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v1.1.6 Fork Choice changes (#2822)

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## Issue Addressed

Resolves: https://github.com/sigp/lighthouse/issues/2741
Includes: https://github.com/sigp/lighthouse/pull/2853 so that we can get ssz static tests passing here on v1.1.6. If we want to merge that first, we can make this diff slightly smaller

## Proposed Changes

- Changes the `justified_epoch` and `finalized_epoch` in the `ProtoArrayNode` each to an `Option<Checkpoint>`. The `Option` is necessary only for the migration, so not ideal. But does allow us to add a default logic to `None` on these fields during the database migration.
- Adds a database migration from a legacy fork choice struct to the new one, search for all necessary block roots in fork choice by iterating through blocks in the db.
- updates related to https://github.com/ethereum/consensus-specs/pull/2727
  -  We will have to update the persisted forkchoice to make sure the justified checkpoint stored is correct according to the updated fork choice logic. This boils down to setting the forkchoice store's justified checkpoint to the justified checkpoint of the block that advanced the finalized checkpoint to the current one. 
  - AFAICT there's no migration steps necessary for the update to allow applying attestations from prior blocks, but would appreciate confirmation on that
- I updated the consensus spec tests to v1.1.6 here, but they will fail until we also implement the proposer score boost updates. I confirmed that the previously failing scenario `new_finalized_slot_is_justified_checkpoint_ancestor` will now pass after the boost updates, but haven't confirmed _all_ tests will pass because I just quickly stubbed out the proposer boost test scenario formatting.
- This PR now also includes proposer boosting https://github.com/ethereum/consensus-specs/pull/2730

## Additional Info
I realized checking justified and finalized roots in fork choice makes it more likely that we trigger this bug: https://github.com/ethereum/consensus-specs/pull/2727

It's possible the combination of justified checkpoint and finalized checkpoint in the forkchoice store is different from in any block in fork choice. So when trying to startup our store's justified checkpoint seems invalid to the rest of fork choice (but it should be valid). When this happens we get an `InvalidBestNode` error and fail to start up. So I'm including that bugfix in this branch.

Todo:

- [x] Fix fork choice tests
- [x] Self review
- [x] Add fix for https://github.com/ethereum/consensus-specs/pull/2727
- [x] Rebase onto Kintusgi 
- [x] Fix `num_active_validators` calculation as @michaelsproul pointed out
- [x] Clean up db migrations

Co-authored-by: realbigsean <seananderson33@gmail.com>
This commit is contained in:
realbigsean
2021-12-13 20:43:22 +00:00
parent e391b32858
commit b22ac95d7f
44 changed files with 1802 additions and 658 deletions
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181
consensus/proto_array/src/proto_array.rs
View File

