prysm-pulse/beacon-chain/blockchain/service.go
2018-09-23 22:36:51 -07:00

355 lines
11 KiB
Go

// Package blockchain defines the life-cycle and status of the beacon chain.
package blockchain
import (
"context"
"fmt"
"math"
"sync"
"time"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/event"
"github.com/prysmaticlabs/prysm/beacon-chain/params"
"github.com/prysmaticlabs/prysm/beacon-chain/powchain"
"github.com/prysmaticlabs/prysm/beacon-chain/types"
"github.com/sirupsen/logrus"
)
var log = logrus.WithField("prefix", "blockchain")
// ChainService represents a service that handles the internal
// logic of managing the full PoS beacon chain.
type ChainService struct {
ctx context.Context
cancel context.CancelFunc
beaconDB ethdb.Database
chain *BeaconChain
web3Service *powchain.Web3Service
incomingBlockFeed *event.Feed
incomingBlockChan chan *types.Block
canonicalBlockFeed *event.Feed
canonicalCrystallizedStateFeed *event.Feed
blocksPendingProcessing [][32]byte
lock sync.Mutex
devMode bool
genesisTimestamp time.Time
}
// Config options for the service.
type Config struct {
BeaconBlockBuf int
IncomingBlockBuf int
Chain *BeaconChain
Web3Service *powchain.Web3Service
BeaconDB ethdb.Database
DevMode bool
}
// NewChainService instantiates a new service instance that will
// be registered into a running beacon node.
func NewChainService(ctx context.Context, cfg *Config) (*ChainService, error) {
ctx, cancel := context.WithCancel(ctx)
return &ChainService{
ctx: ctx,
genesisTimestamp: types.GenesisTime,
chain: cfg.Chain,
cancel: cancel,
beaconDB: cfg.BeaconDB,
web3Service: cfg.Web3Service,
incomingBlockChan: make(chan *types.Block, cfg.IncomingBlockBuf),
incomingBlockFeed: new(event.Feed),
canonicalBlockFeed: new(event.Feed),
canonicalCrystallizedStateFeed: new(event.Feed),
blocksPendingProcessing: [][32]byte{},
devMode: cfg.DevMode,
}, nil
}
// Start a blockchain service's main event loop.
func (c *ChainService) Start() {
// TODO(#474): Fetch the slot: (block, state) DAGs from persistent storage
// to truly continue across sessions.
log.Infof("Starting service")
go c.updateHead(time.NewTicker(time.Second * time.Duration(params.SlotDuration)).C)
go c.blockProcessing()
}
// Stop the blockchain service's main event loop and associated goroutines.
func (c *ChainService) Stop() error {
defer c.cancel()
log.Info("Stopping service")
log.Info("Persisting current active and crystallized states before closing")
if err := c.chain.PersistActiveState(); err != nil {
return fmt.Errorf("Error persisting active state: %v", err)
}
if err := c.chain.PersistCrystallizedState(); err != nil {
return fmt.Errorf("Error persisting crystallized state: %v", err)
}
return nil
}
// CurrentBeaconSlot based on the seconds since genesis.
func (c *ChainService) CurrentBeaconSlot() uint64 {
secondsSinceGenesis := time.Since(c.genesisTimestamp).Seconds()
return uint64(math.Floor(secondsSinceGenesis / 8.0))
}
// CanonicalHead of the current beacon chain.
func (c *ChainService) CanonicalHead() (*types.Block, error) {
return c.chain.CanonicalHead()
}
// CanonicalCrystallizedState of the current beacon chain's head.
func (c *ChainService) CanonicalCrystallizedState() *types.CrystallizedState {
return c.chain.CrystallizedState()
}
// IncomingBlockFeed returns a feed that any service can send incoming p2p blocks into.
