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Update to spec v0.9.1 (#597)

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* Update to spec v0.9.0

* Update to v0.9.1

* Bump spec tags for v0.9.1

* Formatting, fix CI failures

* Resolve accidental KeyPair merge conflict

* Document new BeaconState functions

* Fix incorrect cache drops in `advance_caches`

* Update fork choice for v0.9.1

* Clean up some FIXMEs

* Fix a few docs/logs
This commit is contained in:
Michael Sproul
2019-11-21 11:47:30 +11:00
committed by GitHub
parent b7a0feb725
commit 24e941d175
105 changed files with 1211 additions and 2940 deletions
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138
beacon_node/beacon_chain/src/fork_choice.rs
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@@ -1,10 +1,11 @@
use crate::{metrics, BeaconChain, BeaconChainTypes};
use crate::{errors::BeaconChainError, metrics, BeaconChain, BeaconChainTypes};
use lmd_ghost::LmdGhost;
use state_processing::common::get_attesting_indices;
use parking_lot::RwLock;
use state_processing::{common::get_attesting_indices, per_slot_processing};
use std::sync::Arc;
use store::{Error as StoreError, Store};
use types::{
Attestation, BeaconBlock, BeaconState, BeaconStateError, Epoch, EthSpec, Hash256, Slot,
Attestation, BeaconBlock, BeaconState, BeaconStateError, Checkpoint, EthSpec, Hash256, Slot,
};
type Result<T> = std::result::Result<T, Error>;
@@ -16,6 +17,7 @@ pub enum Error {
BackendError(String),
BeaconStateError(BeaconStateError),
StoreError(StoreError),
BeaconChainError(Box<BeaconChainError>),
}
pub struct ForkChoice<T: BeaconChainTypes> {
@@ -26,6 +28,10 @@ pub struct ForkChoice<T: BeaconChainTypes> {
/// Does not necessarily need to be the _actual_ genesis, it suffices to be the finalized root
/// whenever the struct was instantiated.
genesis_block_root: Hash256,
/// The fork choice rule's current view of the justified checkpoint.
justified_checkpoint: RwLock<Checkpoint>,
/// The best justified checkpoint we've seen, which may be ahead of `justified_checkpoint`.
best_justified_checkpoint: RwLock<Checkpoint>,
}
impl<T: BeaconChainTypes> ForkChoice<T> {
@@ -33,39 +39,91 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
///
/// "Genesis" does not necessarily need to be the absolute genesis, it can be some finalized
/// block.
pub fn new(store: Arc<T::Store>, backend: T::LmdGhost, genesis_block_root: Hash256) -> Self {
pub fn new(
store: Arc<T::Store>,
backend: T::LmdGhost,
genesis_block_root: Hash256,
genesis_slot: Slot,
) -> Self {
let justified_checkpoint = Checkpoint {
epoch: genesis_slot.epoch(T::EthSpec::slots_per_epoch()),
root: genesis_block_root,
};
Self {
store: store.clone(),
backend,
genesis_block_root,
justified_checkpoint: RwLock::new(justified_checkpoint.clone()),
best_justified_checkpoint: RwLock::new(justified_checkpoint),
}
}
/// Determine whether the fork choice's view of the justified checkpoint should be updated.
///
/// To prevent the bouncing attack, an update is allowed only in these conditions:
///
/// * We're in the first SAFE_SLOTS_TO_UPDATE_JUSTIFIED slots of the epoch, or
/// * The new justified checkpoint is a descendant of the current justified checkpoint
fn should_update_justified_checkpoint(
&self,
chain: &BeaconChain<T>,
new_justified_checkpoint: &Checkpoint,
) -> Result<bool> {
if Self::compute_slots_since_epoch_start(chain.slot()?)
< chain.spec.safe_slots_to_update_justified
{
return Ok(true);
}
let justified_checkpoint = self.justified_checkpoint.read().clone();
let current_justified_block = chain
.get_block(&justified_checkpoint.root)?
.ok_or_else(|| Error::MissingBlock(justified_checkpoint.root))?;
let new_justified_block = chain
.get_block(&new_justified_checkpoint.root)?
.ok_or_else(|| Error::MissingBlock(new_justified_checkpoint.root))?;
let slots_per_epoch = T::EthSpec::slots_per_epoch();
Ok(
new_justified_block.slot > justified_checkpoint.epoch.start_slot(slots_per_epoch)
&& chain.get_ancestor_block_root(
new_justified_checkpoint.root,
current_justified_block.slot,
