Lane Open Modes

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

src/web/http/down.rs

@@ -57,7 +57,8 @@ pub(super) async fn handle_down(
         return serve_decoy(request, vhost, true, &runtime).await;
     }
     let _lane_poll = if lane_id.is_some() {
-        let Some(permit) = runtime.try_lane_poll() else {
+        let auxiliary = lane_id.is_some_and(|lane_id| session.lane_poll_is_auxiliary(lane_id));
+        let Some(permit) = runtime.try_lane_poll(auxiliary) else {
             return service_unavailable();
         };
         Some(permit)

src/web/manager.rs

@@ -107,6 +107,7 @@ pub(crate) struct WebProcessRuntime {
     http_connections: Arc<Semaphore>,
     http_handlers: Arc<Semaphore>,
     lane_polls: Arc<Semaphore>,
+    lane_aux_polls: Arc<Semaphore>,
     body_readers: Arc<Semaphore>,
     body_bytes: Arc<Semaphore>,
     stream_handshakes: Arc<Semaphore>,
@@ -146,12 +147,17 @@ impl WebProcessRuntime {
         let websocket_connections = limits
             .max_http_connections
             .saturating_sub(limits.websocket_http_connection_reserve);
+        let lane_poll_limit = limits.max_http_handlers / 2;
+        let lane_aux_poll_limit = (lane_poll_limit / 2).max(1);
         let runtime = Arc::new(Self {
             active_runtime,
             trace,
             http_connections: Arc::new(Semaphore::new(limits.max_http_connections)),
             http_handlers: Arc::new(Semaphore::new(limits.max_http_handlers)),
-            lane_polls: Arc::new(Semaphore::new((limits.max_http_handlers / 2).max(1))),
+            lane_polls: Arc::new(Semaphore::new(
+                lane_poll_limit.saturating_sub(lane_aux_poll_limit),
+            )),
+            lane_aux_polls: Arc::new(Semaphore::new(lane_aux_poll_limit)),
             body_readers: Arc::new(Semaphore::new(limits.max_body_readers)),
             body_bytes: Arc::new(Semaphore::new(limits.max_body_bytes_global)),
             stream_handshakes: Arc::new(Semaphore::new(limits.max_stream_handshakes)),
@@ -225,8 +231,13 @@ impl WebProcessRuntime {
     }
 
     /// Reserves one parked lane poll without exhausting all HTTP handlers.
-    pub(crate) fn try_lane_poll(&self) -> Option<OwnedSemaphorePermit> {
-        let permit = Arc::clone(&self.lane_polls).try_acquire_owned().ok();
+    pub(crate) fn try_lane_poll(&self, auxiliary: bool) -> Option<OwnedSemaphorePermit> {
+        let slots = if auxiliary {
+            &self.lane_aux_polls
+        } else {
+            &self.lane_polls
+        };
+        let permit = Arc::clone(slots).try_acquire_owned().ok();
         if permit.is_none() {
             self.record_limit_hit();
         }

src/web/manager/lifecycle.rs

@@ -119,8 +119,8 @@ impl WebProcessRuntime {
             remove_expired_locked(&mut state, now);
             state.sessions.values().cloned().collect::<Vec<_>>()
         };
-        for session in sessions.into_iter().filter(|session| session.is_idle(now)) {
-            session.close();
+        for session in sessions {
+            session.close_if_due(now);
         }
     }
 }

src/web/manager/session_creation.rs

@@ -354,7 +354,9 @@ impl WebProcessRuntime {
         let identity = session.trace_identity();
         let old_identity = replacement.old_session.trace_identity();
         drop(state);
-        replacement.old_session.finish_carrier_supersede();
+        if replacement.old_session.finish_carrier_supersede() {
+            session.close();
+        }
         if let Some(context) = learning_context {
             self.record_carrier_outcome(context, replacement.old_session.carrier(), false);
         }

