Firebase Realtime Database Observers Stop After NSPOSIXErrorDomain Code=89 Error on iOS (Xcode 15.3, Firebase SDK 11.3.0)

### Description

I'm developing an iOS app with SwiftUI using Xcode 15.3 and Firebase SDK 11.3.0. The app relies on Firebase Realtime Database to monitor foodEntries with observers for real-time updates.

**Implementation Overview:**

Observers Setup: Listens to foodEntries node for .childAdded and .childChanged events.
Connection Monitoring: Uses .info/connected reference and NWPathMonitor to track network status.
Issue:

Approximately 1 in 10 launches, either on app start or when returning from background, I encounter the following console error:

> 2024-10-10 17:49:08.588502+0200 MyApp[22614:2112636] [[FirebaseDatabase]] 11.3.0 - [FirebaseDatabase][I-RDB083016] Error sending web socket data: Error Domain=NSPOSIXErrorDomain Code=89 "Operation canceled" UserInfo={NSDescription=Operation canceled}.

**Consequences**:

**Observers Stop Working:** The observers' callbacks are no longer triggered, halting real-time updates.
**Connection Status Untracked:** The _.info/connected_ reference doesn’t update, preventing detection of connection issues.
**Partial Connectivity:** Data writes may still work, but observers fail post-error.

**Temporary Workaround:**

Sending the app to the background and bringing it back to the foreground resets the Firebase connection, temporarily restoring observer functionality.

**What I've Tried:**

**Reinitializing Observers:** Removing and re-adding observers on connection issues.
**Network Monitoring:** Implemented NWPathMonitor to handle reconnections.
**Error Handling:** Attempted retries on data operation failures.
**App Check Adjustments:** Enforced and removed App Check on the server side without success _(currently testing removal of setAppCheckProviderFactory & AppCheck.appCheck() on client side)_.

**Additional Observation:**

I've noticed that the issue is easier to reproduce on a 3G network compared to a stable Wi-Fi connection, though this is just a guess based on 3-4 days of testing.

**Relevant Configuration:**

```
FirebaseApp.configure()
FirebaseConfiguration.shared.setLoggerLevel(.debug)
Database.database().isPersistenceEnabled = true

class AppCheckProviderFactory: NSObject, AppCheckProviderFactory {
func createProvider(with app: FirebaseApp) -> AppCheckProvider? {
if #available(iOS 14.0, *) {
return AppAttestProvider(app: app)
} else {
return DeviceCheckProvider(app: app)
}
}
}

let providerFactory = AppCheckProviderFactory()
AppCheck.setAppCheckProviderFactory(providerFactory)
_ = AppCheck.appCheck()

```

**Problem:**

It seems that the Firebase initialization code might be causing the connection issue, as .info/connected remains unchanged and observers stop receiving updates after the error.

**Questions:**

**Cause Identification:** Why does the NSPOSIXErrorDomain Code=89 "Operation canceled" error occur, and how does it affect Firebase's WebSocket connections?
**Robust Error Handling:** What are best practices to handle such network-related errors to maintain continuous observer functionality?
**Network Monitoring Integration:** How can I effectively integrate network monitoring to trigger Firebase reconnections without manual app state resets?
**Alternative Solutions:** Are there other approaches or Firebase configurations that can prevent this issue?

**Additional Information:**

**Offline Persistence:** Enabled.
**Environment:** Issue occurs on both simulators and physical devices with stable internet.
**App Lifecycle Management:** Observers are set up when the app becomes active and removed when it resigns active.

Any guidance or examples on resolving this Firebase connection error and ensuring reliable observer functionality would be greatly appreciated!

### Reproducing the issue

```
import FirebaseDatabase
import Network
import Combine

class UserData: ObservableObject {
private let monitor = NWPathMonitor()
private let networkQueue = DispatchQueue(label: "NetworkMonitor")
private var cancellables = Set()

@Published var isAppFirebaseConnected: Bool = false
@Published var isAppNetworkConnected: Bool = false

init() {
setupFirebaseMonitoring()
startNetworkMonitoring()
}

private func setupFirebaseMonitoring() {
let db = Database.database().reference()
let connectedRef = db.child(".info/connected")

connectedRef.observe(.value) { [weak self] snapshot in
if let connected = snapshot.value as? Bool {
DispatchQueue.main.async {
self?.isAppFirebaseConnected = connected
if connected {
print("Firebase is connected.")
// Initialize observers here
self?.initObservers()
} else {
print("Firebase is disconnected.")
self?.removeObservers()
}
}
}
}
}

private func startNetworkMonitoring() {
monitor.pathUpdateHandler = { [weak self] path in
let isConnected = path.status == .satisfied
DispatchQueue.main.async {
self?.isAppNetworkConnected = isConnected
print("Network connection status: \(isConnected ? "Connected" : "Disconnected")")

if isConnected && self?.isAppFirebaseConnected == false {
// Attempt to reconnect Firebase if needed
self?.reconnectFirebase()
}
}
}
monitor.start(queue: networkQueue)
}

private func initObservers() {
let db = Database.database().reference()
db.child("foodEntries").observe(.childAdded) { snapshot in
// Handle new food entry
print("New food entry added: \(snapshot.key)")
}

db.child("foodEntries").observe(.childChanged) { snapshot in
// Handle updated food entry
print("Food entry updated: \(snapshot.key)")
}
}

private func removeObservers() {
let db = Database.database().reference()
db.child("foodEntries").removeAllObservers()
print("Removed all Firebase observers.")
}

private func reconnectFirebase() {
print("Attempting to reconnect Firebase...")
Database.database().goOffline()
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
Database.database().goOnline()
}
}
}
```

### Firebase SDK Version

11.3.0

### Xcode Version

15.3

### Installation Method

Swift Package Manager

### Firebase Product(s)

App Check, Database

### Targeted Platforms

iOS

### Relevant Log Output

```shell
2024-10-10 17:49:08.588502+0200 MyApp[22614:2112636] [[FirebaseDatabase]] 11.3.0 - [FirebaseDatabase][I-RDB083016] Error sending web socket data: Error Domain=NSPOSIXErrorDomain Code=89 "Operation canceled" UserInfo={NSDescription=Operation canceled}.
```

### If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

```json

Replace this line with the contents of your Package.resolved.

```

### If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

```yml

Replace this line with the contents of your Podfile.lock!

```