]> git.bitcoin.ninja Git - ldk-sample/commitdiff
Try to sweep `SpendableOutputs` regularly, and in bulk
authorMatt Corallo <git@bluematt.me>
Sun, 7 May 2023 18:12:20 +0000 (18:12 +0000)
committerMatt Corallo <git@bluematt.me>
Wed, 17 May 2023 13:30:20 +0000 (13:30 +0000)
Rather than trying to sweep `SpendableOutputs` every time we see
one, try to sweep them in bulk once an hour. Then, try to sweep
them repeatedly every hour forever, even after they're claimed.

Fixes #102.

src/main.rs
src/sweep.rs [new file with mode: 0644]

index 0722ff5c58f21938c0a540b1dbccdf39ef5e9dc0..5a3389e83430852276244d548f48e19b131a60c9 100644 (file)
@@ -4,18 +4,19 @@ mod cli;
 mod convert;
 mod disk;
 mod hex_utils;
+mod sweep;
 
 use crate::bitcoind_client::BitcoindClient;
 use crate::disk::FilesystemLogger;
 use bitcoin::blockdata::transaction::Transaction;
 use bitcoin::consensus::encode;
 use bitcoin::network::constants::Network;
-use bitcoin::secp256k1::Secp256k1;
 use bitcoin::BlockHash;
 use bitcoin_bech32::WitnessProgram;
 use lightning::chain;
-use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
-use lightning::chain::keysinterface::{EntropySource, InMemorySigner, KeysManager};
+use lightning::chain::keysinterface::{
+       EntropySource, InMemorySigner, KeysManager, SpendableOutputDescriptor,
+};
 use lightning::chain::{chainmonitor, ChannelMonitorUpdateStatus};
 use lightning::chain::{Filter, Watch};
 use lightning::events::{Event, PaymentFailureReason, PaymentPurpose};
@@ -30,6 +31,7 @@ use lightning::routing::gossip;
 use lightning::routing::gossip::{NodeId, P2PGossipSync};
 use lightning::routing::router::DefaultRouter;
 use lightning::util::config::UserConfig;
+use lightning::util::persist::KVStorePersister;
 use lightning::util::ser::ReadableArgs;
 use lightning_background_processor::{process_events_async, GossipSync};
 use lightning_block_sync::init;
@@ -52,6 +54,8 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, SystemTime};
 
+pub(crate) const PENDING_SPENDABLE_OUTPUT_DIR: &'static str = "pending_spendable_outputs";
+
 pub(crate) enum HTLCStatus {
        Pending,
        Succeeded,
@@ -107,7 +111,7 @@ async fn handle_ldk_events(
        channel_manager: &Arc<ChannelManager>, bitcoind_client: &BitcoindClient,
        network_graph: &NetworkGraph, keys_manager: &KeysManager,
        inbound_payments: &PaymentInfoStorage, outbound_payments: &PaymentInfoStorage,
-       network: Network, event: Event,
+       persister: &Arc<FilesystemPersister>, network: Network, event: Event,
 ) {
        match event {
                Event::FundingGenerationReady {
@@ -331,20 +335,23 @@ async fn handle_ldk_events(
                        });
                }
                Event::SpendableOutputs { outputs } => {
-                       let destination_address = bitcoind_client.get_new_address().await;
-                       let output_descriptors = &outputs.iter().map(|a| a).collect::<Vec<_>>();
-                       let tx_feerate =
-                               bitcoind_client.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
-                       let spending_tx = keys_manager
-                               .spend_spendable_outputs(
-                                       output_descriptors,
-                                       Vec::new(),
-                                       destination_address.script_pubkey(),
-                                       tx_feerate,
-                                       &Secp256k1::new(),
-                               )
-                               .unwrap();
-                       bitcoind_client.broadcast_transaction(&spending_tx);
+                       // SpendableOutputDescriptors, of which outputs is a vec of, are critical to keep track
+                       // of! While a `StaticOutput` descriptor is just an output to a static, well-known key,
+                       // other descriptors are not currently ever regenerated for you by LDK. Once we return
+                       // from this method, the descriptor will be gone, and you may lose track of some funds.
+                       //
+                       // Here we simply persist them to disk, with a background task running which will try
+                       // to spend them regularly (possibly duplicatively/RBF'ing them). These can just be
+                       // treated as normal funds where possible - they are only spendable by us and there is
+                       // no rush to claim them.
+                       for output in outputs {
+                               let key = hex_utils::hex_str(&keys_manager.get_secure_random_bytes());
+                               // Note that if the type here changes our read code needs to change as well.
+                               let output: SpendableOutputDescriptor = output;
+                               persister
+                                       .persist(&format!("{}/{}", PENDING_SPENDABLE_OUTPUT_DIR, key), &output)
+                                       .unwrap();
+                       }
                }
                Event::ChannelPending { channel_id, counterparty_node_id, .. } => {
                        println!(
@@ -693,6 +700,7 @@ async fn start_ldk() {
        let keys_manager_event_listener = Arc::clone(&keys_manager);
        let inbound_payments_event_listener = Arc::clone(&inbound_payments);
        let outbound_payments_event_listener = Arc::clone(&outbound_payments);
+       let persister_event_listener = Arc::clone(&persister);
        let network = args.network;
        let event_handler = move |event: Event| {
                let channel_manager_event_listener = Arc::clone(&channel_manager_event_listener);
@@ -701,6 +709,7 @@ async fn start_ldk() {
                let keys_manager_event_listener = Arc::clone(&keys_manager_event_listener);
                let inbound_payments_event_listener = Arc::clone(&inbound_payments_event_listener);
                let outbound_payments_event_listener = Arc::clone(&outbound_payments_event_listener);
+               let persister_event_listener = Arc::clone(&persister_event_listener);
                async move {
                        handle_ldk_events(
                                &channel_manager_event_listener,
@@ -709,6 +718,7 @@ async fn start_ldk() {
                                &keys_manager_event_listener,
                                &inbound_payments_event_listener,
                                &outbound_payments_event_listener,
+                               &persister_event_listener,
                                network,
                                event,
                        )
@@ -722,7 +732,7 @@ async fn start_ldk() {
        // Step 20: Background Processing
        let (bp_exit, bp_exit_check) = tokio::sync::watch::channel(());
        let background_processor = tokio::spawn(process_events_async(
-               persister,
+               Arc::clone(&persister),
                event_handler,
                chain_monitor.clone(),
                channel_manager.clone(),
@@ -794,7 +804,8 @@ async fn start_ldk() {
                loop {
                        interval.tick().await;
                        // Don't bother trying to announce if we don't have any public channls, though our
-                       // peers should drop such an announcement anyway.
+                       // peers should drop such an announcement anyway. Note that announcement may not
+                       // propagate until we have a channel with 6+ confirmations.
                        if chan_man.list_channels().iter().any(|chan| chan.is_public) {
                                peer_man.broadcast_node_announcement(
                                        [0; 3],
@@ -805,6 +816,14 @@ async fn start_ldk() {
                }
        });
 
