Add speaker notes

2024-06-01 22:05:28 +01:00 · 2024-06-01 22:05:28 +01:00 · 24b9e43712
commit 24b9e43712
parent d5365e0282
1 changed files with 402 additions and 34 deletions
--- a/slides.md
+++ b/slides.md
@ -29,6 +29,19 @@ themeConfig:
  <img src="/dceu24-qrcode.png" width="110px" />
 </div>
 <!--
 - Hi
 - I'm Jake
 - Senior Systems Engineer at Torchbox
 - I'm also on the security team, and as of last week the core team for Wagtail
  - Leading Django-based CMS
 - I exist in many places on the internet
 - Here to talk about Background Workers
  - What they are
  - How to use them
  - Exciting things _hopefully_ coming to Django
 -->
 ---
 layout: center
 ---
@ -50,6 +63,13 @@ flowchart LR
  }
 </style>
 <!--
 - Django is a web framework
 - It's a magic box which turns HTTP requests into HTTP responses
    - What you do inside that box is up to you
    - For something like a blog, that's probably as far as it needs to go
 -->
 ---
 layout: full
 ---
@ -79,12 +99,28 @@ flowchart TD
  }
 </style>
 <!--
 - For a full web application, you need a little more than that
    - Not just "keep information in a database"
    - Notification emails
    - Talk to external services
    - Transcoding video
    - Complex reporting
    - It's 2024, so lots of ML
 - For many of these, you need code which runs outside the magic box
    - You don't want your user waiting whilst these happen
        - If you had to wait whilst YouTube transcoded all your videos, you'd get pretty annoyed
 -->
 ---
 layout: full
 ---
-# Background Workers!
+<v-click>
 # Background Workers?
 </v-click>
 ```mermaid
 flowchart TD
@ -97,7 +133,7 @@ flowchart TD
    R[Reporting]
    ML((Machine<br>Learning))
-    B{{<strong>Background Processing</strong>}}
+    B{{<strong>Background Worker</strong>}}
    U<-->D
@ -112,15 +148,24 @@ flowchart TD
  }
 </style>
 <!--
 - You need a background worker
    - But[click]
    - What are background workers
 - Let you offload complexity outside of the request-response cycle
    - To be run somewhere else, potentially at a later date
 - They keep requests quick
    - Move the slow bits somewhere else
        - So the user doesn't have to wait
    - This improves throughput and latency
 -->
 ---
 layout: section
 ---
-# Background Workers?
+## Background worker architecture
 ---
 layout: fact
 ---
 ```mermaid
 flowchart LR
@ -133,12 +178,29 @@ flowchart LR
    D<----->S<-....->R1 & R2 & R3
 ```
 <!--
 - How does this work?
    - Web process submits a function to be run
    - Stored in the queue store
    - A runner then grabs a task, runs it, and returns the result to the queue store
    - You can retrieve its status later if needed
 -->
 ---
 layout: section
 ---
 # When?
 <!--
 - Background workers are very useful tool
    - But that doesn't mean they're useful for everything, all the time
 - As with all great things: "It depends"
    - The added complexity may not be worth it
    - A few things to consider
 -->
 ---
 layout: cover
 background: https://images.unsplash.com/photo-1518729371765-043e54eb5674?q=80&w=1807&auto=format&fit=crop&ixlib=rb-4.0.3
@ -146,6 +208,15 @@ background: https://images.unsplash.com/photo-1518729371765-043e54eb5674?q=80&w=
 # Does it take time?{.text-right}
 <!--
 - Something which takes time
    - Something which _could_ take time
    - Rather than have the user wait
        - Unable to close the tab or do something else
    - Go off and do it in the background, and let them know whether it's done
        - Even if that's by polling it in the browser
 -->
 ---
 layout: fact
 ---
@ -174,6 +245,15 @@ flowchart BT
    D-.-E & EA & V & R & ML
 ```
 <!--
 - Leaving your infrastructure
    - The core components (Server, DB, Cache etc) you control and can closely monitor
        - And are in a good position to fix it if something goes wrong
    - That's not true for external APIs
        - It's someone else's SRE team
    - Their performance regressions shouldn't affect your app
 -->
 ---
 layout: cover
 background: https://images.unsplash.com/photo-1518770660439-4636190af475?q=80&w=3870&auto=format&fit=crop&ixlib=rb-4.0.3
@ -181,6 +261,15 @@ background: https://images.unsplash.com/photo-1518770660439-4636190af475?q=80&w=
 # Specialized hardware?
 <!--
 - Maybe it's less about when, more about where?
