twisted.py

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# Author: Ovidiu Predescu
# Date: July 2011
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

# Note:  This module's docs are not currently extracted automatically,
# so changes must be made manually to twisted.rst
# TODO: refactor doc build process to use an appropriate virtualenv
"""Bridges between the Twisted reactor and Tornado IOLoop.

This module lets you run applications and libraries written for
Twisted in a Tornado application.  It can be used in two modes,
depending on which library's underlying event loop you want to use.

This module has been tested with Twisted versions 11.0.0 and newer.

Twisted on Tornado
------------------

`TornadoReactor` implements the Twisted reactor interface on top of
the Tornado IOLoop.  To use it, simply call `install` at the beginning
of the application::

    import tornado.platform.twisted
    tornado.platform.twisted.install()
    from twisted.internet import reactor

When the app is ready to start, call `IOLoop.instance().start()`
instead of `reactor.run()`.

It is also possible to create a non-global reactor by calling
`tornado.platform.twisted.TornadoReactor(io_loop)`.  However, if
the `IOLoop` and reactor are to be short-lived (such as those used in
unit tests), additional cleanup may be required.  Specifically, it is
recommended to call::

    reactor.fireSystemEvent('shutdown')
    reactor.disconnectAll()

before closing the `IOLoop`.

Tornado on Twisted
------------------

`TwistedIOLoop` implements the Tornado IOLoop interface on top of the Twisted
reactor.  Recommended usage::

    from tornado.platform.twisted import TwistedIOLoop
    from twisted.internet import reactor
    TwistedIOLoop().install()
    # Set up your tornado application as usual using `IOLoop.instance`
    reactor.run()

`TwistedIOLoop` always uses the global Twisted reactor.
"""

from __future__ import absolute_import, division, print_function, with_statement

import datetime
import functools
import numbers
import socket

import twisted.internet.abstract
from twisted.internet.posixbase import PosixReactorBase
from twisted.internet.interfaces import \
    IReactorFDSet, IDelayedCall, IReactorTime, IReadDescriptor, IWriteDescriptor
from twisted.python import failure, log
from twisted.internet import error
import twisted.names.cache
import twisted.names.client
import twisted.names.hosts
import twisted.names.resolve

from zope.interface import implementer

from tornado.escape import utf8
from tornado import gen
import tornado.ioloop
from tornado.log import app_log
from tornado.netutil import Resolver
from tornado.stack_context import NullContext, wrap
from tornado.ioloop import IOLoop
from tornado.util import timedelta_to_seconds


@implementer(IDelayedCall)
class TornadoDelayedCall(object):
    """DelayedCall object for Tornado."""
    def __init__(self, reactor, seconds, f, *args, **kw):
        self._reactor = reactor
        self._func = functools.partial(f, *args, **kw)
        self._time = self._reactor.seconds() + seconds
        self._timeout = self._reactor._io_loop.add_timeout(self._time,
                                                           self._called)
        self._active = True

    def _called(self):
        self._active = False
        self._reactor._removeDelayedCall(self)
        try:
            self._func()
        except:
            app_log.error("_called caught exception", exc_info=True)

    def getTime(self):
        return self._time

    def cancel(self):
        self._active = False
        self._reactor._io_loop.remove_timeout(self._timeout)
        self._reactor._removeDelayedCall(self)

    def delay(self, seconds):
        self._reactor._io_loop.remove_timeout(self._timeout)
        self._time += seconds
        self._timeout = self._reactor._io_loop.add_timeout(self._time,
                                                           self._called)

    def reset(self, seconds):
        self._reactor._io_loop.remove_timeout(self._timeout)
        self._time = self._reactor.seconds() + seconds
        self._timeout = self._reactor._io_loop.add_timeout(self._time,
                                                           self._called)

    def active(self):
        return self._active


@implementer(IReactorTime, IReactorFDSet)
class TornadoReactor(PosixReactorBase):
    """Twisted reactor built on the Tornado IOLoop.