+       tokio::spawn(sweep::periodic_sweep(
+               ldk_data_dir.clone(),
+               Arc::clone(&keys_manager),
+               Arc::clone(&logger),
+               Arc::clone(&persister),
+               Arc::clone(&bitcoind_client),
+       ));
+
        // Start the CLI.
        cli::poll_for_user_input(
                Arc::clone(&peer_manager),
@@ -814,7 +833,7 @@ async fn start_ldk() {
                Arc::clone(&onion_messenger),
                inbound_payments,
                outbound_payments,
-               ldk_data_dir.clone(),
+               ldk_data_dir,
                network,
                Arc::clone(&logger),
        )
diff --git a/src/sweep.rs b/src/sweep.rs
new file mode 100644 (file)
index 0000000..2a168a7
--- /dev/null
@@ -0,0 +1,127 @@
+use std::io::{Read, Seek, SeekFrom};
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::time::Duration;
+use std::{fs, io};
+
+use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
+use lightning::chain::keysinterface::{EntropySource, KeysManager, SpendableOutputDescriptor};
+use lightning::util::logger::Logger;
+use lightning::util::persist::KVStorePersister;
+use lightning::util::ser::{Readable, WithoutLength};
+
+use bitcoin::secp256k1::Secp256k1;
+
+use crate::hex_utils;
+use crate::BitcoindClient;
+use crate::FilesystemLogger;
+use crate::FilesystemPersister;
+
+/// If we have any pending claimable outputs, we should slowly sweep them to our Bitcoin Core
+/// wallet. We technically don't need to do this - they're ours to spend when we want and can just
+/// use them to build new transactions instead, but we cannot feed them direclty into Bitcoin
+/// Core's wallet so we have to sweep.
+///
+/// Note that this is unececssary for [`SpendableOutputDescriptor::StaticOutput`]s, which *do* have
+/// an associated secret key we could simply import into Bitcoin Core's wallet, but for consistency
+/// we don't do that here either.
+pub(crate) async fn periodic_sweep(
+       ldk_data_dir: String, keys_manager: Arc<KeysManager>, logger: Arc<FilesystemLogger>,
+       persister: Arc<FilesystemPersister>, bitcoind_client: Arc<BitcoindClient>,
+) {
+       // Regularly claim outputs which are exclusively spendable by us and send them to Bitcoin Core.
+       // Note that if you more tightly integrate your wallet with LDK you may not need to do this -
+       // these outputs can just be treated as normal outputs during coin selection.
+       let pending_spendables_dir =
+               format!("{}/{}", crate::PENDING_SPENDABLE_OUTPUT_DIR, ldk_data_dir);
+       let processing_spendables_dir = format!("{}/processing_spendable_outputs", ldk_data_dir);
+       let spendables_dir = format!("{}/spendable_outputs", ldk_data_dir);
+
+       // We batch together claims of all spendable outputs generated each day, however only after
+       // batching any claims of spendable outputs which were generated prior to restart. On a mobile
+       // device we likely won't ever be online for more than a minute, so we have to ensure we sweep
+       // any pending claims on startup, but for an always-online node you may wish to sweep even less
+       // frequently than this (or move the interval await to the top of the loop)!
+       //
+       // There is no particular rush here, we just have to ensure funds are availably by the time we
+       // need to send funds.
+       let mut interval = tokio::time::interval(Duration::from_secs(60 * 60 * 24));
+
+       loop {
+               interval.tick().await; // Note that the first tick completes immediately
+               if let Ok(dir_iter) = fs::read_dir(&pending_spendables_dir) {
+                       // Move any spendable descriptors from pending folder so that we don't have any
+                       // races with new files being added.
+                       for file_res in dir_iter {
+                               let file = file_res.unwrap();
+                               // Only move a file if its a 32-byte-hex'd filename, otherwise it might be a
+                               // temporary file.
+                               if file.file_name().len() == 64 {
+                                       fs::create_dir_all(&processing_spendables_dir).unwrap();
+                                       let mut holding_path = PathBuf::new();
+                                       holding_path.push(&processing_spendables_dir);
