fix(dashboard): keep status responsive when session db locks

(cherry picked from commit a3454dd15d)

hermes_cli/web_server.py

@@ -1120,6 +1120,8 @@ except (ValueError, TypeError):
     )
     _GATEWAY_HEALTH_TIMEOUT = 3.0
 
+_STATUS_ACTIVE_SESSIONS_TIMEOUT = 0.75
+
 # DEPRECATED (scheduled for removal): GATEWAY_HEALTH_URL / GATEWAY_HEALTH_TIMEOUT.
 # Cross-container / cross-host gateway liveness detection will be folded into a
 # first-class dashboard config key so it's no longer Docker-adjacent lore buried
@@ -1170,6 +1172,45 @@ def _probe_gateway_health() -> tuple[bool, dict | None]:
     return False, None
 
 
+def _count_status_active_sessions() -> int:
+    """Return the dashboard status active-session count.
+
+    This is best-effort status garnish, not a critical path.  Use a read-only
+    connection so /api/status never tries to initialise or migrate state.db
+    while another Hermes process is writing to it.
+    """
+    from hermes_state import SessionDB
+
+    db = SessionDB(read_only=True)
+    try:
+        sessions = db.list_sessions_rich(limit=50)
+        now = time.time()
+        return sum(
+            1 for s in sessions
+            if s.get("ended_at") is None
+            and (now - s.get("last_active", s.get("started_at", 0))) < 300
+        )
+    finally:
+        db.close()
+
+
+async def _status_active_sessions() -> int:
+    loop = asyncio.get_running_loop()
+    try:
+        return await asyncio.wait_for(
+            loop.run_in_executor(None, _count_status_active_sessions),
+            timeout=_STATUS_ACTIVE_SESSIONS_TIMEOUT,
+        )
+    except asyncio.TimeoutError:
+        _log.debug(
+            "/api/status active session count exceeded %.2fs; returning 0",
+            _STATUS_ACTIVE_SESSIONS_TIMEOUT,
+        )
+    except Exception as exc:
+        _log.debug("/api/status active session count unavailable: %s", exc)
+    return 0
+
+
 # Image MIME types this endpoint will serve. Extension-allowlisted so an
 # authenticated caller can't pull non-image files through it.
 _MEDIA_CONTENT_TYPES = {
@@ -2485,22 +2526,7 @@ async def get_status(profile: Optional[str] = None):
         if gateway_running and gateway_state is None and remote_health_body is not None:
             gateway_state = "running"
 
-        active_sessions = 0
-        try:
-            from hermes_state import SessionDB
-            db = SessionDB()
-            try:
-                sessions = db.list_sessions_rich(limit=50)
-                now = time.time()
-                active_sessions = sum(
-                    1 for s in sessions
-                    if s.get("ended_at") is None
-                    and (now - s.get("last_active", s.get("started_at", 0))) < 300
-                )
-            finally:
-                db.close()
-        except Exception:
-            pass
+        active_sessions = await _status_active_sessions()
 
         # Busy/drainable readout (NAS lifecycle-safety gate).  active_agents is
         # the in-flight gateway-turn count the gateway now persists at every

tests/hermes_cli/test_web_server.py

@@ -267,6 +267,44 @@ class TestWebServerEndpoints:
         assert "active_sessions" in data
         assert data["can_update_hermes"] is True
 
+    def test_status_active_session_count_uses_read_only_db(self, monkeypatch):
+        import hermes_cli.web_server as web_server
+
+        captured = {}
+
+        class _FakeDB:
+            def __init__(self, *args, **kwargs):
+                captured["read_only"] = kwargs.get("read_only")
+
+            def list_sessions_rich(self, limit):
+                captured["limit"] = limit
+                return [
+                    {"ended_at": None, "last_active": 95},
+                    {"ended_at": 99, "last_active": 99},
+                    {"ended_at": None, "last_active": -300},
+                ]
+
+            def close(self):
+                captured["closed"] = True
+
+        monkeypatch.setattr("hermes_state.SessionDB", _FakeDB)
+        monkeypatch.setattr(web_server.time, "time", lambda: 100)
+
+        assert web_server._count_status_active_sessions() == 1
+        assert captured == {"read_only": True, "limit": 50, "closed": True}
+
+    def test_get_status_degrades_when_active_session_count_fails(self, monkeypatch):
+        import hermes_cli.web_server as web_server
+
+        def _locked_count():
+            raise TimeoutError("database is locked")
+
+        monkeypatch.setattr(web_server, "_count_status_active_sessions", _locked_count)
+
+        resp = self.client.get("/api/status")
+        assert resp.status_code == 200
+        assert resp.json()["active_sessions"] == 0
+
     def test_gateway_drain_begin_writes_marker(self):
         from gateway import drain_control