_ Git - rust-lightning/blob - lightning-background-processor/src/lib.rs

   1 //! Utilities that take care of tasks that (1) need to happen periodically to keep Rust-Lightning
   2 //! running properly, and (2) either can or should be run in the background. See docs for
   3 //! [`BackgroundProcessor`] for more details on the nitty-gritty.
   4
   5 #![deny(broken_intra_doc_links)]
   6 #![deny(missing_docs)]
   7 #![deny(unsafe_code)]
   8
   9 #[macro_use] extern crate lightning;
  10
  11 use lightning::chain;
  12 use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
  13 use lightning::chain::chainmonitor::ChainMonitor;
  14 use lightning::chain::channelmonitor;
  15 use lightning::chain::keysinterface::{Sign, KeysInterface};
  16 use lightning::ln::channelmanager::ChannelManager;
  17 use lightning::ln::msgs::{ChannelMessageHandler, RoutingMessageHandler};
  18 use lightning::ln::peer_handler::{PeerManager, SocketDescriptor};
  19 use lightning::util::events::{EventHandler, EventsProvider};
  20 use lightning::util::logger::Logger;
  21 use std::sync::Arc;
  22 use std::sync::atomic::{AtomicBool, Ordering};
  23 use std::thread;
  24 use std::thread::JoinHandle;
  25 use std::time::{Duration, Instant};
  26 use std::ops::Deref;
  27
  28 /// BackgroundProcessor takes care of tasks that (1) need to happen periodically to keep
  29 /// Rust-Lightning running properly, and (2) either can or should be run in the background. Its
  30 /// responsibilities are:
  31 /// * Monitoring whether the ChannelManager needs to be re-persisted to disk, and if so,
  32 ///   writing it to disk/backups by invoking the callback given to it at startup.
  33 ///   ChannelManager persistence should be done in the background.
  34 /// * Calling `ChannelManager::timer_tick_occurred()` and
  35 ///   `PeerManager::timer_tick_occurred()` every minute (can be done in the
  36 ///   background).
  37 ///
  38 /// Note that if ChannelManager persistence fails and the persisted manager becomes out-of-date,
  39 /// then there is a risk of channels force-closing on startup when the manager realizes it's
  40 /// outdated. However, as long as `ChannelMonitor` backups are sound, no funds besides those used
  41 /// for unilateral chain closure fees are at risk.
  42 pub struct BackgroundProcessor {
  43         stop_thread: Arc<AtomicBool>,
  44         /// May be used to retrieve and handle the error if `BackgroundProcessor`'s thread
  45         /// exits due to an error while persisting.
  46         pub thread_handle: JoinHandle<Result<(), std::io::Error>>,
  47 }
  48
  49 #[cfg(not(test))]
  50 const FRESHNESS_TIMER: u64 = 60;
  51 #[cfg(test)]
  52 const FRESHNESS_TIMER: u64 = 1;
  53
  54 /// Trait which handles persisting a [`ChannelManager`] to disk.
  55 ///
  56 /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
  57 pub trait ChannelManagerPersister<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
  58 where
  59         M::Target: 'static + chain::Watch<Signer>,
  60         T::Target: 'static + BroadcasterInterface,
  61         K::Target: 'static + KeysInterface<Signer = Signer>,
  62         F::Target: 'static + FeeEstimator,
  63         L::Target: 'static + Logger,
  64 {
  65         /// Persist the given [`ChannelManager`] to disk, returning an error if persistence failed
  66         /// (which will cause the [`BackgroundProcessor`] which called this method to exit.
