iOS: throttle bandwidth of e.g. Alamofire - swift

Question

Is it possible to throttle the bandwidth of an upload operation in e.g. Alamofire?I would like to upload data in the background while the user is using the app and up- and downloading more important stuff.Therefore, I would like to throttle the bandwidth in the background under specific circumstances.
The only possibility I found so far is using ASIHTTPRequest, which has a maxBandwidthPerSecond property, but that library is far too old, I would like to use something newer.

Answer 1

The Chilkat API provides a CKOSocket() that provides the possibility to throttle the used bandwidths like this:
// To use bandwidth throttling, the connection should be made using the socket API.
// This provides numerous properties to customize the connection, such as
// BandwidthThrottleDown, BandwidthThrottleUp, ClientIpAddress, ClintPort, Http Proxy,
// KeepAlive, PreferIpv6, RequireSslCertVerify, SoRcvBuf, SoSndBuf, SoReuseAddr,
// SOCKS proxy, TcpNoSDelay, TlsPinSet, TlsCipherSuite, SslAllowedCiphers, etc.
let socket = CkoSocket()
var maxWaitMs: Int = 5000
var success: Bool = socket.Connect("content.dropboxapi.com", port: 443, ssl: true, maxWaitMs: maxWaitMs)
if success != true {
print("\(socket.LastErrorText)")
print("Connect Fail Reason: \(socket.ConnectFailReason.integerValue)")
return
}
// Set the upload bandwidth throttle rate to 50000 bytes per second.
socket.BandwidthThrottleUp = 50000
Check this for further documentation.
The example in the documentation demonstrates how to use upload bandwidth throttling with the REST API. It will upload a file to Drobox using a file stream, with a limit on the bandwidth that can be used for the transfer.

Answer 2

I cannot find anything about Alamofire (swift part) but you could use AFNetwork.
As you can see from this link (AFNetworking/AFNetworking/AFURLRequestSerialization.h) the sources report:
/**
Throttles request bandwidth by limiting the packet size and adding a delay for each chunk read from the upload stream.
When uploading over a 3G or EDGE connection, requests may fail with "request body stream exhausted". Setting a maximum packet size and delay according to the recommended values (`kAFUploadStream3GSuggestedPacketSize` and `kAFUploadStream3GSuggestedDelay`) lowers the risk of the input stream exceeding its allocated bandwidth. Unfortunately, there is no definite way to distinguish between a 3G, EDGE, or LTE connection over `NSURLConnection`. As such, it is not recommended that you throttle bandwidth based solely on network reachability. Instead, you should consider checking for the "request body stream exhausted" in a failure block, and then retrying the request with throttled bandwidth.
#param numberOfBytes Maximum packet size, in number of bytes. The default packet size for an input stream is 16kb.
#param delay Duration of delay each time a packet is read. By default, no delay is set.
*/
- (void)throttleBandwidthWithPacketSize:(NSUInteger)numberOfBytes
delay:(NSTimeInterval)delay;
#end
You could build a your custom "NetworkManager" class in objective-C and easily import it to your swift project.