mirror of
https://gitlab.com/pulsechaincom/lighthouse-pulse.git
synced 2024-12-25 04:57:17 +00:00
Disallow attestation production earlier than head (#2130)
## Issue Addressed The non-finality period on Pyrmont between epochs [`9114`](https://pyrmont.beaconcha.in/epoch/9114) and [`9182`](https://pyrmont.beaconcha.in/epoch/9182) was contributed to by all the `lighthouse_team` validators going down. The nodes saw excessive CPU and RAM usage, resulting in the system to kill the `lighthouse bn` process. The `Restart=on-failure` directive for `systemd` caused the process to bounce in ~10-30m intervals. Diagnosis with `heaptrack` showed that the `BeaconChain::produce_unaggregated_attestation` function was calling `store::beacon_state::get_full_state` and sometimes resulting in a tree hash cache allocation. These allocations were approximately the size of the hosts physical memory and still allocated when `lighthouse bn` was killed by the OS. There was no CPU analysis (e.g., `perf`), but the `BeaconChain::produce_unaggregated_attestation` is very CPU-heavy so it is reasonable to assume it is the cause of the excessive CPU usage, too. ## Proposed Changes `BeaconChain::produce_unaggregated_attestation` has two paths: 1. Fast path: attesting to the head slot or later. 2. Slow path: attesting to a slot earlier than the head block. Path (2) is the only path that calls `store::beacon_state::get_full_state`, therefore it is the path causing this excessive CPU/RAM usage. This PR removes the current functionality of path (2) and replaces it with a static error (`BeaconChainError::AttestingPriorToHead`). This change reduces the generality of `BeaconChain::produce_unaggregated_attestation` (and therefore [`/eth/v1/validator/attestation_data`](https://ethereum.github.io/eth2.0-APIs/#/Validator/produceAttestationData)), but I argue that this functionality is an edge-case and arguably a violation of the [Honest Validator spec](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/validator.md). It's possible that a validator goes back to a prior slot to "catch up" and submit some missed attestations. This change would prevent such behaviour, returning an error. My concerns with this catch-up behaviour is that it is: - Not specified as "honest validator" attesting behaviour. - Is behaviour that is risky for slashing (although, all validator clients *should* have slashing protection and will eventually fail if they do not). - It disguises clock-sync issues between a BN and VC. ## Additional Info It's likely feasible to implement path (2) if we implement some sort of caching mechanism. This would be a multi-week task and this PR gets the issue patched in the short term. I haven't created an issue to add path (2), instead I think we should implement it if we get user-demand.
This commit is contained in:
parent
d9f940613f
commit
b06559ae97
@ -853,37 +853,22 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
|
||||
Cow::Borrowed(&head.beacon_state),
|
||||
)
|
||||
} else {
|
||||
// Note: this method will fail if `slot` is more than `state.block_roots.len()` slots
|
||||
// prior to the head.
|
||||
// We disallow producing attestations *prior* to the current head since such an
|
||||
// attestation would require loading a `BeaconState` from disk. Loading `BeaconState`
|
||||
// from disk is very resource intensive and proposes a DoS risk from validator clients.
|
||||
//
|
||||
// This seems reasonable, producing an attestation at a slot so far
|
||||
// in the past seems useless, definitely in mainnet spec. In minimal spec, when the
|
||||
// block roots only contain two epochs of history, it's possible that you will fail to
|
||||
// produce an attestation that would be valid to be included in a block. Given that
|
||||
// minimal is only for testing, I think this is fine.
|
||||
// Although we generally allow validator clients to do things that might harm us (i.e.,
|
||||
// we trust them), sometimes we need to protect the BN from accidental errors which
|
||||
// could cause it significant harm.
|
||||
//
|
||||
// It is important to note that what's _not_ allowed here is attesting to a slot in the
|
||||
// past. You can still attest to a block an arbitrary distance in the past, just not as
|
||||
// if you are in a slot in the past.
|
||||
let beacon_block_root = *head.beacon_state.get_block_root(slot)?;
|
||||
let state_root = *head.beacon_state.get_state_root(slot)?;
|
||||
|
||||
// Avoid holding a lock on the head whilst doing database reads. Good boi functions
|
||||
// don't hog locks.
