Lemmy PERFORMANCE CRISIS: popular instances with many remote instances following big communities could stop federating outbound for Votes on comments/posts - code path identified (lemmy.ml)

submitted 1 year ago* (last edited 1 year ago) by RoundSparrow@lemmy.ml to c/lemmyperformance@lemmy.ml

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I spent several hours tracing in production (updating the code a dozen times with extra logging) to identify the actual path the lemmy_server code uses for outbound federation of votes to subscribed servers.

Major popular servers, Beehaw, Leemy.world, Lemmy.ml - have a large number of instance servers subscribing to their communities to get copies of every post/comment. Comment votes/likes are the most common activity, and it is proposed that during the PERFORMANCE CRISIS that outbound vote/like sharing be turned off by these overwhelmed servers.

pull request for draft:

https://github.com/LemmyNet/lemmy/compare/main...RocketDerp:lemmy_comment_votes_nofed1:no_federation_of_votes_outbound0

EDIT: LEMMY_SKIP_FEDERATE_VOTES environment variable

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[-] chiisana@lemmy.chiisana.net 5 points 1 year ago

Part of what makes Lemmy (and other voting link aggregators) work is the voting aspect. By taking away outbound vote federation, it forces further consolidation into these popular instances. Thereby further exacerbate the problem because now they’re even more consolidated and the posts and comments eventually becomes the bottleneck for the exact same underlying chatty protocol. For this reason, I’d be vehemently against this change without a pairing PR that allows this information to be requested via a batch pull that the protocol makes available.

this post was submitted on 04 Jul 2023

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Lemmy Server Performance

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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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