We would be creating N NWListener objects and M NWConnection objects in our process' communication subsystem to create server sockets, accepted client sockets on server and client sockets on clients. Both NWConnection and NWListener rely on DispatchQueue to deliver state changes, incoming connections, send/recv completions etc. What DispatchQueues should I use and why? Global Concurrent Dispatch Queue (and which QoS?) for all NWConnection and NWListener One custom concurrent queue (which QoS?) for all NWConnection and NWListener? (Does that anyways get targetted to one of the global queues?) One custom concurrent queue per NWConnection and NWListener though all targetted to Global Concurrent Dispatch Queue (and which QoS?)? One custom concurrent queue per NWConnection and NWListener though all targetted to single target custom concurrent queue? For every option above, how am I impacted in terms of parallelism, concurrency, throughput & latency and how is overall system impacted (with other processes also running)? Seperate questions (sorry for the digression): Are global concurrent queues specific to a process or shared across all processes on a device? Can I safely use setSpecific on global dispatch queues in our app?

I am encountering an issue with my application, BloxOneEndpoint.pkg, which includes two services: rc_service_infoblox – Runs as the root user. Controller Application – Runs as a normal user. Although a thread within rc_service_infoblox is running fine and performing its expected tasks, I notice that the service appears as "Not Responding" in Activity Monitor. Despite normal functionality, this status is concerning, as it may indicate some issue to customer. I would appreciate any insights into why this might be happening and how to resolve it. Is there a specific API or mechanism I should use to ensure the service remains in a "Running" state in Activity Monitor? Thank you for your guidance.

I understand that GCD and it's underlying implementations have evolved over time. And many things have not been shared explicitly in Apple documentation. The most concepts of DispatchQueue (serial and concurrent queues), DispatchQoS, target queue and system provided queues: main and globals etc. I have some doubts & questions to clarify: [Main Dispatch Queue] [Link] Because the main queue doesn't behave entirely like a regular serial queue, it may have unwanted side-effects when used in processes that are not UI apps (daemons). For such processes, the main queue should be avoided. What does it mean? Can you elaborate? [Global Concurrent Dispatch Queues] Are they global to a process or across processes on a device. I believe it is the first case but just wanted to be sure. [Global Concurrent Dispatch Queues] Does system create 4 (for each QoS) * 2 (over-commiting and non-overcommiting queues) = 8 queues in all. When does which type of queue comes into play? [Custom Queue][Target Queue concept] [swift-corelibs-libdispatch/man/dispatch_queue_create.3] QUOTE The default target queue of all dispatch objects created by the application is the default priority global concurrent queue. UNQUOTE Is this stil true? We could not find a mention of this in any latest official apple documentation (though some old forum threads (one more) and github code documentation indicate the same). The official documentation only says: [dispatch_set_target_queue] QUOTE If you want the system to provide a queue that is appropriate for the current object UNQUOTE [dispatch_queue_create_with_target] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT to set the target queue to the default type for the current dispatch queue.UNQUOTE [Dispatch>DispatchQueue>init] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT if you want the system to provide a queue that is appropriate for the current object. UNQUOTE What is the difference between passing target queue as 'nil' vs 'DISPATCH_TARGET_QUEUE_DEFAULT' to DispatchQueue init? [Custom Queue][Target Queue concept] [dispatch_set_target_queue] QUOTE The system doesn't allocate threads to the dispatch queue if it has a target queue, unless that target queue is a global concurrent queue. UNQUOTE The system does allocate threads to the custom dispatch queues that have global concurrent queue as the default target. What does that mean? Why does targetting to global concurrent queues mean in that case? [System / GCD Thread Pool] that excutes work items from DispatchQueue: Is this thread pool per queue? or across queues per process? or across processes per device?

Hi, I have a couple questions about background app refresh. First, is the function RefreshAppContentsOperation() where to implement code that needs to be run in the background? Second, despite importing BackgroundTasks, I am getting the error "cannot find operationQueue in scope". What can I do to resolve that? Thank you. func scheduleAppRefresh() { let request = BGAppRefreshTaskRequest(identifier: "peaceofmindmentalhealth.RoutineRefresh") // Fetch no earlier than 15 minutes from now. request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60) do { try BGTaskScheduler.shared.submit(request) } catch { print("Could not schedule app refresh: \(error)") } } func handleAppRefresh(task: BGAppRefreshTask) { // Schedule a new refresh task. scheduleAppRefresh() // Create an operation that performs the main part of the background task. let operation = RefreshAppContentsOperation() // Provide the background task with an expiration handler that cancels the operation. task.expirationHandler = { operation.cancel() } // Inform the system that the background task is complete // when the operation completes. operation.completionBlock = { task.setTaskCompleted(success: !operation.isCancelled) } // Start the operation. operationQueue.addOperation(operation) } func RefreshAppContentsOperation() -> Operation { }

I've been seeing a high number of BGTaskScheduler related crashes, all of them coming from iOS 18.4. I've encountered this myself once on launch upon installing my app, but haven't been able to reproduce it since, even after doing multiple relaunches and reinstalls. Crash report attached at the bottom of this post. I am not even able to symbolicate the reports despite having the archive on my MacBook: Does anyone know if this is an iOS 18.4 bug or am I doing something wrong when scheduling the task? Below is my code for scheduling the background task on the view that appears when my app launches: .onChange(of: scenePhase) { newPhase in if newPhase == .active { #if !os(macOS) let request = BGAppRefreshTaskRequest(identifier: "notifications") request.earliestBeginDate = Calendar.current.date(byAdding: .hour, value: 3, to: Date()) do { try BGTaskScheduler.shared.submit(request) Logger.notifications.log("Background task scheduled. Earliest begin date: \(request.earliestBeginDate?.description ?? "nil", privacy: .public)") } catch let error { // print("Scheduling Error \(error.localizedDescription)") Logger.notifications.error("Error scheduling background task: \(error.localizedDescription, privacy: .public)") } #endif ... } 2025-02-23_19-53-50.2294_+0000-876d2b8ec083447af883961da90398f00562f781.crash