  67         ///
  68         /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
  69         fn persist_manager(&self, channel_manager: &ChannelManager<Signer, M, T, K, F, L>) -> Result<(), std::io::Error>;
  70 }
  71
  72 impl<Fun, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
  73 ChannelManagerPersister<Signer, M, T, K, F, L> for Fun where
  74         M::Target: 'static + chain::Watch<Signer>,
  75         T::Target: 'static + BroadcasterInterface,
  76         K::Target: 'static + KeysInterface<Signer = Signer>,
  77         F::Target: 'static + FeeEstimator,
  78         L::Target: 'static + Logger,
  79         Fun: Fn(&ChannelManager<Signer, M, T, K, F, L>) -> Result<(), std::io::Error>,
  80 {
  81         fn persist_manager(&self, channel_manager: &ChannelManager<Signer, M, T, K, F, L>) -> Result<(), std::io::Error> {
  82                 self(channel_manager)
  83         }
  84 }
  85
  86 impl BackgroundProcessor {
  87         /// Start a background thread that takes care of responsibilities enumerated in the top-level
  88         /// documentation.
  89         ///
  90         /// If `persist_manager` returns an error, then this thread will return said error (and
  91         /// `start()` will need to be called again to restart the `BackgroundProcessor`). Users should
  92         /// wait on [`thread_handle`]'s `join()` method to be able to tell if and when an error is
  93         /// returned, or implement `persist_manager` such that an error is never returned to the
  94         /// `BackgroundProcessor`
  95         ///
  96         /// `persist_manager` is responsible for writing out the [`ChannelManager`] to disk, and/or
  97         /// uploading to one or more backup services. See [`ChannelManager::write`] for writing out a
  98         /// [`ChannelManager`]. See [`FilesystemPersister::persist_manager`] for Rust-Lightning's
  99         /// provided implementation.
 100         ///
 101         /// [`thread_handle`]: BackgroundProcessor::thread_handle
 102         /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
 103         /// [`ChannelManager::write`]: lightning::ln::channelmanager::ChannelManager#impl-Writeable
 104         /// [`FilesystemPersister::persist_manager`]: lightning_persister::FilesystemPersister::persist_manager
 105         pub fn start<
 106                 Signer: 'static + Sign,
 107                 CF: 'static + Deref + Send + Sync,
 108                 CW: 'static + Deref + Send + Sync,
 109                 T: 'static + Deref + Send + Sync,
 110                 K: 'static + Deref + Send + Sync,
 111                 F: 'static + Deref + Send + Sync,
 112                 L: 'static + Deref + Send + Sync,
 113                 P: 'static + Deref + Send + Sync,
 114                 Descriptor: 'static + SocketDescriptor + Send + Sync,
 115                 CMH: 'static + Deref + Send + Sync,
 116                 RMH: 'static + Deref + Send + Sync,
 117                 EH: 'static + EventHandler + Send + Sync,
 118                 CMP: 'static + Send + ChannelManagerPersister<Signer, CW, T, K, F, L>,
 119                 M: 'static + Deref<Target = ChainMonitor<Signer, CF, T, F, L, P>> + Send + Sync,
 120                 CM: 'static + Deref<Target = ChannelManager<Signer, CW, T, K, F, L>> + Send + Sync,
 121                 PM: 'static + Deref<Target = PeerManager<Descriptor, CMH, RMH, L>> + Send + Sync,
 122         >
 123         (persister: CMP, event_handler: EH, chain_monitor: M, channel_manager: CM, peer_manager: PM, logger: L) -> Self
 124         where
 125                 CF::Target: 'static + chain::Filter,
 126                 CW::Target: 'static + chain::Watch<Signer>,
 127                 T::Target: 'static + BroadcasterInterface,
 128                 K::Target: 'static + KeysInterface<Signer = Signer>,
 129                 F::Target: 'static + FeeEstimator,
 130                 L::Target: 'static + Logger,
 131                 P::Target: 'static + channelmonitor::Persist<Signer>,
 132                 CMH::Target: 'static + ChannelMessageHandler,
 133                 RMH::Target: 'static + RoutingMessageHandler,
 134         {
 135                 let stop_thread = Arc::new(AtomicBool::new(false));
 136                 let stop_thread_clone = stop_thread.clone();
 137                 let handle = thread::spawn(move || -> Result<(), std::io::Error> {
 138                         let mut current_time = Instant::now();
 139                         loop {
 140                                 peer_manager.process_events();
 141                                 channel_manager.process_pending_events(&event_handler);
 142                                 chain_monitor.process_pending_events(&event_handler);
 143                                 let updates_available =
 144                                         channel_manager.await_persistable_update_timeout(Duration::from_millis(100));
 145                                 if updates_available {
 146                                         persister.persist_manager(&*channel_manager)?;
 147                                 }
 148                                 // Exit the loop if the background processor was requested to stop.
