slides/wagtail-caching
1
Fork 0
Code Activity Actions

Add speaker notes

Browse source
This commit is contained in:
Jake Howard 2024-06-11 09:44:18 +01:00
parent 734fba8064
commit 69c0fae0c0
Signed by: jake
GPG key ID: 57AFB45680EDD477
1 changed files with 328 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

354
slides.md
View file

@ -41,6 +41,13 @@ layout: full
<li><mdi-mastodon /> @jake@theorangeone.net</li> <li><mdi-mastodon /> @jake@theorangeone.net</li>
</ul> </ul>
<style>
.slidev-layout {
background-color: #e85537;
}
</style>
<!-- <!--
- Hi - Hi
- I'm Jake - I'm Jake
@ -49,24 +56,40 @@ layout: full
- I exist in many places on the internet - I exist in many places on the internet
--> -->
<style>
.slidev-layout {
background-color: #e85537;
}
</style>
--- ---
layout: fact layout: fact
--- ---
# Disclaimer{style="color: #fd5765;"} # Disclaimer{style="color: #fd5765;"}
<!--
- Disclaimer: This isn't a general performance talk
- Optimising Python, Django and Wagtail are their own topics
- Caching can be a part of optimisation
- But it's not the only part
- It's not a replacement for proper benchmarking and investigations
-->
--- ---
layout: section layout: section
--- ---
# What _is_ caching? # What _is_ caching?
<!--
- What is caching?
- Caching lets your code remember things it's already done
- Reuse a value you've already done the work to calculate
- It's always slower to do something than nothing
- Caching comes in many different forms
- From storing a variable outside a loop
- To caching functions
- To caching entire pages with a CDN
- Mostly focusing on the higher end today
- The higher up the list you are, the more smaller processes you're caching
- And the more performance you can get
-->
--- ---
layout: center layout: center
--- ---
@ -93,12 +116,32 @@ h1 {
</style> </style>
<!--
- Caching may not seem needed at some scales
- Small sites will probably be _fine_ without it
- As your site grows, it becomes more important
- Crash under your own weight and success
- But, you may not notice you need it until it's already an issue
- What runs fine locally may not in production
- A problem with so many things at scale
- If a page gets popular, it'll soon meet with the hug of death
- Or even if it's not that popular, just shared around a bit
- Like the recently-discovered Mastodon issue
-->
--- ---
layout: section layout: section
--- ---
# <logos-wagtail class="fill-white"/> Caching <em>in Wagtail</em> # <logos-wagtail class="fill-white"/> Caching <em>in Wagtail</em>
<!--
- Now, back to Wagtail
- Let's talk about 2 techniques to help you out with caching
- Both are included in all maintained versions of Wagtail
- So you can use them right now!
-->
--- ---
layout: section layout: section
--- ---
@ -106,20 +149,17 @@ layout: section
## 1: ## 1:
# Template Fragment Caching # Template Fragment Caching
<!--
- Template fragment caching
- New ish in 5.2
- Lots of complex words, but quite a simple concept
-->
--- ---
layout: image layout: image-right
image: https://d1nvwtjgmbo5v5.cloudfront.net/media/images/Screen_Shot_2015-05-14_at_09.01.5.2e16d0ba.fill-1200x996.png image: https://d1nvwtjgmbo5v5.cloudfront.net/media/images/Screen_Shot_2015-05-14_at_09.01.5.2e16d0ba.fill-1200x996.png
backgroundSize: cover backgroundSize: cover
--- class: p-0 m-0 bg-black
<style>
.slidev-layout {
background-position: top center !important;
}
</style>
---
layout: none
--- ---
```html ```html
@ -153,12 +193,19 @@ layout: none
</p> </p>
``` ```
<style> <!--
.slidev-page, .slidev-code-wrapper, .slidev-code { - Most of what you build in Wagtail will come out as HTML
height: 100%; - Pages to be shown by the browser
} - But may take lots of intensive actions to create it
</style> - Complex lists / filters or suggestions
- Finding lots of renditions
- Rendering streamfield blocks etc
- These can all be optimised in many different ways
- The deeper down you go, the more complex and often less impactful those optimisations usually are
- Why not cache an entire chunk of template?
