blockchain

Documentation

Overview

Package blockchain defines the life-cycle and status of the beacon chain as well as the Ethereum Serenity beacon chain fork-choice rule based on Casper Proof of Stake finality.

Index

• func BlockAncestor(block *pb.BeaconBlock, slot uint64, beaconDB *db.BeaconDB) (*pb.BeaconBlock, error)
• func LMDGhost(block *pb.BeaconBlock, voteTargets map[[32]byte]*pb.BeaconBlock, ...) (*pb.BeaconBlock, error)
• func VoteCount(block *pb.BeaconBlock, targets map[[32]byte]*pb.BeaconBlock, ...) (int, error)
• type ChainService
  • func NewChainService(ctx context.Context, cfg *Config) (*ChainService, error)
  • func (c *ChainService) ApplyForkChoiceRule(block *pb.BeaconBlock, computedState *pb.BeaconState) error
  • func (c *ChainService) CanonicalBlockFeed() *event.Feed
  • func (c *ChainService) CanonicalStateFeed() *event.Feed
  • func (c *ChainService) IncomingBlockFeed() *event.Feed
  • func (c *ChainService) ReceiveBlock(block *pb.BeaconBlock, beaconState *pb.BeaconState) (*pb.BeaconState, error)
  • func (c *ChainService) Start()
  • func (c *ChainService) Status() error
  • func (c *ChainService) Stop() error
• type Config

Functions

func BlockAncestor

func BlockAncestor(block *pb.BeaconBlock, slot uint64, beaconDB *db.BeaconDB) (*pb.BeaconBlock, error)

BlockAncestor obtains the ancestor at of a block at a certain slot.

Spec pseudocode definition:

Let get_ancestor(store: Store, block: BeaconBlock, slot: SlotNumber) ->
BeaconBlock be the ancestor of block with slot number slot.
The get_ancestor function can be defined recursively as
	def get_ancestor(store: Store, block: BeaconBlock, slot: SlotNumber) ->
	BeaconBlock: return block if block.slot ==
	slot else get_ancestor(store, store.get_parent(block), slot)

func LMDGhost

func LMDGhost(
	block *pb.BeaconBlock,
	voteTargets map[[32]byte]*pb.BeaconBlock,
	observedBlocks []*pb.BeaconBlock,
	beaconDB *db.BeaconDB,
) (*pb.BeaconBlock, error)

LMDGhost applies the Latest Message Driven, Greediest Heaviest Observed Sub-Tree fork-choice rule defined in the Ethereum Serenity specification for the beacon chain.

Spec pseudocode definition:

head = start_block
while 1:
    children = get_children(store, head)
    if len(children) == 0:
        return head
    head = max(children, key=get_vote_count)

func VoteCount

func VoteCount(block *pb.BeaconBlock, targets map[[32]byte]*pb.BeaconBlock, beaconDB *db.BeaconDB) (int, error)

VoteCount determines the number of votes on a beacon block by counting the number of target blocks that have such beacon block as a common ancestor.

Spec pseudocode definition:

def get_vote_count(block: BeaconBlock) -> int:
	return len([target for target in attestation_targets
		if get_ancestor(store, target, block.slot) == block])

Types

type ChainService

type ChainService struct {
	// contains filtered or unexported fields
}

ChainService represents a service that handles the internal logic of managing the full PoS beacon chain.

func NewChainService

func NewChainService(ctx context.Context, cfg *Config) (*ChainService, error)

NewChainService instantiates a new service instance that will be registered into a running beacon node.

func (*ChainService) ApplyForkChoiceRule

func (c *ChainService) ApplyForkChoiceRule(block *pb.BeaconBlock, computedState *pb.BeaconState) error

ApplyForkChoiceRule determines the current beacon chain head using LMD GHOST as a block-vote weighted function to select a canonical head in Ethereum Serenity.

func (*ChainService) CanonicalBlockFeed

func (c *ChainService) CanonicalBlockFeed() *event.Feed

CanonicalBlockFeed returns a channel that is written to whenever a new block is determined to be canonical in the chain.

func (*ChainService) CanonicalStateFeed

func (c *ChainService) CanonicalStateFeed() *event.Feed

CanonicalStateFeed returns a feed that is written to whenever a new state is determined to be canonical in the chain.

func (*ChainService) IncomingBlockFeed

func (c *ChainService) IncomingBlockFeed() *event.Feed

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 (*ChainService) ReceiveBlock

func (c *ChainService) ReceiveBlock(block *pb.BeaconBlock, beaconState *pb.BeaconState) (*pb.BeaconState, error)

ReceiveBlock is a function that defines the operations that are preformed on any block that is received from p2p layer or rpc. It checks the block to see if it passes the pre-processing conditions, if it does then the per slot state transition function is carried out on the block. spec:

 def process_block(block):
     if not block_pre_processing_conditions(block):
         return nil, error

 	# process skipped slots

		while (state.slot < block.slot - 1):
     	state = slot_state_transition(state, block=None)

		# process slot with block
		state = slot_state_transition(state, block)

		# check state root
     if block.state_root == hash(state):
			return state, error
		else:
			return nil, error  # or throw or whatever

func (*ChainService) Start

func (c *ChainService) Start()

Start a blockchain service's main event loop.

func (*ChainService) Status

func (c *ChainService) Status() error

Status always returns nil. TODO(1202): Add service health checks.

func (*ChainService) Stop

func (c *ChainService) Stop() error

Stop the blockchain service's main event loop and associated goroutines.

type Config

type Config struct {
	BeaconBlockBuf   int
	IncomingBlockBuf int
	Web3Service      *powchain.Web3Service
	BeaconDB         *db.BeaconDB
	DevMode          bool
	EnablePOWChain   bool
}

Config options for the service.