Call celery task chain from flask app using celery task signatures

app.py

from flask import Flask, request
from celery import Celer

celery = Celery('sample', backend='rpc://', broker='amqp://guest@localhost//')

app = Flask('sample_api')

upercase = celery.signature('sample.uppercaseme')
lowercase = celery.signature('sample.lowercaseme')

@app.route('/hello/sync', methods=['GET'])
def hello_sync():
    name = request.args.get('name')
    process_chain = (upercase | lowercase)
    task = process_chain.apply_async(kwargs={'value': name})
    processed_name = task.get(timeout=30)
    return 'Hello, {0}!'.format(processed_name)

if __name__ == '__main__':
    app.run(threaded=True)

commands

#Start flask api
flask run

#Start worker
celery -A sample_worker worker

sample_worker.py

from celery import Celery
from celery.utils.log import get_task_logger
import time, datetime

broker_heartbeat=0
app = Celery('sample', backend='rpc://', broker='amqp://guest@localhost//')

logger = get_task_logger('sample')

@app.task
def uppercaseme(value):
    now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    logger.info('Got {0} now: {1}'.format(value, now))
    logger.info('Working hard on uppercasing...')
    time.sleep(30)
    return value.upper()

@app.task
def lowercaseme(value):
    now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    logger.info('Got {0} now: {1}'.format(value, now))
    logger.info('Working hard on lowercasing...')
    time.sleep(30)
    return value.lower()