 149                                 if stop_thread.load(Ordering::Acquire) == true {
 150                                         log_trace!(logger, "Terminating background processor.");
 151                                         return Ok(());
 152                                 }
 153                                 if current_time.elapsed().as_secs() > FRESHNESS_TIMER {
 154                                         log_trace!(logger, "Calling ChannelManager's and PeerManager's timer_tick_occurred");
 155                                         channel_manager.timer_tick_occurred();
 156                                         peer_manager.timer_tick_occurred();
 157                                         current_time = Instant::now();
 158                                 }
 159                         }
 160                 });
 161                 Self { stop_thread: stop_thread_clone, thread_handle: handle }
 162         }
 163
 164         /// Stop `BackgroundProcessor`'s thread.
 165         pub fn stop(self) -> Result<(), std::io::Error> {
 166                 self.stop_thread.store(true, Ordering::Release);
 167                 self.thread_handle.join().unwrap()
 168         }
 169 }
 170
 171 #[cfg(test)]
 172 mod tests {
 173         use bitcoin::blockdata::block::BlockHeader;
 174         use bitcoin::blockdata::constants::genesis_block;
 175         use bitcoin::blockdata::transaction::{Transaction, TxOut};
 176         use bitcoin::network::constants::Network;
 177         use lightning::chain::Confirm;
 178         use lightning::chain::chainmonitor;
 179         use lightning::chain::channelmonitor::ANTI_REORG_DELAY;
 180         use lightning::chain::keysinterface::{InMemorySigner, KeysInterface, KeysManager};
 181         use lightning::chain::transaction::OutPoint;
 182         use lightning::get_event_msg;
 183         use lightning::ln::channelmanager::{BREAKDOWN_TIMEOUT, BestBlock, ChainParameters, ChannelManager, SimpleArcChannelManager};
 184         use lightning::ln::features::InitFeatures;
 185         use lightning::ln::msgs::ChannelMessageHandler;
 186         use lightning::ln::peer_handler::{PeerManager, MessageHandler, SocketDescriptor};
 187         use lightning::util::config::UserConfig;
 188         use lightning::util::events::{Event, MessageSendEventsProvider, MessageSendEvent};
 189         use lightning::util::ser::Writeable;
 190         use lightning::util::test_utils;
 191         use lightning_persister::FilesystemPersister;
 192         use std::fs;
 193         use std::path::PathBuf;
 194         use std::sync::{Arc, Mutex};
 195         use std::time::Duration;
 196         use super::{BackgroundProcessor, FRESHNESS_TIMER};
 197
 198         const EVENT_DEADLINE: u64 = 5 * FRESHNESS_TIMER;
 199
 200         #[derive(Clone, Eq, Hash, PartialEq)]
 201         struct TestDescriptor{}
 202         impl SocketDescriptor for TestDescriptor {
 203                 fn send_data(&mut self, _data: &[u8], _resume_read: bool) -> usize {
 204                         0
 205                 }
 206
 207                 fn disconnect_socket(&mut self) {}
 208         }
 209
 210         type ChainMonitor = chainmonitor::ChainMonitor<InMemorySigner, Arc<test_utils::TestChainSource>, Arc<test_utils::TestBroadcaster>, Arc<test_utils::TestFeeEstimator>, Arc<test_utils::TestLogger>, Arc<FilesystemPersister>>;
 211
 212         struct Node {
 213                 node: Arc<SimpleArcChannelManager<ChainMonitor, test_utils::TestBroadcaster, test_utils::TestFeeEstimator, test_utils::TestLogger>>,
 214                 peer_manager: Arc<PeerManager<TestDescriptor, Arc<test_utils::TestChannelMessageHandler>, Arc<test_utils::TestRoutingMessageHandler>, Arc<test_utils::TestLogger>>>,
 215                 chain_monitor: Arc<ChainMonitor>,
 216                 persister: Arc<FilesystemPersister>,
 217                 tx_broadcaster: Arc<test_utils::TestBroadcaster>,
 218                 logger: Arc<test_utils::TestLogger>,
 219                 best_block: BestBlock,
 220         }
 221
 222         impl Drop for Node {
 223                 fn drop(&mut self) {
 224                         let data_dir = self.persister.get_data_dir();
