fix: prevent main app from blocking notification extension (take 4) - WPB-23511 by samwyndham · Pull Request #4880 · wireapp/wire-ios

samwyndham · 2026-06-22T07:11:20Z

WPB-23511 [iOS] NSE is often getting stuck and expiring

Issue

This is yet another attempt to fix issues with expiring activity. The key decisions this time are:

From the main app (where UIApplication is available) always use the beginBackgroundTask(expirationHandler:) API instead of the performExpiringActivity(withReason:using:) API. This requires no semaphore and in dummy app found that this worked perfectly fine with 1000 simultaneous tasks vs the 64 tasks of performExpiringActivity(withReason:using:).
Deleted the current implementation of withExpiringActivity. I replaced it with a similar method, withBackgroundTask that takes a BackgroundTaskExecuter which is a protocol. In the main app we pass in a AppBackgroundTaskExecuter which uses the beginBackgroundTask(expirationHandler:) API. From the app extensions we currently pass in a PassthroughTaskExecuter which does nothing but perform the task (but could be changed.) The idea is to allow different implementations per target.
From tests I found that we must show the notification within a very short time after UNNotificationServiceExtension.serviceExtensionTimeWillExpire is called. Extending background time doesn't help here. However using performExpiringActivity(withReason:using: does appear to give us more time to allow for clean up. So in this implementation once UNNotificationServiceExtension.serviceExtensionTimeWillExpire is called I cancel the ongoing task using performExpiringActivity(withReason:using: to give us extra time for the cancellation to succeed.
From the share extension I do something similar which is triggered when the the extension enters the background or the user hits cancel - basically give extra time for the cancellation to succeed.
I intentionally didn't abstract cancellation using performExpiringActivity because I feel the necessary Semaphore usage is a hack so we shouldn't encourage it.

Testing

@johnxnguyen Any ideas here? The only thing I can think of is to monitor logging while the app is being used.

Checklist

Title contains a reference JIRA issue number like [WPB-XXX].
Description is filled and free of optional paragraphs.
Adds/updates automated tests.

…(eventID:contentHandler:)` is cancelled

…ypto`.

…piringActivity(reason:block:)`

…ocessInfo:)`

…meout:processInfo:)`" This reverts commit 891ff0b.

samwyndham · 2026-06-22T07:12:58Z

-                block: block
-            )
-        } else {
+        try await withBackgroundTask(


This is now always performed but will use a PassthroughTaskExecuter when called from an app extension.

Copilot

Pull request overview

This PR refactors background-time handling across the main app and app extensions to prevent the main app from blocking the Notification Service Extension (NSE), primarily by replacing performExpiringActivity usage in the main app with UIApplication.beginBackgroundTask(...) via an injectable background-task executor.

Changes:

Introduces BackgroundTaskExecuter + withBackgroundTask(...), and threads the executor through sync/crypto/session construction.
Adds AppBackgroundTaskExecuter (main app) and uses PassthroughTaskExecuter for extensions/tests.
Updates NSE and Share Extension cancellation paths to attempt cleanup under performExpiringActivity(...).

