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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De-facto memory leak (self.lemmyperformance)

submitted 2 years ago by DreadTowel to c/[email protected]

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It looks like the lack of persistent storage for the federated activity queue is leading to instances running out of memory in a matter of hours. See my comment for more details.

Furthermore, this leads to data loss, since there is no other consistency mechanism. I think it might be a high priority issue, taking into account the current momentum behind growth of Lemmy...

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[–] [email protected] 2 points 2 years ago (2 children)

Can you provide a link? Only thing I see on Couchbase is for NoSQL databases.

[–] Gashole711 1 points 2 years ago (2 children)

It is a NoSQL database but the SQL syntax is ANSI SQL compliant. If you moved the queues to Couchbase and let it handle the replication and consistency, you wouldn't have to code for it.

[–] [email protected] 2 points 2 years ago (2 children)

Thanks for checking.
We don't need full database replication. We are just replicating activities that other servers are subscribed to. So the Comments table, only some of the rows will be "replicated". Not sure if/how CouchBase handles this.

[–] Gashole711 1 points 1 year ago

Normally with XDCR you can specify which documents to replicate out of a bucket. It doesn't have to be the entire bucket. So if you had certain types (comments, upvotes, etc) then only those would sync when the target comes online.

I did check into Apache CouchDB, the open source upstream, and replication is there. We use Enterprise Couchbase at work and it's a dream but there are some tools that I use that only use Apache CouchDB (Inkdrop for example). It's worth looking into.

[–] Gashole711 1 points 1 year ago

Buckets are like databases in traditional relational databases. Here's the doc on how to filter which documents get replicated.

https://docs.couchdb.org/en/stable/replication/intro.html#controlling-which-documents-to-replicate

[–] Gashole711 1 points 2 years ago

Actually XDCR is not available in the community edition so that option is gone. Sorry about that.