Bahus / celery-chunkify-task

Efficient celery tasks chunkification

Efficient celery tasks chunkification

This library allows to chunkify a huge bunch of celery tasks into several numbers of chunks which will be executed periodically until the initial queue is not empty.

In other words you may split a huge amount of created tasks in the small chunks of predefined length and distribute your task creation routine among several periodic tasks.

Real life example: you need to send a push-notification for a zillion of your users. If you put every notification into individual task, you have to execute a zillion tasks. How to execute such amount of tasks and do not consume a lot of memory/CPU? How to avoid tasks flooding when we put all the messages in a queue at once and celery workers start producing a high load on our external/internal services?

celery.chunks is not an option, because it still creates all tasks in a memory and attaches a huge blob of data to a message.

Here is the example how to execute 1000 of tasks every 5 seconds:

from django.db.models import Min, Max  
from chunkify import chunkify_task, Chunk  
  
users_queryset = User.objects.active()  
  
def get_initial_chunk(*args, **kwargs):
    """
    Create an chunk of integers based on max and min primary keys.
	"""
    result = users_queryset.aggregate(Min('pk'), Max('pk'))  
    chunk = Chunk(  
        start=result['pk__min'] or 0,  
        size=1000,  
        max=result['pk__max'] or 0,  
    )  
    return chunk  
  
  
@task  
@chunkify_task(  
    sleep_timeout=5,   
    initial_chunk=get_initial_chunk  
)  
def send_push_notifications(chunk: Chunk):
    """Create several tasks based on provided chunk and re-schedule their execution"""
    chunked_qs = (  
        users_queryset  
        .filter(pk__range=chunk.range)  
        .values_list('pk', flat=True)  
        .order_by('pk')   
    )     
  
    for user_id in chunked_qs:  
        send_push_notifications_for_user.delay(user_id)

Then the task function will be re-scheduled to run in sleep_timeout seconds with a next chunk.

chunkify_task

The decorator accepts 3 parameters:

• sleep_timeout – seconds between processing each chunk of tasks
• initial_chunk – either Chunk, DateChunk or DateTimeChunk instance or a callable which returns one of the specified instances.
• chunk_class – Chunk, DateChunk or DateTimeChunk type, will be used to (de)serialize chunks.

Chunk classes

Chunk aka IntChunk – represents chunk data in list of integers, DateChunk and DateTimeChunk – represent date chunks, public API can be explorer via BaseChunk class.