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Fork choice bug fixes (#449)

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* Change reduced tree for adding weightless node

* Add more comments for reduced tree fork choice

* Small refactor on reduced tree for readability

* Move test_harness forking logic into itself

* Add new `AncestorIter` trait to store

* Add unfinished tests to fork choice

* Make `beacon_state.genesis_block_root` public

* Add failing lmd_ghost fork choice tests

* Extend fork_choice tests, create failing test

* Implement Debug for generic ReducedTree

* Add lazy_static to fork choice tests

* Add verify_integrity fn to reduced tree

* Fix bugs in reduced tree

* Ensure all reduced tree tests verify integrity

* Slightly alter reduce tree test params

* Add (failing) reduced tree test

* Fix bug in fork choice

Iter ancestors was not working well with skip slots

* Put maximum depth for common ancestor search

Ensures that we don't search back past the finalized root.

* Add basic finalization tests for reduced tree

* Change fork choice to use beacon_block_root

Previously it was using target_root, which was wrong

* Make ancestor iter return option

* Disable fork choice test when !debug_assertions

* Fix type, removed code fragment

* Tidy some borrow-checker evading

* Lower reduced tree random test iterations
This commit is contained in:
Paul Hauner 2019-07-29 12:08:52 +10:00 committed by GitHub
parent 6de9e5bd6f
commit 7458022fcf
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
8 changed files with 673 additions and 141 deletions
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2
beacon_node/beacon_chain/src/beacon_chain.rs
View File

@ -77,7 +77,7 @@ pub struct BeaconChain<T: BeaconChainTypes> {
/// to `per_slot_processing`.
state: RwLock<BeaconState<T::EthSpec>>,
/// The root of the genesis block.
genesis_block_root: Hash256,
pub genesis_block_root: Hash256,
/// A state-machine that is updated with information from the network and chooses a canonical
/// head block.
pub fork_choice: ForkChoice<T>,

9
beacon_node/beacon_chain/src/fork_choice.rs
View File

@ -125,14 +125,14 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
state: &BeaconState<T::EthSpec>,
attestation: &Attestation,
) -> Result<()> {
// Note: `get_attesting_indices_unsorted` requires that the beacon state caches be built.
let validator_indices = get_attesting_indices_unsorted(
state,
&attestation.data,
&attestation.aggregation_bitfield,
)?;
let block_slot = state.get_attestation_slot(&attestation.data)?;
let block_hash = attestation.data.target_root;
let block_hash = attestation.data.beacon_block_root;
// Ignore any attestations to the zero hash.
//
@ -148,11 +148,6 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
// fine because votes to the genesis block are not useful; all validators implicitly attest
// to genesis just by being present in the chain.
if block_hash != Hash256::zero() {
let block_slot = attestation
.data
.target_epoch
.start_slot(T::EthSpec::slots_per_epoch());
for validator_index in validator_indices {
self.backend
.process_attestation(validator_index, block_hash, block_slot)?;

46
beacon_node/beacon_chain/src/test_utils.rs
View File

@ -64,6 +64,8 @@ where
/// A testing harness which can instantiate a `BeaconChain` and populate it with blocks and
/// attestations.
///
/// Used for testing.
pub struct BeaconChainHarness<L, E>
where
L: LmdGhost<MemoryStore, E>,
@ -337,6 +339,50 @@ where
});
}
/// Creates two forks:
///
/// - The "honest" fork: created by the `honest_validators` who have built `honest_fork_blocks`
/// on the head
/// - The "faulty" fork: created by the `faulty_validators` who skipped a slot and
/// then built `faulty_fork_blocks`.
///
/// Returns `(honest_head, faulty_head)`, the roots of the blocks at the top of each chain.
pub fn generate_two_forks_by_skipping_a_block(
&self,
honest_validators: &[usize],
faulty_validators: &[usize],
honest_fork_blocks: usize,
faulty_fork_blocks: usize,
) -> (Hash256, Hash256) {
let initial_head_slot = self.chain.head().beacon_block.slot;
// Move to the next slot so we may produce some more blocks on the head.
self.advance_slot();
// Extend the chain with blocks where only honest validators agree.
let honest_head = self.extend_chain(
honest_fork_blocks,
BlockStrategy::OnCanonicalHead,
AttestationStrategy::SomeValidators(honest_validators.to_vec()),
);
// Go back to the last block where all agreed, and build blocks upon it where only faulty nodes
// agree.
let faulty_head = self.extend_chain(
faulty_fork_blocks,
BlockStrategy::ForkCanonicalChainAt {
previous_slot: Slot::from(initial_head_slot),
// `initial_head_slot + 2` means one slot is skipped.
first_slot: Slot::from(initial_head_slot + 2),
},
AttestationStrategy::SomeValidators(faulty_validators.to_vec()),
);
assert!(honest_head != faulty_head, "forks should be distinct");
(honest_head, faulty_head)
}
/// Returns the secret key for the given validator index.
fn get_sk(&self, validator_index: usize) -> &SecretKey {
&self.keypairs[validator_index].sk