- With all of that complexity contained within it
- That's the thing people see (sort of)
-->
--- ---
layout: cover layout: cover
@ -169,11 +216,34 @@ background: /website-homepage.png
# My website # My website
### https://theorangeone.net ### https://theorangeone.net
<!--
- An example: My website
- Subtle self-promotion, I know
- It's a relatively simple blog
-->
--- ---
layout: image layout: image
image: /website-posts.png image: /website-posts.png
--- ---
<!--
Here's a list of posts
- Each item has a lot to it
- Title
- Date
- An image (renditions or unsplash)
- Introduction text (automatically generated from page content)
- Tags
- Reading time / Word count
- These all come from a few different places in code
- Database fields
- Model properties
- Template tags
- It'd be nice to cache them all together as they are
- That's fragment caching!
-->
--- ---
layout: none layout: none
--- ---
@ -207,7 +277,7 @@ layout: none
</article> </article>
``` ```
```html {all|3,27|4-26|all} ```html {all|1-3,27|4-26|all}
{% load wagtailcore_tags wagtail_cache %} {% load wagtailcore_tags wagtail_cache %}
{% wagtailpagecache FRAGMENT_CACHE_TTL "listing-item" breadcrumbs show_listing_images %} {% wagtailpagecache FRAGMENT_CACHE_TTL "listing-item" breadcrumbs show_listing_images %}
@ -244,6 +314,28 @@ layout: none
} }
</style> </style>
<!--
- Let's look at the template
- I like to keep reusable components in separate files
- Makes them easier to work with
- And makes fragment caching much easier too
- This has no caching at all
- [click]Let's add some
- It's just 2 lines of change[click]
- The tag might look a bit weird
- It's not an inclusion or a filter
- It's a fully custom template tag
- A name: To uniquely identify this template fragment from others
- A TTL: To determine how long the cache is valid for
- Whatever variables the tag needs
- So if the variables change, the cache is automatically invalidated
- Don't show listing images? Different cache!
- [click]Put the HTML you want in the middle
- It's still a Django template, so calling tags etc is completely fine
- They'll be cached too
- [click]The template is in charge of caching itself
- Keep the complexities hidden, and in 1 place
-->
--- ---
layout: cover layout: cover
@ -251,7 +343,16 @@ background: /website-search.png
class: text-right class: text-right
--- ---
# Search # What about<br>search?
<!--
This is a component, it's used in a few different places
- There's a posts list, and a search
- But the UI for each item is the same
- It takes the same context: A page, and creates the same HTML
- If it looks the same, just on different pages, can I reuse it?
- Yes!
-->
--- ---
layout: center layout: center
@ -271,11 +372,26 @@ code {
} }
</style> </style>
<!--
- Include the template somewhere else, and the cache gets reused
- So long as the right variables are available in context
- Shared components across your site can be accelerated
- As can entire sections like the navbar
-->
--- ---
layout: image layout: image
image: /website-search.png image: /website-search.png
--- ---
<!--
- Caching HTML blocks has a few nice benefits over caching the whole page
- Searches are still performed live, but the display of the results are cached
- Published pages appear immediately, without needing to invalidate a cache
-->
---
layout: full
--- ---
# Updating cached content # Updating cached content
@ -312,6 +428,16 @@ code {
} }
</style> </style>
<!--
If I change a page, I want the content to update
- How does it know when to regenerate the HTML?
- [click]`page.cache_key`
- Custom attribute on all your pages
- [click]You can use it for other things if you need it
- If a change is published, or the page is moved, the cache key changes, so the existing cache is ignored
- And the old cached item will eventually expire
-->
--- ---
layout: center layout: center
--- ---
@ -342,6 +468,19 @@ layout: center
</v-click> </v-click>
<!--
- This might sound familiar
- Django's `{% cache %}`?
