lighthouse/beacon_node/beacon_chain/src/migrate.rs
Michael Sproul 9667dc2f03 Implement checkpoint sync (#2244)
## Issue Addressed

Closes #1891
Closes #1784

## Proposed Changes

Implement checkpoint sync for Lighthouse, enabling it to start from a weak subjectivity checkpoint.

## Additional Info

- [x] Return unavailable status for out-of-range blocks requested by peers (#2561)
- [x] Implement sync daemon for fetching historical blocks (#2561)
- [x] Verify chain hashes (either in `historical_blocks.rs` or the calling module)
- [x] Consistency check for initial block + state
- [x] Fetch the initial state and block from a beacon node HTTP endpoint
- [x] Don't crash fetching beacon states by slot from the API
- [x] Background service for state reconstruction, triggered by CLI flag or API call.

Considered out of scope for this PR:

- Drop the requirement to provide the `--checkpoint-block` (this would require some pretty heavy refactoring of block verification)


Co-authored-by: Diva M <divma@protonmail.com>
2021-09-22 00:37:28 +00:00

616 lines
24 KiB
Rust

use crate::beacon_chain::BEACON_CHAIN_DB_KEY;
use crate::errors::BeaconChainError;
use crate::head_tracker::{HeadTracker, SszHeadTracker};
use crate::persisted_beacon_chain::{PersistedBeaconChain, DUMMY_CANONICAL_HEAD_BLOCK_ROOT};
use parking_lot::Mutex;
use slog::{debug, error, info, warn, Logger};
use std::collections::{HashMap, HashSet};
use std::mem;
use std::sync::{mpsc, Arc};
use std::thread;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use store::hot_cold_store::{migrate_database, HotColdDBError};
use store::iter::RootsIterator;
use store::{Error, ItemStore, StoreItem, StoreOp};
pub use store::{HotColdDB, MemoryStore};
use types::{
BeaconState, BeaconStateError, BeaconStateHash, Checkpoint, Epoch, EthSpec, Hash256,
SignedBeaconBlockHash, Slot,
};
/// Compact at least this frequently, finalization permitting (7 days).
const MAX_COMPACTION_PERIOD_SECONDS: u64 = 604800;
/// Compact at *most* this frequently, to prevent over-compaction during sync (2 hours).
const MIN_COMPACTION_PERIOD_SECONDS: u64 = 7200;
/// Compact after a large finality gap, if we respect `MIN_COMPACTION_PERIOD_SECONDS`.
const COMPACTION_FINALITY_DISTANCE: u64 = 1024;
/// The background migrator runs a thread to perform pruning and migrate state from the hot
/// to the cold database.
pub struct BackgroundMigrator<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
db: Arc<HotColdDB<E, Hot, Cold>>,
#[allow(clippy::type_complexity)]
tx_thread: Option<Mutex<(mpsc::Sender<Notification>, thread::JoinHandle<()>)>>,
/// Genesis block root, for persisting the `PersistedBeaconChain`.
genesis_block_root: Hash256,
log: Logger,
}
#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct MigratorConfig {
pub blocking: bool,
}
impl MigratorConfig {
pub fn blocking(mut self) -> Self {
self.blocking = true;
self
}
}
/// Pruning can be successful, or in rare cases deferred to a later point.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum PruningOutcome {
/// The pruning succeeded and updated the pruning checkpoint from `old_finalized_checkpoint`.
Successful {
old_finalized_checkpoint: Checkpoint,
},
DeferredConcurrentMutation,
}
/// Logic errors that can occur during pruning, none of these should ever happen.
#[derive(Debug)]
pub enum PruningError {
IncorrectFinalizedState {
state_slot: Slot,
new_finalized_slot: Slot,
},
MissingInfoForCanonicalChain {
slot: Slot,
},
UnexpectedEqualStateRoots,
UnexpectedUnequalStateRoots,
}
/// Message sent to the migration thread containing the information it needs to run.
pub enum Notification {
Finalization(FinalizationNotification),
Reconstruction,
}
pub struct FinalizationNotification {
finalized_state_root: BeaconStateHash,
