bringing-background-workers-to-django/slides.md

title	class	highlighter	transition	mdc	monaco	themeConfig	addons
Empowering Django with Background Workers	text-center	shiki	slide-left	true	false	primary #0c4b33	slidev-addon-qrcode

Empowering Django with Background Workers

Jake Howard

• Senior Systems Engineer @ Torchbox
• Security & Performance @ Wagtail

• theorangeone.net
• @RealOrangeOne
• @RealOrangeOne
• @jake@theorangeone.net

---

layout: center

Django isn't just for websites

flowchart LR
    U(User 🧑‍💻)
    D[\Django/]

    U---->|Request|D
    D---->|Response|U

---

layout: full

flowchart BT
    U[User 🧑‍💻]
    D[\Django/]
    DB[(Database)]
    C[(Cache)]
    E>Email]
    EA[External API]
    V[[Video Transcode]]
    ML((Machine Learning))

    U---->|Request|D
    D---->|Response|U

    D-.-DB & E & EA & V & ML & C

---

layout: full

flowchart BT
    U[User 🧑‍💻]
    D[\Django/]
    DB[(Database)]
    C[(Cache)]
    E>Email]
    EA[External API]
    V[[Video Transcode]]
    ML((Machine Learning))
    B{{Background Processing}}

    U--->|Request|D
    D--->|Response|U

    D---B

    D-.-C & DB

    B---E & V & ML & EA
    B---C & DB

---

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Background Workers?

---

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flowchart LR
    D[\Django/]
    S[(Queue Store)]
    R1{Runner}
    R2{Runner}
    R3{Runner}

    D<--->S<-..->R1 & R2 & R3

---

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When?

---

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flowchart BT
    D[\Django/]

    subgraph Fast & Reliable
      DB[(Database)]
      C[(Cache)]
    end

    subgraph Slow / Unreliable
      E>Email]
      EA[External API]
      V[[Video Transcode]]
      ML((Machine Learning))
    end

    D---DB & C

    D-.-E & EA & V & ML

---

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Background Workers in Django

---

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Celery!

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Others...

• Celery
• arq
• Django DB Queue
• Django Lightweight Queue
• Django Too Simple Q
• Django-Q
• Django-Q2
• Dramatiq
• Huey
• RQ
• Taskiq
• ...

---

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Email

---

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from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

import django_rq

def send_email_to_user(user: User):
    email_content = render_to_string("email-template.html", {"user": user})
    send_mail(
      subject="Here is your important customized message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

users_to_email = User.objects.all()

for user in users_to_email.iterator():
    django_rq.enqueue(send_email_to_user, user)

---

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A problem

```python
from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

import django_rq

def send_email_to_user(user: User):
    email_content = render_to_string("email-template.html", {"user": user})
    send_mail(
      subject="Here is your important customized message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

users_to_email = User.objects.all()

for user in users_to_email.iterator():
    django_rq.enqueue(send_email_to_user, user)
```

```python {all|5-7,20|all}
from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

from my_celery_config import app

@app.task
def send_email_to_user(user: User):
    email_content = render_to_string("email-template.html", {"user": user})
    send_mail(
      subject="Here is your important customized message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

users_to_email = User.objects.all()

for user in users_to_email.iterator():
    send_email_to_user.delay(user)
```

---

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Situation:

There are 14 competing standards.

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• Application developers
• Library maintainers
• System Engineers

---

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Ridiculous!

---

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Introducing:

django.tasks*

---

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```python
from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

from my_celery_config import app

@app.task
def send_email_to_user(user: User):
    email_content = render_to_string("email-template.html", {"user": user})
    send_mail(
      subject="Here is your important customized message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

users_to_email = User.objects.all()

for user in users_to_email.iterator():
    send_email_to_user.delay(user)
```

```python {all|5-7,20|all}
from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

from django.tasks import task

@task()
def send_email_to_user(user: User):
    email_content = render_to_string("email-template.html", {"user": user})
    send_mail(
      subject="Here is your important customized message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

users_to_email = User.objects.all()

for user in users_to_email.iterator():
    send_email_to_user.enqueue(user)
```

---

layout: center

from django.contrib.auth.models import User
from django.core.mail import send_mail
from django.template.loader import render_to_string

users_to_email = User.objects.all()

email_content = render_to_string("email-template.html")

for user in users_to_email.iterator():
    send_mail(
      subject="Here is your important message",
      message=email_content
      from_email=None,  # Use the default sender email
      recipient_list=[user.email]
    )

# settings.py
EMAIL_BACKEND = "django.core.mail.backends.tasks.SMTPEmailBackend"

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Q: Why something new?

A: We're not

---

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Why something built-in?

• Reduces barrier to entry
• Improve interoperability
• Reduce cognitive load

---

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Where are we now?

pip install django-tasks

---

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Where are we going?

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Out of scope

• Completion / failed hooks
• Bulk queueing
• Automated task retrying
• Task runner API
• Unified observability
• Cron-based scheduling
• Task timeouts
• Swappable argument serialization

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What's next?

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END