22
beacon_node/beacon_chain/tests/tests.rs
View File

@ -25,7 +25,7 @@ fn get_harness(validator_count: usize) -> BeaconChainHarness<TestForkChoice, Min
}
#[test]
fn fork() {
fn chooses_fork() {
let harness = get_harness(VALIDATOR_COUNT);
let two_thirds = (VALIDATOR_COUNT / 3) * 2;
@ -45,25 +45,11 @@ fn fork() {
AttestationStrategy::AllValidators,
);
// Move to the next slot so we may produce some more blocks on the head.
harness.advance_slot();
// Extend the chain with blocks where only honest validators agree.
let honest_head = harness.extend_chain(
let (honest_head, faulty_head) = harness.generate_two_forks_by_skipping_a_block(
&honest_validators,
&faulty_validators,
honest_fork_blocks,
BlockStrategy::OnCanonicalHead,
AttestationStrategy::SomeValidators(honest_validators.clone()),
);
// Go back to the last block where all agreed, and build blocks upon it where only faulty nodes
// agree.
let faulty_head = harness.extend_chain(
faulty_fork_blocks,
BlockStrategy::ForkCanonicalChainAt {
previous_slot: Slot::from(initial_blocks),
first_slot: Slot::from(initial_blocks + 2),
},
AttestationStrategy::SomeValidators(faulty_validators.clone()),
);
assert!(honest_head != faulty_head, "forks should be distinct");

16
beacon_node/store/src/iter.rs
View File

@ -3,6 +3,22 @@ use std::borrow::Cow;
use std::sync::Arc;
use types::{BeaconBlock, BeaconState, BeaconStateError, EthSpec, Hash256, Slot};
/// Implemented for types that have ancestors (e.g., blocks, states) that may be iterated over.
pub trait AncestorIter<U: Store, I: Iterator> {
/// Returns an iterator over the roots of the ancestors of `self`.
fn try_iter_ancestor_roots(&self, store: Arc<U>) -> Option<I>;
}
impl<'a, U: Store, E: EthSpec> AncestorIter<U, BestBlockRootsIterator<'a, E, U>> for BeaconBlock {
/// Iterates across all the prior block roots of `self`, starting at the most recent and ending
/// at genesis.
fn try_iter_ancestor_roots(&self, store: Arc<U>) -> Option<BestBlockRootsIterator<'a, E, U>> {
let state = store.get::<BeaconState<E>>(&self.state_root).ok()??;
Some(BestBlockRootsIterator::owned(store, state, self.slot))
}
}
#[derive(Clone)]
pub struct StateRootsIterator<'a, T: EthSpec, U> {
store: Arc<U>,

2
eth2/lmd_ghost/Cargo.toml
View File

@ -17,3 +17,5 @@ bls = { path = "../utils/bls" }
slot_clock = { path = "../utils/slot_clock" }
beacon_chain = { path = "../../beacon_node/beacon_chain" }
env_logger = "0.6.0"
lazy_static = "1.3.0"
rand = "0.7"

