WebPerformance with Rails 5.2 - Speaker Deck

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W E B P E R F W I T H R A I L S 5 . 2 S T E FA N W I N T E R M E Y E R

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Please ask questions anytime. It’s going to be a bumpy ride.

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Why are fast webpages important?

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What's the impact of slow sites? Lower conversions and engagement, higher bounce rates... Ilya Grigorik @igrigorik Make The Web Faster, Google

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Yo ho ho and a few billion pages of RUM How speed affects bounce rate @igrigorik

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Usability Engineering 101 Delay User reaction 0 - 100 ms Instant 100 - 300 ms Feels sluggish 300 - 1000 ms Machine is working... 1 s+ Mental context switch 10 s+ I'll come back later... Stay under 250 ms to feel "fast". Stay under 1000 ms to keep users attention. @igrigorik

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Web Search Delay Experiment Type of Delay Delay (ms) Duration (weeks) Impact on Avg. Daily Searches Pre-header 100 4 -0.20 % Pre-header 200 6 -0.59% Post-header 400 6 0.59% Post-ads 200 4 0.30% Source: https://www.igvita.com/slides/2012/webperf-crash-course.pdf

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For many, mobile is the one and only internet device! Country Mobile-only users Egypt 70% India 59% South Africa 57% Indonesia 44% United States 25% onDevice Research @igrigorik

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< 1.000 ms Page Loading Time on G3 ist der Mount Everest.

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The (short) life of our 1000 ms budget 3G (200 ms RTT) 4G(80 ms RTT) Control plane (200-2500 ms) (50-100 ms) DNS lookup 200 ms 80 ms TCP Connection 200 ms 80 ms TLS handshake (200-400 ms) (80-160 ms) HTTP request 200 ms 80 ms Leftover budget 0-400 ms 500-760 ms Network overhead of one HTTP request! @igrigorik

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Some WebPerf Problems can be ﬁxed within Rails but not all. If your page loads 3 MB of JavaScript it will never be fast.

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Webpage Rendering Basics

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Network HTML DOM CSS CSSOM JavaScript Render tree Layout Paint

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Network HTML DOM CSS CSSOM JavaScript Render tree Layout Paint

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Network HTML DOM CSS CSSOM JavaScript Render tree Layout Paint

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Network HTML DOM CSS CSSOM JavaScript Render tree Layout Paint

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Network HTML DOM CSS CSSOM JavaScript Render tree Layout Paint

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The rendering process takes a minimum of 100 ms which we have to subtract from the 1,000 ms.

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Download a ﬁle with HTTP/TCP

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Latency client Zeit 0 ms 80 ms 160 ms 240 ms 320 ms 10 TCP Segmente (14.600 Bytes) 20 TCP Segmente (29.200 Bytes) 40 TCP Segmente (15.592 Bytes) server SYN ACK ACK GET SYN,ACK ACK ACK

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TCP Slow-Start KB 0 55 110 165 220 Roundtrip 1. 2. 3. 4. 214KB 100KB 43KB 14KB 114KB 57KB 29KB 14KB

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Waterfall www.webpagetest.org

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https://www.webpagetest.org/result/ 180316_WK_94121529c3107aae272fa55c65f82216/

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https://www.webpagetest.org/result/ 180316_V3_5a1acad4d9251fe1539e1394b309d80a/

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https://www.webpagetest.org/result/ 180316_5B_de436fb724593d7b746b9c1f89ff3c2d/

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Example Online Shop

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$ rails new shop $ cd shop $ rails g scaffold Category name $ rails g scaffold Product category:references name description price:decimal{8,2} $ rails g scaffold User email first_name last_name password_digest $ rails g scaffold Review user:references product:references rating:integer $ rails db:migrate

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Shop domain model Category name string Product description text name string price decimal (8,2) Review rating integer User email string first_name string last_name string password_digest string

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app/models/product.rb: class Product < ApplicationRecord belongs_to :category has_many :reviews def number_of_stars if reviews.any? reviews.average(:rating).round else nil end end end

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db/seeds.rb: Category.create(name: "A") Category.create(name: "B") Category.create(name: "C") 100.times do Product.create(name: Faker::Food.dish, description: Faker::Food.description, category: Category.all.sample, price: rand(20)) end 50.times do user = User.create(first_name: Faker::Name.first_name, last_name: Faker::Name.last_name) products = Product.all 3.times do Review.create(user: user, product: products.sample, rating: rand(5)) end end

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app/views/products/index.html.erb: […] <% @products.each do |product| %> <%= product.category.name %> <%= product.name %> <%= product.description %> <%= number_to_currency(product.price) %> <% product.number_of_stars.to_i.times do %>

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Completed 200 OK in 497ms (Views: 460.4ms | ActiveRecord: 34.1ms) Development env.

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The (short) life of our 1000 ms budget 3G (200 ms RTT) 4G(80 ms RTT) Control plane (200-2500 ms) (50-100 ms) DNS lookup 200 ms 80 ms TCP Connection 200 ms 80 ms TLS handshake (200-400 ms) (80-160 ms) HTTP request 200 ms 80 ms Leftover budget 0-400 ms 500-760 ms Network overhead of one HTTP request! @igrigorik 497ms And we don’t have product images yet.

