X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning-block-sync%2Fsrc%2Flib.rs;h=321dd57e4713a638c86ba4fc033a89473d0129af;hb=fc77c57c3c6e165d26cb5c1f5d1afee0ecd02589;hp=9228e11f68e7600b0ed735b8a83a095d0633920e;hpb=b1ecfe705d77b1338c7df5e208d76eb6743f270c;p=rust-lightning diff --git a/lightning-block-sync/src/lib.rs b/lightning-block-sync/src/lib.rs index 9228e11f..321dd57e 100644 --- a/lightning-block-sync/src/lib.rs +++ b/lightning-block-sync/src/lib.rs @@ -1,5 +1,9 @@ //! A lightweight client for keeping in sync with chain activity. //! +//! Defines an [`SpvClient`] utility for polling one or more block sources for the best chain tip. +//! It is used to notify listeners of blocks connected or disconnected since the last poll. Useful +//! for keeping a Lightning node in sync with the chain. +//! //! Defines a [`BlockSource`] trait, which is an asynchronous interface for retrieving block headers //! and data. //! @@ -8,12 +12,17 @@ //! //! Both features support either blocking I/O using `std::net::TcpStream` or, with feature `tokio`, //! non-blocking I/O using `tokio::net::TcpStream` from inside a Tokio runtime. -//! -//! [`BlockSource`]: trait.BlockSource.html + +#![deny(broken_intra_doc_links)] +#![deny(missing_docs)] +#![deny(unsafe_code)] + +#![cfg_attr(docsrs, feature(doc_auto_cfg))] #[cfg(any(feature = "rest-client", feature = "rpc-client"))] pub mod http; +pub mod init; pub mod poll; #[cfg(feature = "rest-client")] @@ -31,13 +40,17 @@ mod test_utils; #[cfg(any(feature = "rest-client", feature = "rpc-client"))] mod utils; -use crate::poll::{Poll, ValidatedBlockHeader}; +use crate::poll::{ChainTip, Poll, ValidatedBlockHeader}; use bitcoin::blockdata::block::{Block, BlockHeader}; use bitcoin::hash_types::BlockHash; use bitcoin::util::uint::Uint256; +use lightning::chain; +use lightning::chain::Listen; + use std::future::Future; +use std::ops::Deref; use std::pin::Pin; /// Abstract type for retrieving block headers and data. @@ -48,25 +61,28 @@ pub trait BlockSource : Sync + Send { /// /// Implementations that cannot find headers based on the hash should return a `Transient` error /// when `height_hint` is `None`. - fn get_header<'a>(&'a mut self, header_hash: &'a BlockHash, height_hint: Option) -> AsyncBlockSourceResult<'a, BlockHeaderData>; + fn get_header<'a>(&'a self, header_hash: &'a BlockHash, height_hint: Option) -> AsyncBlockSourceResult<'a, BlockHeaderData>; /// Returns the block for a given hash. A headers-only block source should return a `Transient` /// error. - fn get_block<'a>(&'a mut self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block>; + fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block>; - // TODO: Phrase in terms of `Poll` once added. - /// Returns the hash of the best block and, optionally, its height. When polling a block source, - /// the height is passed to `get_header` to allow for a more efficient lookup. - fn get_best_block<'a>(&'a mut self) -> AsyncBlockSourceResult<(BlockHash, Option)>; + /// Returns the hash of the best block and, optionally, its height. + /// + /// When polling a block source, [`Poll`] implementations may pass the height to [`get_header`] + /// to allow for a more efficient lookup. + /// + /// [`get_header`]: Self::get_header + fn get_best_block<'a>(&'a self) -> AsyncBlockSourceResult<(BlockHash, Option)>; } /// Result type for `BlockSource` requests. -type BlockSourceResult = Result; +pub type BlockSourceResult = Result; // TODO: Replace with BlockSourceResult once `async` trait functions are supported. For details, // see: https://areweasyncyet.rs. /// Result type for asynchronous `BlockSource` requests. -type AsyncBlockSourceResult<'a, T> = Pin> + 'a + Send>>; +pub type AsyncBlockSourceResult<'a, T> = Pin> + 'a + Send>>; /// Error type for `BlockSource` requests. /// @@ -133,15 +149,23 @@ pub struct BlockHeaderData { pub chainwork: Uint256, } -/// Adaptor used for notifying when blocks have been connected or disconnected from the chain. +/// A lightweight client for keeping a listener in sync with the chain, allowing for Simplified +/// Payment Verification (SPV). /// -/// 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 client is parameterized by a chain poller which is responsible for polling one or more block +/// sources for the best chain tip. During this process it detects any chain forks, determines which +/// constitutes the best chain, and updates the listener accordingly