    - Maybe it's more about the hardware it runs on
        - GPUs
        - Loads of RAM
        - External hardware
        - Isolated network
 -->
 ---
 layout: cover
 background: https://images.unsplash.com/photo-1711606815631-38d32cdaec3e?q=80&w=2070&auto=format&fit=crop&ixlib=rb-4.0.3
@ -189,6 +278,17 @@ background: https://images.unsplash.com/photo-1711606815631-38d32cdaec3e?q=80&w=
 ## Example:
 # Complex reporting
 <!--
 - An example: Complex reporting
    - Something analytical, crunching lots of data
    - Initially, it might take a few seconds, which is fine
        - You build a CSV as part of the request with something like `pandas`
    - As your application grows, there'll be more data, so it'll likely take a lot longer
    - Rather than force the user to wait, let them get the data when it's ready
        - They can get back on with their day
        - Web servers can get back to processing other requests
 -->
 ---
 layout: section
 ---
@ -197,30 +297,20 @@ layout: section
 <logos-django class="[&>path]:fill-white! h-fit w-60 -mt-20"/>
---
+<!--
-layout: cover
+- Back to Django
-background: /celery.svg
+    - This is djangocon after all
---
+- In Python and Django, there are lots of different frameworks to achieve this
-
+-->
 # Celery!
 <style>
 .slidev-layout {
    background: white;
    background-size: contain !important;
 }
 </style>
 ---
 layout: image-right
 image: https://images.unsplash.com/photo-1444703686981-a3abbc4d4fe3?q=80&w=1740&auto=format&fit=crop&ixlib=rb-4.0.3
 ---
-# Others...
+# Libraries
-<Transform :scale="1.05">
+- Celery<br><br>
 - ~~Celery~~
 - arq
 - Django DB Queue
 - Django Lightweight Queue
@ -233,7 +323,15 @@ image: https://images.unsplash.com/photo-1444703686981-a3abbc4d4fe3?q=80&w=1740&
 - Taskiq
 - ...
-</Transform>
+<!--
 - All require an external library
        - And possibly some external infrastructure
 - Celery is probably the biggest one
    - But it's not all that exists
 - So many different libraries exist
    - With different strengths / weaknesses
    - Different learning curves (or cliffs)
 -->
 ---
 layout: cover
@ -243,6 +341,14 @@ background: https://images.unsplash.com/photo-1522096823084-2d1aa8411c13?q=80&w=
 ## Example:
 # Email <mdi-email-fast-outline />
 <!--
 - Let's loon at an example, sending an email
    - Very common functionality
 - Let's imagine a CMS
    - For totally unbias reasons
 - When a page is published, send an email to everyone subscribed
 -->
 ---
 layout: center
 ---
@ -266,6 +372,26 @@ for user in page.subscribers.iterator():
    )
 ```
 <!--
 - Here's the code we might write to do that
 1. [click]Find the users to email
 2. [click]Construct the email content
 3. [click]Send the email
 - [click]This works perfectly fine
    - Scales _relatively_ well
    - But has some issues
        - If connecting to the email server takes a while, the user has to wait
            - Usually only a few ms
            - Might take a few seconds
        - Subsequent emails are delayed whilst we process the earlier ones
        - If something goes wrong with one email, the others won't send
            - What if your email gateway is down altogether - do your requests start erroring?
                - How do you handle it if they do?
