Restarting Postgress server during high load cases uncaught exception momoko

[haizaar]

This is the spin-off of #126. When running the following code and restarting the server in the middle, the following exception was raised:

ERROR:tornado.application:Exception in callback (6, <function null_wrapper at 0x7ff9431391b8>)
Traceback (most recent call last):
  File ".../local/lib/python2.7/site-packages/tornado/ioloop.py", line 866, in start
    handler_func(fd_obj, events)
  File ".../local/lib/python2.7/site-packages/tornado/stack_context.py", line 275, in null_wrapper
    return fn(*args, **kwargs)
  File ".../momoko/connection.py", line 713, in _io_callback
    self.ioloop.update_handler(self.fileno, IOLoop.WRITE)
  File ".../local/lib/python2.7/site-packages/tornado/ioloop.py", line 708, in update_handler
    self._impl.modify(fd, events | self.ERROR)
IOError: [Errno 2] No such file or directory

The code that reproduces the issue:

from tornado.ioloop import IOLoop
import momoko
from tornado.gen import engine

if __name__ == '__main__':

    ioloop = IOLoop.instance()
    db = momoko.Pool(
        dsn='dbname=your_db user=your_user password=very_secret_password '
            'host=remote_host port=5432',
        size=1,
        ioloop=ioloop,
    )

    future = db.connect()
    ioloop.add_future(future, lambda f: ioloop.stop())
    ioloop.start()
    future.result()

    @engine
    def never_ending_db_query_loop(callback):
        while True:
            try:
                cursor = yield db.execute('SELECT 1')
                row  = cursor.fetchone()
                print 'db returned: {0}'.format(row[0])
            except Exception as e:
                print e
        callback()

    never_ending_db_query_loop(ioloop.stop)
    ioloop.start()