SchedulingError: Couldn't apply scheduled task downloader: argument must be an int, or have a fileno() method - redis

Question

i have added djcelery and kombu.transport.django to django apps.
settings.py:
import djcelery
djcelery.setup_loader()
from .celery import app as celery_app
BROKER_URL = "redis://abc:abc#localhost:6379/0"
CELERYBEAT_SCHEDULER = "djcelery.schedulers.DatabaseScheduler"
CELERY_TIMEZONE = "Europe/London"
CELERY_ENABLE_UTC = True
# store AsyncResult in redis
CELERY_RESULT_BACKEND = "redis"
REDIS_HOST = "localhost"
REDIS_PORT = 6379
REDIS_DB = 0
REDIS_VHOST = 0
REDIS_USER="xyz"
REDIS_PASSWORD="xyz"
REDIS_CONNECT_RETRY = True
celery.py
from __future__ import absolute_import
import os
from celery import Celery
from django.conf import settings
from . import celeryconfig
# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'config.settings')
app = Celery('apps')
# Using a string here means the worker will not have to
# pickle the object when using Windows.
app.config_from_object('django.conf:settings')
app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)
#app.task(bind=True)
def debug_task(self):
print('Request: {0!r}'.format(self.request))
celery supervisor configuration:
[program:celeryd]
command=/home/vagrant/.virtualenvs/project/bin/python /vagrant/project/manage.py celeryd -B -E -c 1 --settings=config.settings
directory=/vagrant/project
user=vagrant
autostart=true
autorestart=true
stdout_logfile=/var/log/supervisor/celeryd.log
stderr_logfile=/var/log/supervisor/celeryd_err.log
when a task is scheduled using django-celery interface which supposed to download some files, following errors are thrown:
Traceback (most recent call last):
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/beat.py", line 203, in maybe_due
result = self.apply_async(entry, publisher=publisher)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/beat.py", line 259, in apply_async
entry, exc=exc)), sys.exc_info()[2])
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/beat.py", line 251, in apply_async
**entry.options)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/task.py", line 555, in apply_async
**dict(self._get_exec_options(), **options)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/base.py", line 323, in send_task
reply_to=reply_to or self.oid, **options
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/amqp.py", line 302, in publish_task
**kwargs
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/messaging.py", line 168, in publish
routing_key, mandatory, immediate, exchange, declare)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/connection.py", line 440, in _ensured
return fun(*args, **kwargs)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/messaging.py", line 180, in _publish
[maybe_declare(entity) for entity in declare]
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/messaging.py", line 111, in maybe_declare
return maybe_declare(entity, self.channel, retry, **retry_policy)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/common.py", line 99, in maybe_declare
return _maybe_declare(entity)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/common.py", line 110, in _maybe_declare
entity.declare()
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/entity.py", line 505, in declare
self.queue_declare(nowait, passive=False)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/entity.py", line 531, in queue_declare
nowait=nowait)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/transport/virtual/__init__.py", line 447, in queue_declare
return queue_declare_ok_t(queue, self._size(queue), 0)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 651, in _size
sizes = cmds.execute()
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/redis/client.py", line 2157, in execute
conn.disconnect()
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 800, in disconnect
channel._on_connection_disconnect(self)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 461, in _on_connection_disconnect
self.connection.cycle._on_connection_disconnect(connection)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 259, in _on_connection_disconnect
self.poller.unregister(connection._sock)
File "/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/utils/eventio.py", line 85, in unregister
self._epoll.unregister(fd)
SchedulingError: Couldn't apply scheduled task downloader: argument must be an int, or have a fileno() method.
and i'm not getting any clue where from these errors are coming...
any suggestions will be greatly appreciated.
Update 1:
i use django-celery admin interface to schedule a task and task is defined inside an app registered in INSTALLED_APP as follows:
#shared_task
def downloader():
# execute static/shell_scripts/feed_downloader.sh
import subprocess
PROJECT_PATH = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
subprocess.call(PROJECT_PATH+"/static/shell_scripts/feed_downloader.sh", shell=True)
the feed_downloader.sh file calls a django management command which if i execute independetly works fine like:
python manage.py feed_downloader
if i add a print statement just before line no. 85 to check fd parameter in file
/home/vagrant/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/utils/eventio.py
then following messages get printed:
see this <socket._socketobject object at 0x131b750>
see this None
see this <socket._socketobject object at 0x131bc90>
see this None