Add structured logging context fields to LogRecord

Extend LogRecord with peer_id, channel_id, and payment_hash fields from
LDK's Record struct. These structured fields are now available to custom
LogWriter implementations and are automatically appended to log messages
by the built-in FileWriter and LogFacadeWriter.

- Add peer_id, channel_id, payment_hash fields to LogRecord (both uniffi
  and non-uniffi versions)
- Add format_log_context() helper to format fields with truncated hex
- Update FileWriter and LogFacadeWriter to append context to messages
- Update UDL bindings with new LogRecord fields
- Add unit tests for format_log_context and LogFacadeWriter

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: joostjager

bindings/ldk_node.udl

@@ -83,6 +83,9 @@ dictionary LogRecord {
 	string args;
 	string module_path;
 	u32 line;
+	PublicKey? peer_id;
+	ChannelId? channel_id;
+	PaymentHash? payment_hash;
 };
 
 [Trait, WithForeign]

src/logger.rs

@@ -7,14 +7,16 @@
 
 //! Logging-related objects.
 
-#[cfg(not(feature = "uniffi"))]
 use core::fmt;
 use std::fs;
 use std::io::Write;
 use std::path::Path;
 use std::sync::Arc;
 
+use bitcoin::secp256k1::PublicKey;
 use chrono::Utc;
+use lightning::ln::types::ChannelId;
+use lightning::types::payment::PaymentHash;
 pub use lightning::util::logger::Level as LogLevel;
 pub(crate) use lightning::util::logger::{Logger as LdkLogger, Record as LdkRecord};
 pub(crate) use lightning::{log_bytes, log_debug, log_error, log_info, log_trace};
@@ -32,6 +34,73 @@ pub struct LogRecord<'a> {
 	pub module_path: &'a str,
 	/// The line containing the message.
 	pub line: u32,
+	/// The node id of the peer pertaining to the logged record.
+	pub peer_id: Option<PublicKey>,
+	/// The channel id of the channel pertaining to the logged record.
+	pub channel_id: Option<ChannelId>,
+	/// The payment hash pertaining to the logged record.
+	pub payment_hash: Option<PaymentHash>,
+}
+
+/// Structured context fields for log messages.
+///
+/// Implements `Display` to format context fields (channel_id, peer_id, payment_hash) directly
+/// into a formatter, avoiding intermediate heap allocations when used with `format_args!` or
+/// `write!` macros.
+pub struct LogContext<'a> {
+	/// The channel id of the channel pertaining to the logged record.
+	pub channel_id: Option<&'a ChannelId>,
+	/// The node id of the peer pertaining to the logged record.
+	pub peer_id: Option<&'a PublicKey>,
+	/// The payment hash pertaining to the logged record.
+	pub payment_hash: Option<&'a PaymentHash>,
+}
+
+impl<'a> LogContext<'a> {
+	/// Creates a new `LogContext` from the given fields.
+	pub fn new(
+		channel_id: Option<&'a ChannelId>, peer_id: Option<&'a PublicKey>,
+		payment_hash: Option<&'a PaymentHash>,
+	) -> Self {
+		Self { channel_id, peer_id, payment_hash }
+	}
+}
+
+/// Note: LDK's `Record` Display implementation uses fixed-width padded columns and different
+/// formatting for test vs production builds. We intentionally use a simpler format here:
+/// fields are only included when present (no padding), and the format is consistent across
+/// all build configurations.
+impl fmt::Display for LogContext<'_> {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		fn truncate(s: &str) -> &str {
+			&s[..s.len().min(6)]
+		}
+
+		if self.channel_id.is_none() && self.peer_id.is_none() && self.payment_hash.is_none() {
+			return Ok(());
+		}
+
+		write!(f, " (")?;
+		let mut need_space = false;
+		if let Some(c) = self.channel_id {
+			write!(f, "ch:{}", truncate(&c.to_string()))?;
+			need_space = true;
+		}
+		if let Some(p) = self.peer_id {
+			if need_space {
+				write!(f, " ")?;
+			}
+			write!(f, "p:{}", truncate(&p.to_string()))?;
+			need_space = true;
+		}
+		if let Some(h) = self.payment_hash {
+			if need_space {
+				write!(f, " ")?;
+			}
+			write!(f, "h:{}", truncate(&format!("{:?}", h)))?;
+		}
+		write!(f, ")")
+	}
 }
 
