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fix(relay): avoid subscription lock inversion #3412

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tlongwell-block wants to merge 1 commit into from
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fix(relay): avoid subscription lock inversion #3412

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103 changes: 80 additions & 23 deletions crates/buzz-relay/src/subscription.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -164,15 +164,18 @@ impl SubscriptionRegistry {
conn_id: ConnId,
sub_id: &str,
) -> Option<RemovedSubscription> {
if let Some(mut conn_subs) = self.subs.get_mut(&conn_id) {
if let Some((filters, community_id, channel_id)) = conn_subs.remove(sub_id) {
self.remove_from_index(conn_id, sub_id, &filters, community_id, channel_id);
metrics::gauge!("buzz_subscriptions_active").decrement(1.0);
return Some(RemovedSubscription {
community_id,
channel_id,
});
}
let removed = {
let mut conn_subs = self.subs.get_mut(&conn_id)?;
conn_subs.remove(sub_id)
};

if let Some((filters, community_id, channel_id)) = removed {
self.remove_from_index(conn_id, sub_id, &filters, community_id, channel_id);
metrics::gauge!("buzz_subscriptions_active").decrement(1.0);
return Some(RemovedSubscription {
community_id,
channel_id,
});
}
None
}
Expand Down Expand Up @@ -275,15 +278,23 @@ impl SubscriptionRegistry {
channel_id,
kind: event.event.kind,
};
if let Some(candidates) = self.channel_kind_index.get(&(community_id, key)) {
for (conn_id, sub_id) in candidates.iter() {
self.push_match(*conn_id, sub_id, event, &mut results, &mut seen);
if let Some(candidates) = self
.channel_kind_index
.get(&(community_id, key))
.map(|entry| entry.value().clone())
{
for (conn_id, sub_id) in candidates {
self.push_match(conn_id, &sub_id, event, &mut results, &mut seen);
}
}
// Also check wildcard (channel-only, kindless) index.
if let Some(wildcards) = self.channel_wildcard_index.get(&(community_id, channel_id)) {
for (conn_id, sub_id) in wildcards.iter() {
self.push_match(*conn_id, sub_id, event, &mut results, &mut seen);
if let Some(wildcards) = self
.channel_wildcard_index
.get(&(community_id, channel_id))
.map(|entry| entry.value().clone())
{
for (conn_id, sub_id) in wildcards {
self.push_match(conn_id, &sub_id, event, &mut results, &mut seen);
}
}
} else {
Expand All @@ -296,24 +307,33 @@ impl SubscriptionRegistry {
kind: event.event.kind,
p,
};
if let Some(candidates) = self.global_p_kind_index.get(&key) {
for (conn_id, sub_id) in candidates.iter() {
self.push_match(*conn_id, sub_id, event, &mut results, &mut seen);
if let Some(candidates) = self
.global_p_kind_index
.get(&key)
.map(|entry| entry.value().clone())
{
for (conn_id, sub_id) in candidates {
self.push_match(conn_id, &sub_id, event, &mut results, &mut seen);
}
}
}
if let Some(candidates) = self
.global_kind_index
.get(&(community_id, event.event.kind))
.map(|entry| entry.value().clone())
{
for (conn_id, sub_id) in candidates.iter() {
self.push_match(*conn_id, sub_id, event, &mut results, &mut seen);
for (conn_id, sub_id) in candidates {
self.push_match(conn_id, &sub_id, event, &mut results, &mut seen);
}
}
// Also check global wildcard (kindless global subs).
if let Some(wildcards) = self.global_wildcard_index.get(&community_id) {
for (conn_id, sub_id) in wildcards.iter() {
self.push_match(*conn_id, sub_id, event, &mut results, &mut seen);
if let Some(wildcards) = self
.global_wildcard_index
.get(&community_id)
.map(|entry| entry.value().clone())
{
for (conn_id, sub_id) in wildcards {
self.push_match(conn_id, &sub_id, event, &mut results, &mut seen);
}
}
}
Expand Down Expand Up @@ -576,6 +596,8 @@ mod tests {
use buzz_core::StoredEvent;
use chrono::Utc;
use nostr::{EventBuilder, Keys, Kind, Tag};
use std::sync::Arc;
use std::time::{Duration, Instant};

fn make_stored_event(kind: Kind, channel_id: Option<Uuid>) -> StoredEvent {
let keys = Keys::generate();
Expand Down Expand Up @@ -629,6 +651,41 @@ mod tests {
assert!(matches.is_empty());
}

#[test]
fn test_fan_out_concurrent_with_subscription_replacement_completes() {
let registry = Arc::new(SubscriptionRegistry::new());
let conn_id = Uuid::new_v4();
let channel_id = Uuid::new_v4();
let sub_id = "sub1".to_string();
let filters = vec![Filter::new().kind(Kind::TextNote)];
registry.register(conn_id, sub_id.clone(), filters.clone(), Some(channel_id));
let event = Arc::new(make_stored_event(Kind::TextNote, Some(channel_id)));
let deadline = Instant::now() + Duration::from_secs(2);

let fan_out_registry = Arc::clone(&registry);
let fan_out_event = Arc::clone(&event);
let fan_out = std::thread::spawn(move || {
while Instant::now() < deadline {
let _ = fan_out_registry.fan_out(&fan_out_event);
}
});

let replace_registry = Arc::clone(&registry);
let replace = std::thread::spawn(move || {
while Instant::now() < deadline {
replace_registry.register(
conn_id,
sub_id.clone(),
filters.clone(),
Some(channel_id),
);
}
});

fan_out.join().expect("fan-out thread completes");
replace.join().expect("replacement thread completes");
}

#[test]
fn test_subscription_registry_remove_connection() {
let registry = SubscriptionRegistry::new();
Expand Down
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