blocks with the
// acks already delivered.
//
// NOTE: input block should pass sanity check.
func (l *Lattice) addBlockToLattice(
    input *types.Block) (outputBlocks []*types.Block, err error) {

    if tip := l.data.chains[input.Position.ChainID].tip; tip != nil {
        if !input.Position.Newer(&tip.Position) {
            return
        }
    }
    l.pool.addBlock(input)
    // Check tips in pool to check their validity for moving blocks from pool
    // to lattice.
    for {
        hasOutput := false
        for i := uint32(0); i < uint32(len(l.pool)); i++ {
            var tip *types.Block
            if tip = l.pool.tip(i); tip == nil {
                continue
            }
            err = l.data.sanityCheck(tip)
            if err == nil {
                var output []*types.Block
                if output, err = l.data.addBlock(tip); err != nil {
                    l.logger.Error("Sanity Check failed", "error", err)
                    continue
                }
                hasOutput = true
                outputBlocks = append(outputBlocks, output...)
            }
            if _, ok := err.(*ErrAckingBlockNotExists); ok {
                err = nil
                continue
            }
            l.pool.removeTip(i)
        }
        if !hasOutput {
            break
        }
    }

    for _, b := range outputBlocks {
        // TODO(jimmy-dexon): change this name of classic DEXON algorithm.
        if l.debug != nil {
            l.debug.StronglyAcked(b.Hash)
        }
        l.logger.Debug("Calling Application.BlockConfirmed", "block", input)
        l.app.BlockConfirmed(*b.Clone())
        // Purge blocks in pool with the same chainID and lower height.
        l.pool.purgeBlocks(b.Position.ChainID, b.Position.Height)
    }

    return
}

// ProcessBlock adds a block into lattice, and deliver ordered blocks.
// If any block pass sanity check after this block add into lattice, they
// would be returned, too.
//
// NOTE: assume the block passed sanity check.
func (l *Lattice) ProcessBlock(
    input *types.Block) (delivered []*types.Block, err error) {
    var (
        b             *types.Block
        inLattice     []*types.Block
        toDelivered   []*types.Block
        deliveredMode uint32
    )

    l.lock.Lock()
    defer l.lock.Unlock()

    if inLattice, err = l.addBlockToLattice(input); err != nil {
        return
    }

    if len(inLattice) == 0 {
        return
    }

    // Perform total ordering for each block added to lattice.
    for _, b = range inLattice {
        toDelivered, deliveredMode, err = l.toModule.processBlock(b)
        if err != nil {
            // All errors from total ordering is serious, should panic.
            panic(err)
        }
        if len(toDelivered) == 0 {
            continue
        }
        hashes := make(common.Hashes, len(toDelivered))
        for idx := range toDelivered {
            hashes[idx] = toDelivered[idx].Hash
        }
        if l.debug != nil {
            l.debug.TotalOrderingDelivered(hashes, deliveredMode)
        }
        // Perform consensus timestamp module.
        if err = l.ctModule.processBlocks(toDelivered); err != nil {
            return
        }
        delivered = append(delivered, toDelivered...)
    }
    return
}

// NextPosition returns expected position of incoming block for specified chain.
func (l *Lattice) NextPosition(chainID uint32) types.Position {
    l.lock.RLock()
    defer l.lock.RUnlock()
    return l.data.nextPosition(chainID)
}

// PurgeBlocks purges blocks' cache in memory, this is called when the caller
// makes sure those blocks are already saved in db.
func (l *Lattice) PurgeBlocks(blocks []*types.Block) error {
    l.lock.Lock()
    defer l.lock.Unlock()
    return l.data.purgeBlocks(blocks)
}

// AppendConfig adds a new config for upcoming rounds. If a config of round r is
// added, only config in round r + 1 is allowed next.
func (l *Lattice) AppendConfig(round uint64, config *types.Config) (err error) {
    l.lock.Lock()
    defer l.lock.Unlock()
    l.pool.resize(config.NumChains)
    if err = l.data.appendConfig(round, config); err != nil {
        return
    }
    if err = l.toModule.appendConfig(round, config); err != nil {
        return
    }
    if err = l.ctModule.appendConfig(round, config); err != nil {
        return
    }
    return
}

// ProcessFinalizedBlock is used for syncing lattice data.
func (l *Lattice) ProcessFinalizedBlock(b *types.Block) {
    defer func() { l.retryAdd = true }()
    l.lock.Lock()
    defer l.lock.Unlock()
    if err := l.data.addFinalizedBlock(b); err != nil {
        panic(err)
    }
    l.pool.purgeBlocks(b.Position.ChainID, b.Position.Height)
}