Beta version of an URLSession + Combine that detected a 429 HTTP error (rate limit) then delay N seconds and retry.

urlsession+combine_delay_retry.swift

/**
	URL HTTP request to a server with a 
	3 request per 10 seconds rate limit.

	Thanks to combine it's super easy detected
	rate limit and retry after N seconds.

	This is a *beta* version. 
	Things TO-DO...
		
	- Apply `delay` + `retry` only to 429 HTTP error
	- Better performance. Queues?... Maybe
*/
private func performRequest() -> Void
{
	guard let testURL = URL(string: "http://127.0.0.1:5000") else
	{
		return
	}

	let publisher = URLSession.shared.dataTaskPublisher(for: testURL)
		.tryMap { (data: Data, response: URLResponse) -> String? in
			guard let httpResponse = response as? HTTPURLResponse else
			{
				throw MyError.networkError
			}

			if httpResponse.statusCode == 429
			{
				self.isLimitExceed = true

				throw MyError.requestLimitExceed
			}

			return String(data: data, encoding: .utf8)
		}
		.delay(for: 10, scheduler: DispatchQueue.main) // Wait 10 seconds before retry
		.retry(1)                                      // Retry only one more time
		.sink(receiveValue: { (content: String?) -> Void in
			if let content = content
			{
				print(content)
			}
		})        
}

...

enum MyError: Error
{
    case networkError
    case requestLimitExceed
}