fix: close leaked file descriptors on mode switch (#169)

SSE EventSource connections for AIS, ACARS, VDL2, and radiosonde were
not closed when switching modes, causing fd exhaustion after repeated
switches. Also fixes socket leaks on exception paths in AIS/ADS-B
stream parsers, closes subprocess pipes in safe_terminate/cleanup, and
caches skyfield timescale at module level to avoid per-request fd churn.

Closes #169

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routes/adsb.py

@@ -364,6 +364,7 @@ def parse_sbs_stream(service_addr):
     _sbs_error_logged = False
 
     while adsb_using_service:
+        sock = None
         try:
             sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
             sock.settimeout(SBS_SOCKET_TIMEOUT)
@@ -586,7 +587,6 @@ def parse_sbs_stream(service_addr):
                     continue
 
             flush_pending_updates(force=True)
-            sock.close()
             adsb_connected = False
         except OSError as e:
             adsb_connected = False
@@ -594,6 +594,12 @@ def parse_sbs_stream(service_addr):
                 logger.warning(f"SBS connection error: {e}, reconnecting...")
                 _sbs_error_logged = True
             time.sleep(SBS_RECONNECT_DELAY)
+        finally:
+            if sock:
+                try:
+                    sock.close()
+                except OSError:
+                    pass
 
     adsb_connected = False
     logger.info("SBS stream parser stopped")

routes/ais.py

@@ -80,6 +80,7 @@ def parse_ais_stream(port: int):
     _ais_error_logged = True
 
     while ais_running:
+        sock = None
         try:
             sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
             sock.settimeout(AIS_SOCKET_TIMEOUT)
@@ -152,7 +153,6 @@ def parse_ais_stream(port: int):
                 except socket.timeout:
                     continue
 
-            sock.close()
             ais_connected = False
         except OSError as e:
             ais_connected = False
@@ -160,6 +160,12 @@ def parse_ais_stream(port: int):
                 logger.warning(f"AIS connection error: {e}, reconnecting...")
                 _ais_error_logged = True
             time.sleep(AIS_RECONNECT_DELAY)
+        finally:
+            if sock:
+                try:
+                    sock.close()
+                except OSError:
+                    pass
 
     ais_connected = False
     logger.info("AIS stream parser stopped")

routes/satellite.py

@@ -28,6 +28,17 @@ from utils.validation import validate_latitude, validate_longitude, validate_hou
 
 satellite_bp = Blueprint('satellite', __name__, url_prefix='/satellite')
 
+# Cache skyfield timescale to avoid re-downloading/re-parsing per request
+_cached_timescale = None
+
+
+def _get_timescale():
+    global _cached_timescale
+    if _cached_timescale is None:
+        from skyfield.api import load
+        _cached_timescale = load.timescale()
+    return _cached_timescale
+
 # Maximum response size for external requests (1MB)
 MAX_RESPONSE_SIZE = 1024 * 1024
 
@@ -178,7 +189,7 @@ def satellite_dashboard():
 def predict_passes():
     """Calculate satellite passes using skyfield."""
     try:
-        from skyfield.api import load, wgs84, EarthSatellite
+        from skyfield.api import wgs84, EarthSatellite
         from skyfield.almanac import find_discrete
     except ImportError:
         return jsonify({
@@ -219,7 +230,7 @@ def predict_passes():
     }
     name_to_norad = {v: k for k, v in norad_to_name.items()}
 
-    ts = load.timescale()
+    ts = _get_timescale()
     observer = wgs84.latlon(lat, lon)
 
     t0 = ts.now()
@@ -332,7 +343,7 @@ def predict_passes():
 def get_satellite_position():
     """Get real-time positions of satellites."""
     try:
-        from skyfield.api import load, wgs84, EarthSatellite
+        from skyfield.api import wgs84, EarthSatellite
     except ImportError:
         return jsonify({'status': 'error', 'message': 'skyfield not installed'}), 503
 
@@ -361,7 +372,7 @@ def get_satellite_position():
         else:
             satellites.append(sat)
 
-    ts = load.timescale()
+    ts = _get_timescale()
     observer = wgs84.latlon(lat, lon)
     now = ts.now()
     now_dt = now.utc_datetime()

templates/index.html

@@ -4158,6 +4158,10 @@
                 sstv_general: () => typeof SSTVGeneral !== 'undefined' && SSTVGeneral.destroy?.(),
                 websdr: () => typeof WebSDR !== 'undefined' && WebSDR.destroy?.(),
                 spystations: () => typeof SpyStations !== 'undefined' && SpyStations.destroy?.(),
+                ais: () => { if (aisEventSource) { aisEventSource.close(); aisEventSource = null; } },
+                acars: () => { if (acarsMainEventSource) { acarsMainEventSource.close(); acarsMainEventSource = null; } },
+                vdl2: () => { if (vdl2MainEventSource) { vdl2MainEventSource.close(); vdl2MainEventSource = null; } },
+                radiosonde: () => { if (radiosondeEventSource) { radiosondeEventSource.close(); radiosondeEventSource = null; } },
             };
             if (previousMode && previousMode !== mode && moduleDestroyMap[previousMode]) {
                 try { moduleDestroyMap[previousMode](); } catch(e) { console.warn(`[switchMode] destroy ${previousMode} failed:`, e); }