 /// A unit of logging output with metadata to enable filtering `module_path`,
@@ -50,6 +119,12 @@ pub struct LogRecord {
 	pub module_path: String,
 	/// The line containing the message.
 	pub line: u32,
+	/// The node id of the peer pertaining to the logged record.
+	pub peer_id: Option<PublicKey>,
+	/// The channel id of the channel pertaining to the logged record.
+	pub channel_id: Option<ChannelId>,
+	/// The payment hash pertaining to the logged record.
+	pub payment_hash: Option<PaymentHash>,
 }
 
 #[cfg(feature = "uniffi")]
@@ -60,6 +135,9 @@ impl<'a> From<LdkRecord<'a>> for LogRecord {
 			args: record.args.to_string(),
 			module_path: record.module_path.to_string(),
 			line: record.line,
+			peer_id: record.peer_id,
+			channel_id: record.channel_id,
+			payment_hash: record.payment_hash,
 		}
 	}
 }
@@ -72,6 +150,9 @@ impl<'a> From<LdkRecord<'a>> for LogRecord<'a> {
 			args: record.args,
 			module_path: record.module_path,
 			line: record.line,
+			peer_id: record.peer_id,
+			channel_id: record.channel_id,
+			payment_hash: record.payment_hash,
 		}
 	}
 }
@@ -113,19 +194,26 @@ pub(crate) enum Writer {
 
 impl LogWriter for Writer {
 	fn log(&self, record: LogRecord) {
+		let context = LogContext::new(
+			record.channel_id.as_ref(),
+			record.peer_id.as_ref(),
+			record.payment_hash.as_ref(),
+		);
+
 		match self {
 			Writer::FileWriter { file_path, max_log_level } => {
 				if record.level < *max_log_level {
 					return;
 				}
 
 				let log = format!(
-					"{} {:<5} [{}:{}] {}\n",
+					"{} {:<5} [{}:{}] {}{}\n",
 					Utc::now().format("%Y-%m-%d %H:%M:%S%.3f"),
 					record.level.to_string(),
 					record.module_path,
 					record.line,
-					record.args
+					record.args,
+					context,
 				);
 