296
eth2/lmd_ghost/src/reduced_tree.rs
View File

@ -6,9 +6,10 @@
use super::{LmdGhost, Result as SuperResult};
use parking_lot::RwLock;
use std::collections::HashMap;
use std::fmt;
use std::marker::PhantomData;
use std::sync::Arc;
use store::{iter::BestBlockRootsIterator, Error as StoreError, Store};
use store::{iter::BlockRootsIterator, Error as StoreError, Store};
use types::{BeaconBlock, BeaconState, EthSpec, Hash256, Slot};
type Result<T> = std::result::Result<T, Error>;
@ -35,6 +36,23 @@ pub struct ThreadSafeReducedTree<T, E> {
core: RwLock<ReducedTree<T, E>>,
}
impl<T, E> fmt::Debug for ThreadSafeReducedTree<T, E> {
/// `Debug` just defers to the implementation of `self.core`.
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.core.fmt(f)
}
}
impl<T, E> ThreadSafeReducedTree<T, E>
where
T: Store,
E: EthSpec,
{
pub fn verify_integrity(&self) -> std::result::Result<(), String> {
self.core.read().verify_integrity()
}
}
impl<T, E> LmdGhost<T, E> for ThreadSafeReducedTree<T, E>
where
T: Store,
@ -100,6 +118,12 @@ struct ReducedTree<T, E> {
_phantom: PhantomData<E>,
}
impl<T, E> fmt::Debug for ReducedTree<T, E> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.nodes.fmt(f)
}
}
impl<T, E> ReducedTree<T, E>
where
T: Store,
@ -126,6 +150,10 @@ where
}
}
/// Set the root node (the node without any parents) to the given `new_slot` and `new_root`.
///
/// The given `new_root` must be in the block tree (but not necessarily in the reduced tree).
/// Any nodes which are not a descendant of `new_root` will be removed from the store.
pub fn update_root(&mut self, new_slot: Slot, new_root: Hash256) -> Result<()> {
if !self.nodes.contains_key(&new_root) {
let node = Node {
@ -276,19 +304,18 @@ where
Ok(weight)
}
/// Removes the vote from `validator_index` from the reduced tree.
///
/// If the validator had a vote in the tree, the removal of that vote may cause a node to
/// become redundant and removed from the reduced tree.
fn remove_latest_message(&mut self, validator_index: usize) -> Result<()> {
if self.latest_votes.get(validator_index).is_some() {
// Unwrap is safe as prior `if` statements ensures the result is `Some`.
let vote = self.latest_votes.get(validator_index).unwrap();
let should_delete = {
if let Some(vote) = self.latest_votes.get(validator_index).clone() {
self.get_mut_node(vote.hash)?.remove_voter(validator_index);
let node = self.get_node(vote.hash)?.clone();
if let Some(parent_hash) = node.parent_hash {
if node.has_votes() || node.children.len() > 1 {
// A node with votes or more than one child is never removed.
false
} else if node.children.len() == 1 {
// A node which has only one child may be removed.
//
@ -303,13 +330,19 @@ where
parent.replace_child(node.block_hash, node.children[0])?;
}
true
self.nodes.remove(&vote.hash);
} else if node.children.is_empty() {
// Remove the to-be-deleted node from it's parent.
if let Some(parent_hash) = node.parent_hash {
self.get_mut_node(parent_hash)?
.remove_child(node.block_hash)?;
}
self.nodes.remove(&vote.hash);
// A node which has no children may be deleted and potentially it's parent
// too.
self.maybe_delete_node(parent_hash)?;
true
} else {
// It is impossible for a node to have a number of children that is not 0, 1 or
// greater than one.
@ -319,12 +352,6 @@ where
}
} else {
// A node without a parent is the genesis/finalized node and should never be removed.
false
}
};
if should_delete {
self.nodes.remove(&vote.hash);
}
self.latest_votes.insert(validator_index, Some(vote));
@ -333,23 +360,27 @@ where
Ok(())
}
/// Deletes a node if it is unnecessary.