    - That web worker (eg gunicorn) can't process any other requests until this is done
 -->
 ---
 layout: center
 ---
@ -292,6 +418,30 @@ for user in page.subscribers.iterator():
    django_rq.enqueue(send_email_to_user, user)
 ```
 <!--
 - Let's look at an example of how we might use background workers to help with this
    - Use Django-RQ for this
 1. [click]Find the users to email
 2. [click]New: Start a task for each user
 3. [click]Construct the email content
 4. [click]Send the email
 - [click]Most of this is exactly the same
    - If you knew nothing of RQ, you could still maintain this code
 - [click]Moving it to the background just quickly puts an item in the queue
    - And then the user can get back on with their life
    - Emails get sent out by the runners
        - Multiple runners means they get sent out faster
 - [click]Email sending is an easy action to move to the background
    - It's a connection to an external API
        - Variable latency
        - Infrastructure you don't control
    - All of that is simpler to handle when it's already running in the background
 -->
 ---
 layout: center
 ---
@ -351,18 +501,65 @@ for user in page.subscribers.iterator():
  }
 </style>
 <!--
 - There's something I just said which might end up causing issues
    - You'll notice I said "Using RQ" in that example
 - That's because each worker library has its own API
    - Its own features
    - Its own configuration
    - Its own caveats / implementation details
 - What if we wanted to switch to Celery?
    - [click]Well, that's easy
    - [click]Just change a few lines
 - [click]But there in lies the problem
    - You had to make some changes!
    - Sure, they're small, but this is only a tiny amount of code
    - What if you wanted to support both?
 -->
 ---
 layout: image
 image: /situation.png
 backgroundSize: 50%
 ---
 <!--
 - It's hard enough having multiple options
    - But how do you choose between them?
    - If you've used multiple tools, you probably know which is best for you
        - Do you have the time (and patience) to test each one out?
        - Maybe you already have a standard you need to work to
        - Do you need a background worker which supports `asyncio`?
    - If you're new to Django, do you really want to spend the time weighing them all up?
        - Knowing it could bite you as you grow or need a specific feature
        - Requiring a lot of time refactoring in future
 - What about library maintainers
    - What if you built a library which has some background task needs
        - Like, say, Wagtail
        - Do you write and maintain integrations for _all_ task libraries
        - Do you choose the big one(s) and force your users' hands?
        - Do you expose a hook and let your users integrate themselves?
    - It adds a huge maintenance burden, whichever you choose
        - There isn't really a right answer
 -->
 ---
 layout: image
 image: /ridiculous.png
 backgroundSize: 49%
 ---
 <!--
 - There _should_ be one universal standard which combines them all
 - A single API to help developers use a library, without tieing their hands
 - First-party, allowing library developers to depend on it instead of supporting every separate API
 - Scale easily as your needs change
    - Be easy to get started with for small projects
    - But feature-packed for larger deployments
 - Allowing easy stubbing out during tests
    - Tests are important!