)? == Some(justified_checkpoint.root),
)
}
/// Calculate how far `slot` lies from the start of its epoch.
fn compute_slots_since_epoch_start(slot: Slot) -> u64 {
let slots_per_epoch = T::EthSpec::slots_per_epoch();
(slot - slot.epoch(slots_per_epoch).start_slot(slots_per_epoch)).as_u64()
}
/// Run the fork choice rule to determine the head.
pub fn find_head(&self, chain: &BeaconChain<T>) -> Result<Hash256> {
let timer = metrics::start_timer(&metrics::FORK_CHOICE_FIND_HEAD_TIMES);
let start_slot = |epoch: Epoch| epoch.start_slot(T::EthSpec::slots_per_epoch());
// From the specification:
//
// Let justified_head be the descendant of finalized_head with the highest epoch that has
// been justified for at least 1 epoch ... If no such descendant exists,
// set justified_head to finalized_head.
let (start_state, start_block_root, start_block_slot) = {
let state = &chain.head().beacon_state;
// Check if we should update our view of the justified checkpoint.
// Doing this check here should be quasi-equivalent to the update in the `on_tick`
// function of the spec, so long as `find_head` is called at least once during the first
// SAFE_SLOTS_TO_UPDATE_JUSTIFIED slots.
let best_justified_checkpoint = self.best_justified_checkpoint.read();
if self.should_update_justified_checkpoint(chain, &best_justified_checkpoint)? {
*self.justified_checkpoint.write() = best_justified_checkpoint.clone();
}
let (block_root, block_slot) =
if state.current_epoch() + 1 > state.current_justified_checkpoint.epoch {
(
state.current_justified_checkpoint.root,
start_slot(state.current_justified_checkpoint.epoch),
)
} else {
(
state.finalized_checkpoint.root,
start_slot(state.finalized_checkpoint.epoch),
)
};
let current_justified_checkpoint = self.justified_checkpoint.read().clone();
let (block_root, block_justified_slot) = (
current_justified_checkpoint.root,
current_justified_checkpoint
.epoch
.start_slot(T::EthSpec::slots_per_epoch()),
);
let block = chain
.store
@@ -79,12 +137,17 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
block_root
};
let state = chain
.store
.get::<BeaconState<T::EthSpec>>(&block.state_root)?
let mut state = chain
.get_state(&block.state_root)?
.ok_or_else(|| Error::MissingState(block.state_root))?;
(state, block_root, block_slot)
// Fast-forward the state to the start slot of the epoch where it was justified.
for _ in block.slot.as_u64()..block_justified_slot.as_u64() {
per_slot_processing(&mut state, &chain.spec)
.map_err(|e| BeaconChainError::SlotProcessingError(e))?
}
(state, block_root, block_justified_slot)
};
// A function that returns the weight for some validator index.
@@ -107,10 +170,11 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
/// Process all attestations in the given `block`.
///
/// Assumes the block (and therefore it's attestations) are valid. It is a logic error to
/// Assumes the block (and therefore its attestations) are valid. It is a logic error to
/// provide an invalid block.
pub fn process_block(
&self,
chain: &BeaconChain<T>,
state: &BeaconState<T::EthSpec>,
block: &BeaconBlock<T::EthSpec>,
block_root: Hash256,
@@ -133,6 +197,16 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
}
}
// Check if we should update our view of the justified checkpoint
if state.current_justified_checkpoint.epoch > self.justified_checkpoint.read().epoch {
*self.best_justified_checkpoint.write() = state.current_justified_checkpoint.clone();
if self
.should_update_justified_checkpoint(chain, &state.current_justified_checkpoint)?
{
*self.justified_checkpoint.write() = state.current_justified_checkpoint.clone();
}
}
// This does not apply a vote to the block, it just makes fork choice aware of the block so
// it can still be identified as the head even if it doesn't have any votes.
//
@@ -224,6 +298,12 @@ impl From<BeaconStateError> for Error {
}
}
impl From<BeaconChainError> for Error {
fn from(e: BeaconChainError) -> Error {
Error::BeaconChainError(Box::new(e))
}
}
impl From<StoreError> for Error {
fn from(e: StoreError) -> Error {
Error::StoreError(e)