 225                         match fs::remove_dir_all(data_dir.clone()) {
 226                                 Err(e) => println!("Failed to remove test persister directory {}: {}", data_dir, e),
 227                                 _ => {}
 228                         }
 229                 }
 230         }
 231
 232         fn get_full_filepath(filepath: String, filename: String) -> String {
 233                 let mut path = PathBuf::from(filepath);
 234                 path.push(filename);
 235                 path.to_str().unwrap().to_string()
 236         }
 237
 238         fn create_nodes(num_nodes: usize, persist_dir: String) -> Vec<Node> {
 239                 let mut nodes = Vec::new();
 240                 for i in 0..num_nodes {
 241                         let tx_broadcaster = Arc::new(test_utils::TestBroadcaster{txn_broadcasted: Mutex::new(Vec::new()), blocks: Arc::new(Mutex::new(Vec::new()))});
 242                         let fee_estimator = Arc::new(test_utils::TestFeeEstimator { sat_per_kw: 253 });
 243                         let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
 244                         let logger = Arc::new(test_utils::TestLogger::with_id(format!("node {}", i)));
 245                         let persister = Arc::new(FilesystemPersister::new(format!("{}_persister_{}", persist_dir, i)));
 246                         let seed = [i as u8; 32];
 247                         let network = Network::Testnet;
 248                         let now = Duration::from_secs(genesis_block(network).header.time as u64);
 249                         let keys_manager = Arc::new(KeysManager::new(&seed, now.as_secs(), now.subsec_nanos()));
 250                         let chain_monitor = Arc::new(chainmonitor::ChainMonitor::new(Some(chain_source.clone()), tx_broadcaster.clone(), logger.clone(), fee_estimator.clone(), persister.clone()));
 251                         let best_block = BestBlock::from_genesis(network);
 252                         let params = ChainParameters { network, best_block };
 253                         let manager = Arc::new(ChannelManager::new(fee_estimator.clone(), chain_monitor.clone(), tx_broadcaster.clone(), logger.clone(), keys_manager.clone(), UserConfig::default(), params));
 254                         let msg_handler = MessageHandler { chan_handler: Arc::new(test_utils::TestChannelMessageHandler::new()), route_handler: Arc::new(test_utils::TestRoutingMessageHandler::new() )};
 255                         let peer_manager = Arc::new(PeerManager::new(msg_handler, keys_manager.get_node_secret(), &seed, logger.clone()));
 256                         let node = Node { node: manager, peer_manager, chain_monitor, persister, tx_broadcaster, logger, best_block };
 257                         nodes.push(node);
 258                 }
 259                 nodes
 260         }
 261
 262         macro_rules! open_channel {
 263                 ($node_a: expr, $node_b: expr, $channel_value: expr) => {{
 264                         begin_open_channel!($node_a, $node_b, $channel_value);
 265                         let events = $node_a.node.get_and_clear_pending_events();
 266                         assert_eq!(events.len(), 1);
 267                         let (temporary_channel_id, tx) = handle_funding_generation_ready!(events[0], $channel_value);
 268                         end_open_channel!($node_a, $node_b, temporary_channel_id, tx);
 269                         tx
 270                 }}
 271         }
 272
 273         macro_rules! begin_open_channel {
 274                 ($node_a: expr, $node_b: expr, $channel_value: expr) => {{
 275                         $node_a.node.create_channel($node_b.node.get_our_node_id(), $channel_value, 100, 42, None).unwrap();
 276                         $node_b.node.handle_open_channel(&$node_a.node.get_our_node_id(), InitFeatures::known(), &get_event_msg!($node_a, MessageSendEvent::SendOpenChannel, $node_b.node.get_our_node_id()));
 277                         $node_a.node.handle_accept_channel(&$node_b.node.get_our_node_id(), InitFeatures::known(), &get_event_msg!($node_b, MessageSendEvent::SendAcceptChannel, $node_a.node.get_our_node_id()));
 278                 }}
