Add BackgroundProcessor for ChannelManager persistence and other

Other includes calling timer_chan_freshness_every_minute() and in the
future, possibly persisting channel graph data.

This struct is suitable for things that need to happen periodically and
can happen in the background.

Author: valentinewallace

lightning-persister/src/background_processor.rs

@@ -0,0 +1,219 @@
+use lightning::chain;
+use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
+use lightning::chain::keysinterface::{ChannelKeys, KeysInterface};
+use lightning::ln::channelmanager;
+use lightning::ln::channelmanager::ChannelManager;
+use lightning::util::logger::Logger;
+use lightning::util::ser::Writeable;
+use std::mem;
+use std::sync::Arc;
+use std::sync::mpsc::{self, Sender, TryRecvError};
+use std::thread;
+use std::time::{Duration, SystemTime};
+
+/// BackgroundProcesser runs a background thread that monitors whether the ChannelManager it's given on
+/// start has new updates to persist. If it does, then it writes said ChannelManager to disk/backups.
+pub struct BackgroundProcessor {
+	#[cfg(test)]
+	pub thread_terminator: Sender<()>,
+	#[cfg(not(test))]
+	/// Used to send a message to the thread in BackgroundProcessor::start() to exit the thread.
+	thread_terminator: Sender<()>,
+}
+
+impl BackgroundProcessor {
+	/// Start the background thread that checks whether new updates are available for the ChannelManager,
+	/// and writes it to disk if so.
+	/// We also call ChannelManager::timer_chan_freshness_every_min(), since we're already eating the
+	/// cost of running a thread, we may as well pack as many operations into it as make sense.
+	// Mark as must_use because otherwise the result is dropped immediately, resulting in the thread
+	// being terminated.
+	#[must_use]
+	pub fn start<ChanSigner: 'static + ChannelKeys + Writeable, M: 'static + chain::Watch<Keys=ChanSigner>, T: 'static + BroadcasterInterface, K: 'static + KeysInterface<ChanKeySigner=ChanSigner>, F: 'static + FeeEstimator, L: 'static + Logger>(persister: Arc<dyn channelmanager::Persist<ChanSigner, M, T, K, F, L>>, manager: Arc<ChannelManager<ChanSigner, Arc<M>, Arc<T>, Arc<K>, Arc<F>, Arc<L>>>) -> Self {
+		let (sender, receiver) = mpsc::channel();
+		let mutcond = Arc::clone(&manager.persistence_lock);
+		// See ChannelMananger::persistence_lock for more documentation on the persistence process.
+		thread::spawn(move || {
+			let &(ref mtx, ref cvar) = &*mutcond;
+			let mut current_time = SystemTime::now();
+			loop {
+				let mut guard = mtx.lock().unwrap();
+				let result = cvar.wait_timeout(guard, Duration::from_millis(1000)).unwrap();
+				guard = result.0;
+				let saved_res = *guard;
+				mem::drop(guard);
+				if saved_res {
+					if let Err(e) = persister.persist_manager(manager.clone()) {
+						println!("Errored persisting manager: {}", e);
+					};
+				}
+				// If we receive a message from the thread_terminator, we should exit now.
+				match receiver.try_recv() {
+					Ok(_) | Err(TryRecvError::Disconnected) => {
+						println!("Terminating.");
+						break;
+					}
+					Err(TryRecvError::Empty) => {}
+				}
+				match current_time.elapsed() {
+					Ok(elapsed) => {
+						if elapsed.as_secs() > 60 {
+							manager.timer_chan_freshness_every_min();
+							current_time = SystemTime::now();
+						}
+					},
+					Err(e) => println!("Errored retrieving elapsed time: {}", e),
+				}
+			}
+		});
+		Self {
+			thread_terminator: sender,
+		}
+	}
+
+	pub fn stop(&self) {