with any blocks that were +/// connected or disconnected since the last poll. +/// +/// Block headers for the best chain are maintained in the parameterized cache, allowing for a +/// custom cache eviction policy. This offers flexibility to those sensitive to resource usage. +/// Hence, there is a trade-off between a lower memory footprint and potentially increased network +/// I/O as headers are re-fetched during fork detection. +pub struct SpvClient<'a, P: Poll, C: Cache, L: Deref> +where L::Target: chain::Listen { + chain_tip: ValidatedBlockHeader, + chain_poller: P, + chain_notifier: ChainNotifier<'a, C, L>, } /// The `Cache` trait defines behavior for managing a block header cache, where block headers are @@ -154,8 +178,6 @@ pub trait ChainListener { /// 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>; @@ -186,12 +208,78 @@ impl Cache for UnboundedCache { } } +impl<'a, P: Poll, C: Cache, L: Deref> SpvClient<'a, P, C, L> where L::Target: chain::Listen { + /// Creates a new SPV client using `chain_tip` as the best known chain tip. + /// + /// Subsequent calls to [`poll_best_tip`] will poll for the best chain tip using the given chain + /// poller, which may be configured with one or more block sources to query. At least one block + /// source must provide headers back from the best chain tip to its common ancestor with + /// `chain_tip`. + /// * `header_cache` is used to look up and store headers on the best chain + /// * `chain_listener` is notified of any blocks connected or disconnected + /// + /// [`poll_best_tip`]: SpvClient::poll_best_tip + pub fn new( + chain_tip: ValidatedBlockHeader, + chain_poller: P, + header_cache: &'a mut C, + chain_listener: L, + ) -> Self { + let chain_notifier = ChainNotifier { header_cache, chain_listener }; + Self { chain_tip, chain_poller, chain_notifier } + } + + /// Polls for the best tip and updates the chain listener with any connected or disconnected + /// blocks accordingly. + /// + /// Returns the best polled chain tip relative to the previous best known tip and whether any + /// blocks were indeed connected or disconnected. + pub async fn poll_best_tip(&mut self) -> BlockSourceResult<(ChainTip, bool)> { + let chain_tip = self.chain_poller.poll_chain_tip(self.chain_tip).await?; + let blocks_connected = match chain_tip { + ChainTip::Common => false, + ChainTip::Better(chain_tip) => { + debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash); + debug_assert!(chain_tip.chainwork > self.chain_tip.chainwork); + self.update_chain_tip(chain_tip).await + }, + ChainTip::Worse(chain_tip) => { + debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash); + debug_assert!(chain_tip.chainwork <= self.chain_tip.chainwork); + false + }, + }; + Ok((chain_tip, blocks_connected)) + } + + /// Updates the chain tip, syncing the chain listener with any connected or disconnected + /// blocks. Returns whether there were any such blocks. + async fn update_chain_tip(&mut self, best_chain_tip: ValidatedBlockHeader) -> bool { + match self.chain_notifier.synchronize_listener( + best_chain_tip, &self.chain_tip, &mut self.chain_poller).await + { + Ok(_) => { + self.chain_tip = best_chain_tip; + true + }, + Err((_, Some(chain_tip))) if chain_tip.block_hash != self.chain_tip.block_hash => { + self.chain_tip = chain_tip; + true + }, + Err(_) => false, + } + } +} + /// Notifies [listeners] of blocks that have been connected or disconnected from the chain. /// -/// [listeners]: trait.ChainListener.html -struct ChainNotifier { +/// [listeners]: lightning::chain::Listen +pub struct ChainNotifier<'a, C: Cache, L: Deref> where L::Target: chain::Listen { /// Cache for looking up headers before fetching from a block source. - header_cache: C, + header_cache: &'a mut C, + + /// Listener that will be notified of connected or disconnected blocks. + chain_listener: L, } /// Changes made to the chain between subsequent polls that transformed it from having one chain tip @@ -200,6 +288,11 @@ struct ChainNotifier { /// Blocks are given in height-descending order. Therefore, blocks are first disconnected in order /// before new blocks are connected in reverse order. struct ChainDifference { + /// The most recent ancestor common between the chain tips. + /// + /// If there are any disconnected blocks, this is where the chain forked. + common_ancestor: ValidatedBlockHeader, + /// Blocks that were disconnected from the chain since the last