cv(runtime): enforce software GL (LIBGL_ALWAYS_SOFTWARE, llvmpipe), preload GLX/dispatch chain; debug: add ldd output for libGL; build: add libc-bin

Author: z.murodov

nixpacks.toml

@@ -2,7 +2,7 @@
 # Ensure Python is present for Nixpacks Python phase, plus native deps for OpenCV/MediaPipe
 nixPkgs = ['python311', 'libGL', 'libglvnd', 'pkg-config', 'glib', 'zlib', 'mesa', 'xorg.libX11', 'xorg.libXext', 'xorg.libXrender']
 cmds = [
-  'apt-get update -y && DEBIAN_FRONTEND=noninteractive apt-get install -y libgl1 libglvnd0 libglx-mesa0 libgl1-mesa-dri libopengl0 libegl1 libgles2 libglib2.0-0 libxext6 libxrender1 libxfixes3 libsm6 libxcb1 libxau6 libxdmcp6 libglx0 libx11-6 libx11-xcb1 libxrandr2 libxxf86vm1 libxdamage1 libxshmfence1 libdrm2 libexpat1 libstdc++6 libgcc-s1 && ldconfig'
+  'apt-get update -y && DEBIAN_FRONTEND=noninteractive apt-get install -y libgl1 libglvnd0 libglx-mesa0 libgl1-mesa-dri libopengl0 libegl1 libgles2 libglib2.0-0 libxext6 libxrender1 libxfixes3 libsm6 libxcb1 libxau6 libxdmcp6 libglx0 libx11-6 libx11-xcb1 libxrandr2 libxxf86vm1 libxdamage1 libxshmfence1 libdrm2 libexpat1 libstdc++6 libgcc-s1 libc-bin && ldconfig'
 ]
 
 [start]

src/backend/api/system_routes.py

@@ -88,4 +88,13 @@ async def cv_debug():
         except OSError as e:
             info.setdefault("dlopen_errors", []).append({lib: str(e)})
 
+    # If libGL exists, run ldd to see unresolved deps
+    import subprocess
+    for p in info.get("libgl_candidates", [])[:1]:
+        try:
+            out = subprocess.check_output(["/usr/bin/ldd", p], text=True, stderr=subprocess.STDOUT)
+            info["ldd_libGL"] = out
+        except Exception as e:
+            info["ldd_error"] = str(e)
+
     return info

src/cv/video_processor.py

@@ -7,6 +7,9 @@
 
 # Force CPU path for MediaPipe in headless servers (Railway)
 os.environ.setdefault("MEDIAPIPE_DISABLE_GPU", "1")
+os.environ.setdefault("OPENCV_DISABLE_GPU", "1")
+os.environ.setdefault("LIBGL_ALWAYS_SOFTWARE", "1")
+os.environ.setdefault("MESA_LOADER_DRIVER_OVERRIDE", "llvmpipe")
 
 # Ensure system GL libraries are discoverable at runtime (Railway Ubuntu 24.04)
 # Some builds use Nix python which may not see apt-installed libs unless we extend LD_LIBRARY_PATH
@@ -48,6 +51,13 @@
 
 # 2) Fallback to sonames if absolute paths failed
 if not _loaded_gl:
+    # Try preloading GL dispatch/GLX chain first
+    for _dep in ("/usr/lib/x86_64-linux-gnu/libGLdispatch.so.0", "/usr/lib/x86_64-linux-gnu/libGLX.so.0"):
+        try:
+            if os.path.exists(_dep):
+                ctypes.CDLL(_dep, mode=getattr(ctypes, "RTLD_GLOBAL", 0))
+        except OSError:
+            pass
     for _lib in ("libGL.so.1", "libGL.so"):
         try:
             ctypes.CDLL(_lib, mode=getattr(ctypes, "RTLD_GLOBAL", 0))