Crash: RCNConfigRealtime fetchLatestConfig:targetVersion - Collection <__NSSetM: 0x30022aae0> was mutated while being enumerated.

yanz-safe commented 2 months ago

Description

I published the application to AppStore recently. Firebase & Apple captured this crash report for 9/150 of users on launch day. All of them are first-time fresh users.

Initially I had Firebase SDK version 10.29. I found this report and though it might be the same crash and update SDK to 11.3.0. Unfortunately, today crash report was reopened by Firebase on new version of app :(

Using Xcode 15.4 now. Cannot migrate right now.

Reproducing the issue

Was not able to reproduce. Attaching the crash report from Xcode, and code where I configure RemoteConfig and use it.

EnvironmentManager is called almost immediately after the @main app struct initializes.

Expand Crash report / SDK 10.29.0 from Xcode Organiser

Expand Crash report / SDK 11.3.0 from Firebase

SwiftUI app with AppDelegate.

Expand AppDelegate+setupRemoteConfig()

```swift final class AppDelegate: NSObject, UIApplicationDelegate { func application( _ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil ) -> Bool { log("didFinishLaunchingWithOptions", launchOptions as Any) FirebaseApp.configure() setupRemoteConfig() application.registerForRemoteNotifications() return true } private func setupRemoteConfig() { let remoteConfig = RemoteConfig.remoteConfig() let remoteSettings = RemoteConfigSettings() if remoteConfig.lastFetchStatus == .noFetchYet || !isReleaseConfiguration() { remoteSettings.minimumFetchInterval = 0 } remoteConfig.configSettings = remoteSettings remoteConfig.fetchAndActivate { status, error in log("[Remote config] fetchAndActivate status = \(status), error = \(String(describing: error))") } remoteConfig.addOnConfigUpdateListener { update, error in let keys = update?.updatedKeys ?? [] log("[Remote config] Remote config update, error = \(String(describing: error))") let sizes = keys.map { "\($0)-\(remoteConfig[$0].dataValue.count)" } log(sizes) remoteConfig.activate() } } } ```

EnvironmentManager where I want to wait a bit to download the config before app is fully initialized

Expand EnvironmentManager.swift

```swift private func remoteConfiguration(forceRefresh: Bool = false) async -> RemoteConfiguration? { if let _remote, !forceRefresh { return _remote } if remoteConfig.lastFetchStatus == .noFetchYet { do { let result: RemoteConfigUpdate? = try await withTimeout(duration: .seconds(5)) { [remoteConfig] in try await withCheckedThrowingContinuation { continuation in var registration: ConfigUpdateListenerRegistration? registration = remoteConfig.addOnConfigUpdateListener { status, error in guard registration != nil else { return } registration?.remove() registration = nil if let error = error { continuation.resume(throwing: error) } else { continuation.resume(returning: status) } } } } if let result { log("Remote config finished with updatedKeys.count = \(result.updatedKeys.count)") } else { log("Remote config finished without status") } } catch { log("Remote config finished", error) } } let configValue = remoteConfig.configValue(forKey: "app_environments") do { let remoteValue: SafeEnvironmentsRemoteConfig = try configValue.decoded() let available = remoteValue.available .map { $0.build(knownList: Self.known) } .filter { $0.enabled } let config = RemoteConfiguration(default: remoteValue.defaultEnvironmentId, available: available) _remote = config return config } catch { log(error) return nil } } ```

After the app is started I am using some keys like remoteConfig.configValue(forKey: "<key>") and by using @RemoteConfigProperty

Code like this can be ran on background thread:

let remoteConfig: HomeScreenConfig = try RemoteConfig.remoteConfig()
                                .configValue(forKey: "home_screen")
                                .decoded()

Firebase SDK Version

11.3.0

Xcode Version

15.4

Installation Method

Swift Package Manager

Firebase Product(s)

Remote Config

Targeted Platforms

iOS

Relevant Log Output

Log from Firebase report
# Crashlytics - Custom logs
# Application: myproject.dot.com
# Platform: apple
# Version: 2.14 (105)
# Issue: a744604c487d9eb321b8bd6288937e6f
# Session: 75cad5ff805b4c15978e35d124c0e37c_DNE_0_v2
# Date: Thu Oct 03 2024 05:49:06 GMT+0530 (India Standard Time)

 0 | Thu Oct 03 2024 05:48:57 GMT+0530 (India Standard Time) | MyProject/AppDelegate.swift:105> didRegisterForRemoteNotificationsWithDeviceToken, <...>
 1 | Thu Oct 03 2024 05:49:00 GMT+0530 (India Standard Time) | MyProject/AppDelegate.swift:115> Firebase registration token, <...>
 2 | Thu Oct 03 2024 05:49:00 GMT+0530 (India Standard Time) | MyProject/AppDelegate.swift:116> Apple registration token, <...>
 3 | Thu Oct 03 2024 05:49:02 GMT+0530 (India Standard Time) | MyProject/EnvironmentManager.swift:139> Remote config finished, MyProject.TimeoutHandlerError.timeoutOccured
 4 | Thu Oct 03 2024 05:49:02 GMT+0530 (India Standard Time) | MyProject/EnvironmentManager.swift:154> Swift.DecodingError.typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Dictionary<String, Any> but found FirebaseRemoteConfigValueDecoderHelper instead.", underlyingError: nil))
 5 | Thu Oct 03 2024 05:49:05 GMT+0530 (India Standard Time) | screen_view -> SplashScreen
10 | Thu Oct 03 2024 05:49:06 GMT+0530 (India Standard Time) | MyProject/EnvironmentManager.swift:134> Remote config finished with updatedKeys.count = 15

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

Expand Package.resolved snippet

If using CocoaPods, the project's Podfile.lock

na

google-oss-bot commented 2 months ago

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

yanz-safe commented 2 months ago

Looks like one more lock is missing inside of completion handler. propogateErrors does not need to be wrapped, as it has its own lock code.

Screenshot 2024-10-03 at 15 46 17

yanz-safe commented 2 months ago

Created PR with fix https://github.com/firebase/firebase-ios-sdk/pull/13776

firebase / firebase-ios-sdk