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Advanced error handling for syncing (#819)

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* Initial block processing thread design

* Correct compilation issues

* Increase logging and request from all given peers

* Patch peer request bug

* Adds fork choice to block processing

* Adds logging for bug isolation

* Patch syncing for chains with skip-slots

* Bump block processing error logs

* Improve logging for attestation processing

* Randomize peer selection during sync

* Resuming chains restarts from local finalized slot

* Downgrades Arc batches to Rc batches

* Add clippy fixes

* Add advanced error handling for invalid/malicious batches

* Downgrade Rc<Batch> to Option<Batch> to pass processed batches to chains

* Squash edge case rpc and syncing bugs

* Process empty batches which could end chains

* Removes last_processed_id concept to account for ending skip-slot batches

* Add logging for chain purges

* Adds retries to re-request batch logging

* Remove bug finding log

* Add reviewers suggestions

* Revert to master modifications

* Line wrapping

* Revert to master
This commit is contained in:
Age Manning
2020-01-23 19:25:13 +11:00
committed by GitHub
parent 23a35c3767
commit 81b028b805
5 changed files with 195 additions and 93 deletions
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237
beacon_node/network/src/sync/range_sync/chain.rs
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@@ -28,7 +28,7 @@ const BATCH_BUFFER_SIZE: u8 = 5;
/// Invalid batches are attempted to be re-downloaded from other peers. If they cannot be processed
/// after `INVALID_BATCH_LOOKUP_ATTEMPTS` times, the chain is considered faulty and all peers will
/// be downvoted.
const _INVALID_BATCH_LOOKUP_ATTEMPTS: u8 = 3;
const INVALID_BATCH_LOOKUP_ATTEMPTS: u8 = 3;
/// A return type for functions that act on a `Chain` which informs the caller whether the chain
/// has been completed and should be removed or to be kept if further processing is
@@ -71,9 +71,6 @@ pub struct SyncingChain<T: BeaconChainTypes> {
/// The next batch id that needs to be processed.
to_be_processed_id: BatchId,
/// The last batch id that was processed.
last_processed_id: BatchId,
/// The current state of the chain.
pub state: ChainSyncingState,
@@ -122,7 +119,6 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
peer_pool,
to_be_downloaded_id: BatchId(1),
to_be_processed_id: BatchId(1),
last_processed_id: BatchId(0),
state: ChainSyncingState::Stopped,
current_processing_id: None,
sync_send,
@@ -131,6 +127,12 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
}
}
/// Returns the latest slot number that has been processed.
fn current_processed_slot(&self) -> Slot {
self.start_slot
.saturating_add(self.to_be_processed_id.saturating_sub(1u64) * BLOCKS_PER_BATCH)
}
/// A batch of blocks has been received. This function gets run on all chains and should
/// return Some if the request id matches a pending request on this chain, or None if it does
/// not.
@@ -221,16 +223,14 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
}
// Check if there is a batch ready to be processed
while !self.completed_batches.is_empty()
if !self.completed_batches.is_empty()
&& self.completed_batches[0].id == self.to_be_processed_id
{
let batch = self.completed_batches.remove(0);
if batch.downloaded_blocks.is_empty() {
// The batch was empty, consider this processed and move to the next batch
self.processed_batches.push(batch);
*self.to_be_processed_id += 1;
continue;
}
// Note: We now send empty batches to the processor in order to trigger the block
// processor result callback. This is done, because an empty batch could end a chain
// and the logic for removing chains and checking completion is in the callback.
// send the batch to the batch processor thread
return self.process_batch(batch);
@@ -283,27 +283,56 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
let res = match result {
BatchProcessResult::Success => {
*self.to_be_processed_id += 1;
// This variable accounts for skip slots and batches that were not actually
// processed due to having no blocks.
self.last_processed_id = batch.id;
// Remove any validate batches awaiting validation.
// Only batches that have blocks are processed here, therefore all previous batches
// have been correct.
let last_processed_id = self.last_processed_id;
self.processed_batches
.retain(|batch| batch.id.0 >= last_processed_id.0);
// If the processed batch was not empty, we can validate previous invalidated
// blocks
if !batch.downloaded_blocks.is_empty() {
// Remove any batches awaiting validation.
//
// All blocks in processed_batches should be prior batches. As the current
// batch has been processed with blocks in it, all previous batches are valid.
//
// If a previous batch has been validated and it had been re-processed, downvote
// the original peer.
while !self.processed_batches.is_empty() {
let processed_batch = self.processed_batches.remove(0);
if *processed_batch.id >= *batch.id {
crit!(self.log, "A processed batch had a greater id than the current process id";