+                                       holding_path.push(&file.file_name());
+                                       fs::rename(file.path(), holding_path).unwrap();
+                               }
+                       }
+                       // Now concatenate all the pending files we moved into one file in the
+                       // `spendable_outputs` directory and drop the processing directory.
+                       let mut outputs = Vec::new();
+                       if let Ok(processing_iter) = fs::read_dir(&processing_spendables_dir) {
+                               for file_res in processing_iter {
+                                       outputs.append(&mut fs::read(file_res.unwrap().path()).unwrap());
+                               }
+                       }
+                       if !outputs.is_empty() {
+                               let key = hex_utils::hex_str(&keys_manager.get_secure_random_bytes());
+                               persister
+                                       .persist(&format!("spendable_outputs/{}", key), &WithoutLength(&outputs))
+                                       .unwrap();
+                               fs::remove_dir_all(&processing_spendables_dir).unwrap();
+                       }
+               }
+               // Iterate over all the sets of spendable outputs in `spendables_dir` and try to claim
+               // them.
+               // Note that here we try to claim each set of spendable outputs over and over again
+               // forever, even long after its been claimed. While this isn't an issue per se, in practice
+               // you may wish to track when the claiming transaction has confirmed and remove the
+               // spendable outputs set. You may also wish to merge groups of unspent spendable outputs to
+               // combine batches.
+               if let Ok(dir_iter) = fs::read_dir(&spendables_dir) {
+                       for file_res in dir_iter {
+                               let mut outputs: Vec<SpendableOutputDescriptor> = Vec::new();
+                               let mut file = fs::File::open(file_res.unwrap().path()).unwrap();
+                               loop {
+                                       // Check if there are any bytes left to read, and if so read a descriptor.
+                                       match file.read_exact(&mut [0; 1]) {
+                                               Ok(_) => {
+                                                       file.seek(SeekFrom::Current(-1)).unwrap();
+                                               }
+                                               Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => break,
+                                               Err(e) => Err(e).unwrap(),
+                                       }
+                                       outputs.push(Readable::read(&mut file).unwrap());
+                               }
+                               let destination_address = bitcoind_client.get_new_address().await;
+                               let output_descriptors = &outputs.iter().map(|a| a).collect::<Vec<_>>();
+                               let tx_feerate =
+                                       bitcoind_client.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
+                               if let Ok(spending_tx) = keys_manager.spend_spendable_outputs(
+                                       output_descriptors,
+                                       Vec::new(),
+                                       destination_address.script_pubkey(),
+                                       tx_feerate,
+                                       &Secp256k1::new(),
+                               ) {
+                                       // Note that, most likely, we've already sweeped this set of outputs
+                                       // and they're already confirmed on-chain, so this broadcast will fail.
+                                       bitcoind_client.broadcast_transaction(&spending_tx);
+                               } else {
+                                       lightning::log_error!(
+                                               logger,
+                                               "Failed to sweep spendable outputs! This may indicate the outputs are dust. Will try again in a day.");
+                               }
+                       }
+               }
+       }
+}