How to debug celery delays and errors?

I am continuing Django project of someone who is using Celery along with Mandrill. There are daily reports which are sent to customers and due to some reason not a single mail is sent for three days, gets accumulated and sent together after three days. Since I am new to Celery, I want to know how to debug celery delays and errors, what are popular commands and execution path to follow?

Solution

Short tips:

Set debug=True in celery config, it will take you register and execution time for every task.
Install flower, popular tool for monitoring tasks
Use sentry for handy error tracking and aggregation

Happy debugging ;)

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