Building Web Applications with

Kemal

@sdogruyol

paris.rb 

07.06.2016

Serdar Doğruyol

Lead Developer - Protel Turkey

@sdogruyol

  • Rubyist, Crystal enthusiast
  • Ruby Turkey, Crystal Turkey Organizer
  • Open source developer
  • Literally Polyglot

we <3 ruby

Expressive
Powerful
OOP

+

The superb performance of C 

we <3 crystal

Kemal

http://kemalcr.com

Simple
Fast
Featured

  • RESTful
  • Built-in WebSocket
  • JSON
  • Static File Serving
  • Pluggable Middlewares
  • View templating
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

REST

WebSocket

# A simple chat server
require "kemal"

messages = [] of String
sockets = [] of HTTP::WebSocket

public_folder "src/assets"

get "/" do
  render "src/views/index.ecr"
end

ws "/" 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

http://kemal-react-chat.herokuapp.com

View Engine

<h1>This is just like ERB!</h1>

<p>Let's run some Crystal Code</p>

<% some_var = "Serdar %>

<%= Process.pid %>

ECR

h1 This is just like HAML!

p Let's run some Crystal code.

- some_var = "Serdar"
= Process.pid

Slang

Fast

Framework Requests Per Sec Avg. Resp. Time
Kemal(Production) 100238 395.44μs
Sinatra(Puma) 2274 43.82ms
get "/" do 
  "Hello world!"
end

HTTP

Framework CPU (%) Memory (MB)
Crystal(Kemal) 1.85 11.2
ws (Node) 38.95 906.3

Websocket

https://gist.github.com/sdogruyol/bdd400a6eac13e26228e

Who uses Kemal

Crystal for Rubyists

http://www.crystalforrubyists.com

Questions?

Thanks!

@sdogruyol

https://slides.com/sdogruyol/building-web-apps-with-kemal-parisrb

Building Web Applications with Kemal

By Serdar Dogruyol

Building Web Applications with Kemal

  • 694
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