import random

from celery import Celery

app = Celery('add', broker='redis://localhost:6379/0')

@app.task(bind=True)
def add(self, x, y):
    # Get a random number between 1 and 10
    num = random.randint(1, 10)
    print num # To help properly understand output
    try:
        # If number is odd, fail the task
        if num % 2:
            raise Exception()
        # If number is even, succeed the task
        else:
            return x + y
    except Exception as e:
        self.retry(countdown=2, exc=e, max_retries=1)

[2015-07-31 17:47:33,681: INFO/MainProcess] Received task: add.add[64e43f81-0f80-49ac-a068-4c84c689ea16]
[2015-07-31 17:47:33,681: WARNING/Worker-2] 7
[2015-07-31 17:47:33,703: INFO/MainProcess] Received task: add.add[64e43f81-0f80-49ac-a068-4c84c689ea16] eta:[2015-07-31 12:17:35.692557+00:00]
[2015-07-31 17:47:33,704: INFO/MainProcess] Task add.add[64e43f81-0f80-49ac-a068-4c84c689ea16] retry: Retry in 2s: Exception()
[2015-07-31 17:47:36,890: WARNING/Worker-4] 3
[2015-07-31 17:47:36,894: ERROR/MainProcess] Task add.add[64e43f81-0f80-49ac-a068-4c84c689ea16] raised unexpected: Exception()
Traceback (most recent call last):
  File "/Users/akshar/.virtualenvs/hack/lib/python2.7/site-packages/celery/app/trace.py", line 240, in trace_task
  ...
  File "/Users/akshar/Play/Python/hack/add.py", line 15, in add
    raise Exception()
Exception