 279         }
 280
 281         macro_rules! handle_funding_generation_ready {
 282                 ($event: expr, $channel_value: expr) => {{
 283                         match $event {
 284                                 Event::FundingGenerationReady { ref temporary_channel_id, ref channel_value_satoshis, ref output_script, user_channel_id } => {
 285                                         assert_eq!(*channel_value_satoshis, $channel_value);
 286                                         assert_eq!(user_channel_id, 42);
 287
 288                                         let tx = Transaction { version: 1 as i32, lock_time: 0, input: Vec::new(), output: vec![TxOut {
 289                                                 value: *channel_value_satoshis, script_pubkey: output_script.clone(),
 290                                         }]};
 291                                         (*temporary_channel_id, tx)
 292                                 },
 293                                 _ => panic!("Unexpected event"),
 294                         }
 295                 }}
 296         }
 297
 298         macro_rules! end_open_channel {
 299                 ($node_a: expr, $node_b: expr, $temporary_channel_id: expr, $tx: expr) => {{
 300                         $node_a.node.funding_transaction_generated(&$temporary_channel_id, $tx.clone()).unwrap();
 301                         $node_b.node.handle_funding_created(&$node_a.node.get_our_node_id(), &get_event_msg!($node_a, MessageSendEvent::SendFundingCreated, $node_b.node.get_our_node_id()));
 302                         $node_a.node.handle_funding_signed(&$node_b.node.get_our_node_id(), &get_event_msg!($node_b, MessageSendEvent::SendFundingSigned, $node_a.node.get_our_node_id()));
 303                 }}
 304         }
 305
 306         fn confirm_transaction_depth(node: &mut Node, tx: &Transaction, depth: u32) {
 307                 for i in 1..=depth {
 308                         let prev_blockhash = node.best_block.block_hash();
 309                         let height = node.best_block.height() + 1;
 310                         let header = BlockHeader { version: 0x20000000, prev_blockhash, merkle_root: Default::default(), time: height, bits: 42, nonce: 42 };
 311                         let txdata = vec![(0, tx)];
 312                         node.best_block = BestBlock::new(header.block_hash(), height);
 313                         match i {
 314                                 1 => {
 315                                         node.node.transactions_confirmed(&header, &txdata, height);
 316                                         node.chain_monitor.transactions_confirmed(&header, &txdata, height);
 317                                 },
 318                                 x if x == depth => {
 319                                         node.node.best_block_updated(&header, height);
 320                                         node.chain_monitor.best_block_updated(&header, height);
 321                                 },
 322                                 _ => {},
 323                         }
 324                 }
 325         }
 326         fn confirm_transaction(node: &mut Node, tx: &Transaction) {
 327                 confirm_transaction_depth(node, tx, ANTI_REORG_DELAY);
 328         }
 329
 330         #[test]
 331         fn test_background_processor() {
 332                 // Test that when a new channel is created, the ChannelManager needs to be re-persisted with
 333                 // updates. Also test that when new updates are available, the manager signals that it needs
 334                 // re-persistence and is successfully re-persisted.
 335                 let nodes = create_nodes(2, "test_background_processor".to_string());
 336
 337                 // Go through the channel creation process so that each node has something to persist. Since
 338                 // open_channel consumes events, it must complete before starting BackgroundProcessor to
 339                 // avoid a race with processing events.
 340                 let tx = open_channel!(nodes[0], nodes[1], 100000);
 341
 342                 // Initiate the background processors to watch each node.
