generateGeodatabaseWithParameters detecting network error in FetchingResult status

JoshuaHudson

Ok, I have the following code in generateGeodatabaseWithParameters it fires fine and calculates the download speed. The problem I'm having is if a network disruption happens in the AGSResumableTaskJobStatus.FetchingResult status state, I no longer get  status updates, and the call never timeouts. So to the user it just looks like their download has frozen forever. I have a cancel button and I can cancel it but I would rather detect the error and let the user knows that the generate process has failed during that step.

if status == AGSResumableTaskJobStatus.FetchingResult {                                                                 if let userinfo = userInfo  {                                                                         totalBytesDownloaded = userinfo["AGSDownloadProgressTotalBytesDownloaded"] as? NSNumber                                     totalBytesExpected = userinfo["AGSDownloadProgressTotalBytesExpected"] as? NSNumber                                                                         if totalBytesDownloaded != nil && totalBytesExpected != nil {                                                                                 elapsedTime = CACurrentMediaTime() - weakSelf.startTimeMapDl                                         elapsedSeconds = UInt(elapsedTime)                                                                                 if elapsedSeconds > 0 && elapsedSeconds != previousSeconds {                                                                                         var bytesPerSecond = UInt(0)                                                                                         if previousSeconds == 0 {                                                 dispatch_async(dispatch_get_main_queue()) {                                                     weakSelf.currentDownloadSpeedHeaderLabel.text = "Current D/L Speed:"                                                 }                                                 bytesPerSecond = totalBytesDownloaded!.unsignedLongValue / elapsedSeconds                                             }                                             else {                                                 bytesPerSecond = (totalBytesDownloaded!.unsignedLongValue - previousBytesDownloaded.unsignedLongValue ) / (elapsedSeconds - previousSeconds )                                             }                                                                                         //dl speed bounced between 0 and some other number if checked every second, so spreading it out over 3 seconds                                             //for a better UI experience.  It still bounces around, but not as much.                                                                                         let secondsDifference = elapsedSeconds - previousSeconds                                                                                         if secondsDifference > 1 && previousBytesDownloaded.unsignedLongValue != totalBytesDownloaded!.unsignedLongValue {                                                                                               dispatch_async(dispatch_get_main_queue()) {                                                     weakSelf.currentDownloadSpeedLabel.text = "\(NSByteCountFormatter.stringFromByteCount(Int64(bytesPerSecond), countStyle:NSByteCountFormatterCountStyle.File))"                                                 }                                                                                                 previousBytesDownloaded = totalBytesDownloaded!                                                 previousSeconds = elapsedSeconds                                                                                             }                                         }                                     }                                 }                             }

For other status states if there is an error I get a error message in the user info, but that does not populate or fire in the fetching result stage.

This at the top of the method call detects network errors for all states, but since FetchingResults never calls back, it can't run.

weakSelf.agsResumableTaskJob = weakSelf.gdbSyncTask?.generateGeodatabaseWithParameters(params,                         downloadFolderPath: nil,                         useExisting: false,                         status: { status, userInfo in                                                         if let userinfo = userInfo {                                                                 if let error = userinfo["statusRequestError"] {                                                                         print("Error: Could not generate geodatabase. Error details:\(error)")                                     errorOccured = true                                     weakSelf.agsResumableTaskJob?.cancel()                                                                         if error.localizedDescription == "The Internet connection appears to be offline." {                                                                                 dispatch_async(dispatch_get_main_queue()) {                                                                                         let alert = UIAlertController(title: "Network Error",                                                 message: "Could not download the map inventory.Please verify you are connected to the Network and try again.",                                                 preferredStyle: UIAlertControllerStyle.Alert)                                                                                         alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))                                                                                         weakSelf.presentViewController(alert, animated: true, completion: nil)                                         }                                     }                                     else if error.localizedDescription == "A server with the specified hostname could not be found." {                                                                                 dispatch_async(dispatch_get_main_queue()) {                                                                                         let alert = UIAlertController(title: "Network Error",                                                 message: "Could not download the map inventory.Please verify you are connected to the Network and try again.",                                                 preferredStyle: UIAlertControllerStyle.Alert)                                                                                         alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))                                                                                         weakSelf.presentViewController(alert, animated: true, completion: nil)                                         }                                     }                                     else {                                         dispatch_async(dispatch_get_main_queue()) {                                                                                         let alert = UIAlertController(title: "Error",                                                 message: "Could not download the map inventory.Please verify you are connected to the Network and try again.",                                                 preferredStyle: UIAlertControllerStyle.Alert)                                                                                         alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))                                                                                         weakSelf.presentViewController(alert, animated: true, completion: nil)                                         }                                     }                                                                     }                             }

Using the latest sdk build (10.2.5)

DiveshGoyal

Thanks for reporting this, Joshua

I can confirm that the status or completion blocks are not invoked when the download gets interrupted. We will look into this and evaluate what is the best behavior to implement going forward. Thinking about it some more, we don't want to prematurely fail the operation because even a slight hiccup in the network while downloading the result would fail the whole job and require the user to initiate the whole process again. As it stands today, eventhough the download appears to hang indefinitely, it does automatically restart when the network is restored. So on the bright side, it is resilient to transient network conditions. Ideally, we would have some internal timeout beyond which we would notify you and let you make the appropriate decision for your app.

In the meantime, if you want to provide a better UX where the user can put the download on ice when it appears to have hung, you could provide them an option saying "Try downloading later" which could be implemented using the pause/resume methods on AGSResumableTaskJob. It might be a little tricky to know when this option should be presented - but you could try and detect if the status block stops firing for X amount of time in the middle of fetching result, or you could always have a "Cancel" and "Try later" methods along with your download indicator incase the download runs into problems (even though canceling the whole job seems like a harsh thing to do, what you really want is for the user to try again later)