lighthouse/beacon_node/beacon_chain/src/beacon_chain.rs

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use crate::attestation_aggregator::{AttestationAggregator, Outcome as AggregationOutcome};
use crate::cached_beacon_state::CachedBeaconState;
use crate::checkpoint::CheckPoint;
use db::{
stores::{BeaconBlockStore, BeaconStateStore},
ClientDB, DBError,
};
use fork_choice::{ForkChoice, ForkChoiceError};
use log::{debug, trace};
use parking_lot::{RwLock, RwLockReadGuard};
use slot_clock::SlotClock;
use ssz::ssz_encode;
use state_processing::{
BlockProcessable, BlockProcessingError, SlotProcessable, SlotProcessingError,
};
use std::sync::Arc;
use types::{
beacon_state::BeaconStateError,
readers::{BeaconBlockReader, BeaconStateReader},
AttestationData, BeaconBlock, BeaconBlockBody, BeaconState, ChainSpec, Crosslink, Deposit,
Epoch, Eth1Data, FreeAttestation, Hash256, PublicKey, Signature, Slot,
};
#[derive(Debug, PartialEq)]
pub enum Error {
InsufficientValidators,
BadRecentBlockRoots,
BeaconStateError(BeaconStateError),
DBInconsistent(String),
DBError(String),
ForkChoiceError(ForkChoiceError),
MissingBeaconBlock(Hash256),
MissingBeaconState(Hash256),
}
#[derive(Debug, PartialEq)]
pub enum ValidBlock {
/// The block was successfully processed.
Processed,
}
#[derive(Debug, PartialEq)]
pub enum InvalidBlock {
/// The block slot is greater than the present slot.
FutureSlot,
/// The block state_root does not match the generated state.
StateRootMismatch,
/// The blocks parent_root is unknown.
ParentUnknown,
/// There was an error whilst advancing the parent state to the present slot. This condition
/// should not occur, it likely represents an internal error.
SlotProcessingError(SlotProcessingError),
/// The block could not be applied to the state, it is invalid.
PerBlockProcessingError(BlockProcessingError),
}
#[derive(Debug, PartialEq)]
pub enum BlockProcessingOutcome {
/// The block was successfully validated.
ValidBlock(ValidBlock),
/// The block was not successfully validated.
InvalidBlock(InvalidBlock),
}
pub struct BeaconChain<T: ClientDB + Sized, U: SlotClock, F: ForkChoice> {
pub block_store: Arc<BeaconBlockStore<T>>,
pub state_store: Arc<BeaconStateStore<T>>,
pub slot_clock: U,
pub attestation_aggregator: RwLock<AttestationAggregator>,
canonical_head: RwLock<CheckPoint>,
finalized_head: RwLock<CheckPoint>,
pub state: RwLock<BeaconState>,
pub cached_state: RwLock<CachedBeaconState>,
pub spec: ChainSpec,
pub fork_choice: RwLock<F>,
}
impl<T, U, F> BeaconChain<T, U, F>
where
T: ClientDB,
U: SlotClock,
F: ForkChoice,
{
/// Instantiate a new Beacon Chain, from genesis.
pub fn genesis(
state_store: Arc<BeaconStateStore<T>>,
block_store: Arc<BeaconBlockStore<T>>,
slot_clock: U,
genesis_time: u64,
latest_eth1_data: Eth1Data,
initial_validator_deposits: Vec<Deposit>,
spec: ChainSpec,
fork_choice: F,
) -> Result<Self, Error> {
if initial_validator_deposits.is_empty() {
return Err(Error::InsufficientValidators);
}
let genesis_state = BeaconState::genesis(
genesis_time,
initial_validator_deposits,
latest_eth1_data,
&spec,
)?;
let state_root = genesis_state.canonical_root();
state_store.put(&state_root, &ssz_encode(&genesis_state)[..])?;
let genesis_block = BeaconBlock::genesis(state_root, &spec);
let block_root = genesis_block.canonical_root();
block_store.put(&block_root, &ssz_encode(&genesis_block)[..])?;
let cached_state = RwLock::new(CachedBeaconState::from_beacon_state(
genesis_state.clone(),
spec.clone(),
)?);
let finalized_head = RwLock::new(CheckPoint::new(
genesis_block.clone(),
block_root,
genesis_state.clone(),
state_root,
));
let canonical_head = RwLock::new(CheckPoint::new(
genesis_block.clone(),
block_root,
genesis_state.clone(),
state_root,
));
let attestation_aggregator = RwLock::new(AttestationAggregator::new());
Ok(Self {
block_store,
state_store,
slot_clock,
attestation_aggregator,
state: RwLock::new(genesis_state.clone()),
cached_state,
finalized_head,
canonical_head,
spec,
fork_choice: RwLock::new(fork_choice),
})
}
/// Update the canonical head to some new values.
pub fn update_canonical_head(
&self,
new_beacon_block: BeaconBlock,
new_beacon_block_root: Hash256,
new_beacon_state: BeaconState,
new_beacon_state_root: Hash256,
) {
let mut head = self.canonical_head.write();
head.update(
new_beacon_block,
new_beacon_block_root,
new_beacon_state,
new_beacon_state_root,
);
}
/// Returns a read-lock guarded `CheckPoint` struct for reading the head (as chosen by the
/// fork-choice rule).
