Background task on remote notification suspended after a short while - ios

Question

I am using remote notification with content-available: true flag to launch the app in the background on silent push notification and process or fetch updates from remote API. The code executes fine when the app is in the foreground, or in suspended state after previous run.
During tests in background when the application is launched by the system based on incoming silent push notification, the code is processed only partially and the app is quickly suspended after about 150 ms. I expected the app will be given 30 seconds to process the incoming notification and its payload. Do I need to adjust the app capabilities or request a background task if I need more time to process and/or fetch new data?
Deployment target iOS 8, testing on iOS 9. Xcode 7.3.1, Swift 2.2.1.
Capabilities: Background Modes ON, Modes: Remote notifications Enabled
AppDelegate
func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
if let userInfo = userInfo as? [String: AnyObject] {
// Processing of the payload is done in separate Operation class (using Operations framework)
// The completion handler is called on the end of the processing/fetching in that operation
// But in case of launching the app in the background it never reaches the call of the completion handler
let parseNotificationOperation = ParseNotificationOperation(userInfo: userInfo, fetchCompletionHandler: completionHandler)
MainService.shared.enqueueApnsOperation(parseNotificationOperation)
}
}

Answer 1

Martin Koles,
You can make use of expirationHandlers to get extended time for background execution. Though how much time will iOS assign to your app depends on various factore which we cant controll we have noticed mostly it provides till 3 mins for our app to execute in background.
Here is how you can achieve it :)
In you AppDelegate declare,
UIBackgroundTaskIdentifier backgroundTask;
and when you recieve APNS inside didReceiveRemoteNotification write this,
if (!backgroundTask || backgroundTask == UIBackgroundTaskInvalid) {
backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
//do all clean up job here gets called few seconds before expiration
[[UIApplication sharedApplication] endBackgroundTask:backgroundTask];
backgroundTask = UIBackgroundTaskInvalid;
}];
}
EDIT
Just realized you are making use of swift so here is code for you in swift :)
Declare a variable called backgroundTask in AppDelegate,
var backgroundTask : UIBackgroundTaskIdentifier = UIBackgroundTaskInvalid
and use it in your didRecieveRemoteNotification as below,
func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
if let userInfo = userInfo as? [String: AnyObject] {
let parseNotificationOperation = ParseNotificationOperation(userInfo: userInfo, fetchCompletionHandler: completionHandler)
MainService.shared.enqueueApnsOperation(parseNotificationOperation)
if (backgroundTask == UIBackgroundTaskInvalid) {
backgroundTask = UIApplication.sharedApplication().beginBackgroundTaskWithExpirationHandler { () -> Void in
self.endTask()
}
}
}
}
Finally write a method to invalidate your expiration handler once you are done with it :)
func endTask(){
//do all your clean up here, this is called few seconds before the task expires.
UIApplication.sharedApplication().endBackgroundTask(backgroundTask)
backgroundTask = UIBackgroundTaskInvalid;
}
That's it :) Happy coding buddy :)