 343                 let data_dir = nodes[0].persister.get_data_dir();
 344                 let persister = move |node: &ChannelManager<InMemorySigner, Arc<ChainMonitor>, Arc<test_utils::TestBroadcaster>, Arc<KeysManager>, Arc<test_utils::TestFeeEstimator>, Arc<test_utils::TestLogger>>| FilesystemPersister::persist_manager(data_dir.clone(), node);
 345                 let event_handler = |_| {};
 346                 let bg_processor = BackgroundProcessor::start(persister, event_handler, nodes[0].chain_monitor.clone(), nodes[0].node.clone(), nodes[0].peer_manager.clone(), nodes[0].logger.clone());
 347
 348                 macro_rules! check_persisted_data {
 349                         ($node: expr, $filepath: expr, $expected_bytes: expr) => {
 350                                 match $node.write(&mut $expected_bytes) {
 351                                         Ok(()) => {
 352                                                 loop {
 353                                                         match std::fs::read($filepath) {
 354                                                                 Ok(bytes) => {
 355                                                                         if bytes == $expected_bytes {
 356                                                                                 break
 357                                                                         } else {
 358                                                                                 continue
 359                                                                         }
 360                                                                 },
 361                                                                 Err(_) => continue
 362                                                         }
 363                                                 }
 364                                         },
 365                                         Err(e) => panic!("Unexpected error: {}", e)
 366                                 }
 367                         }
 368                 }
 369
 370                 // Check that the initial channel manager data is persisted as expected.
 371                 let filepath = get_full_filepath("test_background_processor_persister_0".to_string(), "manager".to_string());
 372                 let mut expected_bytes = Vec::new();
 373                 check_persisted_data!(nodes[0].node, filepath.clone(), expected_bytes);
 374                 loop {
 375                         if !nodes[0].node.get_persistence_condvar_value() { break }
 376                 }
 377
 378                 // Force-close the channel.
 379                 nodes[0].node.force_close_channel(&OutPoint { txid: tx.txid(), index: 0 }.to_channel_id()).unwrap();
 380
 381                 // Check that the force-close updates are persisted.
 382                 let mut expected_bytes = Vec::new();
 383                 check_persisted_data!(nodes[0].node, filepath.clone(), expected_bytes);
 384                 loop {
 385                         if !nodes[0].node.get_persistence_condvar_value() { break }
 386                 }
 387
 388                 assert!(bg_processor.stop().is_ok());
 389         }
 390
 391         #[test]
 392         fn test_timer_tick_called() {
 393                 // Test that ChannelManager's and PeerManager's `timer_tick_occurred` is called every
 394                 // `FRESHNESS_TIMER`.
 395                 let nodes = create_nodes(1, "test_timer_tick_called".to_string());
 396                 let data_dir = nodes[0].persister.get_data_dir();
 397                 let persister = move |node: &ChannelManager<InMemorySigner, Arc<ChainMonitor>, Arc<test_utils::TestBroadcaster>, Arc<KeysManager>, Arc<test_utils::TestFeeEstimator>, Arc<test_utils::TestLogger>>| FilesystemPersister::persist_manager(data_dir.clone(), node);
 398                 let event_handler = |_| {};
 399                 let bg_processor = BackgroundProcessor::start(persister, event_handler, nodes[0].chain_monitor.clone(), nodes[0].node.clone(), nodes[0].peer_manager.clone(), nodes[0].logger.clone());
 400                 loop {
 401                         let log_entries = nodes[0].logger.lines.lock().unwrap();
 402                         let desired_log = "Calling ChannelManager's and PeerManager's timer_tick_occurred".to_string();
 403                         if log_entries.get(&("lightning_background_processor".to_string(), desired_log)).is_some() {
 404                                 break
 405                         }
 406                 }
 407
 408                 assert!(bg_processor.stop().is_ok());
 409         }
 410
 411         #[test]
 412         fn test_persist_error() {
 413                 // Test that if we encounter an error during manager persistence, the thread panics.