    Since it is intented to be used in applications where the top-level
    event loop is ``io_loop.start()`` rather than ``reactor.run()``,
    it is implemented a little differently than other Twisted reactors.
    We override `mainLoop` instead of `doIteration` and must implement
    timed call functionality on top of `IOLoop.add_timeout` rather than
    using the implementation in `PosixReactorBase`.
    """
    def __init__(self, io_loop=None):
        if not io_loop:
            io_loop = tornado.ioloop.IOLoop.current()
        self._io_loop = io_loop
        self._readers = {}  # map of reader objects to fd
        self._writers = {}  # map of writer objects to fd
        self._fds = {}  # a map of fd to a (reader, writer) tuple
        self._delayedCalls = {}
        PosixReactorBase.__init__(self)
        self.addSystemEventTrigger('during', 'shutdown', self.crash)

        # IOLoop.start() bypasses some of the reactor initialization.
        # Fire off the necessary events if they weren't already triggered
        # by reactor.run().
        def start_if_necessary():
            if not self._started:
                self.fireSystemEvent('startup')
        self._io_loop.add_callback(start_if_necessary)

    # IReactorTime
    def seconds(self):
        return self._io_loop.time()

    def callLater(self, seconds, f, *args, **kw):
        dc = TornadoDelayedCall(self, seconds, f, *args, **kw)
        self._delayedCalls[dc] = True
        return dc

    def getDelayedCalls(self):
        return [x for x in self._delayedCalls if x._active]

    def _removeDelayedCall(self, dc):
        if dc in self._delayedCalls:
            del self._delayedCalls[dc]

    # IReactorThreads
    def callFromThread(self, f, *args, **kw):
        """See `twisted.internet.interfaces.IReactorThreads.callFromThread`"""
        assert callable(f), "%s is not callable" % f
        with NullContext():
            # This NullContext is mainly for an edge case when running
            # TwistedIOLoop on top of a TornadoReactor.
            # TwistedIOLoop.add_callback uses reactor.callFromThread and
            # should not pick up additional StackContexts along the way.
            self._io_loop.add_callback(f, *args, **kw)

    # We don't need the waker code from the super class, Tornado uses
    # its own waker.
    def installWaker(self):
        pass

    def wakeUp(self):
        pass

    # IReactorFDSet
    def _invoke_callback(self, fd, events):
        if fd not in self._fds:
            return
        (reader, writer) = self._fds[fd]
        if reader:
            err = None
            if reader.fileno() == -1:
                err = error.ConnectionLost()
            elif events & IOLoop.READ:
                err = log.callWithLogger(reader, reader.doRead)
            if err is None and events & IOLoop.ERROR:
                err = error.ConnectionLost()
            if err is not None:
                self.removeReader(reader)
                reader.readConnectionLost(failure.Failure(err))
        if writer:
            err = None
            if writer.fileno() == -1:
                err = error.ConnectionLost()
            elif events & IOLoop.WRITE:
                err = log.callWithLogger(writer, writer.doWrite)
            if err is None and events & IOLoop.ERROR:
                err = error.ConnectionLost()
            if err is not None:
                self.removeWriter(writer)
                writer.writeConnectionLost(failure.Failure(err))

    def addReader(self, reader):
        """Add a FileDescriptor for notification of data available to read."""
        if reader in self._readers:
            # Don't add the reader if it's already there
            return
        fd = reader.fileno()
        self._readers[reader] = fd
        if fd in self._fds:
            (_, writer) = self._fds[fd]
            self._fds[fd] = (reader, writer)
            if writer:
                # We already registered this fd for write events,
                # update it for read events as well.
                self._io_loop.update_handler(fd, IOLoop.READ | IOLoop.WRITE)
        else:
            with NullContext():
                self._fds[fd] = (reader, None)
                self._io_loop.add_handler(fd, self._invoke_callback,
                                          IOLoop.READ)

    def addWriter(self, writer):
        """Add a FileDescriptor for notification of data available to write."""
        if writer in self._writers:
            return
        fd = writer.fileno()
        self._writers[writer] = fd
        if fd in self._fds:
            (reader, _) = self._fds[fd]
            self._fds[fd] = (reader, writer)
            if reader:
                # We already registered this fd for read events,
                # update it for write events as well.
                self._io_loop.update_handler(fd, IOLoop.READ | IOLoop.WRITE)
        else:
            with NullContext():
                self._fds[fd] = (None, writer)
                self._io_loop.add_handler(fd, self._invoke_callback,
                                          IOLoop.WRITE)

    def removeReader(self, reader):
        """Remove a Selectable for notification of data available to read."""
        if reader in self._readers:
            fd = self._readers.pop(reader)
            (_, writer) = self._fds[fd]
            if writer:
                # We have a writer so we need to update the IOLoop for
                # write events only.
                self._fds[fd] = (None, writer)
                self._io_loop.update_handler(fd, IOLoop.WRITE)
            else:
                # Since we have no writer registered, we remove the
                # entry from _fds and unregister the handler from the
                # IOLoop
                del self._fds[fd]
                self._io_loop.remove_handler(fd)

    def removeWriter(self, writer):
        """Remove a Selectable for notification of data available to write."""
        if writer in self._writers:
            fd = self._writers.pop(writer)
            (reader, _) = self._fds[fd]
            if reader:
                # We have a reader so we need to update the IOLoop for
                # read events only.
                self._fds[fd] = (reader, None)
                self._io_loop.update_handler(fd, IOLoop.READ)
            else:
                # Since we have no reader registered, we remove the
                # entry from the _fds and unregister the handler from
                # the IOLoop.
                del self._fds[fd]
                self._io_loop.remove_handler(fd)

    def removeAll(self):
        return self._removeAll(self._readers, self._writers)

    def getReaders(self):
        return self._readers.keys()

    def getWriters(self):
        return self._writers.keys()

