4.7 KiB
4.7 KiB
EIP-7594 -- Fork Choice
Table of contents
Introduction
This is the modification of the fork choice accompanying EIP-7594.
Helpers
Modified is_data_available
def is_data_available(beacon_block_root: Root) -> bool:
# `retrieve_column_sidecars` is implementation and context dependent, replacing
# `retrieve_blobs_and_proofs`. For the given block root, it returns all column
# sidecars to custody, or raises an exception if they are not available.
# The p2p network does not guarantee sidecar retrieval outside of
# `MIN_EPOCHS_FOR_DATA_COLUMN_SIDECARS_REQUESTS` epochs.
column_sidecars = retrieve_column_sidecars(beacon_block_root)
return all(
verify_data_column_sidecar_kzg_proofs(column_sidecar)
for column_sidecar in column_sidecars
)
Modified get_head
Note: children of the current head are required to be available in order to be considered by the fork-choice.
def get_head(store: Store) -> Root:
# Get filtered block tree that only includes viable branches
blocks = get_filtered_block_tree(store)
# Execute the LMD-GHOST fork choice
head = store.justified_checkpoint.root
while True:
# Get available children for the current slot
children = [
root for (root, block) in blocks.items()
if (
block.parent_root == head
and is_data_available(root)
)
]
if len(children) == 0:
return head
# Sort by latest attesting balance with ties broken lexicographically
# Ties broken by favoring block with lexicographically higher root
head = max(children, key=lambda root: (get_weight(store, root), root))
Updated fork-choice handlers
Modified on_block
Note: The blob data availability check is removed. We import blocks regardless
of their availability status, and move all filtering to the fork-choice (get_head).
def on_block(store: Store, signed_block: SignedBeaconBlock) -> None:
"""
Run ``on_block`` upon receiving a new block.
"""
block = signed_block.message
# Parent block must be known
assert block.parent_root in store.block_states
# Make a copy of the state to avoid mutability issues
state = copy(store.block_states[block.parent_root])
# Blocks cannot be in the future. If they are, their consideration must be delayed until they are in the past.
assert get_current_slot(store) >= block.slot
# Check that block is later than the finalized epoch slot (optimization to reduce calls to get_ancestor)
finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
assert block.slot > finalized_slot
# Check block is a descendant of the finalized block at the checkpoint finalized slot
finalized_checkpoint_block = get_checkpoint_block(
store,
block.parent_root,
store.finalized_checkpoint.epoch,
)
assert store.finalized_checkpoint.root == finalized_checkpoint_block
# Check the block is valid and compute the post-state
block_root = hash_tree_root(block)
state_transition(state, signed_block, True)
# Add new block to the store
store.blocks[block_root] = block
# Add new state for this block to the store
store.block_states[block_root] = state
# Add block timeliness to the store
time_into_slot = (store.time - store.genesis_time) % SECONDS_PER_SLOT
is_before_attesting_interval = time_into_slot < SECONDS_PER_SLOT // INTERVALS_PER_SLOT
is_timely = get_current_slot(store) == block.slot and is_before_attesting_interval
store.block_timeliness[hash_tree_root(block)] = is_timely
# Add proposer score boost if the block is timely and not conflicting with an existing block
is_first_block = store.proposer_boost_root == Root()
if is_timely and is_first_block:
store.proposer_boost_root = hash_tree_root(block)
# Update checkpoints in store if necessary
update_checkpoints(store, state.current_justified_checkpoint, state.finalized_checkpoint)
# Eagerly compute unrealized justification and finality.
compute_pulled_up_tip(store, block_root)