"""Launch `dvc daemon` command in a separate detached process."""

import inspect

import logging

import os

import platform

import sys

from subprocess import Popen

from dvc.env import DVC_DAEMON

from dvc.utils import fix_env, is_binary

logger = logging.getLogger(__name__)

CREATE_NEW_PROCESS_GROUP = 0x00000200

DETACHED_PROCESS = 0x00000008

def _popen(cmd, **kwargs):

prefix = [sys.executable]

if not is_binary():

prefix += [sys.argv[0]]

return Popen(prefix + cmd, close_fds=True, shell=False, **kwargs)

def _spawn_windows(cmd, env):

from subprocess import STARTF_USESHOWWINDOW, STARTUPINFO

creationflags = CREATE_NEW_PROCESS_GROUP | DETACHED_PROCESS

startupinfo = STARTUPINFO()

startupinfo.dwFlags |= STARTF_USESHOWWINDOW

_popen(

cmd, env=env, creationflags=creationflags, startupinfo=startupinfo,

).communicate()

def _spawn_posix(cmd, env):

from dvc.main import main

# NOTE: using os._exit instead of sys.exit, because dvc built

# with PyInstaller has trouble with SystemExit exception and throws

# errors such as "[26338] Failed to execute script __main__"

try:

pid = os.fork()

if pid > 0:

return

except OSError:

logger.exception("failed at first fork")

os._exit(1) # pylint: disable=protected-access

os.setsid()

try:

pid = os.fork()

if pid > 0:

os._exit(0) # pylint: disable=protected-access

except OSError:

logger.exception("failed at second fork")

os._exit(1) # pylint: disable=protected-access

sys.stdin.close()

sys.stdout.close()

sys.stderr.close()

if platform.system() == "Darwin":

# workaround for MacOS bug

# https://github.com/iterative/dvc/issues/4294

_popen(cmd, env=env).communicate()

else:

os.environ.update(env)

main(cmd)

os._exit(0) # pylint: disable=protected-access

def _spawn(cmd, env):

logger.debug(f"Trying to spawn '{cmd}'")

if os.name == "nt":

_spawn_windows(cmd, env)

elif os.name == "posix":

_spawn_posix(cmd, env)

else:

raise NotImplementedError

logger.debug(f"Spawned '{cmd}'")

def daemon(args):

"""Launch a `dvc daemon` command in a detached process.

Args:

args (list): list of arguments to append to `dvc daemon` command.

"""

if os.environ.get(DVC_DAEMON):

logger.debug("skipping launching a new daemon.")

return

cmd = ["daemon", "-q"] + args

env = fix_env()

file_path = os.path.abspath(inspect.stack()[0][1])

env["PYTHONPATH"] = os.path.dirname(os.path.dirname(file_path))

env[DVC_DAEMON] = "1"

_spawn(cmd, env)