Michael Sproul edf23bb40e Fix attestation shuffling filter (#3629) ... ## Issue Addressed Fix a bug in block production that results in blocks with 0 attestations during the first slot of an epoch. The bug is marked by debug logs of the form: > DEBG Discarding attestation because of missing ancestor, block_root: 0x3cc00d9c9e0883b2d0db8606278f2b8423d4902f9a1ee619258b5b60590e64f8, pivot_slot: 4042591 It occurs when trying to look up the shuffling decision root for an attestation from a slot which is prior to fork choice's finalized block. This happens frequently when proposing in the first slot of the epoch where we have: - `current_epoch == n` - `attestation.data.target.epoch == n - 1` - attestation shuffling epoch `== n - 3` (decision block being the last block of `n - 3`) - `state.finalized_checkpoint.epoch == n - 2` (first block of `n - 2` is finalized) Hence the shuffling decision slot is out of range of the fork choice backwards iterator _by a single slot_. Unfortunately this bug was hidden when we weren't pruning fork choice, and then reintroduced in v2.5.1 when we fixed the pruning (https://github.com/sigp/lighthouse/releases/tag/v2.5.1). There's no way to turn that off or disable the filtering in our current release, so we need a new release to fix this issue. Fortunately, it also does not occur on every epoch boundary because of the gradual pruning of fork choice every 256 blocks (~8 epochs): 01e84b71f5/consensus/proto_array/src/proto_array_fork_choice.rs (L16) 01e84b71f5/consensus/proto_array/src/proto_array.rs (L713-L716) So the probability of proposing a 0-attestation block given a proposal assignment is approximately `1/32 * 1/8 = 0.39%`. ## Proposed Changes - Load the block's shuffling ID from fork choice and verify it against the expected shuffling ID of the head state. This code was initially written before we had settled on a representation of shuffling IDs, so I think it's a nice simplification to make use of them here rather than more ad-hoc logic that fundamentally does the same thing. ## Additional Info Thanks to @moshe-blox for noticing this issue and bringing it to our attention.		2022-10-18 04:02:06 +00:00
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src	Fix attestation shuffling filter (#3629)	2022-10-18 04:02:06 +00:00
tests	Fix attestation shuffling filter (#3629)	2022-10-18 04:02:06 +00:00
Cargo.toml	Impl oneshot_broadcast for committee promises (#3595)	2022-09-21 01:01:50 +00:00