"""
Reprouce hang when using os.fdopen with inaccessible NFS server.

Usage:
    python fdopen_nfs_test.py mountpoint server_address

Example run:

    mount -t example.com mnt
    python fdopen_nfs_test.py mnt example.com
"""

import fcntl
import logging
import os
import subprocess
import sys
import threading
import time

mount = sys.argv[1]
server = sys.argv[2]

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - (%(threadName)s) - %(message)s")

filename = os.path.join(mount, "test")
done = threading.Event()
ready = threading.Event()


def canary():
    logging.info("Blocking access to storage")
    rule = ["-p", "tcp", "-d", server, "--dport", "2049", "-j", "DROP"]
    add_rule = ["iptables", "-A", "OUTPUT"] + rule
    check_rule = ["iptables", "-C", "OUTPUT"] + rule
    del_rule = ["iptables", "-D", "OUTPUT"] + rule
    subprocess.check_call(add_rule)

    logging.info("If this test is hang, please run: %s", " ".join(del_rule))

    ready.set()

    for i in range(20):
        logging.info("check %d", i)
        if done.wait(1):
            break

    if subprocess.call(check_rule, stderr=subprocess.PIPE) == 0:
        logging.info("Unblocking access to storage")
        subprocess.check_call(del_rule)


fd = os.open(filename, os.O_RDWR | os.O_CREAT)

flags = fcntl.fcntl(fd, fcntl.F_GETFD)
flags |= fcntl.FD_CLOEXEC
fcntl.fcntl(fd, fcntl.F_SETFD, flags)

logging.info("Starting canary thread")
threading.Thread(target=canary, name="Canary").start()
ready.wait()

# For some reason blockng NFS takes time to apply.
time.sleep(10)

logging.info("Calling os.fdopen")
with os.fdopen(fd, "r+") as f:
    logging.info("OK")

logging.info("Done")
done.set()

os.unlink(filename)