The Lifecycle of a Rails Request

app/controllers/hello_controller.rb
Hello World
http://skylight.io/hello
class HelloController < ActionController::Base
def index
# ...do stuff here...
render plain: 'Hello World'
end
end

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Meet at Pastini?
where dat
911 SW Taylor St, Portland, OR 97205

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What’s the address for skylight.io?
34.194.84.73

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DNS LOOKUP
Domain Name System

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$ dig skylight.io 
 
; <<>> DiG 9.10.6 <<>> skylight.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32689
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;skylight.io. IN A
;; ANSWER SECTION:
skylight.io. 59 IN A 34.194.84.73
;; Query time: 34 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Apr 29 14:50:34 PDT 2019
;; MSG SIZE rcvd: 56
Terminal

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Terminal
$
 
Trying 34.194.84.73...
Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
Escape character is ‘^]’.
>
telnet 34.194.84.73 80 
 
 
< Connection closed by foreign host.
 
Hi???

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Terminal
$
 
Trying 34.194.84.73...
Connected to ec2-34-194-84-73.compute-1.amazonaws.com.
Escape character is ‘^]’.
>
telnet 34.194.84.73 80 
 
 
< HTTP/1.1 200 OK
< Content-Type: text/plain
< Content-Length: 11
< Date: Thu, 25 Apr 2019 18:52:54 GMT
<
< Hello World
 
GET /hello HTTP/1.1
> Host: skylight.io
>
Hello World

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hey server, can you do me a favor?
What’s up?
If someone ask for /assets/*, can you give it
to them from /var/myapp/public/assets?
Sure thing.
With compression, 404, etc. The usual.

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http://skylight.io/assets/kitten.jpg
location /assets {
alias /var/myapp/public/assets;
gzip_static on;
gzip on;
expires max;
add_header Cache-Control public;
}
nginx.conf
© Kenny Louie, CC BY 2.0

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http://skylight.io/blog
!
location /blog {
}
nginx.conf
!

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server.on_request do |request, response|
request.path # => '/hello'
request.headers # => { host: ... }
response.status = 200
response.body = 'Hello World'
end
MyApp.handle_request(
http_method, # => 'GET'
http_path, # => '/hello'
http_headers # => #
)
# => #
ENV['REQUEST_METHOD'] # => 'GET'
ENV['PATH_INFO'] # => '/hello'
ENV['HTTP_HOST'] # => 'skylight.io'
puts 'Status: 200 OK'
puts
puts 'Hello World'

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Hey, I’ve a request for you to handle.
Sounds good.
It’s a GET request for /hello, Host header is skylight.io
200 OK. Content type is text/plain, body is “Hello World”.

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Hello World
env = {
'REQUEST_METHOD' => 'GET',
'PATH_INFO' => '/hello',
'HTTP_HOST' => 'skylight.io',
# ...
}
status, headers, body = app.call(env)
status # => 200
headers # => { 'Content-Type' => 'text/plain' }
body # => ['Hello World']
server.rb

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Terminal
$
class HelloWorld
def call(env)
if env['PATH_INFO'] == '/hello'
[200, {'Content-Type' => 'text/plain'}, ['Hello World']]
else
[404, {'Content-Type' => 'text/plain'}, ['Not Found']]
end
end
end
app.rb
require_relative 'app'
run HelloWorld.new
conﬁg.ru
rackup
Thin web server (v1.7.2 codename Bachmanity)
Maximum connections set to 1024
Listening on localhost:9292, CTRL+C to stop
Hello World
http://localhost:9292/hello
Not Found
http://localhost:9292/wat

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class HelloWorld
def call(env)
if env['PATH_INFO'] == '/'
[301, {'Location' => '/hello'}, []]
elsif env['PATH_INFO'] == '/hello'
[200, {'Content-Type' => 'text/plain'}, ['Hello World!']]
else
[404, {'Content-Type' => 'text/plain'}, ['Not Found!']]
end
end
end
app.rb

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class Redirect
def initialize(app, from:, to:)
@app = app
@from = from
@to = to
end
def call(env)
if env["PATH_INFO"] == @from
[301, {"Location" => @to}, []]
else
@app.call(env)
end
end
end
class HelloWorld
def call(env)
if env["PATH_INFO"] == '/hello'
[200, {"Content-Type" => "text/plain"}, ["Hello World!"]]
else
[404, {"Content-Type" => "text/plain"}, ["Not Found!"]]
end
end
end
app.rb
run Redirect.new(
HelloWorld.new,
from: '/',
to: '/hello'
)
conﬁg.ru

