[rust-lightning] / background-processor / src / lib.rs

//! Utilities that take care of tasks that (1) need to happen periodically to keep Rust-Lightning
//! running properly, and (2) either can or should be run in the background. See docs for
//! [`BackgroundProcessor`] for more details on the nitty-gritty.

#![deny(broken_intra_doc_links)]
#![deny(missing_docs)]
#![deny(unsafe_code)]

#[macro_use] extern crate lightning;

use lightning::chain;
use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
use lightning::chain::keysinterface::{Sign, KeysInterface};
use lightning::ln::channelmanager::ChannelManager;
use lightning::util::logger::Logger;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;
use std::thread::JoinHandle;
use std::time::{Duration, Instant};

/// BackgroundProcessor takes care of tasks that (1) need to happen periodically to keep
/// Rust-Lightning running properly, and (2) either can or should be run in the background. Its
/// responsibilities are:
/// * Monitoring whether the ChannelManager needs to be re-persisted to disk, and if so,
///   writing it to disk/backups by invoking the callback given to it at startup.
///   ChannelManager persistence should be done in the background.
/// * Calling `ChannelManager::timer_chan_freshness_every_min()` every minute (can be done in the
///   background).
///
/// Note that if ChannelManager persistence fails and the persisted manager becomes out-of-date,
/// then there is a risk of channels force-closing on startup when the manager realizes it's
/// outdated. However, as long as `ChannelMonitor` backups are sound, no funds besides those used
/// for unilateral chain closure fees are at risk.
pub struct BackgroundProcessor {
        stop_thread: Arc<AtomicBool>,
        /// May be used to retrieve and handle the error if `BackgroundProcessor`'s thread
        /// exits due to an error while persisting.
        pub thread_handle: JoinHandle<Result<(), std::io::Error>>,
}

#[cfg(not(test))]
const CHAN_FRESHNESS_TIMER: u64 = 60;
#[cfg(test)]
const CHAN_FRESHNESS_TIMER: u64 = 1;

impl BackgroundProcessor {
        /// Start a background thread that takes care of responsibilities enumerated in the top-level
        /// documentation.
        ///
        /// If `persist_manager` returns an error, then this thread will return said error (and
        /// `start()` will need to be called again to restart the `BackgroundProcessor`). Users should
        /// wait on [`thread_handle`]'s `join()` method to be able to tell if and when an error is
        /// returned, or implement `persist_manager` such that an error is never returned to the
        /// `BackgroundProcessor`
        ///
        /// `persist_manager` is responsible for writing out the [`ChannelManager`] to disk, and/or
        /// uploading to one or more backup services. See [`ChannelManager::write`] for writing out a
        /// [`ChannelManager`]. See [`FilesystemPersister::persist_manager`] for Rust-Lightning's
        /// provided implementation.
        ///
        /// [`thread_handle`]: BackgroundProcessor::thread_handle
        /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
        /// [`ChannelManager::write`]: lightning::ln::channelmanager::ChannelManager#impl-Writeable
        /// [`FilesystemPersister::persist_manager`]: lightning_persister::FilesystemPersister::persist_manager
        pub fn start<PM, Signer, M, T, K, F, L>(persist_manager: PM, manager: Arc<ChannelManager<Signer, Arc<M>, Arc<T>, Arc<K>, Arc<F>, Arc<L>>>, logger: Arc<L>) -> Self
        where Signer: 'static + Sign,
              M: 'static + chain::Watch<Signer>,
              T: 'static + BroadcasterInterface,
              K: 'static + KeysInterface<Signer=Signer>,
              F: 'static + FeeEstimator,
              L: 'static + Logger,
              PM: 'static + Send + Fn(&ChannelManager<Signer, Arc<M>, Arc<T>, Arc<K>, Arc<F>, Arc<L>>) -> Result<(), std::io::Error>,
        {
                let stop_thread = Arc::new(AtomicBool::new(false));
                let stop_thread_clone = stop_thread.clone();
                let handle = thread::spawn(move || -> Result<(), std::io::Error> {
                        let mut current_time = Instant::now();
                        loop {
                                let updates_available = manager.await_persistable_update_timeout(Duration::from_millis(100));
                                if updates_available {
                                        persist_manager(&*manager)?;
                                }
                                // Exit the loop if the background processor was requested to stop.
                                if stop_thread.load(Ordering::Acquire) == true {
                                        log_trace!(logger, "Terminating background processor.");
                                        return Ok(())
                                }
                                if current_time.elapsed().as_secs() > CHAN_FRESHNESS_TIMER {
                                        log_trace!(logger, "Calling manager's timer_chan_freshness_every_min");
                                        manager.timer_chan_freshness_every_min();
                                        current_time = Instant::now();
                                }
                        }
                });
                Self {
                        stop_thread: stop_thread_clone,
                        thread_handle: handle,
                }
        }

