path: root/core/lattice.go

// 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 (
    "sync"
    "time"

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

// Lattice represents a unit to produce a global ordering from multiple chains.
type Lattice struct {
    lock       sync.RWMutex
    authModule *Authenticator
    chainNum   uint32
    app        Application
    debug      Debug
    pool       blockPool
    data       *latticeData
    toModule   *totalOrdering
    ctModule   *consensusTimestamp
    logger     common.Logger
}

// NewLattice constructs an Lattice instance.
func NewLattice(
    dMoment time.Time,
    cfg *types.Config,
    authModule *Authenticator,
    app Application,
    debug Debug,
    db blockdb.BlockDatabase,
    logger common.Logger) (s *Lattice) {
    // Create genesis latticeDataConfig.
    dataConfig := newGenesisLatticeDataConfig(dMoment, cfg)
    toConfig := newGenesisTotalOrderingConfig(dMoment, cfg)
    s = &Lattice{
        authModule: authModule,
        chainNum:   cfg.NumChains,
        app:        app,
        debug:      debug,
        pool:       newBlockPool(cfg.NumChains),
        data:       newLatticeData(db, dataConfig),
        toModule:   newTotalOrdering(toConfig),
        ctModule:   newConsensusTimestamp(dMoment, 0, cfg.NumChains),
        logger:     logger,
    }
    return
}

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

    s.lock.RLock()
    defer s.lock.RUnlock()

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

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

// SanityCheck check if a block is valid.
// If checkRelation is true, it also checks with current lattice status.
//
// If some acking blocks don't exists, Lattice would help to cache this block
// and retry when lattice updated in Lattice.ProcessBlock.
func (s *Lattice) SanityCheck(b *types.Block, checkRelation bool) (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 = s.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
        }
    }
    // Verify data in application layer.
    s.logger.Debug("Calling Application.VerifyBlock", "block", b)
    if !s.app.VerifyBlock(b) {
        err = ErrInvalidBlock
        return err
    }
    if !checkRelation {
        return
    }
    s.lock.RLock()
    defer s.lock.RUnlock()
    if err = s.data.sanityCheck(b); err != nil {
        // Add to block pool, once the lattice updated,
        // would be checked again.
        if err == ErrAckingBlockNotExists {
            s.pool.addBlock(b)
        }
        s.logger.Error("Sanity Check failed", "error", err)
        return
    }
    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 (s *Lattice) ProcessBlock(
    input *types.Block) (verified, delivered []*types.Block, err error) {

    var (
        tip, b        *types.Block
        toDelivered   []*types.Block
        inLattice     []*types.Block
        deliveredMode uint32
    )
    s.lock.Lock()
    defer s.lock.Unlock()
    if inLattice, err = s.data.addBlock(input); err != nil {
        // TODO(mission): if sanity check failed with "acking block doesn't
        //                exists", we should keep it in a pool.
        s.logger.Error("Sanity Check failed when adding blocks", "error", err)
        return
    }
    // TODO(mission): remove this hack, BA related stuffs should not
    //                be done here.
    if s.debug != nil {
        s.debug.StronglyAcked(input.Hash)
    }
    s.logger.Debug("Calling Application.BlockConfirmed", "block", input)
    s.app.BlockConfirmed(*input.Clone())
    // Purge blocks in pool with the same chainID and lower height.
    s.pool.purgeBlocks(input.Position.ChainID, input.Position.Height)
    // Replay tips in pool to check their validity.
    for i := uint32(0); i < s.chainNum; i++ {
        if tip = s.pool.tip(i); tip == nil {
            continue
        }
        err = s.data.sanityCheck(tip)
        if err == nil {
            verified = append(verified, tip)
        }
        if err == ErrAckingBlockNotExists {
            continue
        }
        s.pool.removeTip(i)
    }
    // Perform total ordering for each block added to lattice.
    for _, b = range inLattice {
        toDelivered, deliveredMode, err = s.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 s.debug != nil {
            s.debug.TotalOrderingDelivered(hashes, deliveredMode)
        }
        // Perform timestamp generation.
        if err = s.ctModule.processBlocks(toDelivered); err != nil {
            return
        }
        delivered = append(delivered, toDelivered...)
    }
    return
}

// NextPosition returns expected position of incoming block for that chain.
func (s *Lattice) NextPosition(chainID uint32) types.Position {
    s.lock.RLock()
    defer s.lock.RUnlock()

    return s.data.nextPosition(chainID)
}

// PurgeBlocks from cache of blocks in memory, this is called when the caller
// make sure those blocks are saved to db.
func (s *Lattice) PurgeBlocks(blocks []*types.Block) error {
    s.lock.Lock()
    defer s.lock.Unlock()

    return s.data.purgeBlocks(blocks)
}

// AppendConfig add new configs for upcoming rounds. If you add a config for
// round R, next time you can only add the config for round R+1.
func (s *Lattice) AppendConfig(round uint64, config *types.Config) (err error) {
    s.lock.Lock()
    defer s.lock.Unlock()

    s.pool.resize(config.NumChains)
    if err = s.data.appendConfig(round, config); err != nil {
        return
    }
    if err = s.toModule.appendConfig(round, config); err != nil {
        return
    }
    if err = s.ctModule.appendConfig(round, config); err != nil {
        return
    }
    return
}