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Remove BlockRootTree

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This commit is contained in:
Paul Hauner
2020-01-21 14:26:04 +11:00
parent dcea0b5084
commit c3969e2ce5
7 changed files with 13 additions and 398 deletions
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19
beacon_node/beacon_chain/src/beacon_chain.rs
View File

@@ -30,7 +30,7 @@ use std::time::{Duration, Instant};
use store::iter::{
BlockRootsIterator, ReverseBlockRootIterator, ReverseStateRootIterator, StateRootsIterator,
};
use store::{BlockRootTree, Error as DBError, Migrate, Store};
use store::{Error as DBError, Migrate, Store};
use tree_hash::TreeHash;
use types::*;
@@ -147,8 +147,6 @@ pub struct BeaconChain<T: BeaconChainTypes> {
pub(crate) head_tracker: HeadTracker,
/// Provides a small cache of `BeaconState` and `BeaconBlock`.
pub(crate) checkpoint_cache: CheckPointCache<T::EthSpec>,
/// Cache of block roots for all known forks post-finalization.
pub block_root_tree: Arc<BlockRootTree>,
/// Logging to CLI, etc.
pub(crate) log: Logger,
}
@@ -188,7 +186,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
genesis_block_root: self.genesis_block_root,
ssz_head_tracker: self.head_tracker.to_ssz_container(),
fork_choice: self.fork_choice.as_ssz_container(),
block_root_tree: self.block_root_tree.as_ssz_container(),
block_root_tree: vec![],
};
let key = Hash256::from_slice(&BEACON_CHAIN_DB_KEY.as_bytes());
@@ -1242,8 +1240,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
}
// Check if the block is already known. We know it is post-finalization, so it is
// sufficient to check the block root tree.
if self.block_root_tree.is_known_block_root(&block_root) {
// sufficient to check the fork choice.
if self.fork_choice.contains_block(&block_root) {
return Ok(BlockProcessingOutcome::BlockIsAlreadyKnown);
}
@@ -1400,9 +1398,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
metrics::stop_timer(db_write_timer);
self.block_root_tree
.add_block_root(block_root, block.parent_root, block.slot)?;
self.head_tracker.register_block(block_root, &block);
metrics::inc_counter(&metrics::BLOCK_PROCESSING_SUCCESSES);
@@ -1710,12 +1705,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
max_finality_distance,
);
// Prune in-memory block root tree.
self.block_root_tree.prune_to(
finalized_block_root,
self.heads().into_iter().map(|(block_root, _)| block_root),
);
let _ = self.event_handler.register(EventKind::BeaconFinalization {
epoch: new_finalized_epoch,
root: finalized_block_root,

13
beacon_node/beacon_chain/src/builder.rs
View File

@@ -16,7 +16,7 @@ use slot_clock::{SlotClock, TestingSlotClock};
use std::marker::PhantomData;
use std::sync::Arc;
use std::time::Duration;
use store::{BlockRootTree, Store};
use store::Store;
use types::{BeaconBlock, BeaconState, ChainSpec, EthSpec, Hash256, Slot};
/// An empty struct used to "witness" all the `BeaconChainTypes` traits. It has no user-facing
@@ -72,7 +72,6 @@ pub struct BeaconChainBuilder<T: BeaconChainTypes> {
slot_clock: Option<T::SlotClock>,
persisted_beacon_chain: Option<PersistedBeaconChain<T>>,
head_tracker: Option<HeadTracker>,
block_root_tree: Option<Arc<BlockRootTree>>,
spec: ChainSpec,
log: Option<Logger>,
}
@@ -106,7 +105,6 @@ where
slot_clock: None,
persisted_beacon_chain: None,
head_tracker: None,
block_root_tree: None,
spec: TEthSpec::default_spec(),
log: None,
}
@@ -189,7 +187,6 @@ where
HeadTracker::from_ssz_container(&p.ssz_head_tracker)
.map_err(|e| format!("Failed to decode head tracker for database: {:?}", e))?,
);
self.block_root_tree = Some(Arc::new(p.block_root_tree.clone().into()));
self.persisted_beacon_chain = Some(p);
Ok(self)
@@ -232,11 +229,6 @@ where
)
})?;
self.block_root_tree = Some(Arc::new(BlockRootTree::new(
beacon_block_root,
beacon_block.slot,
)));
self.finalized_checkpoint = Some(CheckPoint {
beacon_block_root,
beacon_block,
@@ -338,9 +330,6 @@ where
.event_handler
.ok_or_else(|| "Cannot build without an event handler".to_string())?,
head_tracker: self.head_tracker.unwrap_or_default(),
block_root_tree: self
.block_root_tree
.ok_or_else(|| "Cannot build without a block root tree".to_string())?,
checkpoint_cache: CheckPointCache::default(),
log: log.clone(),
};

