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- """
- Some light wrappers around Python's multiprocessing, to deal with cleanly
- starting child processes.
- """
- from __future__ import annotations
- import multiprocessing
- import os
- import sys
- from multiprocessing.context import SpawnProcess
- from socket import socket
- from typing import Callable
- from uvicorn.config import Config
- multiprocessing.allow_connection_pickling()
- spawn = multiprocessing.get_context("spawn")
- def get_subprocess(
- config: Config,
- target: Callable[..., None],
- sockets: list[socket],
- ) -> SpawnProcess:
- """
- Called in the parent process, to instantiate a new child process instance.
- The child is not yet started at this point.
- * config - The Uvicorn configuration instance.
- * target - A callable that accepts a list of sockets. In practice this will
- be the `Server.run()` method.
- * sockets - A list of sockets to pass to the server. Sockets are bound once
- by the parent process, and then passed to the child processes.
- """
- # We pass across the stdin fileno, and reopen it in the child process.
- # This is required for some debugging environments.
- try:
- stdin_fileno = sys.stdin.fileno()
- # The `sys.stdin` can be `None`, see https://docs.python.org/3/library/sys.html#sys.__stdin__.
- except (AttributeError, OSError):
- stdin_fileno = None
- kwargs = {
- "config": config,
- "target": target,
- "sockets": sockets,
- "stdin_fileno": stdin_fileno,
- }
- return spawn.Process(target=subprocess_started, kwargs=kwargs)
- def subprocess_started(
- config: Config,
- target: Callable[..., None],
- sockets: list[socket],
- stdin_fileno: int | None,
- ) -> None:
- """
- Called when the child process starts.
- * config - The Uvicorn configuration instance.
- * target - A callable that accepts a list of sockets. In practice this will
- be the `Server.run()` method.
- * sockets - A list of sockets to pass to the server. Sockets are bound once
- by the parent process, and then passed to the child processes.
- * stdin_fileno - The file number of sys.stdin, so that it can be reattached
- to the child process.
- """
- # Re-open stdin.
- if stdin_fileno is not None:
- sys.stdin = os.fdopen(stdin_fileno) # pragma: full coverage
- # Logging needs to be setup again for each child.
- config.configure_logging()
- try:
- # Now we can call into `Server.run(sockets=sockets)`
- target(sockets=sockets)
- except KeyboardInterrupt: # pragma: no cover
- # supress the exception to avoid a traceback from subprocess.Popen
- # the parent already expects us to end, so no vital information is lost
- pass
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