codekingpro/portable-devtools

1"""2Some light wrappers around Python's multiprocessing, to deal with cleanly3starting child processes.4"""5 6from __future__ import annotations7 8import multiprocessing9import os10import sys11from collections.abc import Callable12from multiprocessing.context import SpawnProcess13from socket import socket14 15from uvicorn.config import Config16 17multiprocessing.allow_connection_pickling()18spawn = multiprocessing.get_context("spawn")19 20 21def get_subprocess(22    config: Config,23    target: Callable[..., None],24    sockets: list[socket],25) -> SpawnProcess:26    """27    Called in the parent process, to instantiate a new child process instance.28    The child is not yet started at this point.29 30    * config - The Uvicorn configuration instance.31    * target - A callable that accepts a list of sockets. In practice this will32               be the `Server.run()` method.33    * sockets - A list of sockets to pass to the server. Sockets are bound once34                by the parent process, and then passed to the child processes.35    """36    # We pass across the stdin fileno, and reopen it in the child process.37    # This is required for some debugging environments.38    try:39        stdin_fileno = sys.stdin.fileno()40    # The `sys.stdin` can be `None`, see https://docs.python.org/3/library/sys.html#sys.__stdin__.41    except (AttributeError, OSError):42        stdin_fileno = None43 44    kwargs = {45        "config": config,46        "target": target,47        "sockets": sockets,48        "stdin_fileno": stdin_fileno,49    }50 51    return spawn.Process(target=subprocess_started, kwargs=kwargs)52 53 54def subprocess_started(55    config: Config,56    target: Callable[..., None],57    sockets: list[socket],58    stdin_fileno: int | None,59) -> None:60    """61    Called when the child process starts.62 63    * config - The Uvicorn configuration instance.64    * target - A callable that accepts a list of sockets. In practice this will65               be the `Server.run()` method.66    * sockets - A list of sockets to pass to the server. Sockets are bound once67                by the parent process, and then passed to the child processes.68    * stdin_fileno - The file number of sys.stdin, so that it can be reattached69                     to the child process.70    """71    # Re-open stdin.72    if stdin_fileno is not None:73        sys.stdin = os.fdopen(stdin_fileno)  # pragma: full coverage74 75    # Logging needs to be setup again for each child.76    config.configure_logging()77 78    try:79        # Now we can call into `Server.run(sockets=sockets)`80        target(sockets=sockets)81    except KeyboardInterrupt:  # pragma: no cover82        # suppress the exception to avoid a traceback from subprocess.Popen83        # the parent already expects us to end, so no vital information is lost84        pass85