#[cfg(any(feature = "rest-client", feature = "rpc-client"))]
mod utils;
+use crate::poll::{Poll, ValidatedBlockHeader};
+
use bitcoin::blockdata::block::{Block, BlockHeader};
use bitcoin::hash_types::BlockHash;
use bitcoin::util::uint::Uint256;
/// of equivalent weight.
pub chainwork: Uint256,
}
+
+/// Adaptor used for notifying when blocks have been connected or disconnected from the chain.
+///
+/// Used when needing to replay chain data upon startup or as new chain events occur.
+pub trait ChainListener {
+ /// Notifies the listener that a block was added at the given height.
+ fn block_connected(&mut self, block: &Block, height: u32);
+
+ /// Notifies the listener that a block was removed at the given height.
+ fn block_disconnected(&mut self, header: &BlockHeader, height: u32);
+}
+
+/// The `Cache` trait defines behavior for managing a block header cache, where block headers are
+/// keyed by block hash.
+///
+/// Used by [`ChainNotifier`] to store headers along the best chain, which is important for ensuring
+/// that blocks can be disconnected if they are no longer accessible from a block source (e.g., if
+/// the block source does not store stale forks indefinitely).
+///
+/// Implementations may define how long to retain headers such that it's unlikely they will ever be
+/// needed to disconnect a block. In cases where block sources provide access to headers on stale
+/// forks reliably, caches may be entirely unnecessary.
+///
+/// [`ChainNotifier`]: struct.ChainNotifier.html
+pub trait Cache {
+ /// Retrieves the block header keyed by the given block hash.
+ fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader>;
+
+ /// Called when a block has been connected to the best chain to ensure it is available to be
+ /// disconnected later if needed.
+ fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader);
+
+ /// Called when a block has been disconnected from the best chain. Once disconnected, a block's
+ /// header is no longer needed and thus can be removed.
+ fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader>;
+}
+
+/// Unbounded cache of block headers keyed by block hash.
+pub type UnboundedCache = std::collections::HashMap<BlockHash, ValidatedBlockHeader>;
+
+impl Cache for UnboundedCache {
+ fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader> {
+ self.get(block_hash)
+ }
+
+ fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader) {
+ self.insert(block_hash, block_header);
+ }
+
+ fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader> {
+ self.remove(block_hash)
+ }
+}
+
+/// Notifies [listeners] of blocks that have been connected or disconnected from the chain.
+///
+/// [listeners]: trait.ChainListener.html
+struct ChainNotifier<C: Cache> {
+ /// Cache for looking up headers before fetching from a block source.
+ header_cache: C,
+}
+
+/// Changes made to the chain between subsequent polls that transformed it from having one chain tip
+/// to another.
+///
+/// Blocks are given in height-descending order. Therefore, blocks are first disconnected in order
+/// before new blocks are connected in reverse order.
+struct ChainDifference {
+ /// Blocks that were disconnected from the chain since the last poll.
+ disconnected_blocks: Vec<ValidatedBlockHeader>,
+
+ /// Blocks that were connected to the chain since the last poll.
+ connected_blocks: Vec<ValidatedBlockHeader>,
+}
+
+impl<C: Cache> ChainNotifier<C> {
+ /// Finds the fork point between `new_header` and `old_header`, disconnecting blocks from
+ /// `old_header` to get to that point and then connecting blocks until `new_header`.
+ ///
+ /// Validates headers along the transition path, but doesn't fetch blocks until the chain is
+ /// disconnected to the fork point. Thus, this may return an `Err` that includes where the tip
+ /// ended up which may not be `new_header`. Note that the returned `Err` contains `Some` header
+ /// if and only if the transition from `old_header` to `new_header` is valid.
+ async fn synchronize_listener<L: ChainListener, P: Poll>(
+ &mut self,
+ new_header: ValidatedBlockHeader,
+ old_header: &ValidatedBlockHeader,
+ chain_poller: &mut P,
+ chain_listener: &mut L,
+ ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
+ let mut difference = self.find_difference(new_header, old_header, chain_poller).await
+ .map_err(|e| (e, None))?;
+
+ let mut new_tip = *old_header;
+ for header in difference.disconnected_blocks.drain(..) {
+ if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) {
+ assert_eq!(cached_header, header);
+ }
+ chain_listener.block_disconnected(&header.header, header.height);
+ new_tip = header;
+ }
+
+ for header in difference.connected_blocks.drain(..).rev() {
+ let block = chain_poller
+ .fetch_block(&header).await
+ .or_else(|e| Err((e, Some(new_tip))))?;
+ debug_assert_eq!(block.block_hash, header.block_hash);
+
+ self.header_cache.block_connected(header.block_hash, header);
+ chain_listener.block_connected(&block, header.height);
+ new_tip = header;
+ }
+
+ Ok(())
+ }
+
+ /// Returns the changes needed to produce the chain with `current_header` as its tip from the
+ /// chain with `prev_header` as its tip.
+ ///
+ /// Walks backwards from `current_header` and `prev_header`, finding the common ancestor.
+ async fn find_difference<P: Poll>(
+ &self,
+ current_header: ValidatedBlockHeader,
+ prev_header: &ValidatedBlockHeader,
+ chain_poller: &mut P,
+ ) -> BlockSourceResult<ChainDifference> {
+ let mut disconnected_blocks = Vec::new();
+ let mut connected_blocks = Vec::new();
+ let mut current = current_header;
+ let mut previous = *prev_header;
+ loop {
+ // Found the common ancestor.