finalized_checkpoint: Checkpoint,
head_tracker: Arc<HeadTracker>,
genesis_block_root: Hash256,
}
impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> BackgroundMigrator<E, Hot, Cold> {
/// Create a new `BackgroundMigrator` and spawn its thread if necessary.
pub fn new(
db: Arc<HotColdDB<E, Hot, Cold>>,
config: MigratorConfig,
genesis_block_root: Hash256,
log: Logger,
) -> Self {
let tx_thread = if config.blocking {
None
} else {
Some(Mutex::new(Self::spawn_thread(db.clone(), log.clone())))
};
Self {
db,
tx_thread,
genesis_block_root,
log,
}
}
/// Process a finalized checkpoint from the `BeaconChain`.
///
/// If successful, all forks descending from before the `finalized_checkpoint` will be
/// pruned, and the split point of the database will be advanced to the slot of the finalized
/// checkpoint.
pub fn process_finalization(
&self,
finalized_state_root: BeaconStateHash,
finalized_checkpoint: Checkpoint,
head_tracker: Arc<HeadTracker>,
) -> Result<(), BeaconChainError> {
let notif = FinalizationNotification {
finalized_state_root,
finalized_checkpoint,
head_tracker,
genesis_block_root: self.genesis_block_root,
};
// Send to background thread if configured, otherwise run in foreground.
if let Some(Notification::Finalization(notif)) =
self.send_background_notification(Notification::Finalization(notif))
{
Self::run_migration(self.db.clone(), notif, &self.log);
}
Ok(())
}
pub fn process_reconstruction(&self) {
if let Some(Notification::Reconstruction) =
self.send_background_notification(Notification::Reconstruction)
{
Self::run_reconstruction(self.db.clone(), &self.log);
}
}
pub fn run_reconstruction(db: Arc<HotColdDB<E, Hot, Cold>>, log: &Logger) {
if let Err(e) = db.reconstruct_historic_states() {
error!(
log,
"State reconstruction failed";
"error" => ?e,
);
}
}
/// If configured to run in the background, send `notif` to the background thread.
///
/// Return `None` if the message was sent to the background thread, `Some(notif)` otherwise.
#[must_use = "Message is not processed when this function returns `Some`"]
fn send_background_notification(&self, notif: Notification) -> Option<Notification> {
// Async path, on the background thread.
if let Some(tx_thread) = &self.tx_thread {
let (ref mut tx, ref mut thread) = *tx_thread.lock();
// Restart the background thread if it has crashed.
if let Err(tx_err) = tx.send(notif) {
let (new_tx, new_thread) = Self::spawn_thread(self.db.clone(), self.log.clone());
*tx = new_tx;
let old_thread = mem::replace(thread, new_thread);
// Join the old thread, which will probably have panicked, or may have
// halted normally just now as a result of us dropping the old `mpsc::Sender`.
if let Err(thread_err) = old_thread.join() {
warn!(
self.log,
"Migration thread died, so it was restarted";
"reason" => format!("{:?}", thread_err)
);
}
// Retry at most once, we could recurse but that would risk overflowing the stack.
let _ = tx.send(tx_err.0);
}
None
// Synchronous path, on the current thread.
} else {
Some(notif)
}
}
/// Perform the actual work of `process_finalization`.
fn run_migration(
db: Arc<HotColdDB<E, Hot, Cold>>,
notif: FinalizationNotification,
log: &Logger,
) {
debug!(log, "Database consolidation started");
let finalized_state_root = notif.finalized_state_root;
let finalized_state = match db.get_state(&finalized_state_root.into(), None) {
Ok(Some(state)) => state,
other => {
error!(
log,
"Migrator failed to load state";
"state_root" => ?finalized_state_root,
"error" => ?other
);
return;
}
};
let old_finalized_checkpoint = match Self::prune_abandoned_forks(
db.clone(),
notif.head_tracker,
finalized_state_root,
&finalized_state,
notif.finalized_checkpoint,
notif.genesis_block_root,
log,
) {
Ok(PruningOutcome::Successful {
old_finalized_checkpoint,