3
beacon_node/beacon_chain/src/errors.rs
View File

@@ -5,7 +5,6 @@ use state_processing::per_block_processing::errors::AttestationValidationError;
use state_processing::BlockProcessingError;
use state_processing::SlotProcessingError;
use std::time::Duration;
use store::block_root_tree::BlockRootTreeError;
use types::*;
macro_rules! easy_from_to {
@@ -50,13 +49,11 @@ pub enum BeaconChainError {
InvariantViolated(String),
SszTypesError(SszTypesError),
CanonicalHeadLockTimeout,
BlockRootTreeError(BlockRootTreeError),
}
easy_from_to!(SlotProcessingError, BeaconChainError);
easy_from_to!(AttestationValidationError, BeaconChainError);
easy_from_to!(SszTypesError, BeaconChainError);
easy_from_to!(BlockRootTreeError, BeaconChainError);
#[derive(Debug, PartialEq)]
pub enum BlockProductionError {

5
beacon_node/beacon_chain/src/fork_choice.rs
View File

@@ -119,6 +119,11 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
result
}
/// Returns true if the given block is known to fork choice.
pub fn contains_block(&self, block_root: &Hash256) -> bool {
self.backend.contains_block(block_root)
}
/// Process all attestations in the given `block`.
///
/// Assumes the block (and therefore its attestations) are valid. It is a logic error to

5
beacon_node/beacon_chain/src/persisted_beacon_chain.rs
View File

@@ -4,7 +4,7 @@ use crate::{BeaconChainTypes, CheckPoint};
use operation_pool::PersistedOperationPool;
use ssz::{Decode, Encode};
use ssz_derive::{Decode, Encode};
use store::{DBColumn, Error as StoreError, SimpleStoreItem, SszBlockRootTree};
use store::{DBColumn, Error as StoreError, SimpleStoreItem};
use types::Hash256;
/// 32-byte key for accessing the `PersistedBeaconChain`.
@@ -18,7 +18,8 @@ pub struct PersistedBeaconChain<T: BeaconChainTypes> {
pub genesis_block_root: Hash256,
pub ssz_head_tracker: SszHeadTracker,
pub fork_choice: SszForkChoice,
pub block_root_tree: SszBlockRootTree,
// TODO: remove this.
pub block_root_tree: Vec<u8>,
}
impl<T: BeaconChainTypes> SimpleStoreItem for PersistedBeaconChain<T> {

