Celery

Install

pip install Celery

Create Virtual Host and User

sudo rabbitmqctl add_user <username> <password>
sudo rabbitmqctl add_vhost <vhostname>
sudo rabbitmqctl set_permissions -p <vhostname> <username> ".*" ".*" ".*"

With RabbitMQ

sudo apt-get install rabbitmq-server
# Create rabbitmq user
sudo rabbitmqctl add_user myuser mypassword
# Create rabbitmq vhost
sudo rabbitmqctl add_vhost myvhost
sudo rabbitmqctl set_user_tags myuser mytag
sudo rabbitmqctl set_permissions -p myvhost myuser ".*" ".*" ".*"

Starting/Stopping the RabbitMQ server
To start the server:
$ sudo rabbitmq-server
you can also run it in the background by adding the -detached option (note: only one dash):
$ sudo rabbitmq-server -detached
Never use kill to stop the RabbitMQ server, but rather use the rabbitmqctl command:
$ sudo rabbitmqctl stop

Workers

Launch

celery -A {ProjectName} worker -l info --queues=queuename1,queuename2

SystemD

Service File

[Unit]
Description=CIA Celery Scheduler
After=network.target

[Service]
User=tenkaichi
Group=tenkaichi
EnvironmentFile=/etc/default/celerybeat
WorkingDirectory=/home/tenkaichi/CIA
ExecStart=/bin/sh -c '${CELERY_BIN} -A ${CELERY_APP} beat --loglevel=${CELERYBEAT_LOGLEVEL} --scheduler=${CELERYBEAT_SCHEDULER} --logfile=${CELERYBEAT_LOG_FILE}'
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target

/etc/default/celerybeat

CELERY_BIN="/home/tenkaichi/.virtualenvs/cia/bin/celery"
CELERY_APP="CIA"
CELERYBEAT_CHDIR="/home/tenkaichi/CIA"
CELERYBEAT_SCHEDULER="django_celery_beat.schedulers:DatabaseScheduler"
CELERYBEAT_OPTS=""
CELERYBEAT_LOGLEVEL=debug
CELERYBEAT_LOG_FILE="/home/tenkaichi/CIA/logs/celery_beat.log"
DJANGO_SETTINGS_MODULE="CIA.settings"

Run task at specific time

import datetime

import celery

@celery.shared_task(bind=True)
def add_tag(task, user_id, tag):
    User.objects.filter(id=user_id, tags__ne=tag).update(push__tags=tag)
    return True

user_id = '582ee32a5b9c861c87dc297e'
tag = 'new_tag'
started_at = datetime.datetime(2018, 3, 12, tzinfo=datetime.timezone.utc)
add_tag.apply_async((user_id, tag), eta=started_at)

https://vinta.ws/code/run-a-celery-task-at-a-specific-time.html