}) => old_finalized_checkpoint,
Ok(PruningOutcome::DeferredConcurrentMutation) => {
warn!(
log,
"Pruning deferred because of a concurrent mutation";
"message" => "this is expected only very rarely!"
);
return;
}
Err(e) => {
warn!(log, "Block pruning failed"; "error" => format!("{:?}", e));
return;
}
};
match migrate_database(db.clone(), finalized_state_root.into(), &finalized_state) {
Ok(()) => {}
Err(Error::HotColdDBError(HotColdDBError::FreezeSlotUnaligned(slot))) => {
debug!(
log,
"Database migration postponed, unaligned finalized block";
"slot" => slot.as_u64()
);
}
Err(e) => {
warn!(
log,
"Database migration failed";
"error" => format!("{:?}", e)
);
return;
}
};
// Finally, compact the database so that new free space is properly reclaimed.
if let Err(e) = Self::run_compaction(
db,
old_finalized_checkpoint.epoch,
notif.finalized_checkpoint.epoch,
log,
) {
warn!(log, "Database compaction failed"; "error" => format!("{:?}", e));
}
debug!(log, "Database consolidation complete");
}
/// Spawn a new child thread to run the migration process.
///
/// Return a channel handle for sending requests to the thread.
fn spawn_thread(
db: Arc<HotColdDB<E, Hot, Cold>>,
log: Logger,
) -> (mpsc::Sender<Notification>, thread::JoinHandle<()>) {
let (tx, rx) = mpsc::channel();
let thread = thread::spawn(move || {
while let Ok(notif) = rx.recv() {
// Read the rest of the messages in the channel, preferring any reconstruction
// notification, or the finalization notification with the greatest finalized epoch.
let notif =
rx.try_iter()
.fold(notif, |best, other: Notification| match (&best, &other) {
(Notification::Reconstruction, _)
| (_, Notification::Reconstruction) => Notification::Reconstruction,
(
Notification::Finalization(fin1),
Notification::Finalization(fin2),
) => {
if fin2.finalized_checkpoint.epoch > fin1.finalized_checkpoint.epoch
{
other
} else {
best
}
}
});
match notif {
Notification::Reconstruction => Self::run_reconstruction(db.clone(), &log),
Notification::Finalization(fin) => Self::run_migration(db.clone(), fin, &log),
}
}
});
(tx, thread)
}
/// Traverses live heads and prunes blocks and states of chains that we know can't be built
/// upon because finalization would prohibit it. This is an optimisation intended to save disk
/// space.
#[allow(clippy::too_many_arguments)]
fn prune_abandoned_forks(
store: Arc<HotColdDB<E, Hot, Cold>>,
head_tracker: Arc<HeadTracker>,
new_finalized_state_hash: BeaconStateHash,
new_finalized_state: &BeaconState<E>,
new_finalized_checkpoint: Checkpoint,
genesis_block_root: Hash256,
log: &Logger,
) -> Result<PruningOutcome, BeaconChainError> {
let old_finalized_checkpoint =
store
.load_pruning_checkpoint()?
.unwrap_or_else(|| Checkpoint {
epoch: Epoch::new(0),
root: Hash256::zero(),
});
let old_finalized_slot = old_finalized_checkpoint
.epoch
.start_slot(E::slots_per_epoch());
let new_finalized_slot = new_finalized_checkpoint
.epoch
.start_slot(E::slots_per_epoch());
let new_finalized_block_hash = new_finalized_checkpoint.root.into();
// The finalized state must be for the epoch boundary slot, not the slot of the finalized
// block.
if new_finalized_state.slot() != new_finalized_slot {
return Err(PruningError::IncorrectFinalizedState {
state_slot: new_finalized_state.slot(),
new_finalized_slot,
}
.into());
}
debug!(
log,
"Starting database pruning";
"old_finalized_epoch" => old_finalized_checkpoint.epoch,
"new_finalized_epoch" => new_finalized_checkpoint.epoch,
);
// For each slot between the new finalized checkpoint and the old finalized checkpoint,
// collect the beacon block root and state root of the canonical chain.
let newly_finalized_chain: HashMap<Slot, (SignedBeaconBlockHash, BeaconStateHash)> =
std::iter::once(Ok((
new_finalized_slot,
(new_finalized_block_hash, new_finalized_state_hash),
