From 6b12dd207f31fcf80faca1a649118ad28dee00bf Mon Sep 17 00:00:00 2001 From: Jeffrey Czyz Date: Tue, 20 Apr 2021 10:24:08 -0700 Subject: [PATCH] Define chain::Confirm trait Define a separate trait akin to chain::Listen for notifying when transactions have been confirmed on chain or unconfirmed during a chain reorganization. Whereas chain::Listen is used for block-oriented chain sources, chain::Confirm is used for chain sources supplying data for activity related to transactions and outputs registered via chain::Filter. --- lightning/src/chain/mod.rs | 91 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 87 insertions(+), 4 deletions(-) diff --git a/lightning/src/chain/mod.rs b/lightning/src/chain/mod.rs index 18c7fd55d..7d25a0660 100644 --- a/lightning/src/chain/mod.rs +++ b/lightning/src/chain/mod.rs @@ -16,7 +16,7 @@ use bitcoin::hash_types::{BlockHash, Txid}; use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, MonitorEvent}; use chain::keysinterface::Sign; -use chain::transaction::OutPoint; +use chain::transaction::{OutPoint, TransactionData}; pub mod chaininterface; pub mod chainmonitor; @@ -45,10 +45,13 @@ pub trait Access: Send + Sync { fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result; } -/// The `Listen` trait is used to be notified of when blocks have been connected or disconnected -/// from the chain. +/// The `Listen` trait is used to notify when blocks have been connected or disconnected from the +/// chain. /// -/// Useful when needing to replay chain data upon startup or as new chain events occur. +/// Useful when needing to replay chain data upon startup or as new chain events occur. Clients +/// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`]. +/// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers +/// when needed. pub trait Listen { /// Notifies the listener that a block was added at the given height. fn block_connected(&self, block: &Block, height: u32); @@ -57,6 +60,86 @@ pub trait Listen { fn block_disconnected(&self, header: &BlockHeader, height: u32); } +/// The `Confirm` trait is used to notify when transactions have been confirmed on chain or +/// unconfirmed during a chain reorganization. +/// +/// Clients sourcing chain data using a transaction-oriented API should prefer this interface over +/// [`Listen`]. For instance, an Electrum client may implement [`Filter`] by subscribing to activity +/// related to registered transactions and outputs. Upon notification, it would pass along the +/// matching transactions using this interface. +/// +/// # Use +/// +/// The intended use is as follows: +/// - Call [`transactions_confirmed`] to process any on-chain activity of interest. +/// - Call [`transaction_unconfirmed`] to process any transaction returned by [`get_relevant_txids`] +/// that has been reorganized out of the chain. +/// - Call [`best_block_updated`] whenever a new chain tip becomes available. +/// +/// # Order +/// +/// Clients must call these methods in chain order. Specifically: +/// - Transactions confirmed in a block must be given before transactions confirmed in a later +/// block. +/// - Dependent transactions within the same block must be given in topological order, possibly in +/// separate calls. +/// - Unconfirmed transactions must be given after the original confirmations and before any +/// reconfirmation. +/// +/// See individual method documentation for further details. +/// +/// [`transactions_confirmed`]: Self::transactions_confirmed +/// [`transaction_unconfirmed`]: Self::transaction_unconfirmed +/// [`best_block_updated`]: Self::best_block_updated +/// [`get_relevant_txids`]: Self::get_relevant_txids +pub trait Confirm { + /// Processes transactions confirmed in a block with a given header and height. + /// + /// Should be called for any transactions registered by [`Filter::register_tx`] or any + /// transactions spending an output registered by [`Filter::register_output`]. Such transactions + /// appearing in the same block do not need to be included in the same call; instead, multiple + /// calls with additional transactions may be made so long as they are made in [chain order]. + /// + /// May be called before or after [`best_block_updated`] for the corresponding block. However, + /// in the event of a chain reorganization, it must not be called with a `header` that is no + /// longer in the chain as of the last call to [`best_block_updated`]. + /// + /// [chain order]: Self#order + /// [`best_block_updated`]: Self::best_block_updated + fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32); + + /// Processes a transaction that is no longer confirmed as result of a chain reorganization. + /// + /// Should be called for any transaction returned by [`get_relevant_txids`] if it has been + /// reorganized out of the best chain. Once called, the given transaction should not be returned + /// by [`get_relevant_txids`] unless it has been reconfirmed via [`transactions_confirmed`]. + /// + /// [`get_relevant_txids`]: Self::get_relevant_txids + /// [`transactions_confirmed`]: Self::transactions_confirmed + fn transaction_unconfirmed(&self, txid: &Txid); + + /// Processes an update to the best header connected at the given height. + /// + /// Should be called when a new header is available but may be skipped for intermediary blocks + /// if they become available at the same time. + fn best_block_updated(&self, header: &BlockHeader, height: u32); + + /// Returns transactions that should be monitored for reorganization out of the chain. + /// + /// Should include any transactions passed to [`transactions_confirmed`] that have insufficient + /// confirmations to be safe from a chain reorganization. Should not include any transactions + /// passed to [`transaction_unconfirmed`] unless later reconfirmed. + /// + /// May be called to determine the subset of transactions that must still be monitored for + /// reorganization. Will be idempotent between calls but may change as a result of calls to the + /// other interface methods. Thus, this is useful to determine which transactions may need to be + /// given to [`transaction_unconfirmed`]. + /// + /// [`transactions_confirmed`]: Self::transactions_confirmed + /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed + fn get_relevant_txids(&self) -> Vec; +} + /// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as /// blocks are connected and disconnected. /// -- 2.39.5