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//! Consumer runtime: poll → dedupe → dispatch → ack / retry / dead-letter.
use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;
use futures::future::BoxFuture;
use crate::core::engine::FrozenDiContainer;
use crate::messaging::{
EventContext, EventError, EventHandlerDescriptor, InboundMessage, MessageTransport,
};
type Handler = fn(EventContext) -> BoxFuture<'static, Result<(), EventError>>;
/// Drives one transport against the link-time handler registry.
///
/// Spawn from `ArclyPlugin::on_start`. The dispatch map is frozen at spawn —
/// the polling loop performs immutable `HashMap` reads only.
#[non_exhaustive]
pub struct ConsumerRuntime {
pub transport: Arc<dyn MessageTransport>,
pub container: &'static FrozenDiContainer,
pub poll: Duration,
pub batch: usize,
/// Failed deliveries per message before dead-lettering.
pub max_retries: u32,
/// TTL for the consume-side dedupe claim (when an `IdempotencyStore`
/// is available in the DI container).
pub dedupe_ttl_secs: u64,
/// Messages processed concurrently per polled batch. `0`/`1` keeps the
/// historical strictly-ordered sequential behaviour; higher values trade
/// cross-message ordering within a batch for throughput (per-message
/// dedupe and retries are unaffected — `attempts` is a sharded map).
pub concurrency: usize,
}
impl ConsumerRuntime {
/// Sensible defaults: 300ms poll, batch 32, 3 retries, 1h dedupe TTL,
/// sequential processing. Chain setters to adjust.
pub fn new(
transport: Arc<dyn MessageTransport>,
container: &'static FrozenDiContainer,
) -> Self {
Self {
transport,
container,
poll: Duration::from_millis(300),
batch: 32,
max_retries: 3,
dedupe_ttl_secs: 3600,
concurrency: 1,
}
}
pub fn poll(mut self, v: Duration) -> Self {
self.poll = v;
self
}
pub fn batch(mut self, v: usize) -> Self {
self.batch = v;
self
}
pub fn max_retries(mut self, v: u32) -> Self {
self.max_retries = v;
self
}
pub fn dedupe_ttl_secs(mut self, v: u64) -> Self {
self.dedupe_ttl_secs = v;
self
}
pub fn concurrency(mut self, v: usize) -> Self {
self.concurrency = v;
self
}
pub fn spawn(self) {
// Freeze the dispatch map from the inventory registry — once, here.
let dispatch: HashMap<&'static str, Handler> =
inventory::iter::<&'static EventHandlerDescriptor>
.into_iter()
.map(|d| (d.topic, d.handler))
.collect();
for d in inventory::iter::<&'static EventHandlerDescriptor> {
tracing::info!(
topic = d.topic,
consumer = d.consumer,
"event handler registered"
);
}
let runtime = Arc::new(self);
tokio::spawn(async move {
// Per-key failure counts — sharded so concurrent processing
// never contends on a single lock.
let attempts: Arc<dashmap::DashMap<String, u32>> = Arc::new(dashmap::DashMap::new());
let mut tick = tokio::time::interval(runtime.poll);
let limit = runtime.concurrency.max(1);
loop {
tick.tick().await;
// Drain-aware (like the outbox relay): once shutdown begins,
// stop claiming work — unacked messages redeliver elsewhere.
if crate::observability::health::is_draining() {
tracing::info!("consumer runtime: drain flag set — stopping");
return;
}
let batch = match runtime.transport.poll(runtime.batch).await {
Ok(b) => b,
Err(e) => {
tracing::warn!(error = %e, "transport poll failed — retrying next tick");
continue;
}
};
use futures::StreamExt;
futures::stream::iter(batch)
.for_each_concurrent(limit, |msg| {
let runtime = Arc::clone(&runtime);
let attempts = Arc::clone(&attempts);
let dispatch = &dispatch;
async move {
runtime.process(dispatch, &attempts, msg).await;
}
})
.await;
}
});
}
async fn process(
&self,
dispatch: &HashMap<&'static str, Handler>,
attempts: &dashmap::DashMap<String, u32>,
msg: InboundMessage,
) {
let Some(handler) = dispatch.get(msg.topic.as_str()) else {
// No subscriber for this topic — ack so it doesn't loop forever.
tracing::debug!(topic = %msg.topic, "no handler — acking unrouted message");
let _ = self.transport.ack(&msg).await;
return;
};
// Consume-side dedupe (at-least-once → effectively-once per TTL).
