Kemal RubyConfBrasil 2016

Kemal
Building Lightning Fast Web Applications with Simplicity
1
Serdar Doğruyol
@sdogruyol
RubyConf Brazil
2016

@sdogruyol
Serdar Doğruyol
a.k.a Sedo
• Rubyist, Crystal Evangelist
• Ruby Turkey, Crystal Turkey Organizer
• Open source developer
• Polyglot(ルビー大好き^o^)
3

@sdogruyol
Let’s talk about
Crystal!
6

@sdogruyol 7
Fast as C, slick as Ruby
http://crystal-lang.org

@sdogruyol
Crystal
• Ruby like
• Compiled
• Type inference
• Metaprogramming via Macros
• Native Code
8

@sdogruyol
Simple
Fast
Effective
12

@sdogruyol
Kemal
• HTTP verbs - RESTful
• Built-in WebSocket
• Sessions
• Built-in Parameter Parser
• Static File Serving
• Pluggable Middlewares
• Generic View Templating
13

@sdogruyol 14
require "kemal"
get "/" do
"Hello from Kemal!"
end
Kemal.run
Simple

@sdogruyol 15
require "kemal"
get "/" do
.. show something ..
end
post "/" do
.. create something ..
end
put "/" do
.. replace something ..
end
patch "/" do
.. modify something ..
end
delete "/" do
.. annihilate something ..
end
Kemal.run
HTTP Verbs - REST

@sdogruyol 16
Built-in WebSocket
# A simple chat server
require "kemal"
messages = [] of String
sockets = [] of HTTP::WebSocket
ws "/chat" do |socket|
sockets.push socket
socket.on_message do |message|
messages.push message
sockets.each do |s|
s.send messages.to_json
end
end
end
Kemal.run
http://kemal-react-chat.herokuapp.com/

@sdogruyol 17
Sessions
require "kemal"
get "/" do |ctx|
ctx["username"] = "sdogruyol"
user_id = env.session["user_id"]?
end

@sdogruyol 18
require "kemal"
post "/users/:id" do |ctx|
id = ctx.params.url["id"]
name = ctx.params.json["name"] as String
age = ctx.params.json["age"] as Int32
"User #{id} Name #{name} Age #{age}"
end
Kemal.run
Built-in Parameter Parser
require "kemal"
post "/users/:id" do |ctx|
id = ctx.params.url["id"]
name = ctx.params.body["name"] as String
age = ctx.params.body["age"] as Int32
"User #{id} Name #{name} Age #{age}"
end
Kemal.run
Form Body JSON Body
➜ ~ curl --data "name=serdar&age=27"
http://localhost:3000/users/1
User 1 Name serdar Age 27
➜ ~ curl -H "Content-Type: application/json" -X POST -d
'{"name":"serdar","age": 27}'
http://localhost:3000/users/1
User 1 Name serdar Age 27

@sdogruyol 19
Static File Serving
app/
src/
your_app.cr
public/
js/
jquery.js
app.js
css/
your_app.css
index.html
Serves app/public folder by default. JS / CSS / Image etc. It’s pretty
fast.
Can override like require "kemal"
public_folder "assets"
Kemal.run

@sdogruyol 20
Middlewares
Middlewares are easy to create and lets you encapsulate your logic.
require "kemal"
class MyHandler < HTTP::Handler
def call(context)
puts "Doing some custom stuff here"
call_next context
end
end
add_handler MyHandler.new
Kemal.run

@sdogruyol 21
Middlewares
CommonLogHandler
CommonExceptionHandler
StaticFileHandler
RouteHandler
HTTP Request
HTTP Response
InitHandler call_next
call_next
call_next
call_next
call_next

@sdogruyol 22
Middlewares
Built-in middlewares
• Before / After ﬁlters
• CSRF
• HTTP Basic Auth

@sdogruyol 23
Generic View Templating
Kemal uses Kilt(ala Tilt) as the view engine.
<h1>This is just like ERB!</h1>
<p>Let's run some Crystal Code</p>
<% some_var = "Serdar %>
<%= Process.pid %>
h1 This is just like SLIM!
p Let's run some Crystal code.
- some_var = "Serdar"
= Process.pid
hello.ecr hello.slang
You can render your view like
render "src/views/hello.ecr"
With layout
render "src/views/hello.ecr", "src/views/layouts/layout.ecr"

@sdogruyol 25
0
27500
55000
82500
110000
Sinatra Kemal
100,238
3,673
46,418
2,274
wrk -c100 -d30 localhost:3000
https://gist.github.com/sdogruyol/bbc7f24355d306a19501

@sdogruyol
Let’s talk about a
Real World Application
26

@sdogruyol
Rails is the elephant.
27

@sdogruyol
How many Unicorns does
it take to carry an
elephant?
28

@sdogruyol 29
ETOOMANYUNICORNS

@sdogruyol 30
~150 MB per worker
32 workers
~5GB

@sdogruyol 31
😥
unicorn-worker-killer

@sdogruyol 32
Kemal to the rescue!

@sdogruyol 33
~25 MB per process
1 process
~25 MB

@sdogruyol 34
~150 MB per worker
32 workers
~5GB
~25 MB per process
1 process
~25 MB
vs
~200x less memory
Faster response times

@sdogruyol 35
RequestPerSeconds
100
50
25
10
Avg. Response Time
0 400 800 1200 1600
719.44ms
805.33ms
986.8ms
1,435.62ms
103.56ms
118.67ms
129.13ms
140.86ms
Kemal (1 process) Rails (32 workers)

@sdogruyol 36
KEMAL MAKES YOU FLY!

@sdogruyol
Database
39
• crystal-db: Common DB API
• PostgreSQL
• SQLite
• MySQL
• active_record.cr: AR pattern implementation. This
is not ActiveRecord!

@sdogruyol
Deployment
40
• Cross compilation is still not there yet.
• Better to have Crystal installed in the target machine.
• capistrano-kemal: Capistrano 3 plugin for Kemal
• cap production | staging deploy

@sdogruyol
Fez
41
CLI tool to easily bootstrap new Kemal applications.
• Sass for CSS
• Simple console for debugging (uses icr)
• ES6 (Babel) for JS
• Slang (Slim) for View Template
https://github.com/jwoertink/fez

@sdogruyol
crystalweekly.com
45

@sdogruyol
crystalforrubyists.com
46

@sdogruyol 47
Fatih Akin
@f
Core Contributors
Askin Gedik
@askn

Thanks!
Serdar Doğruyol
@sdogruyol
48

Kemal RubyConfBrasil 2016

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