Example docker-compose config for scaling celery worker with separate code base. It uses the classical addition task as an example. flask-app and flask-celery have seperate codebase (In other words we don't need to have access to the celery task module and don't need to import the celery task in the flask app) and flask-app uses the name attribute of a task and celery.send_task to submit a job without having the access to celery workers code base.
To run the example:
docker-compose build
docker-compose up -d # run in detached mode
Now load http://your-dockermachine-ip:5000/add/2/3 in browser. It should create a task and return a task id.
To check the status of the job hit http://your-dockermachine-ip:5000/check/taskid. It should either show PENDING or the result 5.
To monitor that the worker is working fine go to http://your-dockermachine-ip:5555.It runs a flower server. It should show one worker ready to serve.
To scale the workers, now run docker-compose scale worker=5. This will create 4 more containers each running a worker. http://your-dockermachine-ip:5555 should now show 5 workers waiting for some jobs!