import os
import sys
import multiprocessing
from ctypes import c_bool
from errno import EINTR, ECHILD
from socket import socket, AF_INET, SOCK_STREAM, SOMAXCONN
from signal import signal, SIGHUP, SIGTERM, SIGCHLD, SIG_DFL, SIG_IGN
from pyspark.worker import main as worker_main
from pyspark.serializers import write_int
try:
POOLSIZE = multiprocessing.cpu_count()
except NotImplementedError:
POOLSIZE = 4
exit_flag = multiprocessing.Value(c_bool, False)
def should_exit():
global exit_flag
return exit_flag.value
def compute_real_exit_code(exit_code):
# SystemExit's code can be integer or string, but os._exit only accepts integers
import numbers
if isinstance(exit_code, numbers.Integral):
return exit_code
else:
return 1
def worker(listen_sock):
# Redirect stdout to stderr
os.dup2(2, 1)
# Manager sends SIGHUP to request termination of workers in the pool
def handle_sighup(*args):
assert should_exit()
signal(SIGHUP, handle_sighup)
# Cleanup zombie children
def handle_sigchld(*args):
pid = status = None
try:
while (pid, status) != (0, 0):
pid, status = os.waitpid(0, os.WNOHANG)
except EnvironmentError as err:
if err.errno == EINTR:
# retry
handle_sigchld()
elif err.errno != ECHILD:
raise
signal(SIGCHLD, handle_sigchld)
# Handle clients
while not should_exit():
# Wait until a client arrives or we have to exit
sock = None
while not should_exit() and sock is None:
try:
sock, addr = listen_sock.accept()
except EnvironmentError as err:
if err.errno != EINTR:
raise
if sock is not None:
# Fork a child to handle the client.
# The client is handled in the child so that the manager
# never receives SIGCHLD unless a worker crashes.
if os.fork() == 0:
# Leave the worker pool
signal(SIGHUP, SIG_DFL)
listen_sock.close()
# Handle the client then exit
sockfile = sock.makefile()
exit_code = 0
try:
worker_main(sockfile, sockfile)
except SystemExit as exc:
exit_code = exc.code
finally:
sockfile.close()
sock.close()
os._exit(compute_real_exit_code(exit_code))
else:
sock.close()
def launch_worker(listen_sock):
if os.fork() == 0:
try:
worker(listen_sock)
except Exception as err:
import traceback
traceback.print_exc()
os._exit(1)
else:
assert should_exit()
os._exit(0)
def manager():
# Create a new process group to corral our children
os.setpgid(0, 0)
# Create a listening socket on the AF_INET loopback interface
listen_sock = socket(AF_INET, SOCK_STREAM)
listen_sock.bind(('127.0.0.1', 0))
listen_sock.listen(max(1024, 2 * POOLSIZE, SOMAXCONN))
listen_host, listen_port = listen_sock.getsockname()
write_int(listen_port, sys.stdout)
# Launch initial worker pool
for idx in range(POOLSIZE):
launch_worker(listen_sock)
listen_sock.close()
def shutdown():
global exit_flag
exit_flag.value = True
# Gracefully exit on SIGTERM, don't die on SIGHUP
signal(SIGTERM, lambda signum, frame: shutdown())
signal(SIGHUP, SIG_IGN)
# Cleanup zombie children
def handle_sigchld(*args):
try:
pid, status = os.waitpid(0, os.WNOHANG)
if status != 0 and not should_exit():
raise RuntimeError("worker crashed: %s, %s" % (pid, status))
except EnvironmentError as err:
if err.errno not in (ECHILD, EINTR):
raise
signal(SIGCHLD, handle_sigchld)
# Initialization complete
sys.stdout.close()
try:
while not should_exit():
try:
# Spark tells us to exit by closing stdin
if os.read(0, 512) == '':
shutdown()
except EnvironmentError as err:
if err.errno != EINTR:
shutdown()
raise
finally:
signal(SIGTERM, SIG_DFL)
exit_flag.value = True
# Send SIGHUP to notify workers of shutdown
os.kill(0, SIGHUP)
if __name__ == '__main__':
manager()
