Sample Celery chain usage for processing pipeline

run.py

from celery import chain

from django.core.management.base import BaseCommand

from . import tasks


class Command(BaseCommand):

    def handle(self, *args, **kwargs):
        source_file = args[0]
        chain(
            tasks.fetch.s(source_file),         # Fetch data from remote source
            tasks.blacklist.s(),                # Remove blacklisted records
            tasks.transform.s(),                # Transform raw data ready for loading
            tasks.load.s(),                     # Load into DB
        ).apply_async()

tasks.py

import shutil
import os

from celery import task


@task()
def fetch(fixture_path):
    """
    Fetch a file from a remote location
    """
    destination = "/tmp/source.csv"
    print "Fetching data from %s - saving to %s" % (fixture_path, destination)
    shutil.copyfile(fixture_path, destination)
    return destination


@task()
def blacklist(source_path):
    base, ext = os.path.splitext(source_path)
    destination = "%s-afterblacklist%s" % (base, ext)
    print "Transforming data in %s to %s" % (source_path, destination)
    shutil.copyfile(source_path, destination)
    return destination


@task()
def transform(source_path):
    base, ext = os.path.splitext(source_path)
    destination = "%s-transformed%s" % (base, ext)
    print "Transforming data in %s to %s" % (source_path, destination)
    shutil.copyfile(source_path, destination)
    return destination


@task()
def load(filepath):
    print "Loading data in %s and removing" % filepath
    os.remove(filepath)

Hi! Could any task in chain run some other tasks (e.g.: I want to split raw data into chunks in transform() and process the chunks by another celery tasks in parallel manner)

Hi, Instead of @task, I use @shared_task. When I chain my tasks,

chain(fetch.subtask(resource_id), process.subtask())

I get an error.

TypeError: 'int' object is not iterable