I'm working on an app, whose features depend on users uploading large sets of images and videos. Many of the current users mainly use the app in areas with poor network connectivity. As a result, the uploads often take a long time and cause frustration.
The current implementation uses a foreground configured NSURLSession to perform the uploads, and so the users have to keep the app open in the foreground for the upload to progress. I've been working to convert this to a background configured NSURLSession, with the idea that even if the uploads take a long time, if they're chugging away in the background then the users will get a better experience, and they can benefit from walking in and out of better network conditions throughout the day.
Nsurlsession Download Progress
Download 🔥 https://tiurll.com/2yGaFc 🔥
I implemented this change, and have been testing it using the network link conditioner to simulate poor network conditions. It all works, but I was disappointed to find that the background configured NSURLSession takes much longer to perform the upload than the foreground configured NSURLSession. In fact, if I set it down to "2G Network - Better" an upload of a 5 min video never completes in the background, it seems to timeout and retry indefinitely, while the foreground session completes in just a few minutes.
I used Charles Proxy to inspect the upload requests using both a foreground and background configured session. I observed that the background configured uploads progress at about 10kbs per second (in the ballpark of a 2g speed, I believe) while the foreground uploads progress at about 500kbs per second (much faster than I expect 2g upload to be).
Should I expect any speed difference between requests sent in a background configured NSURLSession vs a foreground NSURLSession? Or is the difference I'm observing simply a result of the background request being throttled correctly while the foreground requests don't seem to be being throttled by the network link conditioner (or at least not to the same degree).
When the background requests fail, there seems to be an indeterminate amount of time before they are retried, sometimes hours. Turning off the network link conditioner (restoring good network) doesn't trigger a retry, and neither does foregrounding the app. As a result, I'm worried that users with intermittent internet access won't have the upload retry during the brief period when they have access, because the OS is still delaying the retry. Is there a way to configure a background NSURLSession to retry more aggressively, or to trigger retries when network conditions improve?
If the app is brought into the foreground, is there a way to force the requests to retry immediately? Or any way to tell if they're currently in progress vs waiting to retry, and use that information to determine whether to leave them be or perhaps cancel and restart them? Is it advisable to simply run the requests in both a foreground and a background session?
Yes, foreground sessions will always receive more system resources because they belong the app that is being viewed by the user at the current time. Many times a background session is scheduled by the system at times when it makes most sense for the system to allocate resources for the session. So naturally the background sessions will be competing against of processes on the system for runtime and this will be slower than foreground sessions.
Going back to my last point, not exactly, this has a lot to do with system resources. There are some exceptions if your app does fall into one of the specific categories. For more on this I'll point you over to a post that Quinn wrote here.
Lastly I want to point you to another post that Quinn wrote that has some more info on running tasks in the background. This info isn't really specific to networking, but you may find some useful info here for the cases you are describing. That post is here.
I have a piece of working code that downloads a file using NSURLDownloadTask, that tracks the download progress using URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:. The progress indicator fill in smoothly - it looks good. I am now refactoring the code to not use session and task delegate methods for various reasons. For progress indication I switched to KVO on the download taks's countOfBytesReceived (the documentation notes that all task properties support key-value observing). It does work, but it looks pretty bad - the intervals between progress incrementation take too long and sometimes never show up at all. To my understanding, I should not explicilty dispatch the task to a background queue - it should be done by the session task itself (or should I?).
I've just implemented background session downloads, and in testing (with 1044 downloadTasks), I'm seeing some strange behavior that's not 100% reproducible. Sometimes when I background the app, when I foreground it (or the OS does), the URLSessionDownloadDelegate's function
Both cases are being called with the exactly same task, session and location. The first call copies the location to a semi-permanent destination (and I confirmed that file is correct), and the second call fails on move because the destination already exists.
I tried resuming one or all of the tasks in applicationDidBecomeActive as suggested in multiple other forums posts, but neither of those seems to resolve the issue. Again, I can work around this (using a combination of totalBytesWritten and the known size of files which have completed downloads), but I'm wondering if I'm missing something obvious.
Before filing a bug, I'm trying to test on iOS 14 and 15 to see if this is a regression, or not. On iOS 14, I received on didFinishDownloadingTo callback where the task's response and error were both nil, which I also take to be a bug.
I'm reading in some places that I shouldn't be testing background tasks on the simulator, is this true? I know you've linked to a guide you posted about testing background sessions multiple times in the past, but the link seems broken (probably due to a change in the structure of the forums). Do you have a current link to that guide?
I started testing on devices, and on iOS 16 I still see the same double-calling bug, and on iOS 14/15 I still see the same no downloadTask.response bug. If I ignore the absence of a response and keep going, then I do not see the double-calling bug on iOS 14/15, as well as the not reporting all bytes downloaded bug (again, even though I'm resuming the first task).
On a device, the reporting of progress doesn't continue at all after resuming after background, as opposed to on the simulator where it just skips some files (seemingly the ones that completed their downloads while backgrounded, but that's difficult to be sure about).
I still can't fix the progress reporting, though. Even with resuming one or all tasks, lots of files just get skipped entirely. I tried using the .progress property of the URLSessionTask and that works well for backgrounding, but the Progress object does not get set up correctly after termination and relaunching, and since it's a read-only property, one can't seem to fix it manually.
Lately I have discovered the Progress class from Foundation which allows us to do just that. This weeks blogpost will show you the basics of Progress by taking you through an example of how to show the progress of downloading an image to the user.
Progress also has a property called localizedDescription and localizedAdditionalDescription which can be used to provide the user with more information on what is happening in your application. Through the kind property you can tell the progress object what its unit represents and to format the progress as such, for example if you set it to ProgressKind.file the localizedAdditionalDescription gives you a byte formatted string.
Our view controller also has a reference to an ImageDownloader which has a method downloadImage(with:completion:) that downloads the image from the passed in URL This method returns a progress object which we will use to update our UI and has a completion handler with an optional image that gets called once the download has finished.
Inside the downloadImage(with:completion) method we create a URLSessionDownloadTask with the passed in url of the image. Since iOS 11 a task has a property called progress that contains the tasks progress object which we can use to update our UI.
When a download action is triggered we call the download function and store the returned progress object in a property called downloadProgress in our view controller. It has a property observer in which we attach the new progress object to the UI. To display the progress in our progress view we set downloadProgress to the observedProgress property of the view. We use KVO to update our progress label every time the localizedAdditionalDescription changes. KVO notifications of properties on Progress are sent from the thread on which the progress was updated and therefore we have to dispatch our update of the progress label onto the main queue to make sure our UI gets updated on the main thread.
The NSURLSession class and related classes provide an API for downloading content via HTTP and HTTPS. The downloading is performed asynchronously, so your application can remain responsive and handle incoming data or errors as they arrive. This class replaces the macOS NSURLConnection class which was deprecated by Apple in macOS 10.11 (El Capitan) in 2015. NSURLSession is available from macOS 10.9 (Mavericks) onwards.
Data tasks send and receive data using NSData objects. Data tasks are intended for short, often interactive requests to a server. Data tasks can return data to your application one piece at a time after each piece of data is received, or all at once through a completion handler. As data tasks do not store the data to a file, they are not supported in background sessions.
In addition to delivering this information to delegates, the NSURLSession provides status and progress properties that you can query if you need to make programmatic decisions based on the current state of the task (with the caveat that its state can change at any time). 152ee80cbc
download supreme duelist stickman mod apk