 -->
 ---
 layout: fact
 ---
@ -375,6 +572,10 @@ layout: fact
  <img src="/django-tasks-qrcode.png" width="110px" />
 </div>
 <!--
 - In progress API spec for first-party background workers in Django
 -->
 ---
 layout: image-right
 image: https://images.unsplash.com/photo-1674027444485-cec3da58eef4?q=80&w=1932&auto=format&fit=crop&ixlib=rb-4.0.3
@ -389,6 +590,19 @@ class: flex items-center text-xl
  - "Dummy"
 - Django 5.2 🤞
  - Backport for 4.2+
 <!--
 - An API contract between worker library maintainers and application developers
    - Compatibility layer between Django and their native APIs
    - Hopefully the promise of "Write once, run anywhere"
 - Built-in worker queues
    - ORM based (production grade)
    - "Immediate" (ie doesn't background anything) loaded by default
    - Dummy (for testing)
 - Hopefully landing in Django 5.2
    - Backwards compatible with Django 4.2, to allow easy adoption
 -->
 ---
 layout: center
 ---
@ -419,7 +633,7 @@ for user in page.subscribers.iterator():
    send_email_to_user.delay(user)
 ```
-```python {all|7-9,20|all}
+```python
 from django.contrib.auth.models import User
 from django.core.mail import send_mail
 from django.template.loader import render_to_string
@ -449,6 +663,21 @@ for user in page.subscribers.iterator():
  }
 </style>
 <!--
 - Let's look at the same code example as before
 - This is tied to Celery
    - If want to support RQ too, I'd have to duplicate some parts
 - Instead, let's rewrite this once to use `django.tasks`[click]
    - Still simple, clear, approachable and easy to use
        - If I say so myself
 - Now, in future, if we swapped to RQ (for whatever reason), exactly 0 lines need to change
    - If a new library comes out, 0 lines need to change
 - If this is in a library, not my own code, I can keep using the library no matter what worker I'm using
    - And the maintainer doesn't need to special case
 - If I want to test this code, I can swap out the backend to an in-memory one, and interrogate it
    - With 0 lines changed
 -->
 ---
 layout: center
 ---
@ -481,6 +710,16 @@ EMAIL_BACKEND = "django.core.mail.backends.tasks.SMTPEmailBackend"
 </v-click>
 <!--
 - In this case, we can actually make it even easier
 - Because email is such a common use case, and so easy to extract
 - Go back to the simple implementation
    - No background workers in sight
 - [click]Use the built-in task email backend
 - Emails are magically sent in the background automatically
    - Without additional work
 -->
 ---
 layout: image-right
 image: /soon.png
@ -489,6 +728,20 @@ class: flex justify-center text-2xl flex-col
 # Q: Why something new?
 <!--
 - I'm sure you're thinking "Why something new?"
    - Celery already has a borderline monopoly on task queues
    - Writing a production-grade task queue is hard
        - As I've been told whilst working on this DEP
    - Why not just vendor something existing?
        - If not Celery, then something else
    - That's not really the goal
        - Shared API contract is
        - The built-in version will hopefully become great
            - But must be done with careful planning and consideration
            - Django needs to remain the stable and reliable base it always has been
 -->
 ---
 layout: image-right
 image: https://images.unsplash.com/photo-1525683879097-8babce1c602a?q=80&w=1335&auto=format&fit=crop&ixlib=rb-4.0.3
@ -504,6 +757,32 @@ class: flex justify-center text-xl flex-col
 - Use what's already there
 - A common API
 <!--
 - Being built-in reduces the battier to entry
 - Integrating becomes much simpler
    - There's 1 API to learn, and it will last you a while
        - Much like the ORM has done for different DB engines
    - A developer can join a new project and already be productive
 - A common API also helps library maintainers
    - Maintaining a large library is work enough
        - Without needing to think about how to move code to the background
    - If Django can take complexity off you, that's great
    - Currently, it's not really an option
        - The burden is just too great
    - With this, no additional dependencies
        - Just import from Django and you're set
        - The user can use what they want
            - Or what's suitable for their scale and use case
    - Now the barrier is reduced, the ecosystem can flourish
        - Libraries can start assuming background workers, without any additional burden
 - The ORM backend should work for the majority of projects
    - If you just want to send emails in the background, you probably don't need Celery
        - It's overkill
        - Even RQ is a bit much
    - A vendored solution makes it the easiest to get started with
        - Tweak some settings, run an extra process, and you're done.
 -->
 ---
 layout: center
 transition: fade
@ -524,6 +803,14 @@ transition: fade
 }
 </style>
 <!--
 - ORM at scale
    - For some scales, an ORM-based worker might not be viable
        - The Sentrys and Instagrams of the world
        - Postgres scales pretty well, but sometimes not well enough
            - And that's ok!
