====== Celery - Distributed Task Queue ======
http://docs.celeryproject.org/en/latest/


===== Instalation =====
  - Install RabbitMQ: <code bash>
aptitude install rabbitmq-server
pip install librabbitmq
</code>
  - Install Celery <code>
pip install celery
pip install django-celery
</code>
(note: make sure there is not south installed on your system when using django >= 1.7)

if unable to start RabbitMQ and <code> ERROR: epmd error for host address (cannot connect to host/port)</code>
in /var/log/rabbitmq/startup_log, put your hostname in /etc/hosts after localhost
===== Django Integration =====
http://celery.readthedocs.org/en/latest/django/first-steps-with-django.html
  - Create project celery config projectname/celery.py: <code python>
from __future__ import absolute_import

import os

from celery import Celery

# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'celertest.settings')

from django.conf import settings

app = Celery('celertest', broker='amqp://guest@localhost//')

# 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.conf.update(CELERY_RESULT_BACKEND='djcelery.backends.database.DatabaseBackend')


@app.task(bind=True)
def debug_task(self):
    print('Request: {0!r}'.format(self.request))
</code>
  - Create myapp/tasks.py<code python>
from __future__ import absolute_import

from celery import shared_task


@shared_task
def add(x, y):
    return x + y


@shared_task
def mul(x, y):
    return x * y


@shared_task
def xsum(numbers):
    return sum(numbers)


@shared_task
def gen_prime(x):
    multiples = []
    results = []
    for i in xrange(2, x+1):
        if i not in multiples:
            results.append(i)
            for j in xrange(i*i, x+1, i):
                multiples.append(j)
    return results
</code>
  - Sync django db (./manage.py syncdb  or ./manage.py makemigrations && migrate)
  - Add djcelery to INSTALLED_APPS and add following lines to project/settings.py:<code python>
CELERYBEAT_SCHEDULER = 'djcelery.schedulers.DatabaseScheduler'
CELERY_RESULT_BACKEND = 'djcelery.backends.database:DatabaseBackend'
</code>
  - Run celery watcher: <code bash>./manage.py celeryd -E</code>
  - Optionaly: run celerycam and celerymon to enable the monitoring via DB:<code bash>
./manage.py celerycam
./manage.py celerymon
</code>