Make Your Django App Reliable with DBOS

This guide shows you how to add the open source DBOS Transact library to your existing Django application to durably execute it and make it resilient to any failure.

In summary you'll need to:

• Start DBOS with your AppConfig's ready method
• Annotate your service methods with DBOS decorators to make them durable
• Start Django with the --noreload flag.

Installation and Requirements

info

The guide is based on the Django quickstart, will show you how to make your application reliable with DBOS Transact.

Setting up the Django quickstart

This application was created with:

python3 -m venv .venv
source .venv/bin/activate
pip install django
django-admin startproject djangodbos .
python manage.py startapp polls

Then, configure djangodbos/settings.py to use Postgres and run python manage.py migrate.

Install DBOS Python with:

pip install dbos

Starting DBOS

In your Django application AppConfig, start DBOS inside the ready method. You can configure the DBOS instance before launching DBOS.

from django.apps import AppConfig
from dbos import DBOS
import os

class PollsConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'polls'

    def ready(self):
        dbos_config = {
            "name": name,
            "database_url": os.environ.get("DBOS_DATABASE_URL"),
        }
        dbos = DBOS(config=dbos_config)
        dbos.launch()
        return super().ready()

Because launching DBOS triggers worfklow recovery, it is advised you call python manage.py runserver with the --noreload flag.

Making Your Views Reliable

You can make a Django view durable by annotating your functions with DBOS decorators.

In this example, we'll augment an existing endpoint callWorkflow to invoke a workflow of two steps.

def callWorkflow(request, a, b):
    return JsonResponse(workflow(a, b))

# Annotate the workflow() function to make it a durable workflow
@DBOS.workflow()
def workflow(a, b):
    res1 = step1(a)
    res2 = step2(b)
    result = res1 + res2
    return {"result": result}

# Make step1() a durable step
@DBOS.step()
def step1(var):
    return var

# Make step2 a durable transaction (special step with ACID properties)
@DBOS.transaction()
def step2(var):
    rows = DBOS.sql_session.execute(sa.text("SELECT 1")).fetchall()
    return var + str(rows[0][0])

Update polls/urls.py and run your app with python manage.py runserver --noreload to access the view at http://localhost:8000/polls/callWorkflow/a/b.