path: root/dex/blockproposer.go

package dex

import (
    "errors"
    "fmt"
    "sync"
    "sync/atomic"
    "time"

    dexCore "github.com/dexon-foundation/dexon-consensus/core"
    coreEcdsa "github.com/dexon-foundation/dexon-consensus/core/crypto/ecdsa"
    "github.com/dexon-foundation/dexon-consensus/core/syncer"
    coreTypes "github.com/dexon-foundation/dexon-consensus/core/types"

    "github.com/dexon-foundation/dexon/core"
    "github.com/dexon-foundation/dexon/dex/db"
    "github.com/dexon-foundation/dexon/log"
    "github.com/dexon-foundation/dexon/rlp"
)

var (
    forceSyncTimeout = 20 * time.Second
)

type blockProposer struct {
    mu        sync.Mutex
    running   int32
    syncing   int32
    proposing int32
    dex       *Dexon
    watchCat  *syncer.WatchCat
    dMoment   time.Time

    wg     sync.WaitGroup
    stopCh chan struct{}
}

func NewBlockProposer(dex *Dexon, watchCat *syncer.WatchCat, dMoment time.Time) *blockProposer {
    return &blockProposer{
        dex:      dex,
        watchCat: watchCat,
        dMoment:  dMoment,
    }
}

func (b *blockProposer) Start() error {
    b.mu.Lock()
    defer b.mu.Unlock()

    if !atomic.CompareAndSwapInt32(&b.running, 0, 1) {
        return fmt.Errorf("block proposer is already running")
    }
    log.Info("Block proposer started")

    b.stopCh = make(chan struct{})
    b.wg.Add(1)
    go func() {
        defer b.wg.Done()
        defer atomic.StoreInt32(&b.running, 0)

        var err error
        var c *dexCore.Consensus
        if b.dMoment.After(time.Now()) {
            c = b.initConsensus()
        } else {
            c, err = b.syncConsensus()
        }

        if err != nil {
            log.Error("Block proposer stopped, before start running", "err", err)
            return
        }

        b.run(c)
        log.Info("Block proposer successfully stopped")
    }()
    return nil
}

func (b *blockProposer) run(c *dexCore.Consensus) {
    log.Info("Start running consensus core")
    go c.Run()
    atomic.StoreInt32(&b.proposing, 1)
    <-b.stopCh
    log.Debug("Block proposer receive stop signal")
}

func (b *blockProposer) Stop() {
    log.Info("Stopping block proposer")
    b.mu.Lock()
    defer b.mu.Unlock()

    if atomic.LoadInt32(&b.running) == 1 {
        b.dex.protocolManager.receiveEnabled = false
        close(b.stopCh)
        b.wg.Wait()
        atomic.StoreInt32(&b.proposing, 0)
    }
    log.Info("Block proposer stopped")
}

func (b *blockProposer) IsCoreSyncing() bool {
    return atomic.LoadInt32(&b.syncing) == 1
}

func (b *blockProposer) IsProposing() bool {
    return atomic.LoadInt32(&b.proposing) == 1
}

func (b *blockProposer) initConsensus() *dexCore.Consensus {
    db := db.NewDatabase(b.dex.chainDb)
    privkey := coreEcdsa.NewPrivateKeyFromECDSA(b.dex.config.PrivateKey)
    return dexCore.NewConsensus(b.dMoment,
        b.dex.app, b.dex.governance, db, b.dex.network, privkey, log.Root())
}

func (b *blockProposer) syncConsensus() (*dexCore.Consensus, error) {
    atomic.StoreInt32(&b.syncing, 1)
    defer atomic.StoreInt32(&b.syncing, 0)

    db := db.NewDatabase(b.dex.chainDb)
    privkey := coreEcdsa.NewPrivateKeyFromECDSA(b.dex.config.PrivateKey)
    consensusSync := syncer.NewConsensus(b.dMoment, b.dex.app, b.dex.governance,
        db, b.dex.network, privkey, log.Root())

    // Start the watchCat.
    log.Info("Starting sync watchCat ...")

    b.watchCat.Start()
    defer b.watchCat.Stop()

