Executing two tasks at the same time with Celery

There are multiple ways to achieve this.

1. Single Worker - Single Queue.

$ celery -A my_app worker -l info  -c 2 -n my_worker

This will start a worker which executes 2 tasks at the same time.

2. Multiple workers - Single Queue.

$ celery -A my_app worker -l info  -c 1 -n my_worker1
$ celery -A my_app worker -l info  -c 1 -n my_worker2

This will start two workers which executes one task at a time. Note both tasks are in the same queue.

3. Multiple workers - Multiple Queues.

$ celery -A my_app worker -l info  -c 1 -n my_worker1 -Q queue1
$ celery -A my_app worker -l info  -c 1 -n my_worker2 -Q queue2

This will start two workers which executes one task at a time. But here you have route the tasks accordingly.

celery_app.send_task('tasks.test1', args=[self.id], kwargs={}, queue='queue1')
celery_app.send_task('tasks.test2', args=[self.id], kwargs={}, queue='queue2')

4. Single worker - All Queues

$ celery -A my_app worker -l info -n my_worker1 

If you don't mention any queue, it will consume from all queues by default.

Call the worker with --autoscale option which would scale up and down processes as required.

--autoscale AUTOSCALE
                       Enable autoscaling by providing max_concurrency,
                       min_concurrency. Example:: --autoscale=10,3 (always
                       keep 3 processes, but grow to 10 if necessary)

example.

celery -A sandbox worker --autoscale=10,0 --loglevel=info