broker: send a heartbeat message every ten messages in the root loop

prunes extraneous data on the hardware signer

broker/src/looper.rs

@@ -5,9 +5,11 @@ use log::*;
 use rocket::tokio::sync::mpsc;
 use secp256k1::PublicKey;
 use sphinx_signer::{parser, sphinx_glyph::topics};
+use std::num::Wrapping;
 use std::sync::atomic::{AtomicU16, Ordering};
 use std::thread;
 use std::time::Duration;
+use vls_protocol::msgs::SerBolt;
 use vls_protocol::{msgs, msgs::Message, Error, Result};
 use vls_proxy::client::Client;
 
@@ -96,6 +98,8 @@ impl<C: 'static + Client> SignerLoop<C> {
     }
 
     fn do_loop(&mut self, settings: Option<Settings>) -> Result<()> {
+        // This counter is only used in the root loop to periodically send heartbeats to the hardware signer
+        let mut send_heartbeat = Wrapping(0u8);
         loop {
             let raw_msg = self.client.read_raw()?;
             // debug!("loop {}: got raw", self.log_prefix);
@@ -141,9 +145,17 @@ impl<C: 'static + Client> SignerLoop<C> {
                     let reply = self.handle_message(raw_msg, catch_init)?;
                     // Write the reply to CLN
                     self.client.write_vec(reply)?;
+                    // Only send heartbeat messages from the root loop, as roothandler alone can process them, not channelhandler
+                    // Send it every ten messages to prune extraneous data on hardware signer
+                    if self.client_id.is_none() && send_heartbeat % Wrapping(10u8) == Wrapping(0u8)
+                    {
+                        let beat = msgs::GetHeartbeat {};
+                        let _ = self.handle_message(beat.as_vec(), false)?;
                     }
                 }
             }
+            send_heartbeat += 1;
+        }
     }
 
     fn handle_message(&mut self, message: Vec<u8>, catch_init: bool) -> Result<Vec<u8>> {