IOS network call prioritization

I want to use good prioritization of network calls in iOS.

So far I am using URLSessionTask.priority

. I create network calls like this:

URLSession.shared.dataTask(with: request) { data, response, error in
    if let data = data, let response = response {
        // Handle response
    } else {
        // Handle error
    }
}
task.priority = priority

      

        
        
        
      

    

The problem is that I can still see that priority 0.0 load tasks take a significant load (up to ~ 60%) from priority 1.0 tasks as soon as they start. Sometimes, priority 1.0 calls are only triggered when more low priority requests have completed. Apple ( documentation ) confirms that:

To specify the host for prioritizing session URL tasks from your application, specify a priority for each task. Prioritization is only a hint and does not guarantee performance. [...] The API does not allow you to determine the effective priority for a task from the point of view of hosts.

I want to implement presumptive loading and caching without degrading the performance of user-initiated requests. This is especially important for devices with poor connectivity.

The solutions I have considered:

• Using Alamofire (but afaik they also have no priority)
• Create a custom solution that will allow concurrent downloads n
  
  , have a priority queue, and interrupt / suspend very low priority requests when high priority requests come in. To me this sounds like something that should already exist, and it also sounds a bit like a fantastic way to shoot yourself in the leg if it goes wrong.

The alternatives I have considered:

• Launch less important calls after making the most important calls
• Do not execute queries at all on bad connections (question about how to detect a bad connection),

I support iOS 9 and newer, but will also look at solutions that don't work on iOS 9.