[channels2] issues with raven

I noticed that the raven library doesn’t play nicely with channels2:

$ ./manage.py runserver
Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x1100558c8>
Traceback (most recent call last):
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    autoreload.raise_last_exception()
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 251, in raise_last_exception
    six.reraise(*_exception)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/apps/registry.py", line 116, in populate
    app_config.ready()
  File "/Users/brianmay/tree/myro/channels/channels/apps.py", line 17, in ready
    monkeypatch_django()
  File "/Users/brianmay/tree/myro/channels/channels/hacks.py", line 10, in monkeypatch_django
    from .management.commands.runserver import Command as RunserverCommand
  File "/Users/brianmay/tree/myro/channels/channels/management/commands/runserver.py", line 4, in <module>
    from daphne.server import Server
  File "/Users/brianmay/tree/myro/daphne/daphne/server.py", line 5, in <module>
    asyncioreactor.install()
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/twisted/internet/asyncioreactor.py", line 322, in install
    installReactor(reactor)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/twisted/internet/main.py", line 32, in installReactor
    raise error.ReactorAlreadyInstalledError("reactor already installed")
twisted.internet.error.ReactorAlreadyInstalledError: reactor already installed

Just to be sure, I put an error condition in twisted/internet/reactor.py to see what stack trace I would get when it is first loaded:

$ ./manage.py runserver
Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x1069a7bf8>
Traceback (most recent call last):
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    autoreload.raise_last_exception()
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 251, in raise_last_exception
    six.reraise(*_exception)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/utils/autoreload.py", line 228, in wrapper
    fn(*args, **kwargs)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/apps/registry.py", line 85, in populate
    app_config = AppConfig.create(entry)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/django/apps/config.py", line 94, in create
    module = import_module(entry)
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 936, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 936, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 936, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 978, in _gcd_import
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/__init__.py", line 54, in <module>
    from raven.base import *  # NOQA
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/base.py", line 37, in <module>
    from raven.conf.remote import RemoteConfig
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/conf/remote.py", line 36, in <module>
    DEFAULT_TRANSPORT = discover_default_transport()
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/conf/remote.py", line 18, in discover_default_transport
    from raven.transport.threaded import ThreadedHTTPTransport
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/transport/__init__.py", line 18, in <module>
    from raven.transport.registry import *  # NOQA
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/transport/registry.py", line 18, in <module>
    from raven.transport.twisted import TwistedHTTPTransport
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/raven/transport/twisted.py", line 16, in <module>
    from twisted.web.client import (
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/twisted/web/client.py", line 39, in <module>
    from twisted.internet import defer, protocol, task, reactor
  File "/Users/brianmay/.pyenv/versions/myrocc2/lib/python3.6/site-packages/twisted/internet/reactor.py", line 35, in <module>
    raise Meow()
NameError: name 'Meow' is not defined

To me, it looks like we have two libraries that both use twisted (not sure I understand why) and as a result clash.

I think raven uses twisted for async http sending stuff, although looking at the stack trace would suggest I would get the same error even if I hacked it to use HTTPTransport instead of TwistedHTTPTransport.

I have no idea what, if any, solution there is to this, or who to blame. However, I think this is going to be an important issue.

[hyliker]

@maxmalysh The simple solution is just to import the daphe.server before the raven in the settings.py like this

import daphne.server # Fixed UserWarning from raven
import raven

[andrewgodwin]

Fixed with 3d8d82be3528cc0150dac0c8ade1f6c306b412e4, provided you put Channels above Raven in the INSTALLED_APPS list, which is the best I can do without modifying Raven to lazy-load its twisted HTTP transport.