- This isn't new, Django has had a cache tag for a very long time
- In fact, 2007
- But it's dangerous to use it with Wagtail unmodified
- Preview content can get cached
- Per-site settings cache the wrong value
- [click]It's only a few small changes to use Wagtail's
- [click]Which wraps this tag, but is aware of the current page and site automatically
- If you modify the page, the cache is automatically invalidated
-->
--- ---
layout: section layout: section
--- ---
@ -349,6 +488,13 @@ layout: section
## 2: ## 2:
# Frontend Caching # Frontend Caching
<!--
- Frontend caching
- You can spend ages optimising a request
- Caching common chunks of HTML
- But not handling the request at all is even better
-->
--- ---
layout: fact layout: fact
--- ---
@ -363,6 +509,13 @@ flowchart LR
CDN-..->W CDN-..->W
``` ```
<!--
- What if we put something in front of Wagtail to serve the requests instead
- A CDN (eg Cloudflare, CloudFront)
- They cache the page, and serve it themselves
- A CDN is generally helping you in 2 main ways:
-->
--- ---
layout: fact layout: fact
--- ---
@ -401,12 +554,32 @@ flowchart TD
CDN-...->W CDN-...->W
``` ```
<!--
Serve a static copy of your website, so your servers aren't processing every request
- Handle many more requests concurrently
- Cloudflare handles 50 million requests per second globally (on average)
- Your servers can't
- Handle more traffic with fewer servers
- Imagine it like converting your site to be static
- 0 Database requests
- 0 templates used
- 0 cache hits
-->
--- ---
layout: image layout: image
image: https://www.cloudflare.com/network-maps/cloudflare-pops-2O04nulSdNrRpJR9fs9OKv.svg image: https://www.cloudflare.com/network-maps/cloudflare-pops-2O04nulSdNrRpJR9fs9OKv.svg
class: bg-white class: bg-white
--- ---
<!--
- Store said cached copy closer to your users
- Reduced latency
- Makes your site seem faster
- Even helps on your Google Lighthouse scores
- Both of these are things you'll want as your website scales
-->
--- ---
layout: cover layout: cover
background: /wagtail-homepage.png background: /wagtail-homepage.png
@ -421,17 +594,27 @@ background: /wagtail-homepage.png
} }
</style> </style>
<!--
- Let's look at an example: Wagtail.org
-->
--- ---
layout: image layout: image
image: /map.jpg image: /map.jpg
transition: fade transition: fade
--- ---
<!--
- Wagtail.org is hosted in Dublin, Ireland (AWS `eu-west-1`)
- But I'm in Arnhem
-->
--- ---
layout: cover layout: cover
background: /map.jpg background: /map.jpg
transition: fade
--- ---
## Arnhem &rarr; Ireland
# ~XXms # ~XXms
<style> <style>
@ -440,6 +623,33 @@ h1 {
} }
</style> </style>
<!--
- XXms away
- But responses are being served quickly
- That's the CDN (Cloudflare, in our case)
-->
---
layout: cover
background: /map.jpg
---
## Arnhem &rarr; XXX
# ~XXms
<style>
h1 {
font-size: 4rem;
}
</style>
<!--
- This was actually served from XXX
- Just XXms to get a response
- Quicker
- Closer to us
-->
--- ---
layout: fact layout: fact
--- ---
@ -461,6 +671,18 @@ flowchart LR
C-.->CDN C-.->CDN
``` ```
<!--
Let's cache our content!
- Put a caching layer between users and the site
- Requests are sent via cache
- Usually just adding a DNS record
- It's always DNS
- Ensure the CDN knows how long to cache pages for
- Cache headers
- Configuration in the CDN itself
- There's another talk about this
-->
--- ---
layout: fact layout: fact
--- ---
@ -486,6 +708,13 @@ flowchart LR
CDN---->W CDN---->W
``` ```
<!--
- Make sure you skip caching authenticated requests (ie the admin)
- These pages are dynamic based on who is viewing them, so we can't cache them easily
- Wagtail does its best to make sure the admin is fast anyway
- May need to include the session id as part of the cache key
-->
--- ---
layout: section layout: section
--- ---
@ -513,12 +742,29 @@ flowchart LR
C-.....->W C-.....->W
``` ```
<!--
- Content is now cached
- Pages load much faster
- Server load should drop drastically
- Might even be able to scale down
- Wagtail.org serves ~70% of all page loads from the CDN
-->
--- ---
layout: image layout: image
image: /wagtail-homepage-typo.png image: /wagtail-homepage-typo.png
transition: fade transition: fade
--- ---
<!--
- Uh oh, there's a typo on one of the pages, better update it
- Easy, just publish an update to the page
- A quick visit to the admin makes that a breeze
- The cache still has the old content
- Users see the incorrect content
- But how does the CDN know the content has changed?