+ if current.block_hash == previous.block_hash {
+ break;
+ }
+
+ // Walk back the chain, finding blocks needed to connect and disconnect. Only walk back
+ // the header with the greater height, or both if equal heights.
+ let current_height = current.height;
+ let previous_height = previous.height;
+ if current_height <= previous_height {
+ disconnected_blocks.push(previous);
+ previous = self.look_up_previous_header(chain_poller, &previous).await?;
+ }
+ if current_height >= previous_height {
+ connected_blocks.push(current);
+ current = self.look_up_previous_header(chain_poller, ¤t).await?;
+ }
+ }
+
+ Ok(ChainDifference { disconnected_blocks, connected_blocks })
+ }
+
+ /// Returns the previous header for the given header, either by looking it up in the cache or
+ /// fetching it if not found.
+ async fn look_up_previous_header<P: Poll>(
+ &self,
+ chain_poller: &mut P,
+ header: &ValidatedBlockHeader,
+ ) -> BlockSourceResult<ValidatedBlockHeader> {
+ match self.header_cache.look_up(&header.header.prev_blockhash) {
+ Some(prev_header) => Ok(*prev_header),
+ None => chain_poller.look_up_previous_header(header).await,
+ }
+ }
+}
+
+#[cfg(test)]
+mod chain_notifier_tests {
+ use crate::test_utils::{Blockchain, MockChainListener};
+ use super::*;
+
+ use bitcoin::network::constants::Network;
+
+ #[tokio::test]
+ async fn sync_from_same_chain() {
+ let mut chain = Blockchain::default().with_height(3);
+
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+ let mut listener = MockChainListener::new()
+ .expect_block_connected(*chain.at_height(2))
+ .expect_block_connected(*new_tip);
+ let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=1) };
+ let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((e, _)) => panic!("Unexpected error: {:?}", e),
+ Ok(_) => {},
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_different_chains() {
+ let mut test_chain = Blockchain::with_network(Network::Testnet).with_height(1);
+ let main_chain = Blockchain::with_network(Network::Bitcoin).with_height(1);
+
+ let new_tip = test_chain.tip();
+ let old_tip = main_chain.tip();
+ let mut listener = MockChainListener::new();
+ let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=1) };
+ let mut poller = poll::ChainPoller::new(&mut test_chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((e, _)) => {
+ assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
+ assert_eq!(e.into_inner().as_ref().to_string(), "genesis block reached");
+ },
+ Ok(_) => panic!("Expected error"),
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_equal_length_fork() {
+ let main_chain = Blockchain::default().with_height(2);
+ let mut fork_chain = main_chain.fork_at_height(1);
+
+ let new_tip = fork_chain.tip();
+ let old_tip = main_chain.tip();
+ let mut listener = MockChainListener::new()
+ .expect_block_disconnected(*old_tip)
+ .expect_block_connected(*new_tip);
+ let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=2) };
+ let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((e, _)) => panic!("Unexpected error: {:?}", e),
+ Ok(_) => {},
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_shorter_fork() {
+ let main_chain = Blockchain::default().with_height(3);
+ let mut fork_chain = main_chain.fork_at_height(1);
+ fork_chain.disconnect_tip();
+
+ let new_tip = fork_chain.tip();
+ let old_tip = main_chain.tip();
+ let mut listener = MockChainListener::new()
+ .expect_block_disconnected(*old_tip)
+ .expect_block_disconnected(*main_chain.at_height(2))
+ .expect_block_connected(*new_tip);
+ let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=3) };
+ let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((e, _)) => panic!("Unexpected error: {:?}", e),
+ Ok(_) => {},
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_longer_fork() {
+ let mut main_chain = Blockchain::default().with_height(3);
+ let mut fork_chain = main_chain.fork_at_height(1);
+ main_chain.disconnect_tip();
+
+ let new_tip = fork_chain.tip();
+ let old_tip = main_chain.tip();
+ let mut listener = MockChainListener::new()
+ .expect_block_disconnected(*old_tip)
+ .expect_block_connected(*fork_chain.at_height(2))
+ .expect_block_connected(*new_tip);
+ let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=2) };
+ let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((e, _)) => panic!("Unexpected error: {:?}", e),
+ Ok(_) => {},
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_chain_without_headers() {
+ let mut chain = Blockchain::default().with_height(3).without_headers();
+
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+ let mut listener = MockChainListener::new();
+ let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=1) };
+ let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((_, tip)) => assert_eq!(tip, None),
+ Ok(_) => panic!("Expected error"),
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_chain_without_any_new_blocks() {
+ let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
+
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+ let mut listener = MockChainListener::new();
+ let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=3) };
+ let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((_, tip)) => assert_eq!(tip, Some(old_tip)),
+ Ok(_) => panic!("Expected error"),
+ }
+ }
+
+ #[tokio::test]
+ async fn sync_from_chain_without_some_new_blocks() {
+ let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
+
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+ let mut listener = MockChainListener::new()
+ .expect_block_connected(*chain.at_height(2));
+ let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=3) };
+ let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ Err((_, tip)) => assert_eq!(tip, Some(chain.at_height(2))),
+ Ok(_) => panic!("Expected error"),
+ }
+ }
+}
projects / rust-lightning / blobdiff