@@ -1,13 +1,16 @@
use crate::error::InvalidBestNodeInfo;
use crate::{error::Error, Block, ExecutionStatus};
use serde_derive::{Deserialize, Serialize};
use ssz::four_byte_option_impl;
use ssz::Encode;
use ssz_derive::{Decode, Encode};
use std::collections::HashMap;
use types::{AttestationShufflingId, Epoch, Hash256, Slot};
use types::{AttestationShufflingId, ChainSpec, Checkpoint, Epoch, EthSpec, Hash256, Slot};
// Define a "legacy" implementation of `Option<usize>` which uses four bytes for encoding the union
// selector.
four_byte_option_impl!(four_byte_option_usize, usize);
four_byte_option_impl!(four_byte_option_checkpoint, Checkpoint);
#[derive(Clone, PartialEq, Debug, Encode, Decode, Serialize, Deserialize)]
pub struct ProtoNode {
@@ -28,59 +31,31 @@ pub struct ProtoNode {
pub root: Hash256,
#[ssz(with = "four_byte_option_usize")]
pub parent: Option<usize>,
pub justified_epoch: Epoch,
pub finalized_epoch: Epoch,
weight: u64,
#[ssz(with = "four_byte_option_checkpoint")]
pub justified_checkpoint: Option<Checkpoint>,
#[ssz(with = "four_byte_option_checkpoint")]
pub finalized_checkpoint: Option<Checkpoint>,
pub weight: u64,
#[ssz(with = "four_byte_option_usize")]
best_child: Option<usize>,
pub best_child: Option<usize>,
#[ssz(with = "four_byte_option_usize")]
best_descendant: Option<usize>,
pub best_descendant: Option<usize>,
/// Indicates if an execution node has marked this block as valid. Also contains the execution
/// block hash.
pub execution_status: ExecutionStatus,
}
/// Only used for SSZ deserialization of the persisted fork choice during the database migration
/// from schema 4 to schema 5.
#[derive(Encode, Decode)]
pub struct LegacyProtoNode {
pub slot: Slot,
pub state_root: Hash256,
pub target_root: Hash256,
pub current_epoch_shuffling_id: AttestationShufflingId,
pub next_epoch_shuffling_id: AttestationShufflingId,
#[derive(PartialEq, Debug, Encode, Decode, Serialize, Deserialize, Copy, Clone)]
pub struct ProposerBoost {
pub root: Hash256,
#[ssz(with = "four_byte_option_usize")]
pub parent: Option<usize>,
pub justified_epoch: Epoch,
pub finalized_epoch: Epoch,
weight: u64,
#[ssz(with = "four_byte_option_usize")]
best_child: Option<usize>,
#[ssz(with = "four_byte_option_usize")]
best_descendant: Option<usize>,
pub score: u64,
}
impl Into<ProtoNode> for LegacyProtoNode {
fn into(self) -> ProtoNode {
ProtoNode {
slot: self.slot,
state_root: self.state_root,
target_root: self.target_root,
current_epoch_shuffling_id: self.current_epoch_shuffling_id,
next_epoch_shuffling_id: self.next_epoch_shuffling_id,
root: self.root,
parent: self.parent,
justified_epoch: self.justified_epoch,
finalized_epoch: self.finalized_epoch,
weight: self.weight,
best_child: self.best_child,
best_descendant: self.best_descendant,
// We set the following execution value as if the block is a pre-merge-fork block. This
// is safe as long as we never import a merge block with the old version of proto-array.
// This will be safe since we can't actually process merge blocks until we've made this
// change to fork choice.
execution_status: ExecutionStatus::irrelevant(),
impl Default for ProposerBoost {
fn default() -> Self {
Self {
root: Hash256::zero(),
score: 0,
}
}
}
@@ -90,10 +65,11 @@ pub struct ProtoArray {
/// Do not attempt to prune the tree unless it has at least this many nodes. Small prunes
/// simply waste time.
pub prune_threshold: usize,
pub justified_epoch: Epoch,
pub finalized_epoch: Epoch,
pub justified_checkpoint: Checkpoint,
pub finalized_checkpoint: Checkpoint,
pub nodes: Vec<ProtoNode>,
pub indices: HashMap<Hash256, usize>,
pub previous_proposer_boost: ProposerBoost,
}
impl ProtoArray {
@@ -110,11 +86,14 @@ impl ProtoArray {
/// - Compare the current node with the parents best-child, updating it if the current node
/// should become the best child.
/// - If required, update the parents best-descendant with the current node or its best-descendant.
pub fn apply_score_changes(
pub fn apply_score_changes<E: EthSpec>(
&mut self,
mut deltas: Vec<i64>,
justified_epoch: Epoch,
finalized_epoch: Epoch,
justified_checkpoint: Checkpoint,
finalized_checkpoint: Checkpoint,
new_balances: &[u64],
proposer_boost_root: Hash256,
spec: &ChainSpec,
) -> Result<(), Error> {
if deltas.len() != self.indices.len() {
return Err(Error::InvalidDeltaLen {
@@ -123,11 +102,16 @@ impl ProtoArray {
});
}
if justified_epoch != self.justified_epoch || finalized_epoch != self.finalized_epoch {
self.justified_epoch = justified_epoch;
self.finalized_epoch = finalized_epoch;
if justified_checkpoint != self.justified_checkpoint
|| finalized_checkpoint != self.finalized_checkpoint
{
self.justified_checkpoint = justified_checkpoint;
self.finalized_checkpoint = finalized_checkpoint;
}
// Default the proposer boost score to zero.
let mut proposer_score = 0;
// Iterate backwards through all indices in `self.nodes`.
for node_index in (0..self.nodes.len()).rev() {
let node = self
@@ -142,11 +126,35 @@ impl ProtoArray {
continue;
}
let node_delta = deltas
let mut node_delta = deltas
.get(node_index)
.copied()