///
/// Any node is unnecessary if all of the following are true:
///
/// - it is not the root node.
/// - it only has one child.
/// - it does not have any votes.
fn maybe_delete_node(&mut self, hash: Hash256) -> Result<()> {
let should_delete = {
let node = self.get_node(hash)?.clone();
if let Some(parent_hash) = node.parent_hash {
if (node.children.len() == 1) && !node.has_votes() {
// Graft the child to it's grandparent.
let child_hash = {
let child_node = self.get_mut_node(node.children[0])?;
child_node.parent_hash = node.parent_hash;
let child_hash = node.children[0];
child_node.block_hash
};
// Graft the single descendant `node` to the `parent` of node.
self.get_mut_node(child_hash)?.parent_hash = Some(parent_hash);
// Graft the grandparent to it's grandchild.
let parent_node = self.get_mut_node(parent_hash)?;
parent_node.replace_child(node.block_hash, child_hash)?;
// Detach `node` from `parent`, replacing it with `child`.
self.get_mut_node(parent_hash)?
.replace_child(hash, child_hash)?;
true
} else {
@ -385,7 +416,7 @@ where
}
fn add_weightless_node(&mut self, slot: Slot, hash: Hash256) -> Result<()> {
if slot >= self.root_slot() && !self.nodes.contains_key(&hash) {
if slot > self.root_slot() && !self.nodes.contains_key(&hash) {
let node = Node {
block_hash: hash,
..Node::default()
@ -393,6 +424,8 @@ where
self.add_node(node)?;
// Read the `parent_hash` from the newly created node. If it has a parent (i.e., it's
// not the root), see if it is superfluous.
if let Some(parent_hash) = self.get_node(hash)?.parent_hash {
self.maybe_delete_node(parent_hash)?;
}
@ -401,75 +434,108 @@ where
Ok(())
}
/// Add `node` to the reduced tree, returning an error if `node` is not rooted in the tree.
fn add_node(&mut self, mut node: Node) -> Result<()> {
// Find the highest (by slot) ancestor of the given hash/block that is in the reduced tree.
let mut prev_in_tree = {
let hash = self
// Find the highest (by slot) ancestor of the given node in the reduced tree.
//
// If this node has no ancestor in the tree, exit early.
let mut prev_in_tree = self
.find_prev_in_tree(node.block_hash)
.ok_or_else(|| Error::NotInTree(node.block_hash))?;
self.get_mut_node(hash)?.clone()
};
let mut added = false;
.ok_or_else(|| Error::NotInTree(node.block_hash))
.and_then(|hash| self.get_node(hash))?
.clone();
// If the ancestor of `node` has children, there are three possible operations:
//
// 1. Graft the `node` between two existing nodes.
// 2. Create another node that will be grafted between two existing nodes, then graft
// `node` to it.
// 3. Graft `node` to an existing node.
if !prev_in_tree.children.is_empty() {
for &child_hash in &prev_in_tree.children {
// 1. Graft the new node between two existing nodes.
//
// If `node` is a descendant of `prev_in_tree` but an ancestor of a child connected to
// `prev_in_tree`.
//
// This means that `node` can be grafted between `prev_in_tree` and the child that is a
// descendant of both `node` and `prev_in_tree`.
if self
.iter_ancestors(child_hash)?
.any(|(ancestor, _slot)| ancestor == node.block_hash)
{
let child = self.get_mut_node(child_hash)?;
// Graft `child` to `node`.
child.parent_hash = Some(node.block_hash);
// Graft `node` to `child`.
node.children.push(child_hash);
// Detach `child` from `prev_in_tree`, replacing it with `node`.
prev_in_tree.replace_child(child_hash, node.block_hash)?;
// Graft `node` to `prev_in_tree`.
node.parent_hash = Some(prev_in_tree.block_hash);
added = true;
break;
}
}
if !added {
// 2. Create another node that will be grafted between two existing nodes, then graft
