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Expand observed attestations capacity (#2266)

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## Issue Addressed

NA

## Proposed Changes

I noticed the following error on one of our nodes:

```
Mar 18 00:03:35 ip-xxxx lighthouse-bn[333503]: Mar 18 00:03:35.103 ERRO Unable to validate aggregate            error: ObservedAttestersError(EpochTooLow { epoch: Epoch(23961), lowest_permissible_epoch: Epoch(23962) }), peer_id: 16Uiu2HAm5GL5KzPLhvfg9MBBFSpBqTVGRFSiTg285oezzWcZzwEv
```

The slot during this log was 766,815 (the last slot of the epoch). I believe this is due to an off-by-one error in `observed_attesters` where we were failing to provide enough capacity to store observations from the previous, current and next epochs. See code comments for further reasoning.

Here's a link to the spec: https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#beacon_aggregate_and_proof

## Additional Info

NA
This commit is contained in:
Paul Hauner 2021-03-29 23:42:34 +00:00
parent 39928d5c69
commit 03cefd0065
1 changed files with 11 additions and 4 deletions
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15
beacon_node/beacon_chain/src/observed_attesters.rs
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@ -252,11 +252,18 @@ impl<T: Item, E: EthSpec> AutoPruningContainer<T, E> {
/// The maximum number of epochs stored in `self`.
fn max_capacity(&self) -> u64 {
// The current epoch and the previous epoch. This is sufficient whilst
// GOSSIP_CLOCK_DISPARITY is 1/2 a slot or less:
// The next, current and previous epochs. We require the next epoch due to the
// `MAXIMUM_GOSSIP_CLOCK_DISPARITY`. We require the previous epoch since the
// specification delcares:
//
// https://github.com/ethereum/eth2.0-specs/pull/1706#issuecomment-610151808
2
// ```
// aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE
// >= current_slot >= aggregate.data.slot
// ```
//
// This means that during the current epoch we will always accept an attestation
// from at least one slot in the previous epoch.
3
}
/// Updates `self` with the current epoch, removing all attestations that become expired