src/web/session.rs

@@ -124,6 +124,8 @@ struct SessionState {
     last_up_sequence: u64,
     last_up_digest: TokenHash,
     carrier_lanes: HashMap<u32, CarrierLane>,
+    lane_open_claims: HashSet<u32>,
+    lane_open_waits: usize,
     next_lane_instance: u64,
     websocket_lane_reservations: HashMap<u32, u16>,
     pending_bytes: usize,
@@ -160,6 +162,7 @@ pub(crate) struct WebSession {
     timeouts: WebTimeoutsConfig,
     state: Mutex<SessionState>,
     down_notify: Arc<Notify>,
+    lane_open_notify: Arc<Notify>,
     cancel: CancellationToken,
     tasks_live: AtomicUsize,
     tasks_done: Arc<Notify>,
@@ -228,6 +231,8 @@ impl WebSession {
                 last_up_sequence: 0,
                 last_up_digest: [0; 32],
                 carrier_lanes,
+                lane_open_claims: HashSet::new(),
+                lane_open_waits: 0,
                 next_lane_instance,
                 websocket_lane_reservations: HashMap::new(),
                 pending_bytes: 0,
@@ -240,6 +245,7 @@ impl WebSession {
                 closed: false,
             }),
             down_notify: Arc::new(Notify::new()),
+            lane_open_notify: Arc::new(Notify::new()),
             cancel: CancellationToken::new(),
             tasks_live: AtomicUsize::new(0),
             tasks_done: Arc::new(Notify::new()),

src/web/session/lifecycle.rs

@@ -13,7 +13,7 @@ struct ReleasedQueues {
 impl WebSession {
     /// Closes carrier state while relay tasks retain their admission until exit.
     pub(crate) fn close(&self) {
-        let Some(released) = self.begin_close(false) else {
+        let Some(released) = self.begin_close(false, None) else {
             return;
         };
         self.finish_close(released, false);
@@ -51,11 +51,13 @@ impl WebSession {
     }
 
     /// Completes manager-owned replacement without unregistering the old session twice.
-    pub(crate) fn finish_carrier_supersede(&self) {
-        let Some(released) = self.begin_close(true) else {
-            return;
+    pub(crate) fn finish_carrier_supersede(&self) -> bool {
+        let close_requested = self.state.lock().close_requested;
+        let Some(released) = self.begin_close(true, None) else {
+            return close_requested;
         };
         self.finish_close(released, true);
+        close_requested
     }
 
     /// Waits for all logical-stream tasks after admission has closed.
@@ -69,20 +71,27 @@ impl WebSession {
         }
     }
 
-    /// Returns whether reconnect grace elapsed without activity.
-    pub(crate) fn is_idle(&self, now: Instant) -> bool {
-        let state = self.state.lock();
-        !state.closed
-            && state.negotiation_phase != SessionNegotiationPhase::Replacing
-            && now.saturating_duration_since(state.last_activity)
-                >= Duration::from_secs(self.timeouts.reconnect_grace_secs)
+    /// Atomically closes a session only when reconnect grace is still due.
+    pub(crate) fn close_if_due(&self, now: Instant) -> bool {
+        let Some(released) = self.begin_close(false, Some(now)) else {
+            return false;
+        };
+        self.finish_close(released, false);
+        true
     }
 
-    fn begin_close(&self, superseded: bool) -> Option<ReleasedQueues> {
+    fn begin_close(&self, superseded: bool, idle_now: Option<Instant>) -> Option<ReleasedQueues> {
         let mut state = self.state.lock();
         if state.closed || (superseded && state.negotiation_phase != SessionNegotiationPhase::Replacing) {
             return None;
         }
+        if let Some(now) = idle_now
+            && (state.negotiation_phase == SessionNegotiationPhase::Replacing
+                || now.saturating_duration_since(state.last_activity)
+                    < Duration::from_secs(self.timeouts.reconnect_grace_secs))
+        {
+            return None;
+        }
         if !superseded && state.negotiation_phase == SessionNegotiationPhase::Replacing {
             state.close_requested = true;
             return None;