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Clone state ahead of block production (sigp#4925)
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* Clone state ahead of block production

* Add pruning and fix logging

* Don't hold 2 states in mem
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@michaelsproul
michaelsproul authored Nov 30, 2023
1 parent 43d9815 commit 547ed1d
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Showing 3 changed files with 117 additions and 21 deletions.
64 changes: 51 additions & 13 deletions beacon_node/beacon_chain/src/beacon_chain.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -482,6 +482,11 @@ pub struct BeaconChain<T: BeaconChainTypes> {
pub data_availability_checker: Arc<DataAvailabilityChecker<T>>,
/// The KZG trusted setup used by this chain.
pub kzg: Option<Arc<Kzg>>,
/// State with complete tree hash cache, ready for block production.
///
/// NB: We can delete this once we have tree-states.
#[allow(clippy::type_complexity)]
pub block_production_state: Arc<Mutex<Option<(Hash256, BlockProductionPreState<T::EthSpec>)>>>,
}

pub enum BeaconBlockResponseType<T: EthSpec> {
Expand Down Expand Up @@ -4030,14 +4035,29 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
);
(re_org_state.pre_state, re_org_state.state_root)
}
// Normal case: proposing a block atop the current head. Use the snapshot cache.
// Normal case: proposing a block atop the current head using the cache.
else if let Some((_, cached_state)) = self
.block_production_state
.lock()
.take()
.filter(|(cached_block_root, _)| *cached_block_root == head_block_root)
{
(cached_state.pre_state, cached_state.state_root)
}
// Fall back to a direct read of the snapshot cache.
else if let Some(pre_state) = self
.snapshot_cache
.try_read_for(BLOCK_PROCESSING_CACHE_LOCK_TIMEOUT)
.and_then(|snapshot_cache| {
snapshot_cache.get_state_for_block_production(head_block_root)
})
{
warn!(
self.log,
"Block production cache miss";
"message" => "falling back to snapshot cache clone",
"slot" => slot
);
(pre_state.pre_state, pre_state.state_root)
} else {
warn!(
Expand Down Expand Up @@ -4161,12 +4181,27 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
drop(proposer_head_timer);
let re_org_parent_block = proposer_head.parent_node.root;

// Only attempt a re-org if we hit the snapshot cache.
// Only attempt a re-org if we hit the block production cache or snapshot cache.
let pre_state = self
.snapshot_cache
.try_read_for(BLOCK_PROCESSING_CACHE_LOCK_TIMEOUT)
.and_then(|snapshot_cache| {
snapshot_cache.get_state_for_block_production(re_org_parent_block)
.block_production_state
.lock()
.take()
.and_then(|(cached_block_root, state)| {
(cached_block_root == re_org_parent_block).then_some(state)
})
.or_else(|| {
warn!(
self.log,
"Block production cache miss";
"message" => "falling back to snapshot cache during re-org",
"slot" => slot,
"block_root" => ?re_org_parent_block
);
self.snapshot_cache
.try_read_for(BLOCK_PROCESSING_CACHE_LOCK_TIMEOUT)
.and_then(|snapshot_cache| {
snapshot_cache.get_state_for_block_production(re_org_parent_block)
})
})
.or_else(|| {
debug!(
Expand Down Expand Up @@ -5326,15 +5361,18 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
///
/// This function will result in a call to `forkchoiceUpdated` on the EL if we're in the
/// tail-end of the slot (as defined by `self.config.prepare_payload_lookahead`).
///
/// Return `Ok(Some(head_block_root))` if this node prepared to propose at the next slot on
/// top of `head_block_root`.
pub async fn prepare_beacon_proposer(
self: &Arc<Self>,
current_slot: Slot,
) -> Result<(), Error> {
) -> Result<Option<Hash256>, Error> {
let prepare_slot = current_slot + 1;

// There's no need to run the proposer preparation routine before the bellatrix fork.
if self.slot_is_prior_to_bellatrix(prepare_slot) {
return Ok(());
return Ok(None);
}

let execution_layer = self
Expand All @@ -5347,7 +5385,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
if !self.config.always_prepare_payload
&& !execution_layer.has_any_proposer_preparation_data().await
{
return Ok(());
return Ok(None);
}

// Load the cached head and its forkchoice update parameters.
Expand Down Expand Up @@ -5394,7 +5432,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
let Some((forkchoice_update_params, Some(pre_payload_attributes))) = maybe_prep_data else {
// Appropriate log messages have already been logged above and in
// `get_pre_payload_attributes`.
return Ok(());
return Ok(None);
};

