[Bug]: Audiobookshelf becomes unusable when adding a lot of books

[lkiesow]

Describe the issue

When adding ~1000 books to my > 2.5.0 (d2aea869) development setup, I noticed that Audiobookshelf became basically unusable for a few minutes since the UI would refresh multiple times a second:

https://github.com/advplyr/audiobookshelf/assets/1008395/edd488ba-9942-4244-99c2-138f9127eb0b

Steps to reproduce the issue

Just generate a lot of new media files in your audiobook folder. For example with:

❯ mkdir test
❯ ffmpeg -f lavfi -i sine=f=220:b=4 -t 10 -c:a aac -ac 1 -b:a 16k test/test.m4a
❯ for i in {1..1000}; do echo -n "${i}: "; a="$(shuf -n 1 /usr/share/dict/words)"; b="$(shuf -n 1 /usr/share/dict/words)"; mkdir "${a}"; cp -v test/test.m4a "${a}/${b}.m4a"; done

Audiobookshelf version

2.5.0 (d2aea869)

How are you running audiobookshelf?

Built from source

[advplyr]

This issue can be resolved in 2 different places in the code.

The cause is that anytime the home page gets a socket event items_added it will make a request to the server to get the home page shelves again if at least one of those items added are in that library. That happens here: https://github.com/advplyr/audiobookshelf/blob/d2aea8695768aa5d2b911730cb5e120379998fe3/client/components/app/BookShelfCategorized.vue#L297

Solution 1: Instead of fetching new categories again we should just insert the new item in the "Recently Added" shelf. The downside is we won't show potentially new authors or series updates until the page is changed/refreshed.

Solution 2: Instead of emitting the items_added event after every 10 new items scanned in, we only emit that event after X number of seconds have passed since the last event. The socket emit happens in the LibraryScanner here: https://github.com/advplyr/audiobookshelf/blob/d2aea8695768aa5d2b911730cb5e120379998fe3/server/scanner/LibraryScanner.js#L207

Solution 1 is better I think but we could do both since other clients may listen to that event as well.

[lkiesow]

I think the first solution is good.

[advplyr]

Fixed in v2.6.0