Part of the blog post - Playing with Chords - Celery which will walk through how to use "chords" structure in Celery - https://adikrishnan.in/2018/05/30/playing-with-chords-celery/

run.py

# Refer https://adikrishnan.in/2018/05/30/playing-with-chords-celery/ for understanding the concept.
from tasks import hello, chord_service, non_chord_service

hello.delay()
chord_service.delay()
non_chord_service.delay()

tasks.py

# Refer https://adikrishnan.in/2018/05/30/playing-with-chords-celery/ for understanding the concept.
import time
import datetime
import subprocess
from celery import Celery, chord

conf = {
    "broker_url": "redis://localhost:6379/7",
    "result_backend": "redis://localhost:6379/7",
    "result_expires": "600"
}

celery_app = Celery()
celery_app.config_from_object(conf)

NUM_OF_ITEMS = 5


@celery_app.task
def hello():
    print("Bello Merld at {}".format(datetime.datetime.now().isoformat()))


@celery_app.task
def run_ping(item_num, func_name):
    start = time.time()
    cmd = "ping adikrishnan.in -c 4"
    res = subprocess.check_output(cmd.split(), universal_newlines=True)
    end = time.time()
    print("Item Number: {}, Function Name: {}, Total time: {:.2f} sec".format(item_num, func_name,
                                                                              end - start))
    return res


@celery_app.task
def chord_service():
    start = time.time()
    chord(run_ping.s(i, chord_service.__name__) for i in range(5))(chord_result.s())
    end = time.time()
    print("{} ended, Total time: {:.2f} sec".format(chord_service.__name__, end - start))


@celery_app.task
def chord_result(res):
    print(res)


@celery_app.task
def non_chord_service():
    start = time.time()
    res_all = [ run_ping(i, non_chord_service.__name__) for i in range(NUM_OF_ITEMS) ]
    end = time.time()
    print(res_all)
    print("{} ended, Total time: {:.2f} sec".format(non_chord_service.__name__, end - start))