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//! Mob-level event bus that merges per-member session streams into a
//! single `mpsc` channel of [`AttributedEvent`]s.
//!
//! The router runs as an independent tokio task:
//! 1. Bootstraps by subscribing to all current roster members.
//! 2. Polls the machine-routed mob event surface for
//! `MemberSpawned`/`MemberRetired` to track roster changes and
//! subscribe/unsubscribe streams.
//! 3. Tags events with [`AttributedEvent`] and forwards to the receiver.
//!
//! Streams for retired members end naturally when sessions are archived.
use crate::event::AttributedEvent;
use crate::ids::{AgentIdentity, AgentRuntimeId, FenceToken, Generation, MeerkatId, ProfileName};
#[cfg(target_arch = "wasm32")]
use crate::tokio;
use super::MobHandle;
use futures::stream::{SelectAll, StreamExt};
use meerkat_core::comms::EventStream;
use std::collections::HashSet;
use std::time::Duration;
use tokio::sync::mpsc;
use tokio_util::sync::CancellationToken;
/// Configuration for the [`MobEventRouter`].
#[derive(Clone, Copy)]
pub struct MobEventRouterConfig {
/// How often to poll the mob event store for roster changes.
pub poll_interval: Duration,
/// Capacity of the output `mpsc` channel.
pub channel_capacity: usize,
}
impl Default for MobEventRouterConfig {
fn default() -> Self {
Self {
poll_interval: Duration::from_millis(500),
channel_capacity: 256,
}
}
}
/// Handle returned by [`spawn_event_router`]. Drop to stop the router.
pub struct MobEventRouterHandle {
/// Receive attributed events from all mob members.
pub event_rx: mpsc::Receiver<AttributedEvent>,
cancel: CancellationToken,
}
impl MobEventRouterHandle {
/// Explicitly cancel the router task.
pub fn cancel(&self) {
self.cancel.cancel();
}
}
impl Drop for MobEventRouterHandle {
fn drop(&mut self) {
self.cancel.cancel();
}
}
/// Spawn the event router task and return its handle.
pub(super) fn spawn_event_router(
handle: MobHandle,
config: MobEventRouterConfig,
) -> MobEventRouterHandle {
let (event_tx, event_rx) = mpsc::channel(config.channel_capacity);
let cancel = CancellationToken::new();
let cancel_clone = cancel.clone();
tokio::spawn(async move {
run_event_router(handle, config, event_tx, cancel_clone).await;
});
MobEventRouterHandle { event_rx, cancel }
}
#[allow(clippy::ignored_unit_patterns)]
async fn run_event_router(
handle: MobHandle,
config: MobEventRouterConfig,
event_tx: mpsc::Sender<AttributedEvent>,
cancel: CancellationToken,
) {
let mut merged: SelectAll<TaggedStream> = SelectAll::new();
let mut tracked_ids: HashSet<MeerkatId> = HashSet::new();
let mut mob_cursor: u64 = 0;
// Bootstrap: subscribe to all current roster members.
{
for entry in handle.list_members().await {
if tracked_ids.contains(&entry.agent_identity) {
continue;
}
// Only mark the member tracked once the subscription actually
// succeeded. Otherwise a transient subscribe failure would
// permanently exclude the member from the event stream.
if let Some(stream) =
subscribe_member(&handle, entry.agent_identity.clone(), entry.role.clone()).await
{
tracked_ids.insert(entry.agent_identity.clone());
merged.push(stream);
}
}
}
// Seed cursor from current event store.
if let Ok(cursor) = handle.events().latest_cursor().await {
mob_cursor = cursor;
}
let mut poll_interval = tokio::time::interval(config.poll_interval);
#[cfg(not(target_arch = "wasm32"))]
poll_interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
loop {
tokio::select! {
() = cancel.cancelled() => break,
// Forward attributed events from member streams.
Some((meerkat_id, profile, envelope)) = merged.next() => {
let identity = AgentIdentity::from(meerkat_id.as_str());
let (runtime_id, fence) = {
let roster = handle.roster().await;
match roster.get_by_identity(&identity) {
Some(entry) => (entry.agent_runtime_id.clone(), entry.fence_token),
None => (
AgentRuntimeId::new(identity, Generation::INITIAL),
FenceToken::new(0),
),
}
};
let attributed = AttributedEvent {
source: runtime_id,
source_fence_token: fence,
role: profile,
envelope,
};
if event_tx.send(attributed).await.is_err() {
// Receiver dropped — shut down.
break;
}
}
// Poll mob events for roster changes.
_ = poll_interval.tick() => {
let new_events = match handle.poll_events(mob_cursor, 100).await {
Ok(evts) => evts,
Err(_) => continue,
};
for mob_event in new_events {
mob_cursor = mob_event.cursor;
match mob_event.kind {
crate::event::MobEventKind::MemberSpawned(ref event) => {
let meerkat_id =
crate::ids::MeerkatId::from(event.agent_identity.as_str());
// Only mark the member tracked once the subscription
// actually succeeded so a transient failure at spawn
// time doesn't permanently exclude them from the
// merged event stream.
if !tracked_ids.contains(&meerkat_id)
&& let Some(stream) = subscribe_member(
&handle,
meerkat_id.clone(),
event.role.clone(),
)
.await
{
tracked_ids.insert(meerkat_id);
merged.push(stream);
}
}
crate::event::MobEventKind::MemberRetired {
ref agent_identity,
..
} => {
let meerkat_id =
crate::ids::MeerkatId::from(agent_identity.as_str());
tracked_ids.remove(&meerkat_id);
}
_ => {}
}
}
}
}
}
}
/// A tagged stream that yields (MeerkatId, ProfileName, EventEnvelope).
type TaggedItem = (
MeerkatId,
ProfileName,
meerkat_core::event::EventEnvelope<meerkat_core::event::AgentEvent>,
);
type TaggedStream = futures::stream::Map<
EventStream,
Box<
dyn FnMut(meerkat_core::event::EventEnvelope<meerkat_core::event::AgentEvent>) -> TaggedItem
+ Send,
>,
>;
async fn subscribe_member(
handle: &MobHandle,
agent_identity: MeerkatId,
profile: ProfileName,
) -> Option<TaggedStream> {
let identity = AgentIdentity::from(agent_identity.as_str());
let stream = match handle.subscribe_agent_events(&identity).await {
Ok(stream) => stream,
Err(error) => {
// Log the failure so callers see why a member is missing from
// the merged event stream. The caller is expected to leave
// this member out of `tracked_ids` so a later tick can retry.
tracing::warn!(
meerkat_id = %agent_identity,
error = %error,
"mob event router: failed to subscribe to member agent events",
);
return None;
}
};
let mid = agent_identity;
let prof = profile;
Some(stream.map(
Box::new(move |envelope| (mid.clone(), prof.clone(), envelope))
as Box<
dyn FnMut(
meerkat_core::event::EventEnvelope<meerkat_core::event::AgentEvent>,
) -> TaggedItem
+ Send,
>,
))
}