Mysterious error when using django server with grequests

Question

Currently, I am running a vagrant server on Ubuntu 14.04 and I test all my django modules by using the simple python manage.py runserver 0.0.0.0:8000

Since I am connecting to the django webserver using chrome through http://localhost:8000 and the server is running on a VM, I am port forwarding through the usage of the following setting in Vagrantfile

config.vm.network "forwarded_port", guest: 8000, host: 8000

Everything runs normally (all modules/views/tests function as expected), however, ever since I started using grequests I get this weird error

Exception happened during processing of request from ('10.0.2.2', 63520)
Traceback (most recent call last):
  File "/home/vagrant/anaconda3/lib/python3.6/socketserver.py", line 639, in process_request_thread
    self.finish_request(request, client_address)
  File "/home/vagrant/anaconda3/lib/python3.6/socketserver.py", line 361, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/home/vagrant/anaconda3/lib/python3.6/socketserver.py", line 696, in __init__
    self.handle()
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/django/core/servers/basehttp.py", line 159, in handle
    self.raw_requestline = self.rfile.readline(65537)
  File "/home/vagrant/anaconda3/lib/python3.6/socket.py", line 586, in readinto
    return self._sock.recv_into(b)
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/gevent/_socket3.py", line 385, in recv_into
    self._wait(self._read_event)
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/gevent/_socket3.py", line 157, in _wait
    self.hub.wait(watcher)
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/gevent/hub.py", line 651, in wait
    result = waiter.get()
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/gevent/hub.py", line 899, in get
    return self.hub.switch()
  File "/home/vagrant/anaconda3/lib/python3.6/site-packages/gevent/hub.py", line 630, in switch
    return RawGreenlet.switch(self)
gevent.hub.LoopExit: ('This operation would block forever', <Hub at 0x7f3b777e8af8 epoll pending=0 ref=0 fileno=34>)

Note that I am not using grequests and that simply importing it seems to cause this error even when it is not being called or anything

Anyone have any ideas?

Asked By: AlanSTACK

||

Source

Answer 1

This is an issue with one of the underlying dependency – gevent, which overrides the default behaviour of python builtin such as time, etc.

You would have to monkeypatch.
Something like:

from gevent import monkey
monkey.patch_all()

Here is the relevant gevent documentation.

I recently ran into this exact issue – so stopped using grequests and implemented my own async requests logic

Answered By: karthikr

Answer 2

Wanted to post an update on this.

New docs on monkey patching are located here

I used this hook that Django added in 1.7 that I found here to run the import.

So in my app.py file I created an app config. (Realized and updated that this breaks the makemigration command, not sure if it will break anything else.)

from django.apps import AppConfig

class MyAppConfig(AppConfig):
        name = 'MyApp'
            def ready(self):
    if ('makemigrations' in sys.argv or 'migrate' in sys.argv):
        pass
    else:
        from gevent import monkey
        monkey.patch_all()

And in my settings.py file in INSTALLED_APPS[….] I added the config into that list.

INSTALLED_APPS = [
    'tracker.apps.MyAppConfig',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'admin_extra_buttons',
]

Seems to have worked for me.

Answered By: K_D

Mysterious error when using django server with grequests

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