state

package
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 Go to latest Published: Apr 22, 2020 License: GPL-3.0 Imports: 21 Imported by: 0

Documentation

Overview

Package state implements the whole state transition function which consists of per slot, per-epoch transitions. It also bootstraps the genesis beacon state for slot 0.

Package state implements the whole state transition function which consists of per slot, per-epoch transitions. It also bootstraps the genesis beacon state for slot 0.

Index

Constants

This section is empty.

Variables

View Source 
var SkipSlotCache = cache.NewSkipSlotCache()

SkipSlotCache exists for the unlikely scenario that is a large gap between the head state and the current slot. If the beacon chain were ever to be stalled for several epochs, it may be difficult or impossible to compute the appropriate beacon state for assignments within a reasonable amount of time.

View Source 
var ValidatorSummary []*precompute.Validator

ValidatorSummary tracks validator's attesting summary on per epoch basis. This gets updated during epoch transition.

Functions

func CalculateStateRoot 

func CalculateStateRoot(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) ([32]byte, error)

CalculateStateRoot defines the procedure for a state transition function. This does not validate any BLS signatures in a block, it is used for calculating the state root of the state for the block proposer to use. This does not modify state.

WARNING: This method does not validate any BLS signatures. This is used for proposer to compute state root before proposing a new block, and this does not modify state.

Spec pseudocode definition: 

def state_transition(state: BeaconState, block: BeaconBlock, validate_state_root: bool=False) -> BeaconState:
  # Process slots (including those with no blocks) since block
  process_slots(state, block.slot)
  # Process block
  process_block(state, block)
  # Return post-state
  return state

func CanProcessEpoch 

func CanProcessEpoch(state *stateTrie.BeaconState) bool

CanProcessEpoch checks the eligibility to process epoch. The epoch can be processed at the end of the last slot of every epoch

Spec pseudocode definition: 

If (state.slot + 1) % SLOTS_PER_EPOCH == 0:

func EmptyGenesisState added in v0.3.0 

func EmptyGenesisState() (*stateTrie.BeaconState, error)

EmptyGenesisState returns an empty beacon state object.

func ExecuteStateTransition 

func ExecuteStateTransition(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) (*stateTrie.BeaconState, error)

ExecuteStateTransition defines the procedure for a state transition function.

Spec pseudocode definition: 

def state_transition(state: BeaconState, block: BeaconBlock, validate_state_root: bool=False) -> BeaconState:
  # Process slots (including those with no blocks) since block
  process_slots(state, block.slot)
  # Process block
  process_block(state, block)
  # Validate state root (`validate_state_root == True` in production)
  if validate_state_root:
      assert block.state_root == hash_tree_root(state)
  # Return post-state
  return state

func ExecuteStateTransitionNoVerifyAttSigs added in v0.3.2 

func ExecuteStateTransitionNoVerifyAttSigs(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) (*stateTrie.BeaconState, error)

ExecuteStateTransitionNoVerifyAttSigs defines the procedure for a state transition function. This does not validate any BLS signatures of attestations in a block, it is used for performing a state transition as quickly as possible. This function should only be used when we can trust the data we're receiving entirely, such as initial sync or for processing past accepted blocks.

WARNING: This method does not validate any signatures in a block. This method also modifies the passed in state.

Spec pseudocode definition: 

def state_transition(state: BeaconState, block: BeaconBlock, validate_state_root: bool=False) -> BeaconState:
  # Process slots (including those with no blocks) since block
  process_slots(state, block.slot)
  # Process block
  process_block(state, block)
  # Return post-state
  return state

func GenesisBeaconState 

func GenesisBeaconState(deposits []*ethpb.Deposit, genesisTime uint64, eth1Data *ethpb.Eth1Data) (*stateTrie.BeaconState, error)

GenesisBeaconState gets called when MinGenesisActiveValidatorCount count of full deposits were made to the deposit contract and the ChainStart log gets emitted.

Spec pseudocode definition: 

	def initialize_beacon_state_from_eth1(eth1_block_hash: Hash,
	  eth1_timestamp: uint64,
	  deposits: Sequence[Deposit]) -> BeaconState:
	  state = BeaconState(
	    genesis_time=eth1_timestamp - eth1_timestamp % SECONDS_PER_DAY + 2 * SECONDS_PER_DAY,
	    eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=len(deposits)),
	    latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
       randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
	  )

	  # Process deposits
	  leaves = list(map(lambda deposit: deposit.data, deposits))
	  for index, deposit in enumerate(deposits):
	    deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
	    state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
	    process_deposit(state, deposit)

	  # Process activations
	  for index, validator in enumerate(state.validators):
	    balance = state.balances[index]
	    validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
	    if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
	    validator.activation_eligibility_epoch = GENESIS_EPOCH
	    validator.activation_epoch = GENESIS_EPOCH

	  # Populate active_index_roots and compact_committees_roots
	  indices_list = List[ValidatorIndex, VALIDATOR_REGISTRY_LIMIT](get_active_validator_indices(state, GENESIS_EPOCH))
	  active_index_root = hash_tree_root(indices_list)
	  committee_root = get_compact_committees_root(state, GENESIS_EPOCH)
	  for index in range(EPOCHS_PER_HISTORICAL_VECTOR):
	    state.active_index_roots[index] = active_index_root
	    state.compact_committees_roots[index] = committee_root
	  return state

This method differs from the spec so as to process deposits beforehand instead of the end of the function.

func IsValidGenesisState 

func IsValidGenesisState(chainStartDepositCount uint64, currentTime uint64) bool

IsValidGenesisState gets called whenever there's a deposit event, it checks whether there's enough effective balance to trigger and if the minimum genesis time arrived already.

