this post was submitted on 27 Jul 2023
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Lemmy Server Performance

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Lemmy Server Performance

lemmy_server uses the Diesel ORM that automatically generates SQL statements. There are serious performance problems in June and July 2023 preventing Lemmy from scaling. Topics include caching, PostgreSQL extensions for troubleshooting, Client/Server Code/SQL Data/server operator apps/sever operator API (performance and storage monitoring), etc.

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IIRC, it was lemmy.ca full copy of live data that was used (copy made on development system, not live server - if I'm following). Shared Saturday July 22 on GitHub was this procedure:

...

Notable is the AUTO_EXPLAIN SQL activation statements:

LOAD 'auto_explain';
SET auto_explain.log_min_duration = 0;
SET auto_explain.log_analyze = true;
SET auto_explain.log_nested_statements = true;

This technique would be of great use for developers doing changes and study of PostgreSQL activity. Thank you!

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[–] [email protected] 4 points 1 year ago (1 children)

Oof yeah, that's not gonna be a fun way to troubleshoot!

Thanks for taking the ball and running with this, looks like it's getting a lot of attention now and hopefully next release will have some juicy sql improvements!

[–] [email protected] 2 points 1 year ago (1 children)

I've really been bothered by the server crashes, especially on lemmy.ml since even before I created my first Lemmy account. so far, I haven't seen anyone able to reproduce the overloads/crashes outside of production servers.

If we can get pg_stat_statatements with on 0.18.3 with pg_stat_statements.track = all out of a real Lemmy database run for 12 or more hours, that is having crashes, I think we might find something that's being overlooked.

[–] [email protected] 3 points 1 year ago (1 children)

We don't get any crashes on ca since I disabled account deletion. Things are stable.

[–] [email protected] 2 points 1 year ago

ok. back to the drawing board.