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"""Helpers for cross-platform multiprocessing support.
"""
import logging
import multiprocessing
import multiprocessing.queues
from multiprocessing.context import ForkProcess as ForkProcessType
from multiprocessing.context import SpawnProcess as SpawnProcessType
from typing import Callable
logger = logging.getLogger(__name__)
ForkContext = multiprocessing.get_context("fork")
SpawnContext = multiprocessing.get_context("spawn")
ForkProcess: Callable[..., ForkProcessType] = ForkContext.Process
SpawnProcess: Callable[..., SpawnProcessType] = SpawnContext.Process
SpawnEvent = SpawnContext.Event
SpawnQueue = SpawnContext.Queue
def join_terminate_close_proc(process: SpawnProcessType, *, timeout: int = 30) -> None:
"""Increasingly aggressively terminate a process.
This function assumes that the process is likely to exit before
the join timeout, driven by some other means, such as the
MonitoringHub router_exit_event. If the process does not exit, then
first terminate() and then kill() will be used to end the process.
In the case of a very mis-behaving process, this function might take
up to 3*timeout to exhaust all termination methods and return.
"""
logger.debug("Joining process")
process.join(timeout)
# run a sequence of increasingly aggressive steps to shut down the process.
if process.is_alive():
logger.error("Process did not join. Terminating.")
process.terminate()
process.join(timeout)
if process.is_alive():
logger.error("Process did not join after terminate. Killing.")
process.kill()
process.join(timeout)
# This kill should not be caught by any signal handlers so it is
# unlikely that this join will timeout. If it does, there isn't
# anything further to do except log an error in the next if-block.
if process.is_alive():
logger.error("Process failed to end")
# don't call close if the process hasn't ended:
# process.close() doesn't work on a running process.
else:
process.close()
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