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perf: Improve presence performance with application-layer cache #1534

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gamesguru wants to merge 4 commits from gamesguru/continuwuity:guru/backports/perf/presence-startup-costs-naive-loop-fix into main
pull from: gamesguru/continuwuity:guru/backports/perf/presence-startup-costs-naive-loop-fix
merge into: continuwuation:main
Conversation 3 Commits 4 Files changed 10 +444 -93
gamesguru commented 2026-03-12 03:46:58 +00:00
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Tested this part of this with a bunch of other things a week or two back.

A very easy optimization to that will drastically reduce network activity and disk I/O.

perf: impl basic presence cache to avoid DB churn
chore: document tech debt/TODOs for presence optimizations
chore: add method for presence: `clear_cache()` for service mgr to call with rest on cache clear

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Tested ~~this~~ *part of this* with a bunch of other things a week or two back. A very easy optimization to that will drastically reduce network activity and disk I/O. ``` perf: impl basic presence cache to avoid DB churn chore: document tech debt/TODOs for presence optimizations chore: add method for presence: `clear_cache()` for service mgr to call with rest on cache clear ``` <!-- In order to help reviewers know what your pull request does at a glance, you should ensure that 1. Your PR title is a short, single sentence describing what you changed 2. You have described in more detail what you have changed, why you have changed it, what the intended effect is, and why you think this will be beneficial to the project. 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perf: address presence timer/DB inefficiencies
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5a87474708
 
perf: impl basic presence cache to avoid DB churn

chore: document tech debt/TODOs for presence optimizations

chore: add method for presence: `clear_cache()` for service mgr to call with rest on cache clear
batch presence updates per server, not room. bundle events and local users under batch requests per a smart policy.
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60d37b038d
 
simplify my refactor of service manager startup logic [performance]

update TODO regarding presence cache and DB reads [low-priority]
nex requested changes 2026-03-13 21:35:45 +00:00
nex left a comment
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The changes to src/service/services.rs seem unnecessary, otherwise I see no issue with this.

The changes to `src/service/services.rs` seem unnecessary, otherwise I see no issue with this.
nex changed title from perf: address presence timer/DB inefficiencies to perf: Improve presence performance with application-layer cache 2026-03-13 21:39:35 +00:00
Jade requested changes 2026-03-13 22:05:13 +00:00
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I've only reviewed down to src/service/presence/data.rs

I've only reviewed down to `src/service/presence/data.rs`
Cargo.toml
@ -342,1 +342,4 @@
[workspace.dependencies.moka]
version = "0.12"
default-features = false
Jade commented 2026-03-13 22:04:34 +00:00
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Pending response: https://matrix.to/#/!ksTlboXVgcyWjv5GrlEeKyQuJ8ZCprnwQx2b6-BQ44Q/$-gNHwsWoHouljwZl11tL0BOYy0rKBOg4qB0tMEOG0ls?via=gingershaped.computer&via=matrix.org&via=continuwuity.org

Pending response: https://matrix.to/#/!ksTlboXVgcyWjv5GrlEeKyQuJ8ZCprnwQx2b6-BQ44Q/$-gNHwsWoHouljwZl11tL0BOYy0rKBOg4qB0tMEOG0ls?via=gingershaped.computer&via=matrix.org&via=continuwuity.org
Cargo.toml
@ -343,0 +343,4 @@
[workspace.dependencies.moka]
version = "0.12"
default-features = false
features = ["sync"]
Jade commented 2026-03-13 21:55:12 +00:00
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Introducing blocking code in an async context is not allowed. Please see the Moka docs for their async implementation.

Introducing blocking code in an async context is not allowed. Please see the Moka docs for their async implementation.
src/service/presence/data.rs
@ -15,2 +16,4 @@
presenceid_presence: Arc<Map>,
userid_presenceid: Arc<Map>,
cache: MokaCache<OwnedUserId, (u64, Presence)>,
locks: MutexMap<OwnedUserId, ()>,
Jade commented 2026-03-13 21:52:28 +00:00
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I am very wary of this - RocksDB should already read from memory in systems with enough spare, and introducing more in memory locks opens the door for performance or deadlock issues.

I would prefer if there was at least some menchmarking or comparison to show if this additional complexity is worth it.

I am very wary of this - RocksDB should already read from memory in systems with enough spare, and introducing more in memory locks opens the door for performance or deadlock issues. I would prefer if there was at least some menchmarking or comparison to show if this additional complexity is worth it.
Henry-Hiles commented 2026-03-13 22:16:37 +00:00
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@Jade wrote in #1534 (comment):

I would prefer if there was at least some menchmarking or comparison to show if this additional complexity is worth it.

s/menchmarking/benchmarking

@Jade wrote in https://forgejo.ellis.link/continuwuation/continuwuity/pulls/1534#issuecomment-26233: > I would prefer if there was at least some menchmarking or comparison to show if this additional complexity is worth it. s/menchmarking/benchmarking
😆 1
src/service/presence/data.rs
@ -130,6 +160,10 @@ impl Data {
}
pub(super) async fn remove_presence(&self, user_id: &UserId) {
let _lock = self.locks.lock(user_id).await;
Jade commented 2026-03-13 22:01:22 +00:00
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This lock is held to the end of the scope, but that is implicit. Either use an explicit drop or a closure to make sure the scope of the lock is clear. Iirc this is in the code style guide.

This lock is held to the end of the scope, but that is implicit. Either use an explicit drop or a closure to make sure the scope of the lock is clear. Iirc this is in the code style guide.
src/service/presence/data.rs
@ -186,1 +222,4 @@
}
#[cfg(test)]
mod tests {
Jade commented 2026-03-13 22:02:53 +00:00
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What are you even testing? Most of these are intrinsic properties of lower levels of the system, and shouldn't be here.

What are you even testing? Most of these are intrinsic properties of lower levels of the system, and shouldn't be here.
gamesguru commented 2026-03-15 02:53:48 +00:00
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I'm actually going to review all the comments before even testing.

I'm not as optimistic as nexy here, I think this could cause problems if the presence dates have a bug in it... idk, worst case all of a sudden your whole timeline gets borked. I've seen weird stuff on the MSC3030 branch

I'm actually going to review all the comments before even testing. I'm not as optimistic as nexy here, I think this could cause problems if the presence dates have a bug in it... idk, worst case all of a sudden your whole timeline gets borked. I've seen weird stuff on the MSC3030 branch
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