Added stop to the container if no device needs frames

app.py

@@ -1,5 +1,9 @@
 #!/usr/bin/env python3
-"""JPEG proxy: prefetch from Frigate per camera/size and serve cover-cropped JPEGs."""
+"""JPEG proxy: prefetch from Frigate per camera/size and serve cover-cropped JPEGs.
+
+Prefetch runs only while clients are requesting a stream; after IDLE_TIMEOUT
+seconds with no hits it pauses until the next request.
+"""
 
 from __future__ import annotations
 
@@ -20,6 +24,8 @@ from PIL import Image
 JPEG_QUALITY = int(os.environ.get("JPEG_QUALITY", "40"))
 FETCH_TIMEOUT = float(os.environ.get("FETCH_TIMEOUT", "5"))
 PREFETCH_HZ = float(os.environ.get("PREFETCH_HZ", "10"))
+# Stop prefetching a stream after this many seconds with no HTTP clients.
+IDLE_TIMEOUT = float(os.environ.get("IDLE_TIMEOUT", "30"))
 DEFAULT_SIZE = int(os.environ.get("DEFAULT_SIZE", "480"))
 MAX_SIZE = int(os.environ.get("MAX_SIZE", "720"))
 MIN_SIZE = int(os.environ.get("MIN_SIZE", "64"))
@@ -58,10 +64,12 @@ class StreamConfig:
 class CameraStream:
     config: StreamConfig
     lock: threading.Lock = field(default_factory=threading.Lock)
+    wake: threading.Event = field(default_factory=threading.Event)
     jpeg: bytes = b""
     etag: str = ""
     width: int = 0
     height: int = 0
+    last_access: float = 0.0
 
     def snapshot(self) -> tuple[bytes, str, int, int]:
         with self.lock:
@@ -74,6 +82,20 @@ class CameraStream:
             self.width = width
             self.height = height
 
+    def touch(self) -> None:
+        with self.lock:
+            self.last_access = time.monotonic()
+        self.wake.set()
+
+    def is_active(self, now: float | None = None) -> bool:
+        if IDLE_TIMEOUT <= 0:
+            return True
+        with self.lock:
+            last = self.last_access
+        if last <= 0:
+            return False
+        return ((now if now is not None else time.monotonic()) - last) < IDLE_TIMEOUT
+
 
 class StreamRegistry:
     def __init__(self, sources: dict[str, CameraSource]) -> None:
@@ -228,7 +250,20 @@ def _prefetch_loop(stream: CameraStream) -> None:
     cfg = stream.config
     session = requests.Session()
     interval = 1.0 / max(PREFETCH_HZ, 0.5)
+    idle = True
     while True:
+        if not stream.is_active():
+            if not idle:
+                print(f"[{cfg.label}] prefetch paused (idle)", flush=True)
+                idle = True
+            stream.wake.wait(timeout=1.0)
+            stream.wake.clear()
+            continue
+
+        if idle:
+            print(f"[{cfg.label}] prefetch active", flush=True)
+            idle = False
+
         started = time.monotonic()
         try:
             source_url = _frigate_url(cfg.source.url, cfg.width, cfg.height, cfg.zoom)
@@ -244,10 +279,13 @@ def _prefetch_loop(stream: CameraStream) -> None:
             print(f"[{cfg.label}] prefetch failed: {exc}", flush=True)
         delay = interval - (time.monotonic() - started)
         if delay > 0:
-            time.sleep(delay)
+            # Wake early if a client touches the stream (or it goes idle).
+            stream.wake.wait(timeout=delay)
+            stream.wake.clear()
 
 
 def _jpeg_response(stream: CameraStream):
+    stream.touch()
     body, etag, width, height = stream.snapshot()
     if not body:
         return "Image not ready", 503, {"Content-Type": "text/plain"}
@@ -288,19 +326,22 @@ def create_app() -> Flask:
 
     @app.get("/health")
     def health():
+        now = time.monotonic()
         result = {}
         for stream in registry.all_streams():
             body, _, width, height = stream.snapshot()
             label = stream.config.label
             result[label] = {
                 "ready": bool(body),
+                "active": stream.is_active(now),
                 "bytes": len(body),
                 "size": f"{width}x{height}",
                 "target": f"{stream.config.width}x{stream.config.height}",
                 "zoom": stream.config.zoom,
                 "source": stream.config.source.url,
             }
-        return {"streams": result}, 200 if any(s["ready"] for s in result.values()) else 503
+        # Healthy once the process is up; streams may be idle with no clients.
+        return {"streams": result, "idle_timeout": IDLE_TIMEOUT}, 200
 
     @app.get("/")
     @app.get("/latest.jpg")