Increase the timeout for RPC responses from Bitcoin Core

Early sample testing showed multiple users hitting
EWOULDBLOCK/EAGAIN waiting for an initial response from Bitcoin
Core while it was doing some long operation (eg UTXO cache
flushing). Instead of only waiting 5 seconds for each attempt, we
now wait a full two minutes, but only for the first header
response, not each byte.

diff --git a/lightning-block-sync/src/http.rs b/lightning-block-sync/src/http.rs
index 1f5f046c0f87dd904820e7f97718b1a3ba16ac15..2cfb8e50593d4aef4dc283f47655b3d6d8b5dc6d 100644 (file)
--- a/lightning-block-sync/src/http.rs
+++ b/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;
 
@@ -209,25 +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)?;