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Fragment Caching

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$ rails dev:cache Development mode is now being cached.

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1. Step Single Row

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app/views/products/index.html.erb: <% @products.each do |product| %> <% cache product do %> <%= product.category.name %> <%= product.name %> <%= product.description %> <%= number_to_currency(product.price) %> <% product.number_of_stars.to_i.times do %>

<% end %> [...] <% end %> <% end %>

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app/views/products/index.html.erb: <% @products.each do |product| %> <% cache product do %> <%= product.category.name %> <%= product.name %> <%= product.description %> <%= number_to_currency(product.price) %> <% product.number_of_stars.to_i.times do %>

<% end %> [...] <% end %> <% end %>

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app/models/review.rb: class Review < ApplicationRecord belongs_to :user belongs_to :product, touch: true end Product description text name string price decimal (8,2) Review rating integer User email string first_name string last_name string password_digest string

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Total Views Activerecord Vanilla 497ms 460 ms 34 ms Fragment Cache Row 79 ms 74,6 ms 1 ms

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2. Step The Complete Table => Russian Doll

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app/views/products/index.html.erb: <% cache @products do %> <% @products.each do |product| %> <% cache product do %> <%= product.category.name %> <%= product.name %> <%= product.description %> <%= number_to_currency(product.price) %> <% product.number_of_stars.to_i.times do %>

<% end %> […] <% end %> <% end %> <% end %>

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app/views/products/index.html.erb: <% cache @products do %> <% @products.each do |product| %> <% cache product do %> <%= product.category.name %> <%= product.name %> <%= product.description %> <%= number_to_currency(product.price) %> <% product.number_of_stars.to_i.times do %>

<% end %> […] <% end %> <% end %> <% end %>

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Total Views Activerecord Vanilla 497ms 460 ms 34 ms Fragment Cache Row 79 ms 74,6 ms 1 ms Fragment Cache Table 53 ms 49,5 ms 0,6 ms

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Use the Database!

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app/models/product.rb: class Product < ApplicationRecord belongs_to :category has_many :reviews def number_of_stars if reviews.any? reviews.average(:rating).round else nil end end end

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app/models/product.rb: class Product < ApplicationRecord belongs_to :category has_many :reviews end $ rails g migration AddNumberOfStarsToProduct number_of_stars:integer $ rails db:migrate

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app/models/product.rb: class Review < ApplicationRecord belongs_to :user belongs_to :product, touch: true after_create :recalculate_product_rating after_destroy :recalculate_product_rating private def recalculate_product_rating rating = product.reviews.average(:rating).round if rating != self.product.number_of_stars product.update_attribute(:number_of_stars, rating) end end end

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Warning:   Fragment Caching is slower the very ﬁrst time. Why? Rails checks if the Fragment Cache exists. When it doesn’t it renders the view and writes the cache.

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HTTP Caching

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Web browsers and proxies don‘t want to fetch webpages twice. They use Last-Modiﬁed and Etag to avoid that.

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The idea of Etags and Last-Modiﬁed

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Web browser: „My user wants to fetch xyz.html. I cached a copy last week. Is that still good?“

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Web server: „xyz.html hasn‘t changed since last week. Go a head with your copy!“ aka 304 Not Modiﬁed

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> curl -I http://0.0.0.0:3000/products HTTP/1.1 200 OK Content-Type: text/html; charset=utf-8 X-Ua-Compatible: IE=Edge Etag: "9a779b80e4b0ac3c60d29807e302deb7" [...] > curl -I http://0.0.0.0:3000/products HTTP/1.1 200 OK Content-Type: text/html; charset=utf-8 X-Ua-Compatible: IE=Edge Etag: "fa8fc1e981833a6885b583d351c4d823"

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> curl -I http://0.0.0.0:3000/products HTTP/1.1 200 OK Content-Type: text/html; charset=utf-8 X-Ua-Compatible: IE=Edge Etag: "9a779b80e4b0ac3c60d29807e302deb7" [...] > curl -I http://0.0.0.0:3000/products HTTP/1.1 200 OK Content-Type: text/html; charset=utf-8 X-Ua-Compatible: IE=Edge Etag: "fa8fc1e981833a6885b583d351c4d823"

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Set the Etag class ProductsController < ApplicationController # GET /products def index @products = Product.all fresh_when :etag => @products end [...] 

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> curl -I http://0.0.0.0:3000/products -c cookies.txt HTTP/1.1 200 OK Etag: "4d348810e69400799e2ab684c0ef4777" > curl -I http://0.0.0.0:3000/products -b cookies.txt HTTP/1.1 200 OK Etag: "4d348810e69400799e2ab684c0ef4777" The cookie is needed for the CSRF-Token.

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> curl -I http://0.0.0.0:3000/products -b cookies.txt --header 'If-None-Match: "4d348810e69400799e2ab684c0ef4777"' HTTP/1.1 304 Not Modified Etag: "4d348810e69400799e2ab684c0ef4777" 304!

