fix: prevent channel monitor loss when remote backup fails

Author: pwltr

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

@@ -23,29 +23,12 @@ class LdkPersister {
 
             val isNew = !file.exists()
 
-            if (BackupClient.skipRemoteBackup) {
-                file.writeBytes(data.write())
-                if (isNew) {
-                    LdkEventEmitter.send(EventTypes.new_channel, body)
-                }
-                return ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_Completed
-            }
-
-            BackupClient.addToPersistQueue(BackupClient.Label.CHANNEL_MONITOR(channelId=channelId), data.write()) { error ->
-                if (error != null) {
-                    LdkEventEmitter.send(EventTypes.native_log, "Failed to persist channel (${channelId}) to remote backup: $error")
-                    return@addToPersistQueue
-                }
-
-                try {
-                    file.writeBytes(data.write())
-                } catch (e: Exception) {
-                    //If this fails we can't do much but LDK will retry on startup
-                    LdkEventEmitter.send(EventTypes.native_log, "Failed to locally persist channel (${channelId}) to disk")
-                    return@addToPersistQueue
-                }
+            // Always write locally first
+            val serialized = data.write()
+            file.writeBytes(serialized)
 
-                //Update chain monitor with successful persist
+            // Update chain monitor on main thread to avoid threading issues
+            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})")
@@ -57,7 +40,16 @@ class LdkPersister {
                 }
             }
 
-            return ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_InProgress
+            // Kick off remote backup asynchronously; never block/skip local persist
+            if (!BackupClient.skipRemoteBackup) {
+                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 ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_Completed
         } catch (e: Exception) {
             return ChannelMonitorUpdateStatus.LDKChannelMonitorUpdateStatus_UnrecoverableError
         }

lib/ios/Classes/LdkPersist.swift

@@ -27,33 +27,17 @@ class LdkPersister: Persist {
             }
 
             let isNew = !FileManager().fileExists(atPath: channelStoragePath.path)
-            
-            // If we're not remotely backing up no need to update status later
-            if BackupClient.skipRemoteBackup {
-                try Data(data.write()).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
-                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
-                do {
-                    try Data(data.write()).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)")
-                    return
-                }
-                                
-                // Update chainmonitor with successful persist
-                let res = Ldk.chainMonitor?.channelMonitorUpdated(fundingTxo: channelFundingOutpoint, completedUpdateId: data.getLatestUpdateId())
+
+            // Always write locally first
+            let serialized = Data(data.write())
+            try serialized.write(to: channelStoragePath)
+
+            // Notify chain monitor on main thread to avoid threading issues
+            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 {
@@ -63,10 +47,19 @@ class LdkPersister: Persist {
                     }
                 }
             }
-            
-            return ChannelMonitorUpdateStatus.InProgress
+
+            // Kick off remote backup asynchronously; log but never block/skip local persist
+            if !BackupClient.skipRemoteBackup {
+                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 ChannelMonitorUpdateStatus.Completed
         } catch {
-            LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed to persist channel (\(channelIdHex)) to disk Error \(error.localizedDescription).")
+            LdkEventEmitter.shared.send(withEvent: .native_log, body: "Error. Failed to locally persist channel (\(channelIdHex)). \(error.localizedDescription)")
             return ChannelMonitorUpdateStatus.UnrecoverableError
         }
     }

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",