"processed_id" => *processed_batch.id,
"current_id" => *batch.id);
}
// add the current batch to processed batches to be verified in the future. We are
if let Some(prev_hash) = processed_batch.original_hash {
// The validated batch has been re-processed
if prev_hash != processed_batch.hash() {
// The re-downloaded version was different
if processed_batch.current_peer != processed_batch.original_peer {
// A new peer sent the correct batch, the previous peer did not
// downvote the original peer
//
// If the same peer corrected it's mistake, we allow it.... for
// now.
debug!(self.log, "Re-processed batch validated. Downvoting original peer";
"batch_id" => *processed_batch.id,
"original_peer" => format!("{}",processed_batch.original_peer),
"new_peer" => format!("{}", processed_batch.current_peer));
network.downvote_peer(processed_batch.original_peer);
}
}
}
}
}
// Add the current batch to processed batches to be verified in the future. We are
// only uncertain about this batch, if it has not returned all blocks.
if batch.downloaded_blocks.len() < BLOCKS_PER_BATCH as usize {
if batch.downloaded_blocks.last().map(|block| block.slot)
!= Some(batch.end_slot.saturating_sub(1u64))
{
self.processed_batches.push(batch);
}
// check if the chain has completed syncing
if self.start_slot + *self.last_processed_id * BLOCKS_PER_BATCH
>= self.target_head_slot
{
if self.current_processed_slot() >= self.target_head_slot {
// chain is completed
ProcessingResult::RemoveChain
} else {
@@ -320,19 +349,104 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
}
}
BatchProcessResult::Failed => {
// batch processing failed
// this could be because this batch is invalid, or a previous invalidated batch
warn!(self.log, "Batch processing failed"; "id" => *batch.id, "peer" => format!("{}", batch.current_peer));
// The batch processing failed
// This could be because this batch is invalid, or a previous invalidated batch
// is invalid. We need to find out which and downvote the peer that has sent us
// an invalid batch.
// firstly remove any validated batches
self.handle_invalid_batch(network, batch)
// check that we have no exceeded the re-process retry counter
if batch.reprocess_retries > INVALID_BATCH_LOOKUP_ATTEMPTS {
// if a batch has exceeded the invalid batch lookup attempts limit, it means
// that it is likely all peers in this chain are are sending invalid batches
// repeatedly and are either malicious or faulty. We drop the chain and
// downvote all peers.
warn!(self.log, "Batch failed to download. Dropping chain and downvoting peers"; "id"=> *batch.id);
for peer_id in self.peer_pool.drain() {
network.downvote_peer(peer_id);
}
ProcessingResult::RemoveChain
} else {
// Handle this invalid batch, that is within the re-process retries limit.
self.handle_invalid_batch(network, batch);
ProcessingResult::KeepChain
}
}
};
Some(res)
}
/// An invalid batch has been received that could not be processed.
///
/// These events occur when a peer as successfully responded with blocks, but the blocks we
/// have received are incorrect or invalid. This indicates the peer has not performed as
/// intended and can result in downvoting a peer.
// TODO: Batches could have been partially downloaded due to RPC size-limit restrictions. We
// need to add logic for partial batch downloads. Potentially, if another peer returns the same
// batch, we try a partial download.
fn handle_invalid_batch(&mut self, network: &mut SyncNetworkContext, batch: Batch<T::EthSpec>) {
// The current batch could not be processed, indicating either the current or previous
// batches are invalid
// The previous batch could be incomplete due to the block sizes being too large to fit in
// a single RPC request or there could be consecutive empty batches which are not supposed
// to be there
// The current (sub-optimal) strategy is to simply re-request all batches that could
// potentially be faulty. If a batch returns a different result than the original and
// results in successful processing, we downvote the original peer that sent us the batch.
// If all batches return the same result, we try this process INVALID_BATCH_LOOKUP_ATTEMPTS
// times before considering the entire chain invalid and downvoting all peers.
// Find any pre-processed batches awaiting validation
while !self.processed_batches.is_empty() {
let past_batch = self.processed_batches.remove(0);
*self.to_be_processed_id = std::cmp::min(*self.to_be_processed_id, *past_batch.id);
self.reprocess_batch(network, past_batch);
}
// re-process the current batch
self.reprocess_batch(network, batch);
}
/// This re-downloads and marks the batch as being re-processed.
///
/// If the re-downloaded batch is different to the original and can be processed, the original
/// peer will be downvoted.
fn reprocess_batch(&mut self, network: &mut SyncNetworkContext, mut batch: Batch<T::EthSpec>) {
// marks the batch as attempting to be reprocessed by hashing the downloaded blocks
batch.original_hash = Some(batch.hash());
// remove previously downloaded blocks
batch.downloaded_blocks.clear();
// increment the re-process counter
batch.reprocess_retries += 1;