// `node` to it.
//
// Note: given that `prev_in_tree` has children and that `node` is not an ancestor of
// any of the children of `prev_in_tree`, we know that `node` is on a different fork to
// all of the children of `prev_in_tree`.
if node.parent_hash.is_none() {
for &child_hash in &prev_in_tree.children {
// Find the highest (by slot) common ancestor between `node` and `child`.
//
// The common ancestor is the last block before `node` and `child` forked.
let ancestor_hash =
self.find_least_common_ancestor(node.block_hash, child_hash)?;
self.find_highest_common_ancestor(node.block_hash, child_hash)?;
// If the block before `node` and `child` forked is _not_ `prev_in_tree` we
// must add this new block into the tree (because it is a decision node
// between two forks).
if ancestor_hash != prev_in_tree.block_hash {
let child = self.get_mut_node(child_hash)?;
// Create a new `common_ancestor` node which represents the `ancestor_hash`
// block, has `prev_in_tree` as the parent and has both `node` and `child`
// as children.
let common_ancestor = Node {
block_hash: ancestor_hash,
parent_hash: Some(prev_in_tree.block_hash),
children: vec![node.block_hash, child_hash],
..Node::default()
};
// Graft `child` and `node` to `common_ancestor`.
child.parent_hash = Some(common_ancestor.block_hash);
node.parent_hash = Some(common_ancestor.block_hash);
prev_in_tree.replace_child(child_hash, ancestor_hash)?;
// Detach `child` from `prev_in_tree`, replacing it with `common_ancestor`.
prev_in_tree.replace_child(child_hash, common_ancestor.block_hash)?;
// Store the new `common_ancestor` node.
self.nodes
.insert(common_ancestor.block_hash, common_ancestor);
added = true;
break;
}
}
}
}
if !added {
if node.parent_hash.is_none() {
// 3. Graft `node` to an existing node.
//
// Graft `node` to `prev_in_tree` and `prev_in_tree` to `node`
node.parent_hash = Some(prev_in_tree.block_hash);
prev_in_tree.children.push(node.block_hash);
}
// Update `prev_in_tree`. A mutable reference was not maintained to satisfy the borrow
// checker.
//
// This is not an ideal solution and results in unnecessary memory copies -- a better
// solution is certainly possible.
// checker. Perhaps there's a better way?
self.nodes.insert(prev_in_tree.block_hash, prev_in_tree);
self.nodes.insert(node.block_hash, node);
@ -485,62 +551,112 @@ where
.and_then(|(root, _slot)| Some(root))
}
/// For the given `child` block hash, return the block's ancestor at the given `target` slot.
fn find_ancestor_at_slot(&self, child: Hash256, target: Slot) -> Result<Hash256> {
let (root, slot) = self
.iter_ancestors(child)?
.find(|(_block, slot)| *slot <= target)
.ok_or_else(|| Error::NotInTree(child))?;
// Explicitly check that the slot is the target in the case that the given child has a slot
// above target.
if slot == target {
Ok(root)
} else {
Err(Error::NotInTree(child))
}
}
/// For the two given block roots (`a_root` and `b_root`), find the first block they share in
/// the tree. Viz, find the block that these two distinct blocks forked from.
fn find_least_common_ancestor(&self, a_root: Hash256, b_root: Hash256) -> Result<Hash256> {
// If the blocks behind `a_root` and `b_root` are not at the same slot, take the highest
// block (by slot) down to be equal with the lower slot.
//
// The result is two roots which identify two blocks at the same height.
let (a_root, b_root) = {
let a = self.get_block(a_root)?;
let b = self.get_block(b_root)?;
fn find_highest_common_ancestor(&self, a_root: Hash256, b_root: Hash256) -> Result<Hash256> {
