Move persist into async part of the sweeper

lightning/src/util/sweep.rs

@@ -382,7 +382,7 @@ where
 		output_spender: O, change_destination_source: D, kv_store: K, logger: L,
 	) -> Self {
 		let outputs = Vec::new();
-		let sweeper_state = Mutex::new(SweeperState { outputs, best_block });
+		let sweeper_state = Mutex::new(SweeperState { outputs, best_block, dirty: false });
 		Self {
 			sweeper_state,
 			pending_sweep: AtomicBool::new(false),
@@ -446,7 +446,10 @@ where
 		}
 		self.persist_state(&*state_lock).map_err(|e| {
 			log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-		})
+		})?;
+		state_lock.dirty = false;
+
+		Ok(())
 	}
 
 	/// Returns a list of the currently tracked spendable outputs.
@@ -503,11 +506,19 @@ where
 
 		// See if there is anything to sweep before requesting a change address.
 		{
-			let sweeper_state = self.sweeper_state.lock().unwrap();
+			let mut sweeper_state = self.sweeper_state.lock().unwrap();
 
 			let cur_height = sweeper_state.best_block.height;
 			let has_respends = sweeper_state.outputs.iter().any(|o| filter_fn(o, cur_height));
 			if !has_respends {
+				// If there is nothing to sweep, we still persist the state if it is dirty.
+				if sweeper_state.dirty {
+					self.persist_state(&sweeper_state).map_err(|e| {
+						log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
+					})?;
+					sweeper_state.dirty = false;
+				}
+
 				return Ok(());
 			}
 		}
@@ -531,7 +542,8 @@ where
 				.collect();
 
 			if respend_descriptors.is_empty() {
-				// It could be that a tx confirmed and there is now nothing to sweep anymore.
+				// It could be that a tx confirmed and there is now nothing to sweep anymore. If there is dirty state,
+				// we'll persist it in the next cycle.
 				return Ok(());
 			}
 
@@ -563,6 +575,7 @@ where
 			self.persist_state(&sweeper_state).map_err(|e| {
 				log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
 			})?;
+			sweeper_state.dirty = false;
 
 			self.broadcaster.broadcast_transactions(&[&spending_tx]);
 		}
@@ -588,6 +601,8 @@ where
 			}
 			true
 		});
+
+		sweeper_state.dirty = true;
 	}
 
 	fn persist_state(&self, sweeper_state: &SweeperState) -> Result<(), io::Error> {
@@ -641,13 +656,17 @@ where
 				}
 			}
 		}
+
+		sweeper_state.dirty = true;
 	}
 
 	fn best_block_updated_internal(
 		&self, sweeper_state: &mut SweeperState, header: &Header, height: u32,
 	) {
 		sweeper_state.best_block = BestBlock::new(header.block_hash(), height);
 		self.prune_confirmed_outputs(sweeper_state);
+
+		sweeper_state.dirty = true;
 	}
 }
 
@@ -671,12 +690,8 @@ where
 		assert_eq!(state_lock.best_block.height, height - 1,
 			"Blocks must be connected in chain-order - the connected block height must be one greater than the previous height");
 
-		self.transactions_confirmed_internal(&mut *state_lock, header, txdata, height);
-		self.best_block_updated_internal(&mut *state_lock, header, height);
-
-		let _ = self.persist_state(&*state_lock).map_err(|e| {
-			log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-		});
+		self.transactions_confirmed_internal(&mut state_lock, header, txdata, height);
+		self.best_block_updated_internal(&mut state_lock, header, height);
 	}
 
 	fn block_disconnected(&self, header: &Header, height: u32) {
@@ -698,9 +713,7 @@ where
 			}
 		}
 
-		self.persist_state(&*state_lock).unwrap_or_else(|e| {
-			log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-		});
+		state_lock.dirty = true;
 	}
 }
 
@@ -720,9 +733,6 @@ where
 	) {
 		let mut state_lock = self.sweeper_state.lock().unwrap();
 		self.transactions_confirmed_internal(&mut *state_lock, header, txdata, height);
-		self.persist_state(&*state_lock).unwrap_or_else(|e| {
-			log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-		});
 	}
 
 	fn transaction_unconfirmed(&self, txid: &Txid) {
@@ -743,18 +753,13 @@ where
 				.filter(|o| o.status.confirmation_height() >= Some(unconf_height))
 				.for_each(|o| o.status.unconfirmed());
 
-			self.persist_state(&*state_lock).unwrap_or_else(|e| {
-				log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-			});
+			state_lock.dirty = true;
 		}
 	}
 
 	fn best_block_updated(&self, header: &Header, height: u32) {
 		let mut state_lock = self.sweeper_state.lock().unwrap();
-		self.best_block_updated_internal(&mut *state_lock, header, height);
-		let _ = self.persist_state(&*state_lock).map_err(|e| {
-			log_error!(self.logger, "Error persisting OutputSweeper: {:?}", e);
-		});
+		self.best_block_updated_internal(&mut state_lock, header, height);
 	}
 
 	fn get_relevant_txids(&self) -> Vec<(Txid, u32, Option<BlockHash>)> {
@@ -783,11 +788,13 @@ where
 struct SweeperState {
 	outputs: Vec<TrackedSpendableOutput>,
 	best_block: BestBlock,
+	dirty: bool,
 }
 
 impl_writeable_tlv_based!(SweeperState, {
 	(0, outputs, required_vec),
 	(2, best_block, required),
+	(_unused, dirty, (static_value, false)),
 });
 
 /// A `enum` signalling to the [`OutputSweeper`] that it should delay spending an output until a