Spec pseudocode definition: 

def is_valid_genesis_state(state: BeaconState) -> bool:
   if state.genesis_time < MIN_GENESIS_TIME:
       return False
   if len(get_active_validator_indices(state, GENESIS_EPOCH)) < MIN_GENESIS_ACTIVE_VALIDATOR_COUNT:
       return False
   return True

This method has been modified from the spec to allow whole states not to be saved but instead only cache the relevant information.

func OptimizedGenesisBeaconState added in v0.3.0 

func OptimizedGenesisBeaconState(genesisTime uint64, preState *stateTrie.BeaconState, eth1Data *ethpb.Eth1Data) (*stateTrie.BeaconState, error)

OptimizedGenesisBeaconState is used to create a state that has already processed deposits. This is to efficiently create a mainnet state at chainstart.

func ProcessBlock 

func ProcessBlock(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) (*stateTrie.BeaconState, error)

ProcessBlock creates a new, modified beacon state by applying block operation transformations as defined in the Ethereum Serenity specification, including processing proposer slashings, processing block attestations, and more.

Spec pseudocode definition: 

def process_block(state: BeaconState, block: BeaconBlock) -> None:
  process_block_header(state, block)
  process_randao(state, block.body)
  process_eth1_data(state, block.body)
  process_operations(state, block.body)

func ProcessBlockForStateRoot added in v0.3.2 

func ProcessBlockForStateRoot(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) (*stateTrie.BeaconState, error)

ProcessBlockForStateRoot processes the state for state root computation. It skips proposer signature and randao signature verifications.

func ProcessBlockNoVerifyAttSigs added in v0.3.2 

func ProcessBlockNoVerifyAttSigs(
	ctx context.Context,
	state *stateTrie.BeaconState,
	signed *ethpb.SignedBeaconBlock,
) (*stateTrie.BeaconState, error)

ProcessBlockNoVerifyAttSigs creates a new, modified beacon state by applying block operation transformations as defined in the Ethereum Serenity specification. It does not validate block attestation signatures.

Spec pseudocode definition: 

def process_block(state: BeaconState, block: BeaconBlock) -> None:
  process_block_header(state, block)
  process_randao(state, block.body)
  process_eth1_data(state, block.body)
  process_operations(state, block.body)

func ProcessEpochPrecompute 

func ProcessEpochPrecompute(ctx context.Context, state *stateTrie.BeaconState) (*stateTrie.BeaconState, error)

ProcessEpochPrecompute describes the per epoch operations that are performed on the beacon state. It's optimized by pre computing validator attested info and epoch total/attested balances upfront.

func ProcessOperations 

func ProcessOperations(
	ctx context.Context,
	state *stateTrie.BeaconState,
	body *ethpb.BeaconBlockBody) (*stateTrie.BeaconState, error)

ProcessOperations processes the operations in the beacon block and updates beacon state with the operations in block.

Spec pseudocode definition: 

def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
  # Verify that outstanding deposits are processed up to the maximum number of deposits
  assert len(body.deposits) == min(MAX_DEPOSITS, state.eth1_data.deposit_count - state.eth1_deposit_index)
  # Verify that there are no duplicate transfers
  assert len(body.transfers) == len(set(body.transfers))

  all_operations = (
      (body.proposer_slashings, process_proposer_slashing),
      (body.attester_slashings, process_attester_slashing),
      (body.attestations, process_attestation),
      (body.deposits, process_deposit),
      (body.voluntary_exits, process_voluntary_exit),
      (body.transfers, process_transfer),
  )  # type: Sequence[Tuple[List, Callable]]
  for operations, function in all_operations:
      for operation in operations:
          function(state, operation)

func ProcessSlot 

func ProcessSlot(ctx context.Context, state *stateTrie.BeaconState) (*stateTrie.BeaconState, error)

ProcessSlot happens every slot and focuses on the slot counter and block roots record updates. It happens regardless if there's an incoming block or not. Spec pseudocode definition: 

def process_slot(state: BeaconState) -> None:
  # Cache state root
  previous_state_root = hash_tree_root(state)
  state.state_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = previous_state_root

  # Cache latest block header state root
  if state.latest_block_header.state_root == Bytes32():
      state.latest_block_header.state_root = previous_state_root

  # Cache block root
  previous_block_root = signing_root(state.latest_block_header)
  state.block_roots[state.slot % SLOTS_PER_HISTORICAL_ROOT] = previous_block_root

func ProcessSlots 

func ProcessSlots(ctx context.Context, state *stateTrie.BeaconState, slot uint64) (*stateTrie.BeaconState, error)

ProcessSlots process through skip skips and apply epoch transition when it's needed

Spec pseudocode definition: 

def process_slots(state: BeaconState, slot: Slot) -> None:
  assert state.slot <= slot
  while state.slot < slot:
      process_slot(state)
      # Process epoch on the first slot of the next epoch
      if (state.slot + 1) % SLOTS_PER_EPOCH == 0:
          process_epoch(state)
      state.slot += 1
  ]

Types

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