ME: Autonomous&Lifecycle-bounded Pool Convergence

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/transport/middle_proxy/pool_nat/http.rs

@@ -0,0 +1,108 @@
+use super::*;
+
+const HTTP_FRESH_TTL: Duration = Duration::from_secs(600);
+const HTTP_MAX_AGE: Duration = Duration::from_secs(1200);
+
+/// A successful HTTP observation has an immutable monotonic timestamp.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(in crate::transport::middle_proxy) struct HttpNatObservation {
+    /// Successful detector result, never updated by a failed refresh.
+    pub(in crate::transport::middle_proxy) ip: IpAddr,
+    /// Original observation time used for both freshness and bounded stale fallback.
+    pub(super) observed_at: tokio::time::Instant,
+}
+
+impl HttpNatObservation {
+    fn usable(self) -> Option<IpAddr> {
+        (self.observed_at.elapsed() < HTTP_MAX_AGE).then_some(self.ip)
+    }
+
+    fn fresh(self) -> bool {
+        self.observed_at.elapsed() < HTTP_FRESH_TTL
+    }
+}
+
+impl MePool {
+    /// Reads a bounded cache snapshot without discovery or data-plane waiting.
+    pub(in crate::transport::middle_proxy) fn cached_http_nat_ip(&self) -> Option<IpAddr> {
+        self.nat_runtime
+            .nat_ip_detected
+            .try_read()
+            .ok()
+            .and_then(|cache| cache.and_then(HttpNatObservation::usable))
+    }
+
+    /// Refreshes once per pool, retaining stale success only within its original grace period.
+    pub(in crate::transport::middle_proxy) async fn maybe_detect_nat_ip(
+        self: &Arc<Self>,
+        local_ip: IpAddr,
+    ) -> Option<IpAddr> {
+        if self.nat_runtime.nat_ip_cfg.is_some() {
+            return self.nat_runtime.nat_ip_cfg;
+        }
+        if !self.nat_runtime.nat_probe
+            || !local_ip.is_ipv4()
+            || !(is_bogon(local_ip) || local_ip.is_loopback() || local_ip.is_unspecified())
+        {
+            return None;
+        }
+        if let Some(cached) = *self.nat_runtime.nat_ip_detected.read().await
+            && cached.fresh()
+        {
+            return Some(cached.ip);
+        }
+        let mut flight = self.nat_runtime.discovery.http.clone().lock_owned().await;
+        let cached = *self.nat_runtime.nat_ip_detected.read().await;
+        if let Some(cached) = cached
+            && cached.fresh()
+        {
+            return Some(cached.ip);
+        }
+        if flight.is_some_and(|until| Instant::now() < until) {
+            return cached.and_then(HttpNatObservation::usable);
+        }
+        let pool = self.clone();
+        let (send, receive) = oneshot::channel();
+        // Discovery owns the flight; cancellation of a handshake cannot cancel publication.
+        self.lifecycle
+            .spawn_producer(async move {
+                let detected = detect_public_ipv4_http(&pool.nat_runtime.http_ip_detect_urls)
+                    .await
+                    .map(IpAddr::V4);
+                if let Some(ip) = detected {
+                    *pool.nat_runtime.nat_ip_detected.write().await = Some(HttpNatObservation {
+                        ip,
+                        observed_at: tokio::time::Instant::now(),
+                    });
+                    *flight = None;
+                    info!(public_ip = %ip, "Auto-detected public IP for NAT translation");
+                } else {
+                    *flight = Some(Instant::now() + HTTP_FAILURE_TTL);
+                }
+                let _ = send.send(());
+            })
+            .ok()?;
+        let _ = receive.await;
+        self.cached_http_nat_ip()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test(start_paused = true)]
+    async fn observation_age_is_not_renewed_by_reads_or_failure() {
+        let cached = HttpNatObservation {
+            ip: "91.108.56.1".parse().unwrap(),
+            observed_at: tokio::time::Instant::now(),
+        };
+        tokio::time::advance(HTTP_FRESH_TTL).await;
+        assert!(!cached.fresh());
+        for _ in 0..100 {
+            assert_eq!(cached.usable(), Some(cached.ip));
+        }
+        tokio::time::advance(HTTP_MAX_AGE - HTTP_FRESH_TTL).await;
+        assert_eq!(cached.usable(), None);
+    }
+}