Bound sync loops in lightning-transaction-sync

If we start syncing from an electrum or esplora server and find
that the chain moved during our sync, we reset and start fresh.
However, if that happens repeatedly, we probably shouldn't just
spin forever. Here we give up after ten attempts and just hope we
can sync properly later.

Author: TheBlueMatt

lightning-transaction-sync/src/electrum.rs

@@ -96,7 +96,12 @@ impl<L: Logger> ElectrumSyncClient<L> {
 		let mut tip_header = tip_notification.header;
 		let mut tip_height = tip_notification.height as u32;
 
-		loop {
+		for _ in 0..100 {
+			if i >= 10 {
+				log_debug!(self.logger, "Giving up trying to do transaction sync after 10 attempts.");
+				break;
+			}
+
 			let pending_registrations = self.queue.lock().unwrap().process_queues(&mut sync_state);
 			let tip_is_new = Some(tip_header.block_hash()) != sync_state.last_sync_hash;
 

lightning-transaction-sync/src/esplora.rs

@@ -100,7 +100,12 @@ impl<L: Logger> EsploraSyncClient<L> {
 
 		let mut tip_hash = maybe_await!(self.client.get_tip_hash())?;
 
-		loop {
+		for i in 0..100 {
+			if i >= 10 {
+				log_debug!(self.logger, "Giving up trying to do transaction sync after 10 attempts.");
+				break;
+			}
+
 			let pending_registrations = self.queue.lock().unwrap().process_queues(&mut sync_state);
 			let tip_is_new = Some(tip_hash) != sync_state.last_sync_hash;