///
/// It is important to note that the `beacon_state` returned may not match the present slot. It
/// is the state as it was when the head block was recieved, which could be some slots prior to
/// now.
pub fn head(&self) -> RwLockReadGuard<CheckPoint> {
self.canonical_head.read()
}
/// Update the justified head to some new values.
pub fn update_finalized_head(
&self,
new_beacon_block: BeaconBlock,
new_beacon_block_root: Hash256,
new_beacon_state: BeaconState,
new_beacon_state_root: Hash256,
) {
let mut finalized_head = self.finalized_head.write();
finalized_head.update(
new_beacon_block,
new_beacon_block_root,
new_beacon_state,
new_beacon_state_root,
);
}
/// Returns a read-lock guarded `CheckPoint` struct for reading the justified head (as chosen,
/// indirectly, by the fork-choice rule).
pub fn finalized_head(&self) -> RwLockReadGuard<CheckPoint> {
self.finalized_head.read()
}
/// Advance the `self.state` `BeaconState` to the supplied slot.
///
/// This will perform per_slot and per_epoch processing as required.
///
/// The `previous_block_root` will be set to the root of the current head block (as determined
/// by the fork-choice rule).
///
/// It is important to note that this is _not_ the state corresponding to the canonical head
/// block, instead it is that state which may or may not have had additional per slot/epoch
/// processing applied to it.
pub fn advance_state(&self, slot: Slot) -> Result<(), SlotProcessingError> {
let state_slot = self.state.read().slot;
let head_block_root = self.head().beacon_block_root;
for _ in state_slot.as_u64()..slot.as_u64() {
self.state
.write()
.per_slot_processing(head_block_root, &self.spec)?;
}
Ok(())
}
/// Returns the validator index (if any) for the given public key.
///
/// Information is retrieved from the present `beacon_state.validator_registry`.
pub fn validator_index(&self, pubkey: &PublicKey) -> Option<usize> {
for (i, validator) in self
.head()
.beacon_state
.validator_registry
.iter()
.enumerate()
{
if validator.pubkey == *pubkey {
return Some(i);
}
}
None
}
/// Reads the slot clock, returns `None` if the slot is unavailable.
///
/// The slot might be unavailable due to an error with the system clock, or if the present time
/// is before genesis (i.e., a negative slot).
///
/// This is distinct to `present_slot`, which simply reads the latest state. If a
/// call to `read_slot_clock` results in a higher slot than a call to `present_slot`,
/// `self.state` should undergo per slot processing.
pub fn read_slot_clock(&self) -> Option<Slot> {
match self.slot_clock.present_slot() {
Ok(Some(some_slot)) => Some(some_slot),
Ok(None) => None,
_ => None,
}
}
/// Returns slot of the present state.
///
/// This is distinct to `read_slot_clock`, which reads from the actual system clock. If
/// `self.state` has not been transitioned it is possible for the system clock to be on a
/// different slot to what is returned from this call.
pub fn present_slot(&self) -> Slot {
self.state.read().slot
}
/// Returns the block proposer for a given slot.
///
/// Information is read from the present `beacon_state` shuffling, so only information from the
/// present and prior epoch is available.
pub fn block_proposer(&self, slot: Slot) -> Result<usize, BeaconStateError> {
trace!("BeaconChain::block_proposer: slot: {}", slot);
let index = self
.state
.read()
.get_beacon_proposer_index(slot, &self.spec)?;
Ok(index)
}
/// Returns the justified slot for the present state.
pub fn justified_epoch(&self) -> Epoch {
self.state.read().justified_epoch
}
/// Returns the attestation slot and shard for a given validator index.
///
/// Information is read from the current state, so only information from the present and prior
/// epoch is available.
pub fn validator_attestion_slot_and_shard(
&self,
validator_index: usize,
) -> Result<Option<(Slot, u64)>, BeaconStateError> {
trace!(
"BeaconChain::validator_attestion_slot_and_shard: validator_index: {}",
validator_index
);
if let Some((slot, shard, _committee)) = self
.cached_state
.read()
.attestation_slot_and_shard_for_validator(validator_index, &self.spec)?
