NSURLSessionDownloadTask keeps retrying when using Background Configuration

Question

I have a problem when it comes to a slow backend and downloading data with background configuration.

NSURLSessionConfiguration *sessionConfig = [NSURLSessionConf         


        

Answer 1

I managed to solve it. I'm not saying my solution is the solution but it's a solution.

The behaviour I'm experiencing is that iOS 7 and iOS 8 prioritises properties differently. I have two places to set these timeout properties, the NSURLSessionConfiguration and in the NSMutableURLRequest. iOS 7 couldn't care less about the requests property and iOS 8 couldn't care less about the configurations property. Right now my solution looks like this:

NSURLSessionConfiguration *sessionConfig;
if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
    sessionConfig = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:identifier];
}
else {
    sessionConfig = [NSURLSessionConfiguration backgroundSessionConfiguration:identifier];
}
if ([[[UIDevice currentDevice] systemVersion] floatValue] < 8.0) {
    sessionConfig.timeoutIntervalForRequest = 5 * 60.0;
}
_backgroundSession = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
    request.timeoutInterval = 5 * 60.0;
}
NSURLSessionDownloadTask *downloadTask = [_backgroundSession downloadTaskWithRequest:request];

I guess one could just not do the systemVersion checks and set both properties to the same value. Although I strongly believe that less code is more I believe even more strongly in not affecting states that does not need to be affected. However I would love to hear peoples opinions. And if someone has a better solution please share.

Oh one more thing. The retrying part will keep happening until timeoutIntervalForResource reaches its default value of 7 days according to the documentation. I have decreased this to 10 minutes.

sessionConfig.timeoutIntervalForResource = 10 * 60;

I'm not saying it should be changed. This is a decision we made for our specific environment setup.

Update

We changed the timeoutIntervalForResource back to the default value of 7 days. We have customers in China for instance and some of them have really poor connection. A master limit of 10 minutes was just silly.

Make sure to check out Sunkas answer for better code quality. My code snippet, however, is spread out over different classes so I can't reuse that approach 100 %.