+		let _ = self.thread_terminator.send(());
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use bitcoin::blockdata::constants::genesis_block;
+	use bitcoin::blockdata::transaction::{Transaction, TxOut};
+	use bitcoin::network::constants::Network;
+	use crate::FilesystemPersister;
+	use crate::utils;
+	use lightning::chain::chainmonitor;
+	use lightning::chain::keysinterface::{InMemoryChannelKeys, KeysManager};
+	use lightning::chain::transaction::OutPoint;
+	use lightning::get_event_msg;
+	use lightning::ln::channelmanager::{ChannelManager, SimpleArcChannelManager};
+	use lightning::ln::features::{InitFeatures};
+	use lightning::ln::msgs::ChannelMessageHandler;
+	use lightning::util::config::UserConfig;
+	use lightning::util::events::{Event, EventsProvider, MessageSendEventsProvider, MessageSendEvent};
+	use lightning::util::ser::{Writeable};
+	use lightning::util::test_utils;
+	use std::fs;
+	use std::sync::{Arc, Mutex};
+	use std::time::Duration;
+	use super::BackgroundProcessor;
+
+	type ChainMonitor = chainmonitor::ChainMonitor<InMemoryChannelKeys, Arc<test_utils::TestChainSource>, Arc<test_utils::TestBroadcaster>, Arc<test_utils::TestFeeEstimator>, Arc<test_utils::TestLogger>, Arc<FilesystemPersister>>;
+
+	struct Node {
+		node: SimpleArcChannelManager<ChainMonitor, test_utils::TestBroadcaster, test_utils::TestFeeEstimator, test_utils::TestLogger>,
+		persister: Arc<FilesystemPersister>
+	}
+
+	fn create_nodes(num_nodes: usize) -> Vec<Node> {
+		let mut nodes = Vec::new();
+		for i in 0..num_nodes {
+			let tx_broadcaster = Arc::new(test_utils::TestBroadcaster{txn_broadcasted: Mutex::new(Vec::new())});
+			let fee_estimator = Arc::new(test_utils::TestFeeEstimator { sat_per_kw: 253 });
+			let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
+			let logger = Arc::new(test_utils::TestLogger::with_id(format!("node {}", i)));
+			let persister = Arc::new(FilesystemPersister::new(format!("persister_{}", i)));
+			let seed = [i as u8; 32];
+			let network = Network::Testnet;
+			let now = Duration::from_secs(genesis_block(network).header.time as u64);
+			let keys_manager = Arc::new(KeysManager::new(&seed, network, now.as_secs(), now.subsec_nanos()));
+			let chain_monitor = Arc::new(chainmonitor::ChainMonitor::new(Some(chain_source.clone()), tx_broadcaster.clone(), logger.clone(), fee_estimator.clone(), persister.clone()));
+			let manager = Arc::new(ChannelManager::new(Network::Testnet, fee_estimator.clone(), chain_monitor.clone(), tx_broadcaster, logger.clone(), keys_manager.clone(), UserConfig::default(), i));
+			let node = Node { node: manager, persister };
+			nodes.push(node);
+		}
+		nodes
+	}
+
+	#[test]
+	fn test_background_processor() {
+		let nodes = create_nodes(2);
+
+		// Initiate the background processors to watch each node.
+		let _processor_0 = BackgroundProcessor::start(nodes[0].persister.clone(), nodes[0].node.clone());
+		let _processor_1 = BackgroundProcessor::start(nodes[1].persister.clone(), nodes[1].node.clone());
+
+		// Go through the channel creation process until each node should have something persisted.
+		let channel_value = 100000;
+		nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), channel_value, 100, 42, None).unwrap();
+		nodes[1].node.handle_open_channel(&nodes[0].node.get_our_node_id(), InitFeatures::known(), &get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id()));
+		nodes[0].node.handle_accept_channel(&nodes[1].node.get_our_node_id(), InitFeatures::known(), &get_event_msg!(nodes[1], MessageSendEvent::SendAcceptChannel, nodes[0].node.get_our_node_id()));