        /// Stop `BackgroundProcessor`'s thread.
        pub fn stop(self) -> Result<(), std::io::Error> {
                self.stop_thread.store(true, Ordering::Release);
                self.thread_handle.join().unwrap()
        }
}

#[cfg(test)]
mod tests {
        use bitcoin::blockdata::constants::genesis_block;
        use bitcoin::blockdata::transaction::{Transaction, TxOut};
        use bitcoin::network::constants::Network;
        use lightning::chain;
        use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
        use lightning::chain::chainmonitor;
        use lightning::chain::keysinterface::{Sign, InMemorySigner, KeysInterface, KeysManager};
        use lightning::chain::transaction::OutPoint;
        use lightning::get_event_msg;
        use lightning::ln::channelmanager::{ChainParameters, 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::logger::Logger;
        use lightning::util::ser::Writeable;
        use lightning::util::test_utils;
        use lightning_persister::FilesystemPersister;
        use std::fs;
        use std::path::PathBuf;
        use std::sync::{Arc, Mutex};
        use std::time::Duration;
        use super::BackgroundProcessor;

        type ChainMonitor = chainmonitor::ChainMonitor<InMemorySigner, Arc<test_utils::TestChainSource>, Arc<test_utils::TestBroadcaster>, Arc<test_utils::TestFeeEstimator>, Arc<test_utils::TestLogger>, Arc<FilesystemPersister>>;

        struct Node {
                node: Arc<SimpleArcChannelManager<ChainMonitor, test_utils::TestBroadcaster, test_utils::TestFeeEstimator, test_utils::TestLogger>>,
                persister: Arc<FilesystemPersister>,
                logger: Arc<test_utils::TestLogger>,
        }

        impl Drop for Node {
                fn drop(&mut self) {
                        let data_dir = self.persister.get_data_dir();
                        match fs::remove_dir_all(data_dir.clone()) {
                                Err(e) => println!("Failed to remove test persister directory {}: {}", data_dir, e),
                                _ => {}
                        }
                }
        }

        fn get_full_filepath(filepath: String, filename: String) -> String {
                let mut path = PathBuf::from(filepath);
                path.push(filename);
                path.to_str().unwrap().to_string()
        }

        fn create_nodes(num_nodes: usize, persist_dir: String) -> 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_{}", persist_dir, i)));
                        let seed = [i as u8; 32];
                        let network = Network::Testnet;
                        let genesis_block = genesis_block(network);
                        let now = Duration::from_secs(genesis_block.header.time as u64);
                        let keys_manager = Arc::new(KeysManager::new(&seed, 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 params = ChainParameters {
                                network,
                                latest_hash: genesis_block.block_hash(),
                                latest_height: 0,
                        };
                        let manager = Arc::new(ChannelManager::new(fee_estimator.clone(), chain_monitor.clone(), tx_broadcaster, logger.clone(), keys_manager.clone(), UserConfig::default(), params));
                        let node = Node { node: manager, persister, logger };
                        nodes.push(node);
                }
                nodes
        }

        macro_rules! open_channel {
                ($node_a: expr, $node_b: expr, $channel_value: expr) => {{
                        $node_a.node.create_channel($node_b.node.get_our_node_id(), $channel_value, 100, 42, None).unwrap();
                        $node_b.node.handle_open_channel(&$node_a.node.get_our_node_id(), InitFeatures::known(), &get_event_msg!($node_a, MessageSendEvent::SendOpenChannel, $node_b.node.get_our_node_id()));
                        $node_a.node.handle_accept_channel(&$node_b.node.get_our_node_id(), InitFeatures::known(), &get_event_msg!($node_b, MessageSendEvent::SendAcceptChannel, $node_a.node.get_our_node_id()));
                        let events = $node_a.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"),
                        };