poll. disconnected_blocks: Vec, @@ -207,45 +300,28 @@ struct ChainDifference { connected_blocks: Vec, } -impl ChainNotifier { - /// 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`. +impl<'a, C: Cache, L: Deref> ChainNotifier<'a, C, L> where L::Target: chain::Listen { + /// Finds the first common ancestor 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( + async fn synchronize_listener( &mut self, new_header: ValidatedBlockHeader, old_header: &ValidatedBlockHeader, chain_poller: &mut P, - chain_listener: &mut L, ) -> Result<(), (BlockSourceError, Option)> { - let mut difference = self.find_difference(new_header, old_header, chain_poller).await + let 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(()) + self.disconnect_blocks(difference.disconnected_blocks); + self.connect_blocks( + difference.common_ancestor, + difference.connected_blocks, + chain_poller, + ).await } /// Returns the changes needed to produce the chain with `current_header` as its tip from the @@ -282,7 +358,8 @@ impl ChainNotifier { } } - Ok(ChainDifference { disconnected_blocks, connected_blocks }) + let common_ancestor = current; + Ok(ChainDifference { common_ancestor, disconnected_blocks, connected_blocks }) } /// Returns the previous header for the given header, either by looking it up in the cache or @@ -297,6 +374,164 @@ impl ChainNotifier { None => chain_poller.look_up_previous_header(header).await, } } + + /// Notifies the chain listeners of disconnected blocks. + fn disconnect_blocks(&mut self, mut disconnected_blocks: Vec) { + for header in disconnected_blocks.drain(..) { + if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) { + assert_eq!(cached_header, header); + } + self.chain_listener.block_disconnected(&header.header, header.height); + } + } + + /// Notifies the chain listeners of connected blocks. + async fn connect_blocks( + &mut self, + mut new_tip: ValidatedBlockHeader, + mut connected_blocks: Vec, + chain_poller: &mut P, + ) -> Result<(), (BlockSourceError, Option)> { + for header in 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); + self.chain_listener.block_connected(&block, header.height); + new_tip = header; + } + + Ok(()) + } +} + +#[cfg(test)] +mod spv_client_tests { + use crate::test_utils::{Blockchain, NullChainListener}; + use super::*; + + use bitcoin::network::constants::Network; + + #[tokio::test] + async fn poll_from_chain_without_headers() { + let mut chain = Blockchain::default().with_height(3).without_headers(); + let best_tip = chain.at_height(1); + + let poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => { + assert_eq!(e.kind(), BlockSourceErrorKind::Persistent); + assert_eq!(e.into_inner().as_ref().to_string(), "header not found"); + }, + Ok(_) => panic!("Expected error"), + } + assert_eq!(client.chain_tip, best_tip); + } + + #[tokio::test] + async fn poll_from_chain_with_common_tip() { + let mut chain = Blockchain::default().with_height(3); + let common_tip = chain.tip(); + + let poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(common_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => panic!("Unexpected error: {:?}", e), + Ok((chain_tip, blocks_connected)) => { + assert_eq!(chain_tip, ChainTip::Common); + assert!(!blocks_connected); + }, + } + assert_eq!(client.chain_tip, common_tip); + } + + #[tokio::test] + async fn poll_from_chain_with_better_tip() { + let mut chain = Blockchain::default().with_height(3); + let new_tip = chain.tip(); + let old_tip = chain.at_height(1); + + let poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => panic!("Unexpected error: {:?}", e), + Ok((chain_tip, blocks_connected)) => { + assert_eq!(chain_tip, ChainTip::Better(new_tip)); + assert!(blocks_connected); + }, + } + assert_eq!(client.chain_tip, new_tip); + } + + #[tokio::test] + async fn poll_from_chain_with_better_tip_and_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 poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => panic!("Unexpected error: {:?}", e), + Ok((chain_tip, blocks_connected)) => { + assert_eq!(chain_tip, ChainTip::Better(new_tip)); + assert!(!blocks_connected); + }, + } + assert_eq!(client.chain_tip, old_tip); + } + + #[tokio::test] + async fn poll_from_chain_with_better_tip_and_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 poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => panic!("Unexpected error: {:?}", e), + Ok((chain_tip, blocks_connected)) => { + assert_eq!