{
Ok(Some((slot, shard)))
} else {
Ok(None)
}
}
/// Produce an `AttestationData` that is valid for the present `slot` and given `shard`.
pub fn produce_attestation_data(&self, shard: u64) -> Result<AttestationData, Error> {
trace!("BeaconChain::produce_attestation_data: shard: {}", shard);
let justified_epoch = self.justified_epoch();
let justified_block_root = *self
.state
.read()
.get_block_root(
justified_epoch.start_slot(self.spec.epoch_length),
&self.spec,
)
.ok_or_else(|| Error::BadRecentBlockRoots)?;
let epoch_boundary_root = *self
.state
.read()
.get_block_root(
self.state.read().current_epoch_start_slot(&self.spec),
&self.spec,
)
.ok_or_else(|| Error::BadRecentBlockRoots)?;
Ok(AttestationData {
slot: self.state.read().slot,
shard,
beacon_block_root: self.head().beacon_block_root,
epoch_boundary_root,
shard_block_root: Hash256::zero(),
latest_crosslink: Crosslink {
epoch: self.state.read().slot.epoch(self.spec.epoch_length),
shard_block_root: Hash256::zero(),
},
justified_epoch,
justified_block_root,
})
}
/// Validate a `FreeAttestation` and either:
///
/// - Create a new `Attestation`.
/// - Aggregate it to an existing `Attestation`.
pub fn process_free_attestation(
&self,
free_attestation: FreeAttestation,
) -> Result<AggregationOutcome, Error> {
let aggregation_outcome = self
.attestation_aggregator
.write()
.process_free_attestation(&self.cached_state.read(), &free_attestation, &self.spec)?;
// return if the attestation is invalid
if !aggregation_outcome.valid {
return Ok(aggregation_outcome);
}
// valid attestation, proceed with fork-choice logic
self.fork_choice.write().add_attestation(
free_attestation.validator_index,
&free_attestation.data.beacon_block_root,
)?;
Ok(aggregation_outcome)
}
/// Dumps the entire canonical chain, from the head to genesis to a vector for analysis.
///
/// This could be a very expensive operation and should only be done in testing/analysis
/// activities.
pub fn chain_dump(&self) -> Result<Vec<CheckPoint>, Error> {
let mut dump = vec![];
let mut last_slot = CheckPoint {
beacon_block: self.head().beacon_block.clone(),
beacon_block_root: self.head().beacon_block_root,
beacon_state: self.head().beacon_state.clone(),
beacon_state_root: self.head().beacon_state_root,
};
dump.push(last_slot.clone());
loop {
let beacon_block_root = last_slot.beacon_block.parent_root;
if beacon_block_root == self.spec.zero_hash {
break; // Genesis has been reached.
}
let beacon_block = self
.block_store
.get_deserialized(&beacon_block_root)?
.ok_or_else(|| {
Error::DBInconsistent(format!("Missing block {}", beacon_block_root))
})?;
let beacon_state_root = beacon_block.state_root;
let beacon_state = self
.state_store
.get_deserialized(&beacon_state_root)?
.ok_or_else(|| {
Error::DBInconsistent(format!("Missing state {}", beacon_state_root))
})?;
let slot = CheckPoint {
beacon_block,
beacon_block_root,
beacon_state,
beacon_state_root,
};
dump.push(slot.clone());
last_slot = slot;
}
Ok(dump)
}
/// Accept some block and attempt to add it to block DAG.
///
/// Will accept blocks from prior slots, however it will reject any block from a future slot.
pub fn process_block(&self, block: BeaconBlock) -> Result<BlockProcessingOutcome, Error> {
debug!("Processing block with slot {}...", block.slot());
let block_root = block.canonical_root();
let present_slot = self.present_slot();
if block.slot > present_slot {
return Ok(BlockProcessingOutcome::InvalidBlock(
InvalidBlock::FutureSlot,
));
}
// Load the blocks parent block from the database, returning invalid if that block is not
// found.
let parent_block_root = block.parent_root;
let parent_block = match self.block_store.get_reader(&parent_block_root)? {
Some(parent_root) => parent_root,
None => {
return Ok(BlockProcessingOutcome::InvalidBlock(
InvalidBlock::ParentUnknown,
));
}
};
// Load the parent blocks state from the database, returning an error if it is not found.
// It is an error because if know the parent block we should also know the parent state.
let parent_state_root = parent_block.state_root();
let parent_state = self
.state_store
.get_reader(&parent_state_root)?
.ok_or_else(|| Error::DBInconsistent(format!("Missing state {}", parent_state_root)))?