 -->
 ---
 layout: center
 ---
@ -543,6 +830,20 @@ layout: center
 }
 </style>
 <!--
 - But the same is also true for Postgres FTS vs ElasticSearch
    - A debate that's been going on for a while
    - And I've had many times
 - ElasticSearch is quite likely better for the ~10% of people who need it
 - But that doesn't mean the other 90% of people won't be happy with PostgreSQL
    - And probably wouldn't benefit from ElasticSearch anyway
    - And definitely won't get a return on the extra hosting cost and complexity
 - They'll be perfectly happy with Postgres FTS
    - Let them get started the easiest way possible
    - We can still invite them into ElasticSearch when they're ready
 -->
 ---
 layout: section
 ---
@ -555,26 +856,46 @@ image: /dep.png
 ---
 ---
-layout: cover
+layout: section
 ---
 # `pip install django-tasks`
-<div class="absolute right-1/2 translate-x-1/2 mt-12">
+<div class="absolute right-1/2 translate-x-1/2 mt-6">
-  <QRCode
+  <img src="/django-tasks-qrcode.png" width="150px" />
    :width="120"
    :height="120"
    data="https://pypi.org/project/django-tasks/"
    :dotsOptions="{ color: 'white' }"
  />
 </div>
 <!--
 - You can play with this right now!
 - Download it, play around with it
    - The dummy backend is great for testing
    - The immediate backend can help get you started
    - The ORM backend is where the magic happens
 - Tell me about all the bugs in my code
    - The more testing we can do now, the better
    - There are still features to implement and improve
 -->
 ---
 layout: section
 ---
 # Where will we be _soon_™?
 <!--
 - More testing
 - Upstreaming
    - The main benefit is in this becoming part of Django
    - The DEP is approved (ish)
    - Once `django-tasks` is in a better state, it can become `django.tasks`
        - Hopefully in time for the 5.2 release window
 - Adoption
    - The more people know about this, the better it is for everyone
    - Developers can start using `django-tasks` now, and swap for `django.tasks` later
        - Or use both side-by-side in older versions of Django / older libraries
        - The 2 will work correctly together inside the same project
 -->
 ---
 layout: cover
 background: /celery.svg
@ -589,6 +910,16 @@ background: /celery.svg
 }
 </style>
 <!--
 - Is this the end for Celery and alike?
    - Not at all!
    - If you're using Celery, you've not made a mistake
        - It's a great choice
        - They have quite a head start
    - This is much more about usability and flexibility
    - If you need certain features, keep using them!
    - But, now you have the option of a nice, Django-native API
 -->
 ---
 layout: image-right
@ -608,6 +939,15 @@ class: flex justify-center flex-col text-xl
 - Swappable argument serialization
 - ...
 <!--
 - The world of background workers is huge
    - Not everything is making it into the initial version(s)
        - And that's ok!
 - Existing libraries have a head start
    - But I hope we can slowly catch them up
    - Bringing the stability and longevity guarantees that come with Django
 -->
 ---
 layout: cover
 background: https://images.unsplash.com/photo-1519187903022-c0055ec4036a?q=80&w=1335&auto=format&fit=crop&ixlib=rb-4.0.3
@ -615,6 +955,19 @@ background: https://images.unsplash.com/photo-1519187903022-c0055ec4036a?q=80&w=
 # The future is bright
 <!--
 - The future is bright though
 - In time, I see more and more people reaching to `django.tasks`
    - Moving work to the background will make Django apps _seem_ faster
        - Improve throughput
        - Reduce latency
        - Improve reliability
    - Gone are the days of needing additional research and testing to find the tooling you need
        - You can use the ones built-in to Django
        - And as you scale, if you find you need to swap something out, you can
            - _without_ rewriting half your application
 -->
 ---
 layout: section
 ---
@ -630,6 +983,21 @@ layout: section
  />
 </div>
 <!--
 - Time to turn the dream into a reality!
 - If you've realised you could use a background queue, give `django_tasks` a try
    - Test it out
    - Report back your issues
    - Suggest improvements
 - If you want to get involved, please do!
    - There's plenty of work to do
    - And I can't do it alone!
 - If you maintain a worker library
    - Or have been burned by one
    - let's chat!
 -->
 ---
 layout: end
 ---