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"""A wait callback to allow psycopg2 cooperation with eventlet.
Use `make_psycopg_green()` to enable eventlet support in Psycopg.
"""
# Copyright (C) 2010 Daniele Varrazzo <daniele.varrazzo@gmail.com>
# and licensed under the MIT license:
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import psycopg2
from psycopg2 import extensions
import eventlet.hubs
def make_psycopg_green():
"""Configure Psycopg to be used with eventlet in non-blocking way."""
if not hasattr(extensions, 'set_wait_callback'):
raise ImportError(
"support for coroutines not available in this Psycopg version (%s)"
% psycopg2.__version__)
extensions.set_wait_callback(eventlet_wait_callback)
def eventlet_wait_callback(conn, timeout=-1):
"""A wait callback useful to allow eventlet to work with Psycopg."""
while 1:
state = conn.poll()
if state == extensions.POLL_OK:
break
elif state == extensions.POLL_READ:
eventlet.hubs.trampoline(conn.fileno(), read=True)
elif state == extensions.POLL_WRITE:
eventlet.hubs.trampoline(conn.fileno(), write=True)
else:
raise psycopg2.OperationalError(
"Bad result from poll: %r" % state)