364
beacon_node/store/src/block_root_tree.rs
View File

@@ -1,364 +0,0 @@
use itertools::Itertools;
use parking_lot::RwLock;
use ssz_derive::{Decode, Encode};
use std::collections::{HashMap, HashSet};
use std::iter::{self, FromIterator};
use types::{Hash256, Slot};
/// In-memory cache of all block roots post-finalization. Includes short-lived forks.
///
/// Used by fork choice to avoid reconstructing hot states just for their block roots.
// NOTE: could possibly be streamlined by combining with the head tracker and/or fork choice
#[derive(Debug)]
pub struct BlockRootTree {
nodes: RwLock<HashMap<Hash256, Node>>,
}
impl Clone for BlockRootTree {
fn clone(&self) -> Self {
Self {
nodes: RwLock::new(self.nodes.read().clone()),
}
}
}
#[derive(Debug, PartialEq)]
pub enum BlockRootTreeError {
PrevUnknown(Hash256),
}
/// Data for a single `block_root` in the tree.
#[derive(Debug, Clone, Encode, Decode)]
struct Node {
/// Hash of the preceding block (should be the parent block).
///
/// A `previous` of `Hash256::zero` indicates the root of the tree.
previous: Hash256,
/// Slot of this node's block.
slot: Slot,
}
impl BlockRootTree {
/// Create a new block root tree where `(root_hash, root_slot)` is considered finalized.
///
/// All subsequent blocks added should descend from the root block.
pub fn new(root_hash: Hash256, root_slot: Slot) -> Self {
Self {
nodes: RwLock::new(HashMap::from_iter(iter::once((
root_hash,
Node {
previous: Hash256::zero(),
slot: root_slot,
},
)))),
}
}
/// Check if `block_root` exists in the tree.
pub fn is_known_block_root(&self, block_root: &Hash256) -> bool {
self.nodes.read().contains_key(block_root)
}
/// Add a new `block_root` to the tree.
///
/// Will return an error if `prev_block_root` doesn't exist in the tree.
pub fn add_block_root(
&self,
block_root: Hash256,
prev_block_root: Hash256,
block_slot: Slot,
) -> Result<(), BlockRootTreeError> {
let mut nodes = self.nodes.write();
if nodes.contains_key(&prev_block_root) {
nodes.insert(
block_root,
Node {
previous: prev_block_root,
slot: block_slot,
},
);
Ok(())
} else {
Err(BlockRootTreeError::PrevUnknown(prev_block_root))
}
}
/// Create a reverse iterator from `block_root` (inclusive).
///
/// Will skip slots, see `every_slot_iter_from` for a non-skipping variant.
pub fn iter_from(&self, block_root: Hash256) -> BlockRootTreeIter {
BlockRootTreeIter {
tree: self,
current_block_root: block_root,
}
}
/// Create a reverse iterator that yields a block root for every slot.
///
/// E.g. if slot 6 is skipped, this iterator will return the block root from slot 5 at slot 6.
pub fn every_slot_iter_from<'a>(
&'a self,
block_root: Hash256,
) -> impl Iterator<Item = (Hash256, Slot)> + 'a {
let mut block_roots = self.iter_from(block_root).peekable();
// Include the value for the first `block_root` if any, then fill in the skipped slots
// between each pair of previous block roots by duplicating the older root.
block_roots
.peek()
.cloned()
.into_iter()
.chain(block_roots.tuple_windows().flat_map(
|((_, high_slot), (low_hash, low_slot))| {
(low_slot.as_u64()..high_slot.as_u64())
.rev()
.map(move |slot| (low_hash, Slot::new(slot)))
},
))
}
/// Prune the tree.
///
/// Only keep block roots descended from `finalized_root`, which lie on a chain leading
/// to one of the heads contained in `heads`.
pub fn prune_to(&self, finalized_root: Hash256, heads: impl IntoIterator<Item = Hash256>) {