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class Redirect
@app = app
@from = from
@to = to
end
def call(env)
[301, {"Location" => @to}, []]
else
@app.call(env)
end
end
end
class HelloWorld
def call(env)
else
end
end
end
app.rb
use Redirect, from: '/', to: '/hello'
run HelloWorld.new
conﬁg.ru

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class Redirect
@app = app
@from = from
@to = to
end
def call(env)
[301, {"Location" => @to}, []]
else
@app.call(env)
end
end
end
class HelloWorld
def call(env)
else
end
end
end
app.rb
use Rack::Deflater
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
use Redirect, from: '/', to: '/hello'
run HelloWorld.new
conﬁg.ru

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require_relative 'config/environment'
run Rails.application
conﬁg.ru
$
Terminal
bin/rails console
>> Rails.application.call({ ...env hash... })

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conﬁg.ru
$
Terminal
bin/rails console
>> env = {
>> 'REQUEST_METHOD' => 'GET',
>> 'PATH_INFO' => ‘/posts/1’,
>> 'HTTP_HOST' => 'localhost',
>> 'HTTP_PORT' => '3000',
>> # ...
>> }
>> Rails.application.call(env)

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conﬁg.ru
$ bin/rails console
>> env = Rack::MockRequest.env_for('http://localhost:3000/posts/1')
>>
Terminal

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conﬁg.ru
$ bin/rails console
>>
Terminal
status, headers, body = Rails.application.call(env)
Processing by PostsController#show as HTML
Parameters: {"id"=>"1"}
CACHE Post Load (0.0ms) SELECT "posts".* FROM "posts" WHERE ...
Rendering posts/show.html.erb within layouts/application
Rendered posts/show.html.erb within layouts/application (0.3ms)
Completed 200 OK in 23ms (Views: 21.1ms | ActiveRecord: 0.0ms)
>> status
=> 200
>> headers
=> { "Content-Type"=>"text/html; charset=utf-8”, ... }
>> puts body.join('')

My Blorgh

Rails is Omakase
There are lots of à la carte software environments in...

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$
Terminal
bin/rails middleware
use Rack::Sendfile
use ActionDispatch::Executor
use ActiveSupport::Cache::Strategy::LocalCache::Middleware
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use ActionDispatch::RemoteIp
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use ActionDispatch::Callbacks
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use ActionDispatch::ContentSecurityPolicy::Middleware
use Rack::Head
use Rack::ETag
use Rack::TempfileReaper
run Blorgh::Application.routes

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require_relative 'boot'
require 'rails/all'
Bundler.require(*Rails.groups)
module Blorgh
class Application < Rails::Application
# Disable cookies
config.middleware.delete ActionDispatch::Cookies
config.middleware.delete ActionDispatch::Session::CookieStore
config.middleware.delete ActionDispatch::Flash
# Add your own middleware
config.middleware.use CaptchaEverywhere
end
end
conﬁg/application.rb

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$
Terminal
use Rack::Sendfile
use Rack::Runtime
use Rack::Head
use Rack::ETag

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$ bin/rails
>>
Terminal
console
status, headers, body = Blorgh::Application.routes.call(env)
Processing by PostsController#show as HTML
Parameters: {"id"=>"1"}
CACHE Post Load (0.0ms) SELECT "posts".* FROM "posts" WHERE ...
Rendering posts/show.html.erb within layouts/application
Rendered posts/show.html.erb within layouts/application (0.3ms)
Completed 200 OK in 23ms (Views: 21.1ms | ActiveRecord: 0.0ms)
>> status
=> 200
>> headers
=> { "Content-Type"=>"text/html; charset=utf-8”, ... }
>> puts body.join('')

My Blorgh

Rails is Omakase
There are lots of à la carte software environments in...