 				fs::OpenOptions::new()
@@ -153,7 +241,7 @@ impl LogWriter for Writer {
 						.target(record.module_path)
 						.module_path(Some(record.module_path))
 						.line(Some(record.line))
-						.args(format_args!("{}", record.args))
+						.args(format_args!("{}{}", record.args, context))
 						.build(),
 				);
 				#[cfg(feature = "uniffi")]
@@ -162,7 +250,7 @@ impl LogWriter for Writer {
 						.target(&record.module_path)
 						.module_path(Some(&record.module_path))
 						.line(Some(record.line))
-						.args(format_args!("{}", record.args))
+						.args(format_args!("{}{}", record.args, context))
 						.build(),
 				);
 			},
@@ -222,3 +310,122 @@ impl LdkLogger for Logger {
 		}
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use std::sync::Mutex;
+
+	/// Tests that LogContext correctly formats all three structured fields
+	/// (channel_id, peer_id, payment_hash) with space prefixes and 6-char truncation.
+	#[test]
+	fn test_log_context_all_fields() {
+		let channel_id = ChannelId::from_bytes([
+			0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00,
+		]);
+		let peer_id = PublicKey::from_slice(&[
+			0x02, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf1, 0x23, 0x45,
+			0x67, 0x89, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf1, 0x23,
+			0x45, 0x67, 0x89, 0xab, 0xcd,
+		])
+		.unwrap();
+		let payment_hash = PaymentHash([
+			0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00,
+		]);
+
+		let context = LogContext::new(Some(&channel_id), Some(&peer_id), Some(&payment_hash));
+
+		assert_eq!(context.to_string(), " (ch:abcdef p:02abcd h:fedcba)");
+	}
+
+	/// Tests that LogContext returns an empty string when no fields are provided.
+	#[test]
+	fn test_log_context_no_fields() {
+		let context = LogContext::new(None, None, None);
+		assert_eq!(context.to_string(), "");
+	}
+
+	/// Tests that LogContext only includes present fields.
+	#[test]
+	fn test_log_context_partial_fields() {
+		let channel_id = ChannelId::from_bytes([
+			0x12, 0x34, 0x56, 0x78, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00,
+		]);
+
+		let context = LogContext::new(Some(&channel_id), None, None);
+		assert_eq!(context.to_string(), " (ch:123456)");
+	}
+
+	/// A minimal log facade logger that captures log output for testing.
+	struct TestLogger {
+		log: Arc<Mutex<String>>,
+	}
+
+	impl log::Log for TestLogger {
+		fn enabled(&self, _metadata: &log::Metadata) -> bool {
+			true
+		}
+
+		fn log(&self, record: &log::Record) {
+			*self.log.lock().unwrap() = record.args().to_string();
+		}
+
+		fn flush(&self) {}
+	}
+
+	/// Tests that LogFacadeWriter appends structured context fields to the log message.
+	#[test]
+	fn test_log_facade_writer_includes_structured_context() {
+		let log = Arc::new(Mutex::new(String::new()));
+		let test_logger = TestLogger { log: log.clone() };
+
+		let _ = log::set_boxed_logger(Box::new(test_logger));
+		log::set_max_level(log::LevelFilter::Trace);
+
+		let writer = Writer::LogFacadeWriter;
+
+		let channel_id = ChannelId::from_bytes([
+			0xab, 0xcd, 0xef, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00,
+		]);
+		let peer_id = PublicKey::from_slice(&[
+			0x02, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf1, 0x23, 0x45,
+			0x67, 0x89, 0xab, 0xcd, 0xef, 0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf1, 0x23,
+			0x45, 0x67, 0x89, 0xab, 0xcd,
+		])
+		.unwrap();
+
+		#[cfg(not(feature = "uniffi"))]
+		let record = LogRecord {
+			level: LogLevel::Info,
+			args: format_args!("Test message"),
+			module_path: "test_module",
+			line: 42,
+			peer_id: Some(peer_id),
+			channel_id: Some(channel_id),
+			payment_hash: None,
+		};
+
+		#[cfg(feature = "uniffi")]
+		let record = LogRecord {
+			level: LogLevel::Info,
+			args: "Test message".to_string(),
+			module_path: "test_module".to_string(),
+			line: 42,
+			peer_id: Some(peer_id),
+			channel_id: Some(channel_id),
+			payment_hash: None,
+		};
+
+		writer.log(record);
+
+		assert_eq!(*log.lock().unwrap(), "Test message (ch:abcdef p:02abcd)");
+	}
+}

tests/common/logging.rs

@@ -1,7 +1,7 @@
 use std::sync::{Arc, Mutex};
 
 use chrono::Utc;
-use ldk_node::logger::{LogLevel, LogRecord, LogWriter};
+use ldk_node::logger::{LogContext, LogLevel, LogRecord, LogWriter};
 #[cfg(not(feature = "uniffi"))]
 use log::Record as LogFacadeRecord;
 use log::{Level as LogFacadeLevel, LevelFilter as LogFacadeLevelFilter, Log as LogFacadeLog};
@@ -156,13 +156,18 @@ impl MultiNodeLogger {
 impl LogWriter for MultiNodeLogger {
 	fn log(&self, record: LogRecord) {
 		let log = format!(
-			"[{}] {} {:<5} [{}:{}] {}\n",
+			"[{}] {} {:<5} [{}:{}] {}{}\n",
 			self.node_id,
 			Utc::now().format("%Y-%m-%d %H:%M:%S%.3f"),
 			record.level.to_string(),
 			record.module_path,
 			record.line,
-			record.args
+			record.args,
+			LogContext::new(
+				record.channel_id.as_ref(),
+				record.peer_id.as_ref(),
+				record.payment_hash.as_ref()
+			),
 		);
 
 		print!("{}", log);