Serialize rebalance trigger checks

Run rebalance trigger checks while holding the balance mutex so concurrent
callers cannot all authorize work from the same stale wallet state.

This keeps trusted and on-chain rebalances from being queued more than
once when rapid payment activity invokes the rebalancer from multiple
paths at the same time.

Author: benthecarman

graduated-rebalancer/src/lib.rs

@@ -256,22 +256,23 @@ where
 
 	/// Does a trusted to lightning rebalance if needed
 	pub async fn do_trusted_rebalance_if_needed(&self) {
+		let _lock = self.balance_mutex.lock().await;
 		if let Some(params) = self.trigger.needs_trusted_rebalance().await {
-			self.do_trusted_rebalance(params).await;
+			self.do_trusted_rebalance_locked(params).await;
 		}
 	}
 
 	/// Does an on-chain to lightning rebalance if needed
 	pub async fn do_onchain_rebalance_if_needed(&self) {
+		let _lock = self.balance_mutex.lock().await;
 		if let Some(params) = self.trigger.needs_onchain_rebalance().await {
-			self.do_onchain_rebalance(params).await;
+			self.do_onchain_rebalance_locked(params).await;
 		}
 	}
 
 	/// Perform a rebalance from trusted to lightning wallet
-	async fn do_trusted_rebalance(&self, params: TriggerParams) {
+	async fn do_trusted_rebalance_locked(&self, params: TriggerParams) {
 		let transfer_amt = params.amount;
-		let _lock = self.balance_mutex.lock().await;
 		log_info!(self.logger, "Initiating rebalance");
 
 		if let Ok(inv) = self.ln_wallet.get_bolt11_invoice(Some(transfer_amt)).await {
@@ -340,9 +341,7 @@ where
 	}
 
 	/// Perform on-chain to lightning rebalance by opening a channel or splicing into an existing one
-	async fn do_onchain_rebalance(&self, params: TriggerParams) {
-		let _lock = self.balance_mutex.lock().await;
-
+	async fn do_onchain_rebalance_locked(&self, params: TriggerParams) {
 		let (channel_outpoint, user_channel_id) = if self.ln_wallet.has_channel_with_lsp() {
 			log_info!(self.logger, "Splicing into channel with LSP with on-chain funds");