// The chain service will subscribe to this feed in order to process incoming blocks.
func (c *ChainService) IncomingBlockFeed() *event.Feed {
return c.incomingBlockFeed
}
// HasStoredState checks if there is any Crystallized/Active State or blocks(not implemented) are
// persisted to the db.
func (c *ChainService) HasStoredState() (bool, error) {
hasCrystallized, err := c.beaconDB.Has(crystallizedStateLookupKey)
if err != nil {
return false, err
}
return hasCrystallized, nil
}
// SaveBlock is a mock which saves a block to the local db using the
// blockhash as the key.
func (c *ChainService) SaveBlock(block *types.Block) error {
return c.chain.saveBlock(block)
}
// ContainsBlock checks if a block for the hash exists in the chain.
// This method must be safe to call from a goroutine.
func (c *ChainService) ContainsBlock(h [32]byte) (bool, error) {
return c.chain.hasBlock(h)
}
// BlockSlotNumberByHash returns the slot number of a block.
func (c *ChainService) BlockSlotNumberByHash(h [32]byte) (uint64, error) {
block, err := c.chain.getBlock(h)
if err != nil {
return 0, fmt.Errorf("could not get block from DB: %v", err)
}
return block.SlotNumber(), nil
}
// CurrentCrystallizedState of the canonical chain.
func (c *ChainService) CurrentCrystallizedState() *types.CrystallizedState {
return c.chain.CrystallizedState()
}
// CurrentActiveState of the canonical chain.
func (c *ChainService) CurrentActiveState() *types.ActiveState {
return c.chain.ActiveState()
}
// CanonicalBlockFeed returns a channel that is written to
// whenever a new block is determined to be canonical in the chain.
func (c *ChainService) CanonicalBlockFeed() *event.Feed {
return c.canonicalBlockFeed
}
// CanonicalCrystallizedStateFeed returns a feed that is written to
// whenever a new crystallized state is determined to be canonical in the chain.
func (c *ChainService) CanonicalCrystallizedStateFeed() *event.Feed {
return c.canonicalCrystallizedStateFeed
}
// CheckForCanonicalBlockBySlot checks if the canonical block for that slot exists
// in the db.
func (c *ChainService) CheckForCanonicalBlockBySlot(slotNumber uint64) (bool, error) {
return c.chain.hasCanonicalBlockForSlot(slotNumber)
}
// CanonicalBlockBySlotNumber retrieves the canonical block for that slot which
// has been saved in the db.
func (c *ChainService) CanonicalBlockBySlotNumber(slotNumber uint64) (*types.Block, error) {
return c.chain.canonicalBlockForSlot(slotNumber)
}
// doesPoWBlockExist checks if the referenced PoW block exists.
func (c *ChainService) doesPoWBlockExist(block *types.Block) bool {
powBlock, err := c.web3Service.Client().BlockByHash(context.Background(), block.PowChainRef())
if err != nil {
log.Debugf("fetching PoW block corresponding to mainchain reference failed: %v", err)
return false
}
return powBlock != nil
}
// updateHead applies the fork choice rule to the beacon chain
// at the start of each new slot interval. The function looks
// at an in-memory slice of block hashes pending processing and
// selects the best block according to the in-protocol fork choice
// rule as canonical. This block is then persisted to storage.
func (c *ChainService) updateHead(slotInterval <-chan time.Time) {
for {
select {
case <-c.ctx.Done():
return
case <-slotInterval:
log.WithField("slotNumber", c.CurrentBeaconSlot()).Info("New beacon slot")
// First, we check if there were any blocks processed in the previous slot.