// Same contract as the HTTP idempotency layer: claim before running,
// `complete` only AFTER success, `release` on failure — so retries of
// a failed delivery pass through instead of being replay-swallowed.
let store = self
.container
.try_get::<Box<dyn crate::web::idempotency::IdempotencyStore>>();
let dedupe_key = format!("consume:{}:{}", msg.topic, msg.idempotency_key);
if let Some(store) = store {
match store.claim(&dedupe_key, self.dedupe_ttl_secs).await {
crate::web::idempotency::IdempotencyDecision::Fresh => {}
crate::web::idempotency::IdempotencyDecision::Unavailable => {}
crate::web::idempotency::IdempotencyDecision::Replay { .. } => {
metrics::counter!("events_deduped_total").increment(1);
let _ = self.transport.ack(&msg).await;
return;
}
crate::web::idempotency::IdempotencyDecision::InFlight => {
// Our own released-then-retried claim or a concurrent
// consumer; requeue and let the next poll settle it.
let _ = self.transport.nack(&msg).await;
return;
}
}
}
// One shared extraction (pipeline::Provenance): the producer's trace
// continues (fresh root when none was carried) and the envelope's
// tenant id is validated against the SAME registry as HTTP traffic.
let provenance = crate::pipeline::Provenance::from_message(&msg, self.container);
// A suspended (or unknown) tenant's queued events must stop being
// processed, exactly like its HTTP requests — park them out of band
// rather than retry-looping or silently processing. Only enforced
// when a TenantRegistry is actually configured.
if msg.tenant.is_some()
&& provenance.tenant.is_none()
&& self
.container
.try_get::<crate::web::tenant::TenantRegistry>()
.is_some()
{
metrics::counter!("events_tenant_rejected_total").increment(1);
tracing::warn!(
topic = %msg.topic,
tenant = msg.tenant.as_deref().unwrap_or(""),
"event tenant suspended or unknown — dead-lettering"
);
if let Some(store) = store {
store.release(&dedupe_key).await;
}
let _ = self
.transport
.dead_letter(&msg, "tenant suspended or unknown")
.await;
return;
}
let ctx = EventContext {
message: msg.clone(),
container: self.container,
trace: provenance.trace,
tenant: provenance.tenant,
};
match handler(ctx).await {
Ok(()) => {
attempts.remove(&msg.idempotency_key);
if let Some(store) = store {
store
.complete(&dedupe_key, 200, b"", self.dedupe_ttl_secs)
.await;
}
metrics::counter!("events_consumed_total", "topic" => msg.topic.clone())
.increment(1);
if let Err(e) = self.transport.ack(&msg).await {
tracing::warn!(error = %e, "ack failed — message may redeliver");
}
}
Err(error) => {
if let Some(store) = store {
store.release(&dedupe_key).await; // allow the retry through
}
// Typed fate: a permanent failure skips the retry budget and
// parks immediately; transient failures take the bounded
// retry path below.
let (reason, poison) = match error {
EventError::DeadLetter(m) => {
metrics::counter!("events_poisoned_total").increment(1);
(m, true)
}
EventError::Retry(m) => (m, false),
};
// Bump-and-read, dropping the shard guard BEFORE any await
// below (dead_letter / nack are async).
let n = {
let mut entry = attempts.entry(msg.idempotency_key.clone()).or_insert(0);
*entry += 1;
*entry
};
if poison || n > self.max_retries {
attempts.remove(&msg.idempotency_key);
metrics::counter!("events_dead_lettered_total").increment(1);
tracing::error!(topic = %msg.topic, key = %msg.idempotency_key,
attempts = n, reason = %reason,
"poison message → dead letter");
// PII never parks raw in the DLQ: dead-lettered payloads
// are masked first (the queue copy already served its
// delivery purpose; the DLQ copy is for forensics).
let mut parked = msg.clone();
if let Some(masker) = self.container.try_get::<crate::compliance::Masker>() {
masker.apply(&mut parked.payload);
}
let _ = self.transport.dead_letter(&parked, &reason).await;
} else {
metrics::counter!("events_retried_total").increment(1);
tracing::warn!(topic = %msg.topic, attempt = n, reason = %reason,
"event handler failed — nack for retry");
let _ = self.transport.nack(&msg).await;
}
}
}
}
}