We set timeout interval for a request by NSMutableURLRequest timeoutInterval. As Apple's document described, it specifies the limit between packets, not the whole request. When we analyse our requests logs, some timeout request exceeded the seconds we set to timeoutInterval. We need timeout the requests accurately.
By reading document and blogs, the timeoutIntervalForRequest property in NSURLSessionConfiguration is the same as timeoutInterval. But the timeoutIntervalForResource property seems fit our requirement.
However, Mattt says in objc.io that timeoutIntervalForResource "should only really be used for background transfers". Can it be used in normal request? Such as query user info. Is it appropriate in this situation?
Thanks very much.
It can be used, but it rarely makes sense to do so.
The expected user experience from an iOS app is that when the user asks to download or view some web-based resource, the fetch should continue, retrying/resuming as needed, until the user explicitly cancels it.
That said, if you're talking about fetching something that isn't requested by the user, or if you are fetching additional optional data that you can live without, adding a resource timeout is probably fine. I'm not sure why you would bother to cancel it, though. After all, if you've already spent the network bandwidth to download half of the data, it probably makes sense to let it finish, or else that time is wasted.
Instead, it is usually better to time out any UI that is blocked by the fetch, if applicable, but continue fetching the request and cache it. That way, the next time the user does something that would cause a similar fetch to occur, you already have the data.
The only exception I can think of would be fetching video fragments or something similar, where if it takes too long, you need to abort the transfer and switch to a different, lower-quality stream. But in most apps, that should be handled by the HLS support in iOS itself, so you don't have to manage that.