    # The following functions are mainly used in twisted-style test cases;
    # it is expected that most users of the TornadoReactor will call
    # IOLoop.start() instead of Reactor.run().
    def stop(self):
        PosixReactorBase.stop(self)
        fire_shutdown = functools.partial(self.fireSystemEvent, "shutdown")
        self._io_loop.add_callback(fire_shutdown)

    def crash(self):
        PosixReactorBase.crash(self)
        self._io_loop.stop()

    def doIteration(self, delay):
        raise NotImplementedError("doIteration")

    def mainLoop(self):
        self._io_loop.start()


class _TestReactor(TornadoReactor):
    """Subclass of TornadoReactor for use in unittests.

    This can't go in the test.py file because of import-order dependencies
    with the Twisted reactor test builder.
    """
    def __init__(self):
        # always use a new ioloop
        super(_TestReactor, self).__init__(IOLoop())

    def listenTCP(self, port, factory, backlog=50, interface=''):
        # default to localhost to avoid firewall prompts on the mac
        if not interface:
            interface = '127.0.0.1'
        return super(_TestReactor, self).listenTCP(
            port, factory, backlog=backlog, interface=interface)

    def listenUDP(self, port, protocol, interface='', maxPacketSize=8192):
        if not interface:
            interface = '127.0.0.1'
        return super(_TestReactor, self).listenUDP(
            port, protocol, interface=interface, maxPacketSize=maxPacketSize)


def install(io_loop=None):
    """Install this package as the default Twisted reactor."""
    if not io_loop:
        io_loop = tornado.ioloop.IOLoop.current()
    reactor = TornadoReactor(io_loop)
    from twisted.internet.main import installReactor
    installReactor(reactor)
    return reactor


@implementer(IReadDescriptor, IWriteDescriptor)
class _FD(object):
    def __init__(self, fd, fileobj, handler):
        self.fd = fd
        self.fileobj = fileobj
        self.handler = handler
        self.reading = False
        self.writing = False
        self.lost = False

    def fileno(self):
        return self.fd

    def doRead(self):
        if not self.lost:
            self.handler(self.fileobj, tornado.ioloop.IOLoop.READ)

    def doWrite(self):
        if not self.lost:
            self.handler(self.fileobj, tornado.ioloop.IOLoop.WRITE)

    def connectionLost(self, reason):
        if not self.lost:
            self.handler(self.fileobj, tornado.ioloop.IOLoop.ERROR)
            self.lost = True

    def logPrefix(self):
        return ''


class TwistedIOLoop(tornado.ioloop.IOLoop):
    """IOLoop implementation that runs on Twisted.

    Uses the global Twisted reactor by default.  To create multiple
    `TwistedIOLoops` in the same process, you must pass a unique reactor
    when constructing each one.

    Not compatible with `tornado.process.Subprocess.set_exit_callback`
    because the ``SIGCHLD`` handlers used by Tornado and Twisted conflict
    with each other.
    """
    def initialize(self, reactor=None):
        if reactor is None:
            import twisted.internet.reactor
            reactor = twisted.internet.reactor
        self.reactor = reactor
        self.fds = {}
        self.reactor.callWhenRunning(self.make_current)

    def close(self, all_fds=False):
        fds = self.fds
        self.reactor.removeAll()
        for c in self.reactor.getDelayedCalls():
            c.cancel()
        if all_fds:
            for fd in fds.values():
                self.close_fd(fd.fileobj)

    def add_handler(self, fd, handler, events):
        if fd in self.fds:
            raise ValueError('fd %s added twice' % fd)
        fd, fileobj = self.split_fd(fd)
        self.fds[fd] = _FD(fd, fileobj, wrap(handler))
        if events & tornado.ioloop.IOLoop.READ:
            self.fds[fd].reading = True
            self.reactor.addReader(self.fds[fd])
        if events & tornado.ioloop.IOLoop.WRITE:
            self.fds[fd].writing = True
            self.reactor.addWriter(self.fds[fd])