// If the execution layer doesn't have any proposer data for this validator then we assume
Expand All @@ -5405,7 +5443,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
.has_proposer_preparation_data(proposer)
.await
{
return Ok(());
return Ok(None);
}

// Fetch payload attributes from the execution layer's cache, or compute them from scratch
Expand Down Expand Up @@ -5500,7 +5538,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
"prepare_slot" => prepare_slot,
"validator" => proposer,
);
return Ok(());
return Ok(None);
};

// If we are close enough to the proposal slot, send an fcU, which will have payload
Expand All @@ -5523,7 +5561,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
.await?;
}

Ok(())
Ok(Some(head_root))
}

pub async fn update_execution_engine_forkchoice(
Expand Down
1 change: 1 addition & 0 deletions beacon_node/beacon_chain/src/builder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -925,6 +925,7 @@ where
.map_err(|e| format!("Error initializing DataAvailabiltyChecker: {:?}", e))?,
),
kzg,
block_production_state: Arc::new(Mutex::new(None)),
};

let head = beacon_chain.head_snapshot();
Expand Down
73 changes: 65 additions & 8 deletions beacon_node/beacon_chain/src/state_advance_timer.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,9 @@ const MAX_ADVANCE_DISTANCE: u64 = 4;
/// impact whilst having 8 epochs without a block is a comfortable grace period.
const MAX_FORK_CHOICE_DISTANCE: u64 = 256;

/// Drop any unused block production state cache after this many slots.
const MAX_BLOCK_PRODUCTION_CACHE_DISTANCE: u64 = 4;

#[derive(Debug)]
enum Error {
BeaconChain(BeaconChainError),
Expand Down Expand Up @@ -227,19 +230,73 @@ async fn state_advance_timer<T: BeaconChainTypes>(

// Prepare proposers so that the node can send payload attributes in the case where
// it decides to abandon a proposer boost re-org.
if let Err(e) = beacon_chain.prepare_beacon_proposer(current_slot).await {
warn!(
log,
"Unable to prepare proposer with lookahead";
"error" => ?e,
"slot" => next_slot,
);
}
let proposer_head = beacon_chain
.prepare_beacon_proposer(current_slot)
.await
.unwrap_or_else(|e| {
warn!(
log,
"Unable to prepare proposer with lookahead";
"error" => ?e,
"slot" => next_slot,
);
None
});

// Use a blocking task to avoid blocking the core executor whilst waiting for locks
// in `ForkChoiceSignalTx`.
beacon_chain.task_executor.clone().spawn_blocking(
move || {
// If we're proposing, clone the head state preemptively so that it isn't on
// the hot path of proposing. We can delete this once we have tree-states.
if let Some(proposer_head) = proposer_head {
let mut cache = beacon_chain.block_production_state.lock();

// Avoid holding two states in memory. It's OK to hold the lock because
// we always lock the block production cache before the snapshot cache
// and we prefer for block production to wait for the block production
// cache if a clone is in-progress.
if cache
.as_ref()
.map_or(false, |(cached_head, _)| *cached_head != proposer_head)
{
drop(cache.take());
}
if let Some(proposer_state) = beacon_chain
.snapshot_cache
.try_read_for(BLOCK_PROCESSING_CACHE_LOCK_TIMEOUT)
.and_then(|snapshot_cache| {
snapshot_cache.get_state_for_block_production(proposer_head)
})
{
*cache = Some((proposer_head, proposer_state));
debug!(
log,
"Cloned state ready for block production";
"head_block_root" => ?proposer_head,
"slot" => next_slot
);
} else {
warn!(
log,
"Block production state missing from snapshot cache";
"head_block_root" => ?proposer_head,
"slot" => next_slot
);
}
} else {
// If we aren't proposing, drop any old block production cache to save
// memory.
let mut cache = beacon_chain.block_production_state.lock();
if let Some((_, state)) = &*cache {
if state.pre_state.slot() + MAX_BLOCK_PRODUCTION_CACHE_DISTANCE
<= current_slot
{
drop(cache.take());
}
}
}

// Signal block proposal for the next slot (if it happens to be waiting).
if let Some(tx) = &beacon_chain.fork_choice_signal_tx {
if let Err(e) = tx.notify_fork_choice_complete(next_slot) {
Expand Down

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