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# encoding: utf-8
"""
Provides some sugar to make Tornado's async stuff more palatable.
"""
import logging
import inspect
import functools
from tornado.ioloop import IOLoop
from tornado.web import RequestHandler, asynchronous as web_async
try:
from inspect import isgeneratorfunction
except ImportError:
# Python < 2.6
def isgeneratorfunction(obj):
return bool((inspect.isfunction(object) or inspect.ismethod(object)) and
obj.func_code.co_flags & CO_GENERATOR)
__version__ = '0.1.0'
class CoroutineRunner:
def __init__(self, io_loop, gen, web_handler):
self.gen = gen
self.io_loop = io_loop
self.web_handler = web_handler
# start the ball rolling...
self.callback_proxy()
def execute_work(self):
return self.work(self.callback_proxy)
def callback_proxy(self, *args):
try:
if len(args) > 0:
if isinstance(args[-1], Exception):
self.work = self.gen.throw(args[-1])
elif (hasattr(args[0], 'error') and
isinstance(args[0].error, Exception)):
self.work = self.gen.throw(args[0].error)
else:
if args[-1] is None:
args = args[:-1]
if len(args) == 1:
self.work = self.gen.send(args[0])
else:
self.work = self.gen.send(args)
else:
self.work = self.gen.next()
self.io_loop.add_callback(self.execute_work)
except StopIteration:
if self.web_handler and not self.web_handler._finished:
self.web_handler.finish()
except Exception, e:
if self.web_handler:
if self.web_handler._headers_written:
logging.error('Exception after headers written',
exc_info=True)
else:
self.web_handler._handle_request_exception(e)
def make_asynchronous_decorator(io_loop):
"""
Creates an asynchronous decorator that uses the given I/O loop.
If the `io_loop` argument is None, the default IOLoop instance will be
used.
For information on how to use such a decorator, see
`swirl.asynchronous`.
"""
if io_loop is None:
io_loop = IOLoop.instance()
# hack because Python 2.x lacks the "nonlocal" keyword
io_loop = [io_loop]
def asynchronous(coroutine):
"""
Allows a function to not use explicit callback functions to respond
to asynchronous events.
"""
if not isgeneratorfunction(coroutine):
# the "coroutine" isn't actually a coroutine; just return
# its result like tornado.web.asynchronous would do
return coroutine
web_async_coroutine = web_async(coroutine)
@functools.wraps(coroutine)
def run_async_routine(*args, **kwargs):
# we check if we're an instancemethod of RequestHandler for better
# intergration
if len(args) > 0 and isinstance(args[0], RequestHandler):
CoroutineRunner(io_loop[0],
web_async_coroutine(*args, **kwargs),
args[0])
else:
CoroutineRunner(io_loop[0],
coroutine(*args, **kwargs), None)
return run_async_routine
return asynchronous
asynchronous = make_asynchronous_decorator(None)