double-fork backfill to fully detach from uWSGI worker

Single fork left the child in the uWSGI process group with inherited
HTTP sockets, causing 502s. Double-fork with setsid() and fd cleanup
so the grandchild is fully orphaned to init.

make_post_sell/lib/karaoke.py

@@ -175,9 +175,28 @@ def backfill_karaoke_async(shop_id, session_factory, app_settings):
 
     pid = os.fork()
     if pid > 0:
-        return  # parent returns immediately
+        # Parent: reap the intermediate child immediately so it doesn't zombie
+        os.waitpid(pid, 0)
+        return
+
+    # Intermediate child: detach fully from uWSGI, then fork again
+    os.setsid()
+    pid2 = os.fork()
+    if pid2 > 0:
+        os._exit(0)  # intermediate child exits — grandchild is orphaned to init
+
+    # --- Grandchild process: fully detached from uWSGI ---
+    # Close inherited file descriptors (uWSGI sockets, HTTP connections)
+    import resource
+    maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
+    if maxfd == resource.RLIM_INFINITY:
+        maxfd = 1024
+    for fd in range(3, maxfd):
+        try:
+            os.close(fd)
+        except OSError:
+            pass
 
-    # --- Child process: independent of uWSGI worker ---
     lock_fd = None
     try:
         # Acquire file lock (guards one-per-shop)