Reviewed changes

Copilot reviewed 51 out of 51 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
WireDomain/Tests/WireDomainTests/Synchronization/PullPendingUpdateEventsSyncV2Tests.swift	Updates `SafeCoreCrypto` construction for new background task executor dependency.
WireDomain/Tests/WireDomainTests/Synchronization/IncrementalSyncV2Tests.swift	Injects `PassthroughTaskExecuter` into `SafeCoreCrypto` and `IncrementalSyncV2`.
WireDomain/Tests/WireDomainTests/Synchronization/IncrementalSyncTests.swift	Injects `PassthroughTaskExecuter` into `IncrementalSync`.
WireDomain/Sources/WireDomain/Synchronization/IncrementalSyncV2.swift	Wraps live sync processing in `withBackgroundTask(...)` using injected executor.
WireDomain/Sources/WireDomain/Synchronization/IncrementalSync.swift	Wraps live sync processing in `withBackgroundTask(...)` using injected executor.
WireDomain/Sources/WireDomain/Notifications/Protocols/NotificationServiceProtocol.swift	Removes protocol (NSE wiring now uses concrete type).
WireDomain/Sources/WireDomain/Notifications/NotificationServiceExtension.swift	Removes protocol conformance; adds `hasOnGoingTask` + async `cancel()`.
WireDomain/Sources/WireDomain/Notifications/Components/NSEUserScope.swift	Threads background task executor into user/client scopes; simplifies `processPayload` call.
WireDomain/Sources/WireDomain/Notifications/Components/NSEFlow.swift	Uses a shared `PassthroughTaskExecuter` for NSE-scoped components.
WireDomain/Sources/WireDomain/Notifications/Components/NSEClientScope.swift	Refactors payload processing tasks/monitoring and injects background task executor into crypto provider.
WireDomain/Sources/WireDomain/Components/UserSessionComponent.swift	Adds background task executor dependency and passes it to child components.
WireDomain/Sources/WireDomain/Components/ClientSessionComponent.swift	Adds background task executor dependency and injects into sync implementations.
wire-ios/Wire-iOS/Sources/AppRootRouter.swift	Adds background task executor dependency for app root construction.
wire-ios/Wire-iOS/Sources/AppDelegate.swift	Constructs `AppBackgroundTaskExecuter` and passes it into session/app wiring.
wire-ios/Wire-iOS/Sources/AppBackgroundTaskExecuter.swift	Adds main-app executor using `UIApplication.beginBackgroundTask(...)`.
wire-ios/Wire-iOS Share Extension/Sources/Content/PostContent.swift	Adds logging and uses `performExpiringActivity(...)` to allow cancellation cleanup.
wire-ios/Wire Notification Service Extension/NotificationService.swift	Switches to concrete `NotificationServiceExtension`; cancels ongoing work on expiry with expiring activity + timeout.
wire-ios-system/Tests/ExpiringActivityTests.swift	Removes expiring-activity tests (old mechanism removed).
wire-ios-system/Source/ExpiringActivity.swift	Removes `withExpiringActivity(...)` implementation.
wire-ios-system/Source/BackgroundTasks.swift	Introduces executor protocol, passthrough executor, and helper `withBackgroundTask(...)`.
wire-ios-sync-engine/Tests/Source/UserSession/ZMUserSessionTestsBase.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-sync-engine/Tests/Source/UserSession/ZMUserSessionTests_NetworkState.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-sync-engine/Tests/Source/Use cases/CheckOneOnOneConversationIsReadyUseCaseTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-sync-engine/Tests/Source/Synchronization/SyncAgentTests.swift	Injects `PassthroughTaskExecuter` into `SyncAgent`.
wire-ios-sync-engine/Tests/Source/E2EI/CertificateRevocationListsCheckerTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-sync-engine/Source/UserSession/ZMUserSession/ZMUserSessionBuilder.swift	Supplies a `PassthroughTaskExecuter` for builder-created sessions.
wire-ios-sync-engine/Source/UserSession/ZMUserSession/ZMUserSession.swift	Threads executor through session/component/sync strategy construction.
wire-ios-sync-engine/Source/Synchronization/SyncAgent.swift	Replaces `withExpiringActivity(...)` with `withBackgroundTask(...)`.
wire-ios-sync-engine/Source/Synchronization/StrategyDirectory.swift	Adds executor parameter and passes it into strategy factory.
wire-ios-sync-engine/Source/SessionManager/UserSessionLoader.swift	Replaces direct `UIApplication.shared` background-task manager usage with injected executor.
wire-ios-sync-engine/Source/SessionManager/SessionManager.swift	Stores executor and passes it into loaders and related wiring.
wire-ios-share-engine/WireShareEngineTests/BaseSharingSessionTests.swift	Injects `PassthroughTaskExecuter` into strategy directory.
wire-ios-share-engine/Sources/StrategyFactory.swift	Adds executor dependency to strategy wiring.
wire-ios-share-engine/Sources/SharingSessionLoader.swift	Uses a `PassthroughTaskExecuter` and injects into crypto + strategies.
wire-ios-share-engine/Sources/SharingSession.swift	Uses a `PassthroughTaskExecuter` and injects into crypto + strategies.
wire-ios-request-strategy/Tests/Helpers/ProteusClientSimulator.swift	Updates `CoreCryptoProvider` init for executor dependency.
wire-ios-request-strategy/Tests/Helpers/MessagingTestBase.swift	Updates `CoreCryptoProvider` init for executor dependency.
wire-ios-request-strategy/Sources/Message Sending/MessageSenderTests.swift	Injects `PassthroughTaskExecuter` into `MessageSender` construction in tests.
wire-ios-request-strategy/Sources/Message Sending/MessageSender.swift	Wraps send/broadcast operations with `withBackgroundTask(...)` using injected executor.
wire-ios-request-strategy/Sources/E2EIdentity/E2EIKeyPackageRotatorTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/UseCases/IsUserE2EICertifiedUseCaseTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/Proteus/ProteusServiceTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/MLS/MLSServiceTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/MLS/MLSEncryptionServiceTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/MLS/MLSActionExecutorTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/E2EIdentity/E2EIVerificationStatusServiceTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Tests/E2EIdentity/E2EIServiceTests.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Support/Sources/CoreCryptoMocksEnvelope.swift	Updates `SafeCoreCrypto` construction for executor dependency.
wire-ios-data-model/Source/Utilis/BackgroundTaskManager.swift	Removes old `UIApplication` background task abstraction.
wire-ios-data-model/Source/Core Crypto/SafeCoreCrypto.swift	Moves transaction wrapping to `withBackgroundTask(...)`.
wire-ios-data-model/Source/Core Crypto/CoreCryptoProvider.swift	Replaces optional background task manager with required executor injection.

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github-actions · 2026-06-22T07:20:33Z