Increase the timeout for RPC responses from Bitcoin Core

lightning-block-sync/Cargo.toml

@@ -16,7 +16,7 @@ rpc-client = [ "serde", "serde_json", "chunked_transfer" ]
 [dependencies]
 bitcoin = "0.26"
 lightning = { version = "0.0.14", path = "../lightning" }
-tokio = { version = "1.0", features = [ "io-util", "net" ], optional = true }
+tokio = { version = "1.0", features = [ "io-util", "net", "time" ], optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 serde_json = { version = "1.0", optional = true }
 chunked_transfer = { version = "1.4", optional = true }

lightning-block-sync/src/http.rs

@@ -24,6 +24,12 @@ use std::net::TcpStream;
 /// Timeout for operations on TCP streams.
 const TCP_STREAM_TIMEOUT: Duration = Duration::from_secs(5);
 
+/// Timeout for reading the first byte of a response. This is separate from the general read
+/// timeout as it is not uncommon for Bitcoin Core to be blocked waiting on UTXO cache flushes for
+/// upwards of a minute or more. Note that we always retry once when we time out, so the maximum
+/// time we allow Bitcoin Core to block for is twice this value.
+const TCP_STREAM_RESPONSE_TIMEOUT: Duration = Duration::from_secs(120);
+
 /// Maximum HTTP message header size in bytes.
 const MAX_HTTP_MESSAGE_HEADER_SIZE: usize = 8192;
 
@@ -158,16 +164,19 @@ impl HttpClient {
 		let endpoint = self.stream.peer_addr().unwrap();
 		match self.send_request(request).await {
 			Ok(bytes) => Ok(bytes),
-			Err(e) => match e.kind() {
-				std::io::ErrorKind::ConnectionReset |
-				std::io::ErrorKind::ConnectionAborted |
-				std::io::ErrorKind::UnexpectedEof => {
-					// Reconnect if the connection was closed. This may happen if the server's
-					// keep-alive limits are reached.
-					*self = Self::connect(endpoint)?;
-					self.send_request(request).await
-				},
-				_ => Err(e),
+			Err(_) => {
+				// Reconnect and retry on fail. This can happen if the connection was closed after
+				// the keep-alive limits are reached, or generally if the request timed out due to
+				// Bitcoin Core being stuck on a long-running operation or its RPC queue being
+				// full.
+				// Block 100ms before retrying the request as in many cases the source of the error
+				// may be persistent for some time.
+				#[cfg(feature = "tokio")]
+				tokio::time::sleep(Duration::from_millis(100)).await;
+				#[cfg(not(feature = "tokio"))]
+				std::thread::sleep(Duration::from_millis(100));
+				*self = Self::connect(endpoint)?;
+				self.send_request(request).await
 			},
 		}
 	}
@@ -206,25 +215,44 @@ impl HttpClient {
 		#[cfg(not(feature = "tokio"))]
 		let mut reader = std::io::BufReader::new(limited_stream);
 
-		macro_rules! read_line { () => { {
-			let mut line = String::new();
-			#[cfg(feature = "tokio")]
-			let bytes_read = reader.read_line(&mut line).await?;
-			#[cfg(not(feature = "tokio"))]
-			let bytes_read = reader.read_line(&mut line)?;
-
-			match bytes_read {
-				0 => None,
-				_ => {
-					// Remove trailing CRLF
-					if line.ends_with('\n') { line.pop(); if line.ends_with('\r') { line.pop(); } }
-					Some(line)
-				},
-			}
-		} } }
+		macro_rules! read_line {
+			() => { read_line!(0) };
+			($retry_count: expr) => { {
+				let mut line = String::new();
+				let mut timeout_count: u64 = 0;
+				let bytes_read = loop {
+					#[cfg(feature = "tokio")]
+					let read_res = reader.read_line(&mut line).await;
+					#[cfg(not(feature = "tokio"))]
+					let read_res = reader.read_line(&mut line);
+					match read_res {
+						Ok(bytes_read) => break bytes_read,
+						Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
+							timeout_count += 1;
+							if timeout_count > $retry_count {
+								return Err(e);
+							} else {
+								continue;
+							}
+						}
+						Err(e) => return Err(e),
+					}
+				};
+
+				match bytes_read {
+					0 => None,
+					_ => {
+						// Remove trailing CRLF
+						if line.ends_with('\n') { line.pop(); if line.ends_with('\r') { line.pop(); } }
+						Some(line)
+					},
+				}
+			} }
+		}
 
 		// Read and parse status line
-		let status_line = read_line!()
+		// Note that we allow retrying a few times to reach TCP_STREAM_RESPONSE_TIMEOUT.
+		let status_line = read_line!(TCP_STREAM_RESPONSE_TIMEOUT.as_secs() / TCP_STREAM_TIMEOUT.as_secs())
 			.ok_or(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "no status line"))?;
 		let status = HttpStatus::parse(&status_line)?;