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Win-Win of a 304 • The Browser doesn’t have to download everything. • The Server doesn’t have to render the view which is the most time consuming bit.

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Not good enough?

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Writing the initial cache wastes a lot of time.

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Let‘s preheat the cache in off business hours! Cron is your friend.

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Use the night to preheat your cache. And don‘t be afraid of brute force!

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A U T O B A H N

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The fastest page is delivered by Nginx without ever contacting Ruby on Rails.

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├── Gemﬁle ├── [...] ├── public │ ├── 404.html │ ├── 422.html │ ├── 500.html │ ├── favicon.ico │ └── robots.txt ├── [...] That‘s already done for the ﬁles in the public directory.

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Is there an easy way to save complete pages which are rendered by the Rails framework?

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Add caches_page to your controller to save views as static gz ﬁles in your public directory: caches_page :index, :show, :gzip => :true Add gem actionpack-page_caching for Rails 5.2

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Brute Force is your friend! During the night the server has a hard time to stay awake any way.

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Tricky part: How to delete out of date gz ﬁles?

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after_update :expire_cache before_destroy :expire_cache private def expire_cache ActionController::Base.expire_page(Rails.application.routes.url_h elpers.company_path(self)) ActionController::Base.expire_page(Rails.application.routes.url_h elpers.companies_path) end app/models/product.rb

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caches_page vs. !current_user.nil? ???

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caches_page is good to cache customized user content too. It just takes more thinking.

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Let us assume a user base of 10,000,000 people.

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/tmp ᐅ wget http://www.railsconf.com/2013/talks --2013-04-27 21:04:24-- http://www.railsconf.com/2013/talks Resolving www.railsconf.com... 107.20.162.205 Connecting to www.railsconf.com|107.20.162.205|:80... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] Saving to: ‘talks’ [ <=> ] 74,321 258KB/ s in 0.3s 2013-04-27 21:04:25 (258 KB/s) - ‘talks’ saved [74321] /tmp ᐅ du -hs talks 76K talks /tmp ᐅ gzip talks /tmp ᐅ du -hs talks.gz 28K talks.gz /tmp ᐅ

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/tmp ᐅ du -hs talks.gz 28K talks.gz 28K * 10,000,000 = 0,26 TB

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28K * 10,000,000 = 0,26 TB Harddrive space is cheap. By saving the files non-gz and using a data deduplication file system you just need 5-10% of the 0,26 TB. Nginx can gzip the files on the fly.

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Nginx will happily read a cookie and ﬁnd the pre- rendered page in a given directory structure.

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To setup a complex page_cache system is a lot of work. You have to tackle not only Rails but Nginx too. It does increase the snappiness of your application but might not be worth the effort for small systems.

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HTTP/1.2 vs. HTTP/2

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HTTP/2 provides an average WebPerformance improvement of 20%. It’s a no-brainer. You have to use it!

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CDNs, HTTP/2 and Rails 5.2

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Long story short:  In many cases where a CDN made sense with HTTP/1.1 it doesn’t make sense any more. Try to deliver everything from your Rails server.

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Active Storage

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Active Storage should be used to minimize image ﬁle size and to deliver different formats to different browsers.    JPEG, PNG or WebP

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Apache vs. Nginx

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It doesn’t matter!  Use the one you like most.

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Brotli vs. gzip

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Always offer both. Brotli can be used to save bandwidth and CPU-Resources.

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Heroku vs. Bare Metal

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Heroku is good for a quick start but has never been a good choice for good WebPerformance. Bare Metal is the way to go if you need maximum WebPerformance.    BTW: It’s cheaper too.

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P R E L O A D I N G U N D P R E F E T C H I N G

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P R E L O A D I N G U N D P R E F E T C H I N G

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M A N U A L D N S - P R E F E T C H http://www.chromium.org/developers/design-documents/dns-prefetching „Most common names like google.com and yahoo.com are resolved so often that most local ISP's name resolvers can answer in closer to 80-120ms. If the domain name in question is an uncommon name, then a query may have to go through numerous resolvers up and down the hierarchy, and the delay can average closer to 200-300ms.“

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P R E F E T C H http://www.whatwg.org/specs/web-apps/current-work/#link-type-prefetch „The prefetch keyword indicates that preemptively fetching and caching the specified resource is likely to be beneficial, as it is highly likely that the user will require this resource.“ T I P P : " A C C E P T - R A N G E S : B Y T E S “ H E A D E R

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P R E R E N D E R

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Y O U C A N T E L L N G I N X T O P U S H T H O S E F I L E S V I A H T T P / 2 .

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The Most Important Tool?

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Set a Time Budget! If you run out of your time budget you have to cancel features on your website.

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Is WebPerformance really so hard?

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The WebPerf Bible. => https://hpbn.co

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20% Discount-Code: RubyAndRails

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@wintermeyer

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sw@wintermeyer-consulting.de last name | twitter | github e-mail