Level 1 (0 points)
I'm getting a
Error Domain=NSURLErrorDomain Code=-997 "Lost connection to background transfer service"
when I lock my screen after starting a background download process. I'm using Alamofire but I assume this would happen on a regular URLSession as well (because internally Alamofire is using URLSession). The downloads continue to work if I soft close the app but as soon as I lock my device, it start throwing this error.
The URLSession is created this way:
let config = URLSessionConfiguration.background(withIdentifier: "MySession")
config.isDiscretionary = true
config.sessionSendsLaunchEvents = true
config.shouldUseExtendedBackgroundIdleMode = true
I looked at the Console to see if any daemon crashed but couldn't find any. I see three errors right after locking the screen:
BKLogEvent: couldn't find CombinedSequence properties
Task <>.<48> finished with error - code: -999
Task <>.<48> load failed with error Error Domain=NSURLErrorDomain Code=-997 "Lost connection to background transfer service" UserInfo={NSErrorFailingURLStringKey=, NSErrorFailingURLKey=, _NSURLErrorRelatedURLSessionTaskErrorKey=, _NSURLErrorFailingURLSessionTaskErrorKey=, NSLocalizedDescription=Lost connection to background transfer service} [-997]
The error._userInfo is:
▿ Optional<AnyObject> ▿ some : 5 elements ▿ 0 : 2 elements - key : NSErrorFailingURLStringKey - value : https://www.myweb.com/api ▿ 1 : 2 elements - key : NSErrorFailingURLKey - value : https://www.myweb.com/api ▿ 2 : 2 elements - key : _NSURLErrorRelatedURLSessionTaskErrorKey ▿ value : 2 elements - 0 : BackgroundDataTask <C39E-2FC73>.<27> - 1 : LocalDataTask <C39E-2FC73>.<27> ▿ 3 : 2 elements - key : _NSURLErrorFailingURLSessionTaskErrorKey - value : BackgroundDataTask <C39E-2FC73>.<27> ▿ 4 : 2 elements - key : NSLocalizedDescription - value : Lost connection to background transfer service
I've about 300 of these background tasks. They will continue to work as long as I don't lock my device but as soon as I lock the device it starts throwing this error. My initial thought was that it was some sort of File protection errors but the userInfo from error doesn't point that way.
Apple Staff 