let mut a_iter = self.iter_ancestors(a_root)?;
let mut b_iter = self.iter_ancestors(b_root)?;
if a.slot > b.slot {
(self.find_ancestor_at_slot(a_root, b.slot)?, b_root)
} else if b.slot > a.slot {
(a_root, self.find_ancestor_at_slot(b_root, a.slot)?)
// Combines the `next()` fns on the `a_iter` and `b_iter` and returns the roots of two
// blocks at the same slot, or `None` if we have gone past genesis or the root of this tree.
let mut iter_blocks_at_same_height = || -> Option<(Hash256, Hash256)> {
match (a_iter.next(), b_iter.next()) {
(Some((mut a_root, a_slot)), Some((mut b_root, b_slot))) => {
// If either of the slots are lower than the root of this tree, exit early.
if a_slot < self.root.1 || b_slot < self.root.1 {
None
} else {
(a_root, b_root)
if a_slot < b_slot {
for _ in a_slot.as_u64()..b_slot.as_u64() {
b_root = b_iter.next()?.0;
}
} else if a_slot > b_slot {
for _ in b_slot.as_u64()..a_slot.as_u64() {
a_root = a_iter.next()?.0;
}
}
Some((a_root, b_root))
}
}
_ => None,
}
};
let ((a_root, _a_slot), (_b_root, _b_slot)) = self
.iter_ancestors(a_root)?
.zip(self.iter_ancestors(b_root)?)
.find(|((a_root, _), (b_root, _))| a_root == b_root)
.ok_or_else(|| Error::NoCommonAncestor((a_root, b_root)))?;
Ok(a_root)
loop {
match iter_blocks_at_same_height() {
Some((a_root, b_root)) if a_root == b_root => break Ok(a_root),
Some(_) => (),
None => break Err(Error::NoCommonAncestor((a_root, b_root))),
}
}
}
fn iter_ancestors(&self, child: Hash256) -> Result<BestBlockRootsIterator<E, T>> {
fn iter_ancestors(&self, child: Hash256) -> Result<BlockRootsIterator<E, T>> {
let block = self.get_block(child)?;
let state = self.get_state(block.state_root)?;
Ok(BestBlockRootsIterator::owned(
Ok(BlockRootsIterator::owned(
self.store.clone(),
state,
block.slot - 1,
))
}
/// Verify the integrity of `self`. Returns `Ok(())` if the tree has integrity, otherwise returns `Err(description)`.
///
/// Tries to detect the following erroneous conditions:
///
/// - Dangling references inside the tree.
/// - Any scenario where there's not exactly one root node.
///
/// ## Notes
///
/// Computationally intensive, likely only useful during testing.
pub fn verify_integrity(&self) -> std::result::Result<(), String> {
let num_root_nodes = self
.nodes
.iter()
.filter(|(_key, node)| node.parent_hash.is_none())
.count();
if num_root_nodes != 1 {
return Err(format!(
"Tree has {} roots, should have exactly one.",
num_root_nodes
));
}
let verify_node_exists = |key: Hash256, msg: String| -> std::result::Result<(), String> {
if self.nodes.contains_key(&key) {
Ok(())
} else {
Err(msg)
}
};
// Iterate through all the nodes and ensure all references they store are valid.
self.nodes
.iter()
.map(|(_key, node)| {
if let Some(parent_hash) = node.parent_hash {
verify_node_exists(parent_hash, "parent must exist".to_string())?;
}
node.children
.iter()
.map(|child| verify_node_exists(*child, "child_must_exist".to_string()))
.collect::<std::result::Result<(), String>>()?;
verify_node_exists(node.block_hash, "block hash must exist".to_string())?;
Ok(())
})
.collect::<std::result::Result<(), String>>()?;
Ok(())
}
fn get_node(&self, hash: Hash256) -> Result<&Node> {
self.nodes
.get(&hash)
@ -595,6 +711,18 @@ impl Node {
Ok(())
}
pub fn remove_child(&mut self, child: Hash256) -> Result<()> {
let i = self
.children
.iter()
.position(|&c| c == child)
.ok_or_else(|| Error::MissingChild(child))?;
self.children.remove(i);
Ok(())
}
pub fn remove_voter(&mut self, voter: usize) -> Option<usize> {
let i = self.voters.iter().position(|&v| v == voter)?;
Some(self.voters.remove(i))

