Fallback Download URL for CN Server

[gingerbreap]

I'm wondering if fallback to alternative CDN would be possible when downloading assets for CN Server. As this comment mentioned in #28:

It seemed like nuverse used multiple servers for downloading. In my situation, it connected to the following servers (in connection sequence order, or see the last screenshot):

https://lf3-j1gamecdn-cn.dailygn.com
https://lf6-j1gamecdn-cn.dailygn.com
https://lf9-j1gamecdn-cn.dailygn.com
https://lf26-j1gamecdn-cn.dailygn.com

I've tried to modify my local copy of ...... SEKAI_AB_INFO_ENDPOINT & SEKAI_AB_INFO_ENDPOINT being https://lf26-j1gamecdn-cn.dailygn.com (which I tested to be the fastest in my region).

If it's possible to fallback to an alternative server when download speed is too slow or cannot failing to download certain files, it would be much better for downloading the entire folder.

[mos9527]

If it's possible to fallback to an alternative server when download speed is too slow or cannot failing to download certain files...

We can probe the CDNs first then decide which one(s) to use with some kind of heuristic like how the game does it by itself - this should be quite doable and would certainly help alleviate Anti-DDoS protection (if they had any).

I should implement this once I got more free time on hand.

failing to download certain files, it would be much better for downloading the entire folder.

However this doesn't help much with corrput downloads if the issue is on client side networking. Like experiencing Incomplete Reads due to faulty proxies, etc.

This problem is pretty tricky - and can in many ways lead to (an unfortunate amount of) over engineering if AbCache were to handle all those cases. Writing a good and robust file downloader is hard...

Perhaps (having an option) to off-load this to an external downloader (like aria2) would be the ultimate solution if bulk download is really desired.

Also not downloading everything and only pick files on-demand could be a concession but a solution too