Fix prometheus metrics

Use a singleton to prevent attempt to rebind socket on page reload.

metrics.py

@@ -0,0 +1,23 @@
+import threading
+from prometheus_client import Counter, start_http_server
+
+_lock = threading.Lock()
+_registry = None
+_metrics = None
+
+def get_metrics():
+    global _metrics
+    with _lock:
+        if _metrics is None:
+            start_http_server(9110)
+            _metrics = {
+                "people_in": Counter(
+                    "people_in_count",
+                    "Number of people who entered",
+                ),
+                "people_out": Counter(
+                    "people_out_count",
+                    "Number of people who exited",
+                ),
+            }
+        return _metrics

streamlit_app.py

@@ -6,18 +6,9 @@ from utils.zones import draw_count_line_horizontal, draw_count_line_vertical
 import tempfile
 import time
 
-from prometheus_client import Gauge, start_http_server
+from metrics import get_metrics
 
-# Nur einmal beim ersten Start starten
-if "prom" not in st.session_state:
-    # Starte Prometheus-Metrik-Server (z. B. auf Port 9100)
-    start_http_server(9100)
-
-    # Metriken definieren
-    st.session_state.prom = {
-        'people_in': Gauge("people_in_count", "Number of people who entered"),
-        'people_out': Gauge("people_out_count", "Number of people who exited"),
-    }
+metrics = get_metrics()
 
 st.set_page_config(layout="wide", page_title="People Counter")
 
@@ -33,7 +24,7 @@ if start_button and STREAM_URL:
 
     stframe = st.empty()
     model = YOLO("yolo_weights/yolo11n.pt")
-    counter = Counter(line_orientation)
+    counter = Counter(line_orientation, metrics)
 
     cap = cv2.VideoCapture(STREAM_URL)
 
@@ -62,8 +53,6 @@ if start_button and STREAM_URL:
                 for box, track_id in zip(boxes.xywh.cpu(), boxes.id.cpu())
             ]
             counter.update(tracks, line_position)
-            st.session_state.prom['people_in'].set(counter.in_count)
-            st.session_state.prom['people_out'].set(counter.out_count)
 
         if line_orientation == 'horizontal':
             draw_count_line_horizontal(frame, line_position)

utils/counter.py

@@ -1,9 +1,10 @@
 class Counter:
-    def __init__(self, line_orientation):
+    def __init__(self, line_orientation, metrics):
         self.in_count = 0
         self.out_count = 0
         self.track_memory = {}
         self.line_orientation = line_orientation
+        self.metrics = metrics
 
     def update(self, tracks, line_position):
         for track in tracks:
@@ -27,5 +28,7 @@ class Counter:
 
             if prev < line_position <= center:
                 self.in_count += 1
+                self.metrics["people_in"].inc()
             elif prev > line_position >= center:
                 self.out_count += 1
+                self.metrics["people_out"].inc()