359
eth2/lmd_ghost/tests/test.rs Normal file
View File

@ -0,0 +1,359 @@
#![cfg(not(debug_assertions))]
#[macro_use]
extern crate lazy_static;
use beacon_chain::test_utils::{
AttestationStrategy, BeaconChainHarness as BaseBeaconChainHarness, BlockStrategy,
};
use lmd_ghost::{LmdGhost, ThreadSafeReducedTree as BaseThreadSafeReducedTree};
use rand::{prelude::*, rngs::StdRng};
use std::sync::Arc;
use store::{
iter::{AncestorIter, BestBlockRootsIterator},
MemoryStore, Store,
};
use types::{BeaconBlock, EthSpec, Hash256, MinimalEthSpec, Slot};
// Should ideally be divisible by 3.
pub const VALIDATOR_COUNT: usize = 3 * 8;
type TestEthSpec = MinimalEthSpec;
type ThreadSafeReducedTree = BaseThreadSafeReducedTree<MemoryStore, TestEthSpec>;
type BeaconChainHarness = BaseBeaconChainHarness<ThreadSafeReducedTree, TestEthSpec>;
type RootAndSlot = (Hash256, Slot);
lazy_static! {
/// A lazy-static instance of a `BeaconChainHarness` that contains two forks.
///
/// Reduces test setup time by providing a common harness.
static ref FORKED_HARNESS: ForkedHarness = ForkedHarness::new();
}
/// Contains a `BeaconChainHarness` that has two forks, caused by a validator skipping a slot and
/// then some validators building on one head and some on the other.
///
/// Care should be taken to ensure that the `ForkedHarness` does not expose any interior mutability
/// from it's fields. This would cause cross-contamination between tests when used with
/// `lazy_static`.
struct ForkedHarness {
/// Private (not `pub`) because the `BeaconChainHarness` has interior mutability. We
/// don't expose it to avoid contamination between tests.
harness: BeaconChainHarness,
pub genesis_block_root: Hash256,
pub genesis_block: BeaconBlock,
pub honest_head: RootAndSlot,
pub faulty_head: RootAndSlot,
pub honest_roots: Vec<RootAndSlot>,
pub faulty_roots: Vec<RootAndSlot>,
}
impl ForkedHarness {
/// A new standard instance of with constant parameters.
pub fn new() -> Self {
// let (harness, honest_roots, faulty_roots) = get_harness_containing_two_forks();
let harness = BeaconChainHarness::new(VALIDATOR_COUNT);
// Move past the zero slot.
harness.advance_slot();
let delay = TestEthSpec::default_spec().min_attestation_inclusion_delay as usize;
let initial_blocks = delay + 5;
// Build an initial chain where all validators agree.
harness.extend_chain(
initial_blocks,
BlockStrategy::OnCanonicalHead,
AttestationStrategy::AllValidators,
);
let two_thirds = (VALIDATOR_COUNT / 3) * 2;
let honest_validators: Vec<usize> = (0..two_thirds).collect();
let faulty_validators: Vec<usize> = (two_thirds..VALIDATOR_COUNT).collect();
let honest_fork_blocks = delay + 5;
let faulty_fork_blocks = delay + 5;
let (honest_head, faulty_head) = harness.generate_two_forks_by_skipping_a_block(
&honest_validators,
&faulty_validators,
honest_fork_blocks,
faulty_fork_blocks,
);
let mut honest_roots =
get_ancestor_roots::<TestEthSpec, _>(harness.chain.store.clone(), honest_head);
honest_roots.insert(
0,
(honest_head, get_slot_for_block_root(&harness, honest_head)),
);
let mut faulty_roots =
get_ancestor_roots::<TestEthSpec, _>(harness.chain.store.clone(), faulty_head);
faulty_roots.insert(
0,
(faulty_head, get_slot_for_block_root(&harness, faulty_head)),
);
let genesis_block_root = harness.chain.genesis_block_root;
let genesis_block = harness
.chain
.store
.get::<BeaconBlock>(&genesis_block_root)
.expect("Genesis block should exist")
.expect("DB should not error");
Self {
harness,
genesis_block_root,
genesis_block,
honest_head: *honest_roots.last().expect("Chain cannot be empty"),
faulty_head: *faulty_roots.last().expect("Chain cannot be empty"),
honest_roots,
faulty_roots,
}
}
pub fn store_clone(&self) -> MemoryStore {
(*self.harness.chain.store).clone()
}
/// Return a brand-new, empty fork choice with a reference to `harness.store`.
pub fn new_fork_choice(&self) -> ThreadSafeReducedTree {
// Take a full clone of the store built by the harness.
//
// Taking a clone here ensures that each fork choice gets it's own store so there is no
// cross-contamination between tests.
let store: MemoryStore = self.store_clone();
ThreadSafeReducedTree::new(
Arc::new(store),
&self.genesis_block,
self.genesis_block_root,
)
}
pub fn all_block_roots(&self) -> Vec<RootAndSlot> {
let mut all_roots = self.honest_roots.clone();
all_roots.append(&mut self.faulty_roots.clone());
all_roots.dedup();
all_roots
}
pub fn weight_function(_validator_index: usize) -> Option<u64> {
Some(1)
}
}
/// Helper: returns all the ancestor roots and slots for a given block_root.
fn get_ancestor_roots<E: EthSpec, U: Store>(
store: Arc<U>,
block_root: Hash256,
) -> Vec<(Hash256, Slot)> {
let block = store
.get::<BeaconBlock>(&block_root)
.expect("block should exist")
.expect("store should not error");
<BeaconBlock as AncestorIter<_, BestBlockRootsIterator<E, _>>>::try_iter_ancestor_roots(
&block, store,
)
.expect("should be able to create ancestor iter")
.collect()
}
/// Helper: returns the slot for some block_root.
fn get_slot_for_block_root(harness: &BeaconChainHarness, block_root: Hash256) -> Slot {