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Rails.application.routes.draw do
resources :posts
end
conﬁg/routes.rb

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get '/posts' => 'posts#index'
get '/posts/new' => 'posts#new'
post '/posts' => 'posts#create'
get '/posts/:id' => 'posts#show'
get '/posts/:id/edit' => 'posts#edit'
put '/posts/:id' => 'posts#update'
delete '/posts/:id' => 'posts#destroy'
end
conﬁg/routes.rb

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get '/posts' => 'posts#index'
get '/posts/new' => 'posts#new'
post '/posts' => 'posts#create'
get '/posts/:id' => 'posts#show'
get '/posts/:id/edit' => 'posts#edit'
put '/posts/:id' => 'posts#update'
delete '/posts/:id' => 'posts#destroy'
end
conﬁg/routes.rb
PostsController.action(:index)

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class ActionController::Base
def self.action(name)
->(env) {
request = ActionDispatch::Request.new(env)
response = ActionDispatch::Response.new(request)
controller = self.new(request, response)
controller.process_action(name)
response.to_a
}
end
attr_reader :request, :response, :params
def initialize(request, response)
@request = request
@response = response
@params = request.params
end
def process_action(name)
event = 'process_action.action_controller'
payload = {
controller: self.class.name,
action: action_name,
# ...
}
ActiveSupport::Notifications.instrument(event, payload) do
self.send(name)
end
end
end
rails/actionpack/lib/action_controller/base.rb

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class BlorghRoutes
def call(env)
verb = env['REQUEST_METHOD']
path = env['PATH_INFO']
if verb == 'GET' && path == '/posts'
PostsController.action(:index).call(env)
elsif verb == 'GET' && path == '/posts/new'
PostsController.action(:new).call(env)
elsif verb == ‘POST' && path == '/posts'
PostsController.action(:create).call(env)
elsif verb == 'GET' && path =~ %r(/posts/.+)
PostsController.action(:show).call(env)
elsif verb == 'GET' && path =~ %r(/posts/.+/edit)
PostsController.action(:edit).call(env)
elsif verb == 'PUT' && path =~ %r(/posts)
PostsController.action(:update).call(env)
elsif verb == 'DELETE' && path = %r(/posts/.+)
PostsController.action(:destroy).call(env)
else
[404, {'Content-Type': 'text-plain', ...}, ['Not Found!']]
end
end
end
blorgh_routes.rb

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class BlorghRoutes
def call(env)
verb = env['REQUEST_METHOD']
path = env['PATH_INFO']
if verb == 'GET' && path == '/posts'
PostsController.action(:index).call(env)
elsif verb == 'GET' && path == '/posts/new'
PostsController.action(:new).call(env)
elsif verb == 'GET' && path == '/posts'
PostsController.action(:create).call(env)
elsif verb == 'GET' && path =~ %r(/posts/.+)
PostsController.action(:show).call(env)
elsif verb == 'GET' && path =~ %r(/posts/.+/edit)
PostsController.action(:edit).call(env)
elsif verb == 'PUT' && path =~ %r(/posts)
PostsController.action(:update).call(env)
elsif verb == 'DELETE' && path = %r(/posts/.+)
PostsController.action(:destroy).call(env)
else
[404, {'Content-Type': 'text-plain', ...}, ['Not Found!']]
end
end
end
https://youtu.be/lEC-QoZeBkM

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get '/hello' => HelloWorld.new
get '/hello' => ->(env) {
[200, {'Content-Type': 'text/plain'}, ['Hello World!']
}
# redirect(...) returns a Rack app!
get '/' => redirect('/hello')
mount Sidekiq::Web, at: '/sidekiq'
end
conﬁg/routes.rb

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get '/posts' => PostsController.action(:index)
get '/posts/new' => PostsController.action(:new)
post '/posts' => PostsController.action(:create)
get '/posts/:id' => PostsController.action(:show)
get '/posts/:id/edit' => PostsController.action(:edit)
put '/posts/:id' => PostsController.action(:update)
delete '/posts/:id' => PostsController.action(:destroy)
end
conﬁg/routes.rb

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Hello World
class HelloController < ActionController::Base
def index
# ...do stuff here...
render plain: 'Hello World'
end
end

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$
Terminal
use Skylight::Middleware
use Rack::Sendfile
use Rack::Runtime
use Rack::Head
use Rack::ETag

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class ActionController::Base
def self.action(name)
->(env) {
request = ActionDispatch::Request.new(env)
response = ActionDispatch::Response.new(request)
controller = self.new(request, response)
controller.process_action(name)
response.to_a
}
end
attr_reader :request, :response, :params
def initialize(request, response)
@request = request
@response = response
@params = request.params
end
def process_action(name)
event = 'process_action.action_controller'
payload = {
controller: self.class.name,
action: action_name,
# ...
}
ActiveSupport::Notifications.instrument(event, payload) do
self.send(name)
end
end
end
rails/actionpack/lib/action_controller/base.rb

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skylight.io

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The Lifecycle of a Rails Request

The Lifecycle of a Rails Request

Godfrey Chan

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