fix(dirty): detect parent death and self-terminate

Add ppid monitoring to dirty arbiter's worker monitor loop. If the
main arbiter dies unexpectedly (SIGKILL, crash, OOM), the dirty
arbiter detects the parent change and shuts itself down gracefully.

This complements the existing orphan cleanup on startup.

gunicorn/dirty/arbiter.py

@@ -196,6 +196,14 @@ class DirtyArbiter:
         """Periodically check worker health and manage pool."""
         while self.alive:
             await asyncio.sleep(1.0)
+
+            # Check if parent (main arbiter) died unexpectedly
+            if os.getppid() != self.ppid:
+                self.log.warning("Parent changed, shutting down dirty arbiter")
+                self.alive = False
+                self._shutdown()
+                return
+
             await self.murder_workers()
             await self.manage_workers()
 

tests/test_dirty_arbiter.py

@@ -894,6 +894,7 @@ class TestDirtyArbiterWorkerMonitor:
 
         arbiter = DirtyArbiter(cfg=cfg, log=log)
         arbiter.pid = os.getpid()
+        arbiter.ppid = os.getppid()  # Match actual parent for ppid check
         arbiter.alive = True
 
         monitor_calls = 0
@@ -917,6 +918,38 @@ class TestDirtyArbiterWorkerMonitor:
 
         arbiter._cleanup_sync()
 
+    @pytest.mark.asyncio
+    async def test_worker_monitor_detects_parent_death(self):
+        """Test worker monitor exits when parent dies."""
+        cfg = Config()
+        cfg.set("dirty_workers", 0)
+        log = MockLog()
+
+        arbiter = DirtyArbiter(cfg=cfg, log=log)
+        arbiter.pid = os.getpid()
+        arbiter.ppid = 99999  # Fake parent PID that doesn't match os.getppid()
+        arbiter.alive = True
+
+        shutdown_called = []
+
+        def mock_shutdown():
+            shutdown_called.append(True)
+
+        arbiter._shutdown = mock_shutdown
+
+        # Run monitor - should detect parent change and exit
+        await arbiter._worker_monitor()
+
+        # Should have detected parent death
+        assert arbiter.alive is False
+        assert len(shutdown_called) == 1
+
+        # Check log message
+        log_messages = [msg for level, msg in log.messages if level == "warning"]
+        assert any("Parent changed" in msg for msg in log_messages)
+
+        arbiter._cleanup_sync()
+
 
 class TestDirtyArbiterHandleSigchld:
     """Tests for SIGCHLD handling."""