After a battle with the same problem and a bit of research, I found a solution that seems to work well.
Download the Amazon AWS SDK for iOS and add it to your project:
http://aws.amazon.com/sdkforios/
Then run the load test with a custom class NSOperationas described here:
Using delegates, operations, and queues
A protocol AmazonServiceRequestDelegateis the key to getting progress updates, similar to what it does AFNetworking.
In particular, I need this method:
-(void)request:(AmazonServiceRequest *)request didSendData:(NSInteger)bytesWritten
totalBytesWritten:(NSInteger)totalBytesWritten
totalBytesExpectedToWrite:(NSInteger)totalBytesExpectedToWrite;
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