|
||||
drop(head);
|
||||
|
||||
let mut state = self
|
||||
.get_state(&state_root, Some(slot))?
|
||||
.ok_or(Error::MissingBeaconState(state_root))?;
|
||||
|
||||
state.build_committee_cache(RelativeEpoch::Current, &self.spec)?;
|
||||
|
||||
self.produce_unaggregated_attestation_for_block(
|
||||
slot,
|
||||
index,
|
||||
beacon_block_root,
|
||||
Cow::Owned(state),
|
||||
)
|
||||
// This case is particularity harmful since the HTTP API can effectively call this
|
||||
// function an unlimited amount of times. If `n` validators all happen to call it at
|
||||
// the same time, we're going to load `n` states (and tree hash caches) into memory all
|
||||
// at once. With `n >= 10` we're looking at hundreds of MB or GBs of RAM.
|
||||
Err(Error::AttestingPriorToHead {
|
||||
head_slot: head.beacon_block.slot(),
|
||||
request_slot: slot,
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
|
@ -92,6 +92,10 @@ pub enum BeaconChainError {
|
||||
},
|
||||
WeakSubjectivtyVerificationFailure,
|
||||
WeakSubjectivtyShutdownError(TrySendError<&'static str>),
|
||||
AttestingPriorToHead {
|
||||
head_slot: Slot,
|
||||
request_slot: Slot,
|
||||
},
|
||||
}
|
||||
|
||||
easy_from_to!(SlotProcessingError, BeaconChainError);
|
||||
|
@ -25,6 +25,7 @@ lazy_static! {
|
||||
#[test]
|
||||
fn produces_attestations() {
|
||||
let num_blocks_produced = MainnetEthSpec::slots_per_epoch() * 4;
|
||||
let additional_slots_tested = MainnetEthSpec::slots_per_epoch() * 3;
|
||||
|
||||
let harness = BeaconChainHarness::new_with_store_config(
|
||||
MainnetEthSpec,
|
||||
@ -32,38 +33,32 @@ fn produces_attestations() {
|
||||
StoreConfig::default(),
|
||||
);
|
||||
|
||||
// Skip past the genesis slot.
|
||||
harness.advance_slot();
|
||||
|
||||
harness.extend_chain(
|
||||
num_blocks_produced as usize,
|
||||
BlockStrategy::OnCanonicalHead,
|
||||
AttestationStrategy::AllValidators,
|
||||
);
|
||||
|
||||
let chain = &harness.chain;
|
||||
|
||||
let state = &harness.chain.head().expect("should get head").beacon_state;
|
||||
assert_eq!(state.slot, num_blocks_produced, "head should have updated");
|
||||
assert_ne!(
|
||||
state.finalized_checkpoint.epoch, 0,
|
||||
"head should have updated"
|
||||
);
|
||||
|
||||
let current_slot = chain.slot().expect("should get slot");
|
||||
|
||||
// Test all valid committee indices for all slots in the chain.
|
||||
for slot in 0..=current_slot.as_u64() + MainnetEthSpec::slots_per_epoch() * 3 {
|
||||
// for slot in 0..=current_slot.as_u64() + MainnetEthSpec::slots_per_epoch() * 3 {
|
||||
for slot in 0..=num_blocks_produced + additional_slots_tested {
|
||||
if slot > 0 && slot <= num_blocks_produced {
|
||||
harness.advance_slot();
|
||||
|
||||
harness.extend_chain(
|
||||
1,
|
||||
BlockStrategy::OnCanonicalHead,
|
||||
AttestationStrategy::AllValidators,
|
||||
);
|
||||
}
|
||||
|
||||
let slot = Slot::from(slot);
|
||||
let mut state = chain
|
||||
.state_at_slot(slot, StateSkipConfig::WithStateRoots)
|
||||
.expect("should get state");
|
||||
|
||||
let block_slot = if slot > current_slot {
|
||||
current_slot
|
||||
} else {
|
||||
let block_slot = if slot <= num_blocks_produced {
|
||||
slot
|
||||
} else {
|
||||
Slot::from(num_blocks_produced)
|
||||
};
|
||||
|
||||
let block = chain
|
||||
.block_at_slot(block_slot)
|
||||
.expect("should get block")
|
||||
|
Loading…
Reference in New Issue
Block a user