Fix zombie process accumulation from git operations in cloud environment

  Git commands spawn helper processes (git-credential-helper, git-remote-https, ssh)
  that become zombies when the main git process exits before children complete. This
  is problematic in cloud/container environments where the application runs as PID 1
  or under minimal init systems that don't reliably reap orphaned processes.

  Added SIGCHLD signal handler to automatically reap zombie processes system-wide
  using non-blocking waitpid(), preventing resource leaks without affecting normal
  git operations.

Author: Neha Singla

jupyterlab_git/git.py

@@ -22,6 +22,7 @@
 import tornado.locks
 from jupyter_server.utils import ensure_async
 from nbdime import diff_notebooks, merge_notebooks
+import signal
 
 from .log import get_logger
 
@@ -55,6 +56,36 @@
 execution_lock = tornado.locks.Lock()
 
 
+def sigchld_handler(signum, frame):
+    """Handle SIGCHLD to reap zombie processes from git operations.
+
+    Git commands often spawn helper processes (git-credential-helper, git-remote-https,
+    ssh, git-upload-pack, git-receive-pack) that can become zombie processes when the
+    main git process exits before its children complete.
+
+    This is particularly problematic in cloud/container environments where:
+    - The application runs as PID 1 or under minimal init systems
+    - Standard init process zombie reaping may be unreliable or slow
+    - Resource constraints can cause zombie accumulation
+
+    This handler automatically reaps any zombie processes to prevent system resource leaks.
+    """
+    while True:
+        try:
+            # Reap child processes non-blockingly
+            pid, status = os.waitpid(-1, os.WNOHANG)
+            if pid == 0:  # No more children to reap
+                break
+            get_logger().debug(f"Reaped child process {pid} with status {status}")
+        except OSError:
+            # No child processes or other error
+            break
+
+
+# Set up SIGCHLD handler for automatic zombie reaping
+signal.signal(signal.SIGCHLD, sigchld_handler)
+
+
 class State(IntEnum):
     """Git repository state."""