    // Feed the current block we have in local blockchain.
    cb := b.dex.blockchain.CurrentBlock()
    if cb.NumberU64() > 0 {
        var block coreTypes.Block
        if err := rlp.DecodeBytes(cb.Header().DexconMeta, &block); err != nil {
            panic(err)
        }
        b.watchCat.Feed(block.Position)
    }

    blocksToSync := func(coreHeight, height uint64) []*coreTypes.Block {
        var blocks []*coreTypes.Block
        for coreHeight < height {
            var block coreTypes.Block
            b := b.dex.blockchain.GetBlockByNumber(coreHeight + 1)
            if err := rlp.DecodeBytes(b.Header().DexconMeta, &block); err != nil {
                panic(err)
            }
            blocks = append(blocks, &block)
            coreHeight = coreHeight + 1
        }
        return blocks
    }

    // Sync all blocks in compaction chain to core.
    _, coreHeight := db.GetCompactionChainTipInfo()

    // Stop receiving block proposer message when syncing.
    b.dex.protocolManager.receiveEnabled = false

Loop:
    for {
        currentBlock := b.dex.blockchain.CurrentBlock()
        log.Debug("Syncing compaction chain", "core height", coreHeight,
            "height", currentBlock.NumberU64())
        blocks := blocksToSync(coreHeight, currentBlock.NumberU64())

        if len(blocks) == 0 {
            log.Debug("No new block to sync", "current", currentBlock.NumberU64())
            break Loop
        }
        b.watchCat.Feed(blocks[len(blocks)-1].Position)

        log.Debug("Filling compaction chain", "num", len(blocks),
            "first", blocks[0].Finalization.Height,
            "last", blocks[len(blocks)-1].Finalization.Height)
        if _, err := consensusSync.SyncBlocks(blocks, false); err != nil {
            log.Debug("SyncBlocks fail", "err", err)
            return nil, err
        }
        coreHeight = blocks[len(blocks)-1].Finalization.Height

        select {
        case <-b.stopCh:
            return nil, errors.New("early stop")
        default:
        }
    }

    ch := make(chan core.ChainHeadEvent)
    sub := b.dex.blockchain.SubscribeChainHeadEvent(ch)
    defer sub.Unsubscribe()

    log.Debug("Listen chain head event until synced")

    // Listen chain head event until synced.
ListenLoop:
    for {
        select {
        case ev := <-ch:
            blocks := blocksToSync(coreHeight, ev.Block.NumberU64())
            b.watchCat.Feed(blocks[len(blocks)-1].Position)

            if len(blocks) > 0 {
                log.Debug("Filling compaction chain", "num", len(blocks),
                    "first", blocks[0].Finalization.Height,
                    "last", blocks[len(blocks)-1].Finalization.Height)
                synced, err := consensusSync.SyncBlocks(blocks, true)
                if err != nil {
                    log.Error("SyncBlocks fail", "err", err)
                    return nil, err
                }
                if !b.dex.protocolManager.receiveEnabled {
                    // Start receiving block proposer message.
                    b.dex.protocolManager.receiveEnabled = true
                }
                if synced {
                    log.Debug("Consensus core synced")
                    break ListenLoop
                }
                coreHeight = blocks[len(blocks)-1].Finalization.Height
            }
        case <-sub.Err():
            log.Debug("System stopped when syncing consensus core")
            return nil, errors.New("system stop")
        case <-b.stopCh:
            log.Debug("Early stop, before consensus core can run")
            return nil, errors.New("early stop")
        case <-time.After(forceSyncTimeout):
            log.Debug("no new chain head for a while")
            if p := b.dex.protocolManager.peers.BestPeer(); p != nil {
                log.Debug("try force sync with peer", "id", p.id)
                b.dex.protocolManager.synchronise(p, true)
            } else {
                log.Debug("no peer to sync")
            }
        case <-b.watchCat.Meow():
            log.Info("WatchCat signaled to stop syncing")

            // Sleep until the next consensus start time slot.
            // The interval T_i need to meet the following requirement:
            //
            //   T_i > T_timeout + T_panic + T_restart
            //
            // Currently, T_timeout = 120, T_panic = 60, T_restart ~ 60
            //
            // We set T_i = 600 to be safe.

            interval := int64(600)
            nextDMoment := (time.Now().Unix()/interval + 1) * interval
            log.Info("Sleeping until next starting time", "time", nextDMoment)
            time.Sleep(time.Duration(nextDMoment-time.Now().Unix()) * time.Second)

            consensusSync.ForceSync(true)
            break ListenLoop
        }
    }

    return consensusSync.GetSyncedConsensus()
}