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"""A wait callback to allow psycopg2 cooperation with eventlet.
Use `patch_psycopg()` to enable eventlet support in Psycopg.
"""
# Copyright (C) 2010-2018 Daniele Varrazzo <daniele.varrazzo@gmail.com>
# All rights reserved. See COPYING file for details.
from __future__ import absolute_import
import psycopg2
from psycopg2 import extensions
from eventlet.hubs import trampoline
def patch_psycopg():
"""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:
trampoline(conn.fileno(), read=True)
elif state == extensions.POLL_WRITE:
trampoline(conn.fileno(), write=True)
else:
raise psycopg2.OperationalError("Bad result from poll: %r" % state)
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