.ok_or(Error::InvalidNodeDelta(node_index))?;
// If we find the node for which the proposer boost was previously applied, decrease
// the delta by the previous score amount.
if self.previous_proposer_boost.root != Hash256::zero()
&& self.previous_proposer_boost.root == node.root
{
node_delta = node_delta
.checked_sub(self.previous_proposer_boost.score as i64)
.ok_or(Error::DeltaOverflow(node_index))?;
}
// If we find the node matching the current proposer boost root, increase
// the delta by the new score amount.
//
// https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/fork-choice.md#get_latest_attesting_balance
if let Some(proposer_score_boost) = spec.proposer_score_boost {
if proposer_boost_root != Hash256::zero() && proposer_boost_root == node.root {
proposer_score =
calculate_proposer_boost::<E>(new_balances, proposer_score_boost)
.ok_or(Error::ProposerBoostOverflow(node_index))?;
node_delta = node_delta
.checked_add(proposer_score as i64)
.ok_or(Error::DeltaOverflow(node_index))?;
}
}
// Apply the delta to the node.
if node_delta < 0 {
// Note: I am conflicted about whether to use `saturating_sub` or `checked_sub`
@@ -180,6 +188,12 @@ impl ProtoArray {
}
}
// After applying all deltas, update the `previous_proposer_boost`.
self.previous_proposer_boost = ProposerBoost {
root: proposer_boost_root,
score: proposer_score,
};
// A second time, iterate backwards through all indices in `self.nodes`.
//
// We _must_ perform these functions separate from the weight-updating loop above to ensure
@@ -221,8 +235,8 @@ impl ProtoArray {
parent: block
.parent_root
.and_then(|parent| self.indices.get(&parent).copied()),
justified_epoch: block.justified_epoch,
finalized_epoch: block.finalized_epoch,
justified_checkpoint: Some(block.justified_checkpoint),
finalized_checkpoint: Some(block.finalized_checkpoint),
weight: 0,
best_child: None,
best_descendant: None,
@@ -315,14 +329,14 @@ impl ProtoArray {
// Perform a sanity check that the node is indeed valid to be the head.
if !self.node_is_viable_for_head(best_node) {
return Err(Error::InvalidBestNode {
return Err(Error::InvalidBestNode(Box::new(InvalidBestNodeInfo {
start_root: *justified_root,
justified_epoch: self.justified_epoch,
finalized_epoch: self.finalized_epoch,
justified_checkpoint: self.justified_checkpoint,
finalized_checkpoint: self.finalized_checkpoint,
head_root: justified_node.root,
head_justified_epoch: justified_node.justified_epoch,
head_finalized_epoch: justified_node.finalized_epoch,
});
head_justified_checkpoint: justified_node.justified_checkpoint,
head_finalized_checkpoint: justified_node.finalized_checkpoint,
})));
}
Ok(best_node.root)
@@ -523,9 +537,16 @@ impl ProtoArray {
/// Any node that has a different finalized or justified epoch should not be viable for the
/// head.
fn node_is_viable_for_head(&self, node: &ProtoNode) -> bool {
(node.justified_epoch == self.justified_epoch || self.justified_epoch == Epoch::new(0))
&& (node.finalized_epoch == self.finalized_epoch
|| self.finalized_epoch == Epoch::new(0))
if let (Some(node_justified_checkpoint), Some(node_finalized_checkpoint)) =
(node.justified_checkpoint, node.finalized_checkpoint)
{
(node_justified_checkpoint == self.justified_checkpoint
|| self.justified_checkpoint.epoch == Epoch::new(0))
&& (node_finalized_checkpoint == self.finalized_checkpoint
|| self.finalized_checkpoint.epoch == Epoch::new(0))
} else {
false
}
}
/// Return a reverse iterator over the nodes which comprise the chain ending at `block_root`.
@@ -549,6 +570,38 @@ impl ProtoArray {
}
}
/// A helper method to calculate the proposer boost based on the given `validator_balances`.
/// This does *not* do any verification about whether a boost should or should not be applied.
/// The `validator_balances` array used here is assumed to be structured like the one stored in
/// the `BalancesCache`, where *effective* balances are stored and inactive balances are defaulted
/// to zero.
///
/// Returns `None` if there is an overflow or underflow when calculating the score.
///
/// https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/fork-choice.md#get_latest_attesting_balance
fn calculate_proposer_boost<E: EthSpec>(
validator_balances: &[u64],
proposer_score_boost: u64,
) -> Option<u64> {
let mut total_balance: u64 = 0;
let mut num_validators: u64 = 0;
for &balance in validator_balances {
// We need to filter zero balances here to get an accurate active validator count.
// This is because we default inactive validator balances to zero when creating
// this balances array.
if balance != 0 {
total_balance = total_balance.checked_add(balance)?;
num_validators = num_validators.checked_add(1)?;
}
}
let average_balance = total_balance.checked_div(num_validators)?;
let committee_size = num_validators.checked_div(E::slots_per_epoch())?;
let committee_weight = committee_size.checked_mul(average_balance)?;
committee_weight
.checked_mul(proposer_score_boost)?
.checked_div(100)
}
/// Reverse iterator over one path through a `ProtoArray`.
pub struct Iter<'a> {
next_node_index: Option<usize>,