let mut keep = HashSet::new();
keep.insert(finalized_root);
for head_block_root in heads.into_iter() {
// Iterate backwards until we reach a portion of the chain that we've already decided
// to keep. This also discards the pre-finalization block roots.
let mut keep_head = false;
let head_blocks = self
.iter_from(head_block_root)
.map(|(block_root, _)| block_root)
.inspect(|block_root| {
if block_root == &finalized_root {
keep_head = true;
}
})
.take_while(|block_root| !keep.contains(&block_root))
.collect::<HashSet<_>>();
// If the head descends from the finalized root, keep it. Else throw it out.
if keep_head {
keep.extend(head_blocks);
}
}
self.nodes
.write()
.retain(|block_root, _| keep.contains(block_root));
}
pub fn as_ssz_container(&self) -> SszBlockRootTree {
SszBlockRootTree {
nodes: Vec::from_iter(self.nodes.read().clone()),
}
}
}
/// Simple (skipping) iterator for `BlockRootTree`.
#[derive(Debug)]
pub struct BlockRootTreeIter<'a> {
tree: &'a BlockRootTree,
current_block_root: Hash256,
}
impl<'a> Iterator for BlockRootTreeIter<'a> {
type Item = (Hash256, Slot);
fn next(&mut self) -> Option<Self::Item> {
// Genesis
if self.current_block_root.is_zero() {
None
} else {
let block_root = self.current_block_root;
self.tree.nodes.read().get(&block_root).map(|node| {
self.current_block_root = node.previous;
(block_root, node.slot)
})
}
}
}
/// Serializable version of `BlockRootTree` that can be persisted to disk.
#[derive(Debug, Clone, Encode, Decode)]
pub struct SszBlockRootTree {
nodes: Vec<(Hash256, Node)>,
}
impl Into<BlockRootTree> for SszBlockRootTree {
fn into(self) -> BlockRootTree {
BlockRootTree {
nodes: RwLock::new(HashMap::from_iter(self.nodes)),
}
}
}
#[cfg(test)]
mod test {
use super::*;
fn int_hash(x: u64) -> Hash256 {
Hash256::from_low_u64_be(x)
}
fn check_iter_from(
block_tree: &BlockRootTree,
start_block_root: Hash256,
expected: &[(Hash256, Slot)],
) {
assert_eq!(
&block_tree.iter_from(start_block_root).collect::<Vec<_>>()[..],
expected
);
}
fn check_every_slot_iter_from(
block_tree: &BlockRootTree,
start_block_root: Hash256,
expected: &[(Hash256, Slot)],
) {
assert_eq!(
&block_tree
.every_slot_iter_from(start_block_root)
.collect::<Vec<_>>()[..],
expected
);
}
#[test]
fn single_chain() {
let block_tree = BlockRootTree::new(int_hash(1), Slot::new(1));
for i in 2..100 {
block_tree
.add_block_root(int_hash(i), int_hash(i - 1), Slot::new(i))
.expect("add_block_root ok");
let expected = (1..i + 1)
.rev()
.map(|j| (int_hash(j), Slot::new(j)))
.collect::<Vec<_>>();
check_iter_from(&block_tree, int_hash(i), &expected);
check_every_slot_iter_from(&block_tree, int_hash(i), &expected);
// Still OK after pruning.
block_tree.prune_to(int_hash(1), vec![int_hash(i)]);
check_iter_from(&block_tree, int_hash(i), &expected);
check_every_slot_iter_from(&block_tree, int_hash(i), &expected);
}
}
#[test]
fn skips_of_2() {
let block_tree = BlockRootTree::new(int_hash(1), Slot::new(1));
let step_length = 2u64;
for i in (1 + step_length..100).step_by(step_length as usize) {
block_tree
.add_block_root(int_hash(i), int_hash(i - step_length), Slot::new(i))
.expect("add_block_root ok");
let sparse_expected = (1..i + 1)
.rev()
.step_by(step_length as usize)
.map(|j| (int_hash(j), Slot::new(j)))
.collect_vec();
let every_slot_expected = (1..i + 1)
.rev()
.map(|j| {