harness
.chain
.store
.get::<BeaconBlock>(&block_root)
.expect("head block should exist")
.expect("DB should not error")
.slot
}
const RANDOM_ITERATIONS: usize = 50;
const RANDOM_ACTIONS_PER_ITERATION: usize = 100;
/// Create a single LMD instance and have one validator vote in reverse (highest to lowest slot)
/// down the chain.
#[test]
fn random_scenario() {
let harness = &FORKED_HARNESS;
let block_roots = harness.all_block_roots();
let validators: Vec<usize> = (0..VALIDATOR_COUNT).collect();
let mut rng = StdRng::seed_from_u64(9375205782030385); // Keyboard mash.
for _ in 0..RANDOM_ITERATIONS {
let lmd = harness.new_fork_choice();
for _ in 0..RANDOM_ACTIONS_PER_ITERATION {
let (root, slot) = block_roots[rng.next_u64() as usize % block_roots.len()];
let validator_index = validators[rng.next_u64() as usize % validators.len()];
lmd.process_attestation(validator_index, root, slot)
.expect("fork choice should accept randomly-placed attestations");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"New tree should have integrity"
);
}
}
}
/// Create a single LMD instance and have one validator vote in reverse (highest to lowest slot)
/// down the chain.
#[test]
fn single_voter_persistent_instance_reverse_order() {
let harness = &FORKED_HARNESS;
let lmd = harness.new_fork_choice();
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"New tree should have integrity"
);
for (root, slot) in harness.honest_roots.iter().rev() {
lmd.process_attestation(0, *root, *slot)
.expect("fork choice should accept attestations to honest roots in reverse");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained whilst processing attestations"
);
}
// The honest head should be selected.
let (head_root, head_slot) = harness.honest_roots.first().unwrap();
let (finalized_root, _) = harness.honest_roots.last().unwrap();
assert_eq!(
lmd.find_head(*head_slot, *finalized_root, ForkedHarness::weight_function),
Ok(*head_root),
"Honest head should be selected"
);
}
/// A single validator applies a single vote to each block in the honest fork, using a new tree
/// each time.
#[test]
fn single_voter_many_instance_honest_blocks_voting_forwards() {
let harness = &FORKED_HARNESS;
for (root, slot) in &harness.honest_roots {
let lmd = harness.new_fork_choice();
lmd.process_attestation(0, *root, *slot)
.expect("fork choice should accept attestations to honest roots");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained whilst processing attestations"
);
}
}
/// Same as above, but in reverse order (votes on the highest honest block first).
#[test]
fn single_voter_many_instance_honest_blocks_voting_in_reverse() {
let harness = &FORKED_HARNESS;
// Same as above, but in reverse order (votes on the highest honest block first).
for (root, slot) in harness.honest_roots.iter().rev() {
let lmd = harness.new_fork_choice();
lmd.process_attestation(0, *root, *slot)
.expect("fork choice should accept attestations to honest roots in reverse");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained whilst processing attestations"
);
}
}
/// A single validator applies a single vote to each block in the faulty fork, using a new tree
/// each time.
#[test]
fn single_voter_many_instance_faulty_blocks_voting_forwards() {
let harness = &FORKED_HARNESS;
for (root, slot) in &harness.faulty_roots {
let lmd = harness.new_fork_choice();
lmd.process_attestation(0, *root, *slot)
.expect("fork choice should accept attestations to faulty roots");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained whilst processing attestations"
);
}
}
/// Same as above, but in reverse order (votes on the highest faulty block first).
#[test]
fn single_voter_many_instance_faulty_blocks_voting_in_reverse() {
let harness = &FORKED_HARNESS;
for (root, slot) in harness.faulty_roots.iter().rev() {
let lmd = harness.new_fork_choice();
lmd.process_attestation(0, *root, *slot)
.expect("fork choice should accept attestations to faulty roots in reverse");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained whilst processing attestations"
);
}
}
/// Ensures that the finalized root can be set to all values in `roots`.
fn test_update_finalized_root(roots: &[(Hash256, Slot)]) {
let harness = &FORKED_HARNESS;
let lmd = harness.new_fork_choice();
for (root, _slot) in roots.iter().rev() {
let block = harness
.store_clone()
.get::<BeaconBlock>(root)
.expect("block should exist")
.expect("db should not error");
lmd.update_finalized_root(&block, *root)
.expect("finalized root should update for faulty fork");
assert_eq!(
lmd.verify_integrity(),
Ok(()),
"Tree integrity should be maintained after updating the finalized root"
);
}
}
/// Iterates from low-to-high slot through the faulty roots, updating the finalized root.
#[test]
fn update_finalized_root_faulty() {
let harness = &FORKED_HARNESS;
test_update_finalized_root(&harness.faulty_roots)
}
/// Iterates from low-to-high slot through the honest roots, updating the finalized root.
#[test]
fn update_finalized_root_honest() {
let harness = &FORKED_HARNESS;
test_update_finalized_root(&harness.honest_roots)
}