Example for Celery 4.4.0 with timezoned beat task

.celery timezones.md

Example for timezoned beat task with Celery 4.4.0. Two ways to create datetime object inside crontab's nowfun that seemingly produce same result actually behave differentlty.

app.py

from datetime import datetime

import pytz
from celery import Celery
from celery.schedules import crontab

app = Celery(
    "worker",
    broker="pyamqp://rabbitmq:5672/",
)


@app.task
def say_hello():
    print("TIME TO HELLO")


def nowfun():
    # this does not work: datetime.now(tzinfo=pytz.timezone("US/Eastern"))
    # and this does:      pytz.timezone("US/Eastern").fromutc(datetime.utcnow())

    return pytz.timezone("US/Eastern").fromutc(datetime.utcnow())


app.conf.timezone = "UTC"
app.conf.beat_schedule = {
    "say_hello": {
        "task": "app.say_hello",
        "schedule": crontab(hour=4, minute=30, nowfun=nowfun),
    }
}

docker-compose.yml

version: "3.7"
services:
  rabbitmq:
    image: rabbitmq:3-management
    ports:
      - 5672:5672
      - 15672:15672
  worker:
    image: worker
    build:
      context: ./
      dockerfile: Dockerfile
    command: celery -A app worker -B
    stdin_open: true
    tty: true
    volumes:
      - ./src:/code
    depends_on:
      - rabbitmq

Dockerfile

FROM python:3.7.12-bullseye

WORKDIR /code

COPY ./requirements.txt .
RUN python -m pip install -r requirements.txt

COPY app.py /code

CMD celery -A app worker -B

requirements.txt

celery==4.4.0
pytz