Converse/Prosody optimization: don't use vCards for avatars, but custom front-end code.

[JohnXLivingston]

Is your feature request related to a problem? Please describe. Displaying avatars for chat user currently use the XMPP vCards. This can induce a heavy load: each time a user joins, he will ask for all other users vCards. When hundreds of users join at the same time it can be an issue. For people using the web interface, we could shortcut the XMPP server/vcards to directly get avatars from Peertube, and/or we should lazy-load them when they are actually displayed.

NlNet expert suggested to add some lazy loading for avatars. We could for example remove avatars from user list, and just load them when users are sending messages.

To avoid performance issue on very large rooms, @jcbrand suggest the following: https://github.com/JohnXLivingston/peertube-plugin-livechat/issues/95#issuecomment-1253621683

Describe the solution you'd like Here is the solution I suggested (but better ideas have come up later on): https://github.com/JohnXLivingston/peertube-plugin-livechat/issues/95#issuecomment-1253636691

• [x] Design a test with several users joining at once
• [x] implement one of:
  • [ ] Customize ConverseJS to shortcut XMPP server for avatars
  • [x] "Lazy load" avatars: don't load unnecessary avatars (when not visible, as when the occupant list is closed)
• [x] Run stress test and publish a report

Reference: NlNet-task-12

[JohnXLivingston]

Here are some performance tests, concerning a first implementation test: https://github.com/JohnXLivingston/livechat-perf-test/tree/main/tests/40-dont-load-unecessary-vards

Needs more tweaking.

[JohnXLivingston]

Finally i didn't implement front-end avatar loading. This could add some privacy issues:

• if we make request to remote uri, an attacker could steal IP address
• by default, MUC occupants JID are hidden (using occupant id instead) for non-moderator users, so querying avatars from the front-end could leak some data
• this could implied various security issue with federation handling (as remote data can't be trusted)

So i only implemented a sort of lazy-loading: we don't load all vCards/avatars when the participant list is hidden (which is the case by default when you join a chat).

I also optimized Peertube user parallel loading (see #309).

So, to fix this issue, here are the involved commits:

• https://github.com/JohnXLivingston/peertube-plugin-livechat/commit/98c9bb8788a5be5a8a9f57d4e40c7d708ce064e9
• https://github.com/JohnXLivingston/peertube-plugin-livechat/commit/5cdbcec3e8ae7db73238a76cda13148d62453699
• https://github.com/JohnXLivingston/peertube-plugin-livechat/commit/91b44497bde97c61173cfe946c75853967566694
• https://github.com/JohnXLivingston/peertube-plugin-livechat/commit/a8e3524a94565d72443800d84efb0c5cdb650ca8
• https://github.com/JohnXLivingston/converse.js/commit/00ee4fc70d56af1f4d2387ef67576264ae79d497
• https://github.com/JohnXLivingston/converse.js/commit/9fff09f75a3f65a970506c3fd1796feaba552845
• https://github.com/JohnXLivingston/converse.js/commit/b6f9a82daf52d04434e75a7ab224cb525082d082

And here some performance measurements: https://github.com/JohnXLivingston/livechat-perf-test/tree/main/tests/40-dont-load-unecessary-vards#run-02