+		let events = nodes[0].node.get_and_clear_pending_events();
+		assert_eq!(events.len(), 1);
+		let (temporary_channel_id, tx, funding_output) = match events[0] {
+			Event::FundingGenerationReady { ref temporary_channel_id, ref channel_value_satoshis, ref output_script, user_channel_id } => {
+				assert_eq!(*channel_value_satoshis, channel_value);
+				assert_eq!(user_channel_id, 42);
+
+				let tx = Transaction { version: 1 as i32, lock_time: 0, input: Vec::new(), output: vec![TxOut {
+					value: *channel_value_satoshis, script_pubkey: output_script.clone(),
+				}]};
+				let funding_outpoint = OutPoint { txid: tx.txid(), index: 0 };
+				(*temporary_channel_id, tx, funding_outpoint)
+			},
+			_ => panic!("Unexpected event"),
+		};
+
+		nodes[0].node.funding_transaction_generated(&temporary_channel_id, funding_output);
+		nodes[1].node.handle_funding_created(&nodes[0].node.get_our_node_id(), &get_event_msg!(nodes[0], MessageSendEvent::SendFundingCreated, nodes[1].node.get_our_node_id()));
+		nodes[0].node.handle_funding_signed(&nodes[1].node.get_our_node_id(), &get_event_msg!(nodes[1], MessageSendEvent::SendFundingSigned, nodes[0].node.get_our_node_id()));
+
+		macro_rules! check_persisted_data {
+			($node: expr, $filepath: expr) => {
+				let bytes = loop {
+					match std::fs::read($filepath) {
+						Ok(bytes) => break bytes,
+						Err(_) => continue
+					}
+				};
+				let mut expected_bytes = Vec::new();
+				assert!($node.write(&mut expected_bytes).is_ok());
+				assert_eq!(bytes, expected_bytes);
+			}
+		}
+
+		// Check that the initial channel manager data is persisted as expected.
+		let filepath_0 = utils::get_full_filepath("persister_0".to_string(), "manager".to_string());
+		let filepath_1 = utils::get_full_filepath("persister_1".to_string(), "manager".to_string());
+		check_persisted_data!(nodes[0].node, filepath_0.clone());
+		check_persisted_data!(nodes[1].node, filepath_1.clone());
+
+		// Save the current bytes then trigger another update.
+		let current_bytes = std::fs::read(filepath_0.clone()).unwrap();
+
+		// Force-close the channel.
+		nodes[0].node.force_close_channel(&OutPoint { txid: tx.txid(), index: 0 }.to_channel_id());
+
+		// Loop until what's written on disk changes.
+		loop {
+			match std::fs::read(filepath_0.clone()) {
+				Ok(bytes) => {
+					if bytes == current_bytes { continue } else { break }
+				},
+				Err(_) => continue
+			}
+		};
+		// Make sure the update was persisted properly.
+		check_persisted_data!(nodes[0].node, filepath_0.clone());
+		// TODO(val): `Drop` is never called on the FilesystemPersisters (causing their directories to linger). why?
+		let _ = fs::remove_dir_all("persister_0");
+		let _ = fs::remove_dir_all("persister_1");
+	}
+
+	#[test]
+	fn test_stop_bg_thread() {
+		let nodes = create_nodes(1);
+		let bg_processor = BackgroundProcessor::start(nodes[0].persister.clone(), nodes[0].node.clone());
+
+		// Stop the background processor and check that it terminated.
+		println!("is this where we're calling stop");
+		bg_processor.stop();
+		loop {
+			match bg_processor.thread_terminator.send(()) {
+				Err(_) => break, // A send operation can only fail if the receiving end is disconnected.
+				Ok(()) => continue
+			}
+		}
+	}
+}

lightning-persister/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod background_processor;
 pub(crate) mod utils;
 
 extern crate lightning;