let nearest = 1 + (j - 1) / step_length * step_length;
(int_hash(nearest), Slot::new(j))
})
.collect_vec();
check_iter_from(&block_tree, int_hash(i), &sparse_expected);
check_every_slot_iter_from(&block_tree, int_hash(i), &every_slot_expected);
// Still OK after pruning.
block_tree.prune_to(int_hash(1), vec![int_hash(i)]);
check_iter_from(&block_tree, int_hash(i), &sparse_expected);
check_every_slot_iter_from(&block_tree, int_hash(i), &every_slot_expected);
}
}
#[test]
fn prune_small_fork() {
let tree = BlockRootTree::new(int_hash(1), Slot::new(1));
// Space between fork hash values
let offset = 1000;
let num_blocks = 50;
let fork1_start = 2;
let fork2_start = 2 + offset;
tree.add_block_root(int_hash(fork1_start), int_hash(1), Slot::new(2))
.expect("add first block of left fork");
tree.add_block_root(int_hash(fork2_start), int_hash(1), Slot::new(2))
.expect("add first block of right fork");
for i in 3..num_blocks {
tree.add_block_root(int_hash(i), int_hash(i - 1), Slot::new(i))
.expect("add block to left fork");
tree.add_block_root(int_hash(i + offset), int_hash(i + offset - 1), Slot::new(i))
.expect("add block to right fork");
}
let root = (int_hash(1), Slot::new(1));
let (all_fork1_blocks, all_fork2_blocks): (Vec<_>, Vec<_>) = (2..num_blocks)
.rev()
.map(|i| {
(
(int_hash(i), Slot::new(i)),
(int_hash(i + offset), Slot::new(i)),
)
})
.chain(iter::once((root, root)))
.unzip();
let fork1_head = int_hash(num_blocks - 1);
let fork2_head = int_hash(num_blocks + offset - 1);
// Check that pruning with both heads preserves both chains.
let both_tree = tree.clone();
both_tree.prune_to(root.0, vec![fork1_head, fork2_head]);
check_iter_from(&both_tree, fork1_head, &all_fork1_blocks);
check_iter_from(&both_tree, fork2_head, &all_fork2_blocks);
// Check that pruning to either of the single chains leaves just that chain in the tree.
let fork1_tree = tree.clone();
fork1_tree.prune_to(root.0, vec![fork1_head]);
check_iter_from(&fork1_tree, fork1_head, &all_fork1_blocks);
check_iter_from(&fork1_tree, fork2_head, &[]);
let fork2_tree = tree.clone();
fork2_tree.prune_to(root.0, vec![fork2_head]);
check_iter_from(&fork2_tree, fork1_head, &[]);
check_iter_from(&fork2_tree, fork2_head, &all_fork2_blocks);
// Check that advancing the finalized root onto one side completely removes the other
// side.
let fin_tree = tree.clone();
let prune_point = num_blocks / 2;
let remaining_fork1_blocks = all_fork1_blocks
.clone()
.into_iter()
.take_while(|(_, slot)| *slot >= prune_point)
.collect_vec();
fin_tree.prune_to(int_hash(prune_point), vec![fork1_head, fork2_head]);
check_iter_from(&fin_tree, fork1_head, &remaining_fork1_blocks);
check_iter_from(&fin_tree, fork2_head, &[]);
}
#[test]
fn iter_zero() {
let block_tree = BlockRootTree::new(int_hash(0), Slot::new(0));
assert_eq!(block_tree.iter_from(int_hash(0)).count(), 0);
assert_eq!(block_tree.every_slot_iter_from(int_hash(0)).count(), 0);
}
}

2
beacon_node/store/src/lib.rs
View File

@@ -11,7 +11,6 @@
extern crate lazy_static;
mod block_at_slot;
pub mod block_root_tree;
pub mod chunked_iter;
pub mod chunked_vector;
pub mod config;
@@ -29,7 +28,6 @@ pub mod migrate;
use std::sync::Arc;
pub use self::block_root_tree::{BlockRootTree, SszBlockRootTree};
pub use self::config::StoreConfig;
pub use self::hot_cold_store::HotColdDB as DiskStore;
pub use self::leveldb_store::LevelDB as SimpleDiskStore;