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|
#[derive(Clone, Default)]
pub struct EventHub {
inner: std::sync::Arc<std::sync::Mutex<EventHubState>>,
}
#[derive(Default)]
struct EventHubState {
next_sequence: u64,
events: Vec<(u64, crate::api::schema::EventEnvelope)>,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(super) enum EventHistoryError {
Lost,
Unavailable,
}
impl EventHub {
const MAX_EVENTS: usize = 512;
pub fn push(&self, event: crate::api::schema::EventEnvelope) {
let Ok(mut state) = self.inner.lock() else {
return;
};
state.next_sequence += 1;
let sequence = state.next_sequence;
state.events.push((sequence, event));
let overflow = state.events.len().saturating_sub(Self::MAX_EVENTS);
if overflow > 0 {
state.events.drain(0..overflow);
}
}
pub fn events_after(&self, sequence: u64) -> Vec<(u64, crate::api::schema::EventEnvelope)> {
let Ok(state) = self.inner.lock() else {
return Vec::new();
};
state
.events
.iter()
.filter(|(event_sequence, _)| *event_sequence > sequence)
.cloned()
.collect()
}
pub(super) fn events_after_checked(
&self,
sequence: u64,
) -> Result<Vec<(u64, crate::api::schema::EventEnvelope)>, EventHistoryError> {
let state = self
.inner
.lock()
.map_err(|_| EventHistoryError::Unavailable)?;
if state
.events
.first()
.is_some_and(|(first, _)| sequence < first.saturating_sub(1))
{
return Err(EventHistoryError::Lost);
}
Ok(state
.events
.iter()
.filter(|(event_sequence, _)| *event_sequence > sequence)
.cloned()
.collect())
}
pub fn current_sequence(&self) -> u64 {
let Ok(state) = self.inner.lock() else {
return 0;
};
state.next_sequence
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::api::schema::{EventData, EventEnvelope, EventKind};
fn event() -> EventEnvelope {
EventEnvelope {
event: EventKind::WorkspaceFocused,
data: EventData::WorkspaceFocused {
workspace_id: "workspace_1".into(),
},
}
}
#[test]
fn checked_history_distinguishes_retained_boundary_from_lost_events() {
let hub = EventHub::default();
assert!(hub.events_after_checked(0).unwrap().is_empty());
for _ in 0..EventHub::MAX_EVENTS {
hub.push(event());
}
assert_eq!(
hub.events_after_checked(0).unwrap().len(),
EventHub::MAX_EVENTS
);
hub.push(event());
assert_eq!(hub.events_after_checked(0), Err(EventHistoryError::Lost));
let retained = hub.events_after_checked(1).unwrap();
assert_eq!(retained.len(), EventHub::MAX_EVENTS);
assert_eq!(retained.first().unwrap().0, 2);
assert_eq!(retained.last().unwrap().0, hub.current_sequence());
assert!(hub
.events_after_checked(hub.current_sequence())
.unwrap()
.is_empty());
}
#[test]
fn checked_history_reports_unavailable_instead_of_empty_after_poison() {
let hub = EventHub::default();
assert!(std::panic::catch_unwind(|| {
let _guard = hub.inner.lock().unwrap();
panic!("poison the test event history");
})
.is_err());
assert_eq!(
hub.events_after_checked(0),
Err(EventHistoryError::Unavailable)
);
}
}
|