// If there is, we fetch the first one from the DB.
if len(c.blocksPendingProcessing) == 0 {
continue
}
// Naive fork choice rule: we pick the first block we processed for the previous slot
// as canonical.
block, err := c.chain.getBlock(c.blocksPendingProcessing[0])
if err != nil {
log.Errorf("Could not get block: %v", err)
continue
}
h, err := block.Hash()
if err != nil {
log.Errorf("Could not hash incoming block: %v", err)
continue
}
log.Info("Applying fork choice rule")
parentBlock, err := c.chain.getBlock(block.ParentHash())
if err != nil {
log.Errorf("Failed to get parent of block 0x%x", h)
continue
}
cState := c.chain.CrystallizedState()
aState := c.chain.ActiveState()
var stateTransitioned bool
for cState.IsCycleTransition(parentBlock.SlotNumber()) {
cState, aState, err = cState.NewStateRecalculations(aState, block)
if err != nil {
log.Errorf("Initialize new cycle transition failed: %v", err)
continue
}
stateTransitioned = true
}
aState, err = aState.CalculateNewActiveState(block, cState, parentBlock.SlotNumber())
if err != nil {
log.Errorf("Compute active state failed: %v", err)
continue
}
if err := c.chain.SetActiveState(aState); err != nil {
log.Errorf("Write active state to disk failed: %v", err)
continue
}
if stateTransitioned {
if err := c.chain.SetCrystallizedState(cState); err != nil {
log.Errorf("Write crystallized state to disk failed: %v", err)
continue
}
}
// Save canonical block hash with slot number to DB.
if err := c.chain.saveCanonicalSlotNumber(block.SlotNumber(), h); err != nil {
log.Errorf("Unable to save slot number to db: %v", err)
continue
}
// Save canonical block to DB.
if err := c.chain.saveCanonicalBlock(block); err != nil {
log.Errorf("Unable to save block to db: %v", err)
continue
}
log.WithField("blockHash", fmt.Sprintf("0x%x", h)).Info("Canonical block determined")
// We fire events that notify listeners of a new block (or crystallized state in
// the case of a state transition). This is useful for the beacon node's gRPC
// server to stream these events to beacon clients.
if stateTransitioned {
c.canonicalCrystallizedStateFeed.Send(cState)
}
c.canonicalBlockFeed.Send(block)
// Clear the blocks pending processing, mutex lock for thread safety
// in updating this slice.
c.lock.Lock()
c.blocksPendingProcessing = [][32]byte{}
c.lock.Unlock()
}
}
}
func (c *ChainService) blockProcessing() {
subBlock := c.incomingBlockFeed.Subscribe(c.incomingBlockChan)
defer subBlock.Unsubscribe()
for {
select {
case <-c.ctx.Done():
log.Debug("Chain service context closed, exiting goroutine")
return
// Listen for a newly received incoming block from the sync service.
case block := <-c.incomingBlockChan:
blockHash, err := block.Hash()
if err != nil {
log.Errorf("Failed to get hash of block: %v", err)
continue
}
if !c.devMode && !c.doesPoWBlockExist(block) {
log.Debugf("Proof-of-Work chain reference in block does not exist")
continue
}
// Check if we have received the parent block.
parentExists, err := c.chain.hasBlock(block.ParentHash())
if err != nil {
log.Errorf("Could not check existence of parent: %v", err)
continue
}
if !parentExists {
log.Debugf("Block points to nil parent: %v", err)
continue
}
parent, err := c.chain.getBlock(block.ParentHash())
if err != nil {
log.Debugf("Could not get parent block: %v", err)
continue
}
aState := c.chain.ActiveState()
cState := c.chain.CrystallizedState()
if valid := block.IsValid(c, aState, cState, parent.SlotNumber()); !valid {
log.Debugf("Block failed validity conditions: %v", err)
continue
}
if err := c.chain.saveBlock(block); err != nil {
log.Errorf("Failed to save block: %v", err)
continue
}
log.Infof("Finished processing received block: %x", blockHash)
// We push the hash of the block we just stored to a pending processing
// slice the fork choice rule will utilize.
c.lock.Lock()
c.blocksPendingProcessing = append(c.blocksPendingProcessing, blockHash)
c.lock.Unlock()
log.Info("Finished processing received block")
}
}
}