import logging

import select

import socket

import time

from .exceptions import WaitTimeout

logger = logging.getLogger(__name__)

def waitfor(condition, help=None, timeout=10, poll_interval=0.1):

if not help:

help = (condition.__doc__ or repr(condition)).strip()

expires = time.monotonic() + timeout

while time.monotonic() < expires:

logger.debug('Polling for %s ...', help)

rv = condition()

if rv:

logger.debug('Polling for %s successful: %r.', help, rv)

return rv

time.sleep(poll_interval)

raise WaitTimeout('Timeout expired')

def wait_for_ssh(port, timeout=10):

def ssh_tcp():

logger.debug('SSH: trying to connect to port %d ...', port)

try:

sock = socket.create_connection(('localhost', port))

except OSError as e:

logger.debug('SSH: got an OSError: %s', e)

return False

else:

sock.setblocking(0)

logger.debug('SSH: connected, reading 3 bytes ...')

ready = select.select([sock], [], [], 0.1)

logger.debug('SSH: ready: %r', ready)

if not ready[0]:

logger.debug('SSH: no data ready')

return False

buffer = sock.recv(3)

logger.debug('SSH: received %s', buffer)

if buffer == b'SSH':

logger.debug('SSH: success!')

return True

waitfor(ssh_tcp, timeout=timeout)