.into_beacon_state()
.ok_or_else(|| {
Error::DBInconsistent(format!("State SSZ invalid {}", parent_state_root))
})?;
// TODO: check the block proposer signature BEFORE doing a state transition. This will
// significantly lower exposure surface to DoS attacks.
// Transition the parent state to the present slot.
let mut state = parent_state;
for _ in state.slot.as_u64()..present_slot.as_u64() {
if let Err(e) = state.per_slot_processing(parent_block_root, &self.spec) {
return Ok(BlockProcessingOutcome::InvalidBlock(
InvalidBlock::SlotProcessingError(e),
));
}
}
// Apply the received block to its parent state (which has been transitioned into this
// slot).
if let Err(e) = state.per_block_processing(&block, &self.spec) {
return Ok(BlockProcessingOutcome::InvalidBlock(
InvalidBlock::PerBlockProcessingError(e),
));
}
let state_root = state.canonical_root();
if block.state_root != state_root {
return Ok(BlockProcessingOutcome::InvalidBlock(
InvalidBlock::StateRootMismatch,
));
}
// Store the block and state.
self.block_store.put(&block_root, &ssz_encode(&block)[..])?;
self.state_store.put(&state_root, &ssz_encode(&state)[..])?;
// run the fork_choice add_block logic
self.fork_choice.write().add_block(&block, &block_root)?;
// If the parent block was the parent_block, automatically update the canonical head.
//
// TODO: this is a first-in-best-dressed scenario that is not ideal; fork_choice should be
// run instead.
if self.head().beacon_block_root == parent_block_root {
self.update_canonical_head(
block.clone(),
block_root.clone(),
state.clone(),
state_root,
);
// Update the local state variable.
*self.state.write() = state.clone();
// Update the cached state variable.
*self.cached_state.write() =
CachedBeaconState::from_beacon_state(state.clone(), self.spec.clone())?;
}
Ok(BlockProcessingOutcome::ValidBlock(ValidBlock::Processed))
}
/// Produce a new block at the present slot.
///
/// The produced block will not be inherently valid, it must be signed by a block producer.
/// Block signing is out of the scope of this function and should be done by a separate program.
pub fn produce_block(&self, randao_reveal: Signature) -> Option<(BeaconBlock, BeaconState)> {
debug!("Producing block at slot {}...", self.state.read().slot);
let mut state = self.state.read().clone();
trace!("Finding attestations for new block...");
let attestations = self
.attestation_aggregator
.read()
.get_attestations_for_state(&state, &self.spec);
trace!(
"Inserting {} attestation(s) into new block.",
attestations.len()
);
let parent_root = *state.get_block_root(state.slot.saturating_sub(1_u64), &self.spec)?;
let mut block = BeaconBlock {
slot: state.slot,
parent_root,
state_root: Hash256::zero(), // Updated after the state is calculated.
randao_reveal,
eth1_data: Eth1Data {
// TODO: replace with real data
deposit_root: Hash256::zero(),
block_hash: Hash256::zero(),
},
signature: self.spec.empty_signature.clone(), // To be completed by a validator.
body: BeaconBlockBody {
proposer_slashings: vec![],
attester_slashings: vec![],
attestations,
deposits: vec![],
exits: vec![],
},
};
trace!("BeaconChain::produce_block: updating state for new block.",);
let result =
state.per_block_processing_without_verifying_block_signature(&block, &self.spec);
trace!(
"BeaconNode::produce_block: state processing result: {:?}",
result
);
result.ok()?;
let state_root = state.canonical_root();
block.state_root = state_root;
trace!("Block produced.");
Some((block, state))
}
// TODO: Left this as is, modify later
pub fn fork_choice(&self) -> Result<(), Error> {
let present_head = self.finalized_head().beacon_block_root;
let new_head = self.fork_choice.write().find_head(&present_head)?;
if new_head != present_head {
let block = self
.block_store
.get_deserialized(&new_head)?
.ok_or_else(|| Error::MissingBeaconBlock(new_head))?;
let block_root = block.canonical_root();
let state = self
.state_store
.get_deserialized(&block.state_root)?
.ok_or_else(|| Error::MissingBeaconState(block.state_root))?;
let state_root = state.canonical_root();
self.update_canonical_head(block, block_root, state, state_root);
}
Ok(())
}
}
impl From<DBError> for Error {
fn from(e: DBError) -> Error {
Error::DBError(e.message)
}
}
impl From<ForkChoiceError> for Error {
fn from(e: ForkChoiceError) -> Error {
Error::ForkChoiceError(e)
}
}
impl From<BeaconStateError> for Error {
fn from(e: BeaconStateError) -> Error {
Error::BeaconStateError(e)
}
}