"""
Reprouce hang when using io.FileIO with inaccessible NFS server.

Usage:
    python fileio_nfs_test.py mountpoint/filename server_address

Example run:

    mount -t example.com mnt
    touch mnt/file
    python fileio_nfs_test.py mnt/file example.com
"""

import io
import logging
import mmap
import os
import subprocess
import sys
import threading
import time

from contextlib import closing

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

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

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(30):
        logging.info("check %d", i)
        if done.wait(1):
            break

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


logging.info("pid=%d", os.getpid())

logging.info("Opening %s", filename)
fd = os.open(filename, os.O_RDWR | os.O_DIRECT)
logging.info("OK fd=%d", fd)

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

# For some reason adding iptables rule is not applied immediatelly.
logging.info("Waiting until storage is blocked...")
time.sleep(10)

logging.info("Opening io.FileIO")
with closing(io.FileIO(fd, "r+", closefd=True)) as file:
    logging.info("OK")

    logging.info("Creating mmap")
    with closing(mmap.mmap(-1, 1024 * 16, mmap.MAP_SHARED)) as buf:
        logging.info("OK")

        logging.info("Filling mmap")
        buf.write("x" * len(buf))
        logging.info("OK")

        logging.info("Writing mmap to storage")
        pos = 0
        while pos < len(buf):
            wbuf = buffer(buf, pos)
            pos += file.write(wbuf)
        logging.info("OK")

    logging.info("Syncing")
    os.fsync(file.fileno())
    logging.info("OK")

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