                        $node_a.node.funding_transaction_generated(&temporary_channel_id, funding_output);
                        $node_b.node.handle_funding_created(&$node_a.node.get_our_node_id(), &get_event_msg!($node_a, MessageSendEvent::SendFundingCreated, $node_b.node.get_our_node_id()));
                        $node_a.node.handle_funding_signed(&$node_b.node.get_our_node_id(), &get_event_msg!($node_b, MessageSendEvent::SendFundingSigned, $node_a.node.get_our_node_id()));
                        tx
                }}
        }

        #[test]
        fn test_background_processor() {
                // Test that when a new channel is created, the ChannelManager needs to be re-persisted with
                // updates. Also test that when new updates are available, the manager signals that it needs
                // re-persistence and is successfully re-persisted.
                let nodes = create_nodes(2, "test_background_processor".to_string());

                // Initiate the background processors to watch each node.
                let data_dir = nodes[0].persister.get_data_dir();
                let callback = 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);
                let bg_processor = BackgroundProcessor::start(callback, nodes[0].node.clone(), nodes[0].logger.clone());

                // Go through the channel creation process until each node should have something persisted.
                let tx = open_channel!(nodes[0], nodes[1], 100000);

                macro_rules! check_persisted_data {
                        ($node: expr, $filepath: expr, $expected_bytes: expr) => {
                                match $node.write(&mut $expected_bytes) {
                                        Ok(()) => {
                                                loop {
                                                        match std::fs::read($filepath) {
                                                                Ok(bytes) => {
                                                                        if bytes == $expected_bytes {
                                                                                break
                                                                        } else {
                                                                                continue
                                                                        }
                                                                },
                                                                Err(_) => continue
                                                        }
                                                }
                                        },
                                        Err(e) => panic!("Unexpected error: {}", e)
                                }
                        }
                }

                // Check that the initial channel manager data is persisted as expected.
                let filepath = get_full_filepath("test_background_processor_persister_0".to_string(), "manager".to_string());
                let mut expected_bytes = Vec::new();
                check_persisted_data!(nodes[0].node, filepath.clone(), expected_bytes);
                loop {
                        if !nodes[0].node.get_persistence_condvar_value() { break }
                }

                // Force-close the channel.
                nodes[0].node.force_close_channel(&OutPoint { txid: tx.txid(), index: 0 }.to_channel_id()).unwrap();

                // Check that the force-close updates are persisted.
                let mut expected_bytes = Vec::new();
                check_persisted_data!(nodes[0].node, filepath.clone(), expected_bytes);
                loop {
                        if !nodes[0].node.get_persistence_condvar_value() { break }
                }

                assert!(bg_processor.stop().is_ok());
        }

        #[test]
        fn test_chan_freshness_called() {
                // Test that ChannelManager's `timer_chan_freshness_every_min` is called every
                // `CHAN_FRESHNESS_TIMER`.
                let nodes = create_nodes(1, "test_chan_freshness_called".to_string());
                let data_dir = nodes[0].persister.get_data_dir();
                let callback = 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);
                let bg_processor = BackgroundProcessor::start(callback, nodes[0].node.clone(), nodes[0].logger.clone());
                loop {
                        let log_entries = nodes[0].logger.lines.lock().unwrap();
                        let desired_log = "Calling manager's timer_chan_freshness_every_min".to_string();
                        if log_entries.get(&("lightning_background_processor".to_string(), desired_log)).is_some() {
                                break
                        }
                }

                assert!(bg_processor.stop().is_ok());
        }

        #[test]
        fn test_persist_error() {
                // Test that if we encounter an error during manager persistence, the thread panics.
                fn persist_manager<Signer, M, T, K, F, L>(_data: &ChannelManager<Signer, Arc<M>, Arc<T>, Arc<K>, Arc<F>, Arc<L>>) -> Result<(), std::io::Error>
                where Signer: 'static + Sign,
                      M: 'static + chain::Watch<Signer>,
                      T: 'static + BroadcasterInterface,
                      K: 'static + KeysInterface<Signer=Signer>,
                      F: 'static + FeeEstimator,
                      L: 'static + Logger,
                {
                        Err(std::io::Error::new(std::io::ErrorKind::Other, "test"))
                }

                let nodes = create_nodes(2, "test_persist_error".to_string());
                let bg_processor = BackgroundProcessor::start(persist_manager, nodes[0].node.clone(), nodes[0].logger.clone());
                open_channel!(nodes[0], nodes[1], 100000);

                let _ = bg_processor.thread_handle.join().unwrap().expect_err("Errored persisting manager: test");
        }
}