 414                 let nodes = create_nodes(2, "test_persist_error".to_string());
 415                 open_channel!(nodes[0], nodes[1], 100000);
 416
 417                 let persister = |_: &_| Err(std::io::Error::new(std::io::ErrorKind::Other, "test"));
 418                 let event_handler = |_| {};
 419                 let bg_processor = BackgroundProcessor::start(persister, event_handler, nodes[0].chain_monitor.clone(), nodes[0].node.clone(), nodes[0].peer_manager.clone(), nodes[0].logger.clone());
 420                 let _ = bg_processor.thread_handle.join().unwrap().expect_err("Errored persisting manager: test");
 421         }
 422
 423         #[test]
 424         fn test_background_event_handling() {
 425                 let mut nodes = create_nodes(2, "test_background_event_handling".to_string());
 426                 let channel_value = 100000;
 427                 let data_dir = nodes[0].persister.get_data_dir();
 428                 let persister = move |node: &_| FilesystemPersister::persist_manager(data_dir.clone(), node);
 429
 430                 // Set up a background event handler for FundingGenerationReady events.
 431                 let (sender, receiver) = std::sync::mpsc::sync_channel(1);
 432                 let event_handler = move |event| {
 433                         sender.send(handle_funding_generation_ready!(event, channel_value)).unwrap();
 434                 };
 435                 let bg_processor = BackgroundProcessor::start(persister.clone(), event_handler, nodes[0].chain_monitor.clone(), nodes[0].node.clone(), nodes[0].peer_manager.clone(), nodes[0].logger.clone());
 436
 437                 // Open a channel and check that the FundingGenerationReady event was handled.
 438                 begin_open_channel!(nodes[0], nodes[1], channel_value);
 439                 let (temporary_channel_id, funding_tx) = receiver
 440                         .recv_timeout(Duration::from_secs(EVENT_DEADLINE))
 441                         .expect("FundingGenerationReady not handled within deadline");
 442                 end_open_channel!(nodes[0], nodes[1], temporary_channel_id, funding_tx);
 443
 444                 // Confirm the funding transaction.
 445                 confirm_transaction(&mut nodes[0], &funding_tx);
 446                 let as_funding = get_event_msg!(nodes[0], MessageSendEvent::SendFundingLocked, nodes[1].node.get_our_node_id());
 447                 confirm_transaction(&mut nodes[1], &funding_tx);
 448                 let bs_funding = get_event_msg!(nodes[1], MessageSendEvent::SendFundingLocked, nodes[0].node.get_our_node_id());
 449                 nodes[0].node.handle_funding_locked(&nodes[1].node.get_our_node_id(), &bs_funding);
 450                 let _as_channel_update = get_event_msg!(nodes[0], MessageSendEvent::SendChannelUpdate, nodes[1].node.get_our_node_id());
 451                 nodes[1].node.handle_funding_locked(&nodes[0].node.get_our_node_id(), &as_funding);
 452                 let _bs_channel_update = get_event_msg!(nodes[1], MessageSendEvent::SendChannelUpdate, nodes[0].node.get_our_node_id());
 453
 454                 assert!(bg_processor.stop().is_ok());
 455
 456                 // Set up a background event handler for SpendableOutputs events.
 457                 let (sender, receiver) = std::sync::mpsc::sync_channel(1);
 458                 let event_handler = move |event| sender.send(event).unwrap();
 459                 let bg_processor = BackgroundProcessor::start(persister, event_handler, nodes[0].chain_monitor.clone(), nodes[0].node.clone(), nodes[0].peer_manager.clone(), nodes[0].logger.clone());
 460
 461                 // Force close the channel and check that the SpendableOutputs event was handled.
 462                 nodes[0].node.force_close_channel(&nodes[0].node.list_channels()[0].channel_id).unwrap();
 463                 let commitment_tx = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
 464                 confirm_transaction_depth(&mut nodes[0], &commitment_tx, BREAKDOWN_TIMEOUT as u32);
 465                 let event = receiver
 466                         .recv_timeout(Duration::from_secs(EVENT_DEADLINE))
 467                         .expect("SpendableOutputs not handled within deadline");
 468                 match event {
 469                         Event::SpendableOutputs { .. } => {},
 470                         _ => panic!("Unexpected event: {:?}", event),
 471                 }
 472
 473                 assert!(bg_processor.stop().is_ok());
 474         }
 475 }