    def update_handler(self, fd, events):
        fd, fileobj = self.split_fd(fd)
        if events & tornado.ioloop.IOLoop.READ:
            if not self.fds[fd].reading:
                self.fds[fd].reading = True
                self.reactor.addReader(self.fds[fd])
        else:
            if self.fds[fd].reading:
                self.fds[fd].reading = False
                self.reactor.removeReader(self.fds[fd])
        if events & tornado.ioloop.IOLoop.WRITE:
            if not self.fds[fd].writing:
                self.fds[fd].writing = True
                self.reactor.addWriter(self.fds[fd])
        else:
            if self.fds[fd].writing:
                self.fds[fd].writing = False
                self.reactor.removeWriter(self.fds[fd])

    def remove_handler(self, fd):
        fd, fileobj = self.split_fd(fd)
        if fd not in self.fds:
            return
        self.fds[fd].lost = True
        if self.fds[fd].reading:
            self.reactor.removeReader(self.fds[fd])
        if self.fds[fd].writing:
            self.reactor.removeWriter(self.fds[fd])
        del self.fds[fd]

    def start(self):
        self._setup_logging()
        self.reactor.run()

    def stop(self):
        self.reactor.crash()

    def add_timeout(self, deadline, callback, *args, **kwargs):
        # This method could be simplified (since tornado 4.0) by
        # overriding call_at instead of add_timeout, but we leave it
        # for now as a test of backwards-compatibility.
        if isinstance(deadline, numbers.Real):
            delay = max(deadline - self.time(), 0)
        elif isinstance(deadline, datetime.timedelta):
            delay = timedelta_to_seconds(deadline)
        else:
            raise TypeError("Unsupported deadline %r")
        return self.reactor.callLater(
            delay, self._run_callback,
            functools.partial(wrap(callback), *args, **kwargs))

    def remove_timeout(self, timeout):
        if timeout.active():
            timeout.cancel()

    def add_callback(self, callback, *args, **kwargs):
        self.reactor.callFromThread(
            self._run_callback,
            functools.partial(wrap(callback), *args, **kwargs))

    def add_callback_from_signal(self, callback, *args, **kwargs):
        self.add_callback(callback, *args, **kwargs)


class TwistedResolver(Resolver):
    """Twisted-based asynchronous resolver.

    This is a non-blocking and non-threaded resolver.  It is
    recommended only when threads cannot be used, since it has
    limitations compared to the standard ``getaddrinfo``-based
    `~tornado.netutil.Resolver` and
    `~tornado.netutil.ThreadedResolver`.  Specifically, it returns at
    most one result, and arguments other than ``host`` and ``family``
    are ignored.  It may fail to resolve when ``family`` is not
    ``socket.AF_UNSPEC``.

    Requires Twisted 12.1 or newer.
    """
    def initialize(self, io_loop=None):
        self.io_loop = io_loop or IOLoop.current()
        # partial copy of twisted.names.client.createResolver, which doesn't
        # allow for a reactor to be passed in.
        self.reactor = tornado.platform.twisted.TornadoReactor(io_loop)

        host_resolver = twisted.names.hosts.Resolver('/etc/hosts')
        cache_resolver = twisted.names.cache.CacheResolver(reactor=self.reactor)
        real_resolver = twisted.names.client.Resolver('/etc/resolv.conf',
                                                      reactor=self.reactor)
        self.resolver = twisted.names.resolve.ResolverChain(
            [host_resolver, cache_resolver, real_resolver])

    @gen.coroutine
    def resolve(self, host, port, family=0):
        # getHostByName doesn't accept IP addresses, so if the input
        # looks like an IP address just return it immediately.
        if twisted.internet.abstract.isIPAddress(host):
            resolved = host
            resolved_family = socket.AF_INET
        elif twisted.internet.abstract.isIPv6Address(host):
            resolved = host
            resolved_family = socket.AF_INET6
        else:
            deferred = self.resolver.getHostByName(utf8(host))
            resolved = yield gen.Task(deferred.addBoth)
            if isinstance(resolved, failure.Failure):
                resolved.raiseException()
            elif twisted.internet.abstract.isIPAddress(resolved):
                resolved_family = socket.AF_INET
            elif twisted.internet.abstract.isIPv6Address(resolved):
                resolved_family = socket.AF_INET6
            else:
                resolved_family = socket.AF_UNSPEC
        if family != socket.AF_UNSPEC and family != resolved_family:
            raise Exception('Requested socket family %d but got %d' %
                            (family, resolved_family))
        result = [
            (resolved_family, (resolved, port)),
        ]
        raise gen.Return(result)