-->
--- ---
layout: cover layout: cover
background: /wagtail-homepage-typo.png background: /wagtail-homepage-typo.png
@ -526,6 +772,15 @@ background: /wagtail-homepage-typo.png
# It doesn't* # It doesn't*
<!--
- Simple: It doesn't!
- The whole point of it is it doesn't need to hit Wagtail for every request
- So it can't know
- The cache will expire _eventually_
- What if it needs to go out sooner
- What if it's more serious than just a typo
-->
--- ---
layout: section layout: section
--- ---
@ -534,6 +789,12 @@ layout: section
# Frontend Cache Invalidation # Frontend Cache Invalidation
### Wagtail secret sauce <logos-wagtail class="fill-white"/> ### Wagtail secret sauce <logos-wagtail class="fill-white"/>
<!--
- Frontend cache invalidation!
- Wagtail to the rescue
- Some magic Wagtail sauce
-->
--- ---
layout: fact layout: fact
--- ---
@ -557,6 +818,12 @@ flowchart LR
W-.->|Frontend Cache Invalidation|CDN W-.->|Frontend Cache Invalidation|CDN
``` ```
<!--
- Tighter integrations between Wagtail and the CDN
- Allows Wagtail to instruct the CDN to clear its cache for a given page
- Purging the cache much quicker
-->
--- ---
layout: center layout: center
--- ---
@ -606,6 +873,16 @@ code {
} }
</style> </style>
<!--
- Integrating is simple
- [click]Add entry to `INSTALLED_APPS`
- [click]dd credentials and configuration
- Wagtail supports quite a few backends!
- [click]That's it!
- All the hooks into all the right places are set up for you!
- You can customize this as you need for listing pages / custom configuration etc
-->
--- ---
layout: fact layout: fact
--- ---
@ -628,6 +905,13 @@ flowchart LR
CDN-.->C CDN-.->C
``` ```
<!--
- When you publish a page, it'll automatically be purged
- It can take a minute or so, depending on your CDN
- Usually much faster than that
- Then when a user loads the page, it's cached, and subsequent loads go back to being lightning fast
-->
--- ---
layout: cover layout: cover
background: https://d1nvwtjgmbo5v5.cloudfront.net/media/images/Screen_Shot_2015-05-14_at_09.01.5.2e16d0ba.fill-1200x996.png background: https://d1nvwtjgmbo5v5.cloudfront.net/media/images/Screen_Shot_2015-05-14_at_09.01.5.2e16d0ba.fill-1200x996.png
@ -635,6 +919,17 @@ background: https://d1nvwtjgmbo5v5.cloudfront.net/media/images/Screen_Shot_2015-
# Conclusion # Conclusion
<!--
- When most people think of "performance", they tend to think "database queries"
- Which is true, that's where a lot of time goes
- But there's more to optimising a site than sprinkling `select_related` / `prefetch_related`
- It's faster to do less than to do more
- It's faster still to do nothing than something
- The higher up the stack your cache is, the more impactful it can be
- More of your code is cached
- But a slow page is still a slow page, even if it's not called as often
-->
--- ---
layout: cover layout: cover
--- ---
@ -653,6 +948,13 @@ layout: cover
</Transform> </Transform>
<!--
- So why repeat yourself? Make things faster!
- [click]Users are happier
- [click]Servers are happier
- [click]The planet is happier.
-->
--- ---
layout: end layout: end
--- ---