Den of Clojure

preso.md

Heroku @ Den of Clojure

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About James Ward

Java Developer since: 1997

First Programming Language: Pascal

Favorite Programming Language: x86 Assembler

• http://www.jamesward.com
• http://twitter.com/_JamesWard
• http://plus.google.com/101156657838073927919
• http://github.com/jamesward
• http://www.linkedin.com/in/jamesward
• http://stackoverflow.com/users/77409

Heroku Clojure Quick Start

Seven steps to the Cloud

1. project.clj

    (defproject hello-world "0.0.1"
      :dependencies [[org.clojure/clojure "1.3.0"]
                     [ring/ring-jetty-adapter "1.0.1"]])
   

2. src/web.clj

    (ns web
      (:use [ring.adapter.jetty :only [run-jetty]]))
    
    (defn app [req]
      {:status 200
       :headers {"Content-Type" "text/plain"}
       :body "Hello, world"})
    
    (defn -main [port]
      (run-jetty app {:port (Integer. port)}))
   

3. Procfile

    web: lein trampoline run -m web $PORT
   

4. Commit the files to a Git repo:

    git init
    git add Procfile project.clj src
    git commit -m init
   

5. Create a new app on Heroku:

    heroku create
   

6. Push the app to Heroku:

    git push heroku master
   

7. Open the app:

    heroku open
   

Heroku Basics

So simple.

Deployment

1. Copy git repo to Heroku:

    git push heroku master
   

2. Heroku uses a "Buildpack" to compile code

3. Heroku creates a "slug" file

4. Heroku deploys "slug" onto a "dyno"

5. Heroku starts the process

Terminology

User has 0 or more Applications

Application has 1 git repository

Application has 0 or more Processes

Process is defined in a Procfile

Process named "web" can listen on one port for HTTP

Process runs on 0 or more Dynos

Dynos are isolated (LXC) and managed execution environments

Application has 0 more more external resources - Heroku Add-ons

Buildpack receives a git push and produces a "slug"

Slug contains the non-system dependencies for all Processes

Dynos are ephemeral and stateless

HTTP(s) requests are randomly routed to the "web" Dynos

Pricing

$0.05 / dyno hour

750 free dyno hours per application per month

The Heroku CLI

$ heroku help

• Logging

  Logplex = central logging system

  All router messages -> Logplex

  All dyno stdout -> Logplex

  CLI Access to Logplex

    $ heroku logs -t
  

  API Access to Logplex

  https://api-docs.heroku.com/logs

  Syslog drains from Logplex

  https://devcenter.heroku.com/articles/logging#syslog_drains

• Scaling

  Allocate dynos to a process

  CLI

    $ heroku scale web=50
  

  API

  https://api-docs.heroku.com/ps#POST/apps/ps/scale

• Process Report

  CLI

    $ heroku ps
  

  API

  https://api-docs.heroku.com/ps#GET/apps/ps

• App Config

  Config through Environment Variables

  CLI

    $ heroku config
    $ heroku config:add FOO=bar
  

  API

  https://api-docs.heroku.com/config

• Releases / Versioning

  Slug file changes, Config changes, and Add-on changes are all versioned

  CLI

    $ heroku releases
    $ heroku rollback
  

  API

  https://api-docs.heroku.com/releases

• Collaborators

  Give multiple users access to an application

  CLI

    $ heroku sharing:add foo@heroku.com
  

  API

  https://api-docs.heroku.com/collaborators

• One-off Processes

  Run a command on a new dyno

  CLI

    $ heroku run bash
  

  API

  https://api-docs.heroku.com/ps#POST/apps/ps

Heroku Add-ons

Add-ons are third party cloud services for things like caching, databases, monitoring, management, etc

• Add an Add-on

  CLI

    $ heroku addons:add loggly:mole
  

  Web Browser

  https://addons.heroku.com/loggly

  API

  https://api-docs.heroku.com/addons

Noir on Heroku

Small and simple is wonderful.

• project.clj

    (defproject hello-clojure-compojure "0.1.0-SNAPSHOT"
      :main web
      :dependencies [[org.clojure/clojure "1.4.0"]
                     [noir "1.2.1"]])
  

• src/web.clj

    (ns web
      (:use noir.core)
      (:require [noir.server :as server]))
    
    (defpage "/" [] "hello, world")
    
    (server/start (Integer/parseInt (or (System/getenv "PORT") "8080")))
  

• Procfile

    web: lein trampoline run
  

Heroku for Clojure

Links to help you get started.

https://devcenter.heroku.com/articles/clojure

https://devcenter.heroku.com/articles/clojure-support

https://devcenter.heroku.com/articles/clojure-web-application

https://github.com/jamesward/hello-clojure-noir

https://github.com/jamesward/hello-clojure-compojure

https://github.com/jamesward/hello-clojure-ring-jetty