)))
.chain(
RootsIterator::new(store.clone(), new_finalized_state).map(|res| {
res.map(|(block_root, state_root, slot)| {
(slot, (block_root.into(), state_root.into()))
})
}),
)
.take_while(|res| {
res.as_ref()
.map_or(true, |(slot, _)| *slot >= old_finalized_slot)
})
.collect::<Result<_, _>>()?;
// We don't know which blocks are shared among abandoned chains, so we buffer and delete
// everything in one fell swoop.
let mut abandoned_blocks: HashSet<SignedBeaconBlockHash> = HashSet::new();
let mut abandoned_states: HashSet<(Slot, BeaconStateHash)> = HashSet::new();
let mut abandoned_heads: HashSet<Hash256> = HashSet::new();
let heads = head_tracker.heads();
debug!(
log,
"Extra pruning information";
"old_finalized_root" => format!("{:?}", old_finalized_checkpoint.root),
"new_finalized_root" => format!("{:?}", new_finalized_checkpoint.root),
"head_count" => heads.len(),
);
for (head_hash, head_slot) in heads {
// Load head block. If it fails with a decode error, it's likely a reverted block,
// so delete it from the head tracker but leave it and its states in the database
// This is suboptimal as it wastes disk space, but it's difficult to fix. A re-sync
// can be used to reclaim the space.
let head_state_root = match store.get_block(&head_hash) {
Ok(Some(block)) => block.state_root(),
Ok(None) => {
return Err(BeaconStateError::MissingBeaconBlock(head_hash.into()).into())
}
Err(Error::SszDecodeError(e)) => {
warn!(
log,
"Forgetting invalid head block";
"block_root" => ?head_hash,
"error" => ?e,
);
abandoned_heads.insert(head_hash);
continue;
}
Err(e) => return Err(e.into()),
};
let mut potentially_abandoned_head = Some(head_hash);
let mut potentially_abandoned_blocks = vec![];
// Iterate backwards from this head, staging blocks and states for deletion.
let iter = std::iter::once(Ok((head_hash, head_state_root, head_slot)))
.chain(RootsIterator::from_block(store.clone(), head_hash)?);
for maybe_tuple in iter {
let (block_root, state_root, slot) = maybe_tuple?;
let block_root = SignedBeaconBlockHash::from(block_root);
let state_root = BeaconStateHash::from(state_root);
match newly_finalized_chain.get(&slot) {
// If there's no information about a slot on the finalized chain, then
// it should be because it's ahead of the new finalized slot. Stage
// the fork's block and state for possible deletion.
None => {
if slot > new_finalized_slot {
potentially_abandoned_blocks.push((
slot,
Some(block_root),
Some(state_root),
));
} else if slot >= old_finalized_slot {
return Err(PruningError::MissingInfoForCanonicalChain { slot }.into());
} else {
// We must assume here any candidate chains include the old finalized
// checkpoint, i.e. there aren't any forks starting at a block that is a
// strict ancestor of old_finalized_checkpoint.
warn!(
log,
"Found a chain that should already have been pruned";
"head_block_root" => format!("{:?}", head_hash),
"head_slot" => head_slot,
);
potentially_abandoned_head.take();
break;
}
}
Some((finalized_block_root, finalized_state_root)) => {
// This fork descends from a newly finalized block, we can stop.
if block_root == *finalized_block_root {
// Sanity check: if the slot and block root match, then the
// state roots should match too.
if state_root != *finalized_state_root {
return Err(PruningError::UnexpectedUnequalStateRoots.into());
}
// If the fork descends from the whole finalized chain,
// do not prune it. Otherwise continue to delete all
// of the blocks and states that have been staged for
// deletion so far.
if slot == new_finalized_slot {
potentially_abandoned_blocks.clear();
potentially_abandoned_head.take();
}
// If there are skipped slots on the fork to be pruned, then
// we will have just staged the common block for deletion.
// Unstage it.