// attempt to find another peer to download the batch from (this potentially doubles up
// requests on a single peer)
let current_peer = &batch.current_peer;
let new_peer = self
.peer_pool
.iter()
.find(|peer| *peer != current_peer)
.unwrap_or_else(|| current_peer);
batch.current_peer = new_peer.clone();
debug!(self.log, "Re-requesting batch";
"start_slot" => batch.start_slot,
"end_slot" => batch.end_slot,
"id" => *batch.id,
"peer" => format!("{}", batch.current_peer),
"head_root"=> format!("{}", batch.head_root),
"retries" => batch.retries,
"re-processes" => batch.reprocess_retries);
self.send_batch(network, batch);
}
pub fn stop_syncing(&mut self) {
self.state = ChainSyncingState::Stopped;
}
@@ -351,17 +465,11 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
// to start from this point and re-index all subsequent batches starting from one
// (effectively creating a new chain).
if local_finalized_slot.as_u64()
> self
.start_slot
.as_u64()
.saturating_add(*self.last_processed_id * BLOCKS_PER_BATCH)
{
if local_finalized_slot > self.current_processed_slot() {
debug!(self.log, "Updating chain's progress";
"prev_completed_slot" => self.start_slot + *self.last_processed_id*BLOCKS_PER_BATCH,
"prev_completed_slot" => self.current_processed_slot(),
"new_completed_slot" => local_finalized_slot.as_u64());
// Re-index batches
*self.last_processed_id = 0;
*self.to_be_downloaded_id = 1;
*self.to_be_processed_id = 1;
@@ -386,7 +494,7 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
self.peer_pool.insert(peer_id.clone());
// do not request blocks if the chain is not syncing
if let ChainSyncingState::Stopped = self.state {
debug!(self.log, "Peer added to a non-syncing chain"; "peer_id" => format!("{:?}", peer_id));
debug!(self.log, "Peer added to a non-syncing chain"; "peer_id" => format!("{}", peer_id));
return;
}
@@ -465,47 +573,8 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
}
}
/// An invalid batch has been received that could not be processed.
///
/// These events occur when a peer as successfully responded with blocks, but the blocks we
/// have received are incorrect or invalid. This indicates the peer has not performed as
/// intended and can result in downvoting a peer.
fn handle_invalid_batch(
&mut self,
network: &mut SyncNetworkContext,
_batch: Batch<T::EthSpec>,
) -> ProcessingResult {
// The current batch could not be processed, indicating either the current or previous
// batches are invalid
// The previous batch could be incomplete due to the block sizes being too large to fit in
// a single RPC request or there could be consecutive empty batches which are not supposed
// to be there
// The current (sub-optimal) strategy is to simply re-request all batches that could
// potentially be faulty. If a batch returns a different result than the original and
// results in successful processing, we downvote the original peer that sent us the batch.
// If all batches return the same result, we try this process INVALID_BATCH_LOOKUP_ATTEMPTS
// times before considering the entire chain invalid and downvoting all peers.
// Firstly, check if there are any past batches that could be invalid.
if !self.processed_batches.is_empty() {
// try and re-download this batch from other peers
}
//TODO: Implement this logic
// Currently just fail the chain, and drop all associated peers, removing them from the
// peer pool, to prevent re-status
for peer_id in self.peer_pool.drain() {
network.downvote_peer(peer_id);
}
ProcessingResult::RemoveChain
}
/// Attempts to request the next required batches from the peer pool if the chain is syncing.
/// It will exhaust the peer pool and left over batches until the batch buffer is reached or
/// all peers are exhausted.
/// Attempts to request the next required batches from the peer pool if the chain is syncing. It will exhaust the peer
/// pool and left over batches until the batch buffer is reached or all peers are exhausted.
fn request_batches(&mut self, network: &mut SyncNetworkContext) {
if let ChainSyncingState::Syncing = self.state {
while self.send_range_request(network) {}
@@ -518,7 +587,12 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
// find the next pending batch and request it from the peer
if let Some(peer_id) = self.get_next_peer() {
if let Some(batch) = self.get_next_batch(peer_id) {
debug!(self.log, "Requesting batch"; "start_slot" => batch.start_slot, "end_slot" => batch.end_slot, "id" => *batch.id, "peer" => format!("{:?}", batch.current_peer), "head_root"=> format!("{}", batch.head_root));
debug!(self.log, "Requesting batch";
"start_slot" => batch.start_slot,
"end_slot" => batch.end_slot,
"id" => *batch.id,
"peer" => format!("{}", batch.current_peer),
"head_root"=> format!("{}", batch.head_root));
// send the batch
self.send_batch(network, batch);
return true;
@@ -531,6 +605,7 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
///
/// This is used to create the next request.
fn get_next_peer(&self) -> Option<PeerId> {
// TODO: Optimize this by combining with above two functions.
// randomize the peers for load balancing
let mut rng = rand::thread_rng();
let mut peers = self.peer_pool.iter().collect::<Vec<_>>();