Exit with status 3 when worker starts failed (#1077)

* fix: exit with status 3 when worker starts failed to aviod infinite start/stop cycles

* docs: fixes spelling error

* style: lint the code

* fix: replace magic exit code

Co-authored-by: fanchunke <fanchunke@laiye.com>

uvicorn/workers.py

@@ -1,8 +1,10 @@
 import asyncio
 import logging
 import signal
+import sys
 from typing import Any
 
+from gunicorn.arbiter import Arbiter
 from gunicorn.workers.base import Worker
 
 from uvicorn.config import Config
@@ -75,6 +77,11 @@ def run(self) -> None:
         server = Server(config=self.config)
         loop = asyncio.get_event_loop()
         loop.run_until_complete(server.serve(sockets=self.sockets))
+        # Exit with status 3 when worker starts failed, so Gunicorn
+        # can shut it down to avoid infinite start/stop cycles.
+        # See: https://github.com/encode/uvicorn/issues/1066
+        if not server.started:
+            sys.exit(Arbiter.WORKER_BOOT_ERROR)
 
     async def callback_notify(self) -> None:
         self.notify()