fix: persist channel locally in case remote backup fails

Author: pwltr

lib/android/src/main/java/com/reactnativeldk/classes/LdkPersister.kt

@@ -22,23 +22,52 @@ class LdkPersister {
             val file = File(LdkModule.channelStoragePath + "/" + channelId  + ".bin")
 
             val isNew = !file.exists()
+            val serialized = data.write()
 
+            // If we're not remotely backing up, write locally and return
             if (BackupClient.skipRemoteBackup) {
-                file.writeBytes(data.write())
+                file.writeBytes(serialized)
                 if (isNew) {
                     LdkEventEmitter.send(EventTypes.new_channel, body)
                 }
                 return ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_Completed
             }
 
-            BackupClient.addToPersistQueue(BackupClient.Label.CHANNEL_MONITOR(channelId=channelId), data.write()) { error ->
+            // For new channels: write locally first to prevent loss if app is killed during backup
+            // Then try remote backup asynchronously
+            if (isNew) {
+                file.writeBytes(serialized)
+                
+                // Update chain monitor on main thread
+                LdkModule.reactContext?.runOnUiThread {
+                    val res = LdkModule.chainMonitor?.channel_monitor_updated(channelFundingOutpoint, data._latest_update_id)
+                    if (res == null || !res.is_ok) {
+                        LdkEventEmitter.send(EventTypes.native_log, "Failed to update chain monitor with persisted channel (${channelId})")
+                    } else {
+                        LdkEventEmitter.send(EventTypes.native_log, "Persisted channel (${channelId}) to disk")
+                        LdkEventEmitter.send(EventTypes.new_channel, body)
+                    }
+                }
+                
+                // Kick off remote backup asynchronously (non-blocking)
+                BackupClient.addToPersistQueue(BackupClient.Label.CHANNEL_MONITOR(channelId=channelId), serialized) { error ->
+                    if (error != null) {
+                        LdkEventEmitter.send(EventTypes.native_log, "Warning. Remote backup failed for new channel (${channelId}), but channel was persisted locally. $error")
+                    }
+                }
+                
+                return ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_Completed
+            }
+
+            // For updates: try remote backup first, then write locally on success (original behavior)
+            BackupClient.addToPersistQueue(BackupClient.Label.CHANNEL_MONITOR(channelId=channelId), serialized) { error ->
                 if (error != null) {
                     LdkEventEmitter.send(EventTypes.native_log, "Failed to persist channel (${channelId}) to remote backup: $error")
                     return@addToPersistQueue
                 }
 
                 try {
-                    file.writeBytes(data.write())
+                    file.writeBytes(serialized)
                 } catch (e: Exception) {
                     //If this fails we can't do much but LDK will retry on startup
                     LdkEventEmitter.send(EventTypes.native_log, "Failed to locally persist channel (${channelId}) to disk")
@@ -51,9 +80,6 @@ class LdkPersister {
                     LdkEventEmitter.send(EventTypes.native_log, "Failed to update chain monitor with persisted channel (${channelId})")
                 } else {
                     LdkEventEmitter.send(EventTypes.native_log, "Persisted channel (${channelId}) to disk")
-                    if (isNew) {
-                        LdkEventEmitter.send(EventTypes.new_channel, body)
-                    }
                 }
             }
 

lib/ios/Classes/LdkPersist.swift

@@ -27,25 +27,56 @@ class LdkPersister: Persist {
             }
 
             let isNew = !FileManager().fileExists(atPath: channelStoragePath.path)
+            let serialized = Data(data.write())
 
             // If we're not remotely backing up no need to update status later
             if BackupClient.skipRemoteBackup {
-                try Data(data.write()).write(to: channelStoragePath)
+                try serialized.write(to: channelStoragePath)
                 if isNew {
                     LdkEventEmitter.shared.send(withEvent: .new_channel, body: body)
                 }
                 return ChannelMonitorUpdateStatus.Completed
             }
-                         
-            BackupClient.addToPersistQueue(.channelMonitor(id: channelIdHex), data.write()) { error in
+            
+            // For new channels: write locally first to prevent loss if app is killed during backup
+            // Then try remote backup asynchronously
+            if isNew {
+                try serialized.write(to: channelStoragePath)
+                
+                // Notify chain monitor on main thread
+                DispatchQueue.main.async {
+                    let res = Ldk.chainMonitor?.channelMonitorUpdated(
+                        fundingTxo: channelFundingOutpoint,
+                        completedUpdateId: data.getLatestUpdateId()
+                    )
+                    if let error = res?.getError() {
+                        LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed to update chain monitor for channel (\(channelIdHex)) Error \(error.getValueType()).")
+                    } else {
+                        LdkEventEmitter.shared.send(withEvent: .native_log, body: "Persisted channel \(channelIdHex). Update ID: \(data.getLatestUpdateId())")
+                        LdkEventEmitter.shared.send(withEvent: .new_channel, body: body)
+                    }
+                }
+                
+                // Kick off remote backup asynchronously (non-blocking)
+                BackupClient.addToPersistQueue(.channelMonitor(id: channelIdHex), [UInt8](serialized)) { error in
+                    if let error {
+                        LdkEventEmitter.shared.send(withEvent: .native_log, body: "Warning. Remote backup failed for new channel (\(channelIdHex)), but channel was persisted locally. \(error.localizedDescription)")
+                    }
+                }
+                
+                return ChannelMonitorUpdateStatus.Completed
+            }
+            
+            // For updates: try remote backup first, then write locally on success (original behavior)
+            BackupClient.addToPersistQueue(.channelMonitor(id: channelIdHex), [UInt8](serialized)) { error in
                 if let error {
                     LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed persist channel on remote server (\(channelIdHex)). \(error.localizedDescription)")
                     return
                 }
 
-                // Callback for when the persist queue queue entry is processed
+                // Callback for when the persist queue entry is processed
                 do {
-                    try Data(data.write()).write(to: channelStoragePath)
+                    try serialized.write(to: channelStoragePath)
                 } catch {
                     // If this fails we can't do much but LDK will retry on startup
                     LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed to locally persist channel (\(channelIdHex)). \(error.localizedDescription)")
@@ -58,9 +89,6 @@ class LdkPersister: Persist {
                     LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed to update chain monitor for channel (\(channelIdHex)) Error \(error.getValueType()).")
                 } else {
                     LdkEventEmitter.shared.send(withEvent: .native_log, body: "Persisted channel \(channelIdHex). Update ID: \(data.getLatestUpdateId())")
-                    if isNew {
-                        LdkEventEmitter.shared.send(withEvent: .new_channel, body: body)
-                    }
                 }
             }
 

lib/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@synonymdev/react-native-ldk",
   "title": "React Native LDK",
-  "version": "0.0.160",
+  "version": "0.0.161",
   "description": "React Native wrapper for LDK",
   "main": "./dist/index.js",
   "types": "./dist/index.d.ts",