templates/partials/modes/acars.html

@@ -254,7 +254,9 @@
 
         acarsMainEventSource.onerror = function() {
             setTimeout(() => {
-                if (document.getElementById('stopAcarsBtn').style.display === 'block') {
+                const panel = document.getElementById('acarsMode');
+                if (panel && panel.classList.contains('active') &&
+                    document.getElementById('stopAcarsBtn').style.display === 'block') {
                     startAcarsMainSSE();
                 }
             }, 2000);

templates/partials/modes/ais.html

@@ -164,7 +164,9 @@
 
         aisEventSource.onerror = function() {
             setTimeout(() => {
-                if (document.getElementById('stopAisBtn').style.display === 'block') {
+                const panel = document.getElementById('aisMode');
+                if (panel && panel.classList.contains('active') &&
+                    document.getElementById('stopAisBtn').style.display === 'block') {
                     startAisSSE();
                 }
             }, 2000);

templates/partials/modes/radiosonde.html

@@ -220,7 +220,9 @@
 
         radiosondeEventSource.onerror = function() {
             setTimeout(() => {
-                if (document.getElementById('stopRadiosondeBtn').style.display === 'block') {
+                const panel = document.getElementById('radiosondeMode');
+                if (panel && panel.classList.contains('active') &&
+                    document.getElementById('stopRadiosondeBtn').style.display === 'block') {
                     startRadiosondeSSE();
                 }
             }, 2000);

templates/partials/modes/vdl2.html

@@ -212,7 +212,9 @@
 
         vdl2MainEventSource.onerror = function() {
             setTimeout(() => {
-                if (document.getElementById('stopVdl2Btn').style.display === 'block') {
+                const panel = document.getElementById('vdl2Mode');
+                if (panel && panel.classList.contains('active') &&
+                    document.getElementById('stopVdl2Btn').style.display === 'block') {
                     startVdl2MainSSE();
                 }
             }, 2000);

utils/process.py

@@ -34,6 +34,16 @@ def unregister_process(process: subprocess.Popen) -> None:
             _spawned_processes.remove(process)
 
 
+def close_process_pipes(process: subprocess.Popen) -> None:
+    """Close stdin/stdout/stderr pipes on a subprocess to free file descriptors."""
+    for pipe in (process.stdin, process.stdout, process.stderr):
+        if pipe:
+            try:
+                pipe.close()
+            except OSError:
+                pass
+
+
 def cleanup_all_processes() -> None:
     """Clean up all registered processes on exit."""
     logger.info("Cleaning up all spawned processes...")
@@ -47,6 +57,7 @@ def cleanup_all_processes() -> None:
                     process.kill()
                 except Exception as e:
                     logger.warning(f"Error cleaning up process: {e}")
+            close_process_pipes(process)
         _spawned_processes.clear()
 
 
@@ -66,12 +77,14 @@ def safe_terminate(process: subprocess.Popen | None, timeout: float = 2.0) -> bo
 
     if process.poll() is not None:
         # Already dead
+        close_process_pipes(process)
         unregister_process(process)
         return False
 
     try:
         process.terminate()
         process.wait(timeout=timeout)
+        close_process_pipes(process)
         unregister_process(process)
         return True
     except subprocess.TimeoutExpired:
@@ -80,10 +93,12 @@ def safe_terminate(process: subprocess.Popen | None, timeout: float = 2.0) -> bo
             process.wait(timeout=3)
         except subprocess.TimeoutExpired:
             pass
+        close_process_pipes(process)
         unregister_process(process)
         return True
     except Exception as e:
         logger.warning(f"Error terminating process: {e}")
+        close_process_pipes(process)
         return False
 
 

utils/weather_sat_predict.py

@@ -13,6 +13,17 @@ from utils.weather_sat import WEATHER_SATELLITES
 
 logger = get_logger('intercept.weather_sat_predict')
 
+# Cache skyfield timescale to avoid re-downloading/re-parsing per request
+_cached_timescale = None
+
+
+def _get_timescale():
+    global _cached_timescale
+    if _cached_timescale is None:
+        from skyfield.api import load
+        _cached_timescale = load.timescale()
+    return _cached_timescale
+
 
 def _format_utc_iso(dt: datetime.datetime) -> str:
     """Return an ISO8601 UTC timestamp with a single timezone designator."""
@@ -48,7 +59,7 @@ def predict_passes(
         ImportError: If skyfield is not installed.
     """
     from skyfield.almanac import find_discrete
-    from skyfield.api import EarthSatellite, load, wgs84
+    from skyfield.api import EarthSatellite, wgs84
 
     from data.satellites import TLE_SATELLITES
 
@@ -61,7 +72,7 @@ def predict_passes(
     except ImportError:
         pass
 
-    ts = load.timescale()
+    ts = _get_timescale()
     observer = wgs84.latlon(lat, lon)
     t0 = ts.now()
     t1 = ts.utc(t0.utc_datetime() + datetime.timedelta(hours=hours))