(chain_tip, ChainTip::Better(new_tip)); + assert!(blocks_connected); + }, + } + assert_eq!(client.chain_tip, chain.at_height(2)); + } + + #[tokio::test] + async fn poll_from_chain_with_worse_tip() { + let mut chain = Blockchain::default().with_height(3); + let best_tip = chain.tip(); + chain.disconnect_tip(); + let worse_tip = chain.tip(); + + let poller = poll::ChainPoller::new(&mut chain, Network::Testnet); + let mut cache = UnboundedCache::new(); + let mut listener = NullChainListener {}; + let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener); + match client.poll_best_tip().await { + Err(e) => panic!("Unexpected error: {:?}", e), + Ok((chain_tip, blocks_connected)) => { + assert_eq!(chain_tip, ChainTip::Worse(worse_tip)); + assert!(!blocks_connected); + }, + } + assert_eq!(client.chain_tip, best_tip); + } } #[cfg(test)] @@ -312,12 +547,15 @@ mod chain_notifier_tests { let new_tip = chain.tip(); let old_tip = chain.at_height(1); - let mut listener = MockChainListener::new() + let chain_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 notifier = ChainNotifier { + header_cache: &mut chain.header_cache(0..=1), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((e, _)) => panic!("Unexpected error: {:?}", e), Ok(_) => {}, } @@ -330,10 +568,13 @@ mod chain_notifier_tests { 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 chain_listener = &MockChainListener::new(); + let mut notifier = ChainNotifier { + header_cache: &mut main_chain.header_cache(0..=1), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut test_chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((e, _)) => { assert_eq!(e.kind(), BlockSourceErrorKind::Persistent); assert_eq!(e.into_inner().as_ref().to_string(), "genesis block reached"); @@ -349,12 +590,15 @@ mod chain_notifier_tests { let new_tip = fork_chain.tip(); let old_tip = main_chain.tip(); - let mut listener = MockChainListener::new() + let chain_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 notifier = ChainNotifier { + header_cache: &mut main_chain.header_cache(0..=2), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((e, _)) => panic!("Unexpected error: {:?}", e), Ok(_) => {}, } @@ -368,13 +612,16 @@ mod chain_notifier_tests { let new_tip = fork_chain.tip(); let old_tip = main_chain.tip(); - let mut listener = MockChainListener::new() + let chain_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 notifier = ChainNotifier { + header_cache: &mut main_chain.header_cache(0..=3), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((e, _)) => panic!("Unexpected error: {:?}", e), Ok(_) => {}, } @@ -388,13 +635,16 @@ mod chain_notifier_tests { let new_tip = fork_chain.tip(); let old_tip = main_chain.tip(); - let mut listener = MockChainListener::new() + let chain_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 notifier = ChainNotifier { + header_cache: &mut main_chain.header_cache(0..=2), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((e, _)) => panic!("Unexpected error: {:?}", e), Ok(_) => {}, } @@ -406,10 +656,13 @@ mod chain_notifier_tests { 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 chain_listener = &MockChainListener::new(); + let mut notifier = ChainNotifier { + header_cache: &mut chain.header_cache(0..=1), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((_, tip)) => assert_eq!(tip, None), Ok(_) => panic!("Expected error"), } @@ -421,10 +674,13 @@ mod chain_notifier_tests { 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 chain_listener = &MockChainListener::new(); + let mut notifier = ChainNotifier { + header_cache: &mut chain.header_cache(0..=3), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((_, tip)) => assert_eq!(tip, Some(old_tip)), Ok(_) => panic!("Expected error"), } @@ -436,11 +692,14 @@ mod chain_notifier_tests { let new_tip = chain.tip(); let old_tip = chain.at_height(1); - let mut listener = MockChainListener::new() + let chain_listener = &MockChainListener::new() .expect_block_connected(*chain.at_height(2)); - let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=3) }; + let mut notifier = ChainNotifier { + header_cache: &mut chain.header_cache(0..=3), + chain_listener, + }; let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet); - match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await { + match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await { Err((_, tip)) => assert_eq!(tip, Some(chain.at_height(2))), Ok(_) => panic!("Expected error"), }