else {
for (_, block_root, _) in
potentially_abandoned_blocks.iter_mut().rev()
{
if block_root.as_ref() == Some(finalized_block_root) {
*block_root = None;
} else {
break;
}
}
}
break;
} else {
if state_root == *finalized_state_root {
return Err(PruningError::UnexpectedEqualStateRoots.into());
}
potentially_abandoned_blocks.push((
slot,
Some(block_root),
Some(state_root),
));
}
}
}
}
if let Some(abandoned_head) = potentially_abandoned_head {
debug!(
log,
"Pruning head";
"head_block_root" => format!("{:?}", abandoned_head),
"head_slot" => head_slot,
);
abandoned_heads.insert(abandoned_head);
abandoned_blocks.extend(
potentially_abandoned_blocks
.iter()
.filter_map(|(_, maybe_block_hash, _)| *maybe_block_hash),
);
abandoned_states.extend(potentially_abandoned_blocks.iter().filter_map(
|(slot, _, maybe_state_hash)| maybe_state_hash.map(|sr| (*slot, sr)),
));
}
}
// Update the head tracker before the database, so that we maintain the invariant
// that a block present in the head tracker is present in the database.
// See https://github.com/sigp/lighthouse/issues/1557
let mut head_tracker_lock = head_tracker.0.write();
// Check that all the heads to be deleted are still present. The absence of any
// head indicates a race, that will likely resolve itself, so we defer pruning until
// later.
for head_hash in &abandoned_heads {
if !head_tracker_lock.contains_key(head_hash) {
return Ok(PruningOutcome::DeferredConcurrentMutation);
}
}
// Then remove them for real.
for head_hash in abandoned_heads {
head_tracker_lock.remove(&head_hash);
}
let batch: Vec<StoreOp<E>> = abandoned_blocks
.into_iter()
.map(Into::into)
.map(StoreOp::DeleteBlock)
.chain(
abandoned_states
.into_iter()
.map(|(slot, state_hash)| StoreOp::DeleteState(state_hash.into(), Some(slot))),
)
.collect();
let mut kv_batch = store.convert_to_kv_batch(&batch)?;
// Persist the head in case the process is killed or crashes here. This prevents
// the head tracker reverting after our mutation above.
let persisted_head = PersistedBeaconChain {
_canonical_head_block_root: DUMMY_CANONICAL_HEAD_BLOCK_ROOT,
genesis_block_root,
ssz_head_tracker: SszHeadTracker::from_map(&*head_tracker_lock),
};
drop(head_tracker_lock);
kv_batch.push(persisted_head.as_kv_store_op(BEACON_CHAIN_DB_KEY));
// Persist the new finalized checkpoint as the pruning checkpoint.
kv_batch.push(store.pruning_checkpoint_store_op(new_finalized_checkpoint));
store.hot_db.do_atomically(kv_batch)?;
debug!(log, "Database pruning complete");
Ok(PruningOutcome::Successful {
old_finalized_checkpoint,
})
}
/// Compact the database if it has been more than `COMPACTION_PERIOD_SECONDS` since it
/// was last compacted.
pub fn run_compaction(
db: Arc<HotColdDB<E, Hot, Cold>>,
old_finalized_epoch: Epoch,
new_finalized_epoch: Epoch,
log: &Logger,
) -> Result<(), Error> {
if !db.compact_on_prune() {
return Ok(());
}
let last_compaction_timestamp = db
.load_compaction_timestamp()?
.unwrap_or_else(|| Duration::from_secs(0));
let start_time = SystemTime::now()
.duration_since(UNIX_EPOCH)
.unwrap_or(last_compaction_timestamp);
let seconds_since_last_compaction = start_time
.checked_sub(last_compaction_timestamp)
.as_ref()
.map_or(0, Duration::as_secs);
if seconds_since_last_compaction > MAX_COMPACTION_PERIOD_SECONDS
|| (new_finalized_epoch - old_finalized_epoch > COMPACTION_FINALITY_DISTANCE
&& seconds_since_last_compaction > MIN_COMPACTION_PERIOD_SECONDS)
{
info!(
log,
"Starting database compaction";
"old_finalized_epoch" => old_finalized_epoch,
"new_finalized_epoch" => new_finalized_epoch,
);
db.compact()?;
let finish_time = SystemTime::now()
.duration_since(UNIX_EPOCH)
.unwrap_or(start_time);
db.store_compaction_timestamp(finish_time)?;
info!(log, "Database compaction complete");
}
Ok(())
}
}