I'm trying to download a few thousand images (using an authenticated get request). This explanation of parallel downloading was a great answer to the problem of handling massive parallel asynchronous downloads. But that solution no longer works for me, and now in v11.2 there are completely new URL-related functions...

The function URLDownloadSubmit is supposed to replace URLFetchAsynchronous, but I'm finding that it's not asynchronous and very slow. Here's what my code looks like now using URLDownloadSubmit, and it's clearly downloading things sequentially:

Has anyone come across this in v11.2 and know how to address it?

• Even if I DistributeDefinitions and then ParallelMap my submitting function, nothing happens:
• This is gonna be some throttle at the asynchronous task level. If you look at the DownValues I think URLFetchAsynchronous has an implementation at the CURL level, hence the difference. It looks buggy to me. Ask support. – b3m2a1 Oct 16 '17 at 20:51
• Just from the DownValues it looks like they're trying to move away from using an external library for all of this stuff, which makes sense, but the transition is gonna be a bit bumpy. Until PacletFind["CURLLink"] is empty (which probably won't be until V15 or something), the old stuff will work. – b3m2a1 Oct 17 '17 at 3:18