What is the best approach for adding cron jobs (scheduled tasks) for a particular service in docker-compose

Question

I'm using a docker-compose. I have a web and a worker service.

version: '3'
services:
  web:
    build: .
    environment:
      - "*"
    links:
      - redis
      - memcached
    ports:
      - "80:8001"
      - "443:8001"

  worker:
    build: .
    command: ["/bin/bash", "/home/django/start_celery.sh"]
    environment:
      - "*"
    links:
      - redis
      - memcached

  memcached:
    image: memcached
    ports:
      - "11211:11211"

  redis:
    image: redis
    ports:
      - "6379:6379"

I need to run crons (scheduled tasks) on worker service.

And I dont want to hardcode the crontab in Dockerfile as I'm using same dockerfile for both the services.

So what is the best approach for this?

Answer 1

You can try the following Opensource tool for scheduling crons in the docker-compose.

https://github.com/mcuadros/ofelia

eg:

 [job-service-run "service-executed-on-new-container"]
 schedule = 0,20,40 * * * *
 image = ubuntu
 network = swarm_network
 command =  touch /tmp/example

In case you are planning to utilize the image in any of the cloud platforms.

For Eg.

AWS: You can also have a look at ECS scheduler

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/scheduled_tasks.html

GCP: Kubernetes Engine CronScheduler

https://cloud.google.com/kubernetes-engine/docs/how-to/cronjobs