Working with Celery and Django Database Transactions

In this article, we'll look at how to prevent a Celery task dependent on a Django database transaction from executing before the database commits the transaction. This is a fairly common issue.

Objectives

After reading, you should be able to:

  1. Describe what a database transaction is and how to use it in Django
  2. Explain why you might get a DoesNotExist error in a Celery worker and how to solve it
  3. Prevent a task from executing before the database commits a transaction

What is a database transaction?

A database transaction is a unit of work that is either committed (applied to the database) or rolled back (undone from the database) as a unit.

Most databases use the following pattern:

  1. Begin the transaction.
  2. Execute a set of data manipulations and/or queries.
  3. If no error occurs, then commit the transaction.
  4. If an error occurs, then roll back the transaction.

As you can see, a transaction is a very useful way to keep your data far away from chaos.

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