David Gouldin @Heroku gave a talk at Py Con 2015 - check it out.

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Heroku 101
!
dgouldin@heroku.com
@dgouldin

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What is Heroku?
The application platform

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You write your app.
We do the rest.

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LOW HIGH
SCALE
drag to scale

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5 Billion
requests per day
3+ Million
Apps Created
125+
Add-on services

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What’s a Heroku app?

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The Twelve-Factor app
12factor.net

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Let’s dive in!

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Assumptions
You want to learn about Heroku.
You know (a bit) of Python.
You have Python, pip, and virtualenv*.

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*install.python-guide.org

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Install the Toolbelt
toolbelt.heroku.com

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$ heroku login
Log in

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X. Dev/prod parity
12factor.net/dev-prod-parity

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Create a Flask app
devcenter.heroku.com/articles/getting-started-with-python

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$ mkdir hello-heroku
$ cd hello-heroku
$ virtualenv venv
$ source venv/bin/activate
$ pip install Flask gunicorn
Create a vitualenv and install requirements

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import os
from flask import Flask
!
app = Flask(__name__)
!
@app.route('/')
def hello():
return 'Hello World!'
hello.py

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web: gunicorn hello:app
Procfile

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VI. Processes
12factor.net/

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$ foreman start
Start the app

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X. Dev/prod parity
12factor.net/dev-prod-parity

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$ pip freeze > requirements.txt
Freeze dependencies

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II. Dependencies
12factor.net/

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Store the app in git
devcenter.heroku.com/articles/git

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venv
*.pyc
.gitignore

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$ git init
$ git add .
$ git commit -m "initial commit"
Store the app in git

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I. Single codebase
12factor.net/

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Create and deploy
the application

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$ heroku create
$ git push heroku master
...
-----> Launching... done, v2
http://happy-pycon-2015.herokuapp.com
deployed to Heroku
$ heroku open
Create and deploy the app

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V. Build, release, run
12factor.net/build-release-run

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Logging

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$ heroku logs --tail
Viewing logs

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import os
from flask import Flask
!
app = Flask(__name__)
!
import logging
logging.basicConfig(level=logging.DEBUG)
!
@app.route('/')
def hello():
logging.info("saying hello")
return 'Hello World!'
hello.py

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$ git add .
$ git commit -m "add logging"
$ git push heroku master
Commit and deploy again

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$ heroku logs --tail
Viewing logs

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XI. Logs as event streams
12factor.net/

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Configuration variables
devcenter.heroku.com/articles/config-vars

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import os
import logging
from flask import Flask
!
app = Flask(__name__)
logging.basicConfig(level=logging.DEBUG)
!
@app.route('/')
def hello():
logging.info("saying hello")
name = os.environ.get('NAME', 'World')
return 'Hello {}!'.format(name)
hello.py

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$ NAME=David foreman start
Try it out locally

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$ echo "NAME=David" > .env
Store local env vars in .env
(don’t forget to add it to .gitignore)

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$ foreman start
Try it out locally

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$ git add .
$ git commit -m "add name"
$ git push heroku master
Commit and deploy

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$ heroku config:set NAME=David
Setting config vars and restarting happy-pycon-2015... done, v6
!
$ heroku config:get NAME
David
!
$ heroku config
=== happy-pycon-2015 Config Vars
NAME: David
!
$ heroku config:unset NAME
Unsetting NAME and restarting happy-pycon-2015... done, v7
Managing config vars

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III. Store config in the environment
12factor.net/

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Releases
devcenter.heroku.com/articles/releases

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$ heroku releases
=== happy-pycon-2015 Releases
v7 Remove NAME config vars dgouldin@heroku.com 2015/04/07 12:41:49
v6 Deploy df3cf06 dgouldin@heroku.com 2015/04/07 12:40:32
v5 Set NAME config vars dgouldin@heroku.com 2015/04/07 12:35:30
v4 Deploy 5bebf9b dgouldin@heroku.com 2015/04/07 12:34:27
v3 Deploy 69398b3 dgouldin@heroku.com 2015/04/07 12:18:08
v2 Enable Logplex dgouldin@heroku.com 2015/04/07 12:16:20
v1 Initial release dgouldin@heroku.com 2015/04/07 12:16:17
Release history

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I. One codebase, many deploys
12factor.net/

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Addons
addons.heroku.com

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$ heroku addons:create rediscloud
Adding rediscloud on happy-pycon-2015... done, v8 (free)
Use `heroku addons:docs rediscloud` to view documentation.
Adding an addon

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import os
import redis
from flask import Flask
!
app = Flask(__name__)
db = redis.from_url(os.environ['REDISCLOUD_URL'])
!
@app.route('/')
def hello():
name = db.get(‘name') or 'World'
return 'Hello %s!' % name
!
@app.route('/setname/<name>')
def setname(name):
db.set('name', name)
return 'Name updated.'
hello.py

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IV. Treat backing services as attached resources
12factor.net/

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$ pip install redis
$ pip freeze > requirements.txt
Dependencies

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$ git add .
$ git commit -m "use redis for name"
$ git push heroku master
Commit and deploy

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X. Dev/prod parity?
Uh oh…

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$ foreman start
13:03:34 web.1 | started with pid 24492
...
13:03:34 web.1 | 2015-04-07 13:03:34 [24495] [ERROR] Exception in worker process:
13:03:34 web.1 | Traceback (most recent call last):
...
13:03:34 web.1 | KeyError: 'REDISCLOUD_URL'
...
13:03:34 web.1 | 2015-04-07 13:03:34 [24495] [INFO] Worker exiting (pid: 24495)
13:03:34 web.1 | 2015-04-07 13:03:34 [24492] [INFO] Shutting down: Master
13:03:34 web.1 | 2015-04-07 13:03:34 [24492] [INFO] Reason: Worker failed to boot.
13:03:34 web.1 | exited with code 3
13:03:34 system | sending SIGTERM to all processes
SIGTERM received
Uh oh…

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Some solutions:
Only run remotely
Homebrew - brew.sh
Vagrant - vagrantup.com
Docker - docker.io

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Scaling and performance
devcenter.heroku.com/articles/scaling

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$ heroku ps:scale web=2
Scaling dynos... done, now running web at 2:1X.
!
$ heroku ps:scale web=10
Scaling dynos... done, now running web at 10:1X.
!
$ heroku ps:scale web=5:2X
Scaling dynos... done, now running web at 5:2X.
!
$ heroku ps:scale web=1:PX
Scaling dynos... done, now running web at 1:PX.
!
$ heroku ps:scale web=1:1X
Scaling dynos... done, now running web at 1:1X.
Scaling

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Understanding performance
devcenter.heroku.com/articles/optimizing-dyno-usage

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VIII. Concurrency via processes
12factor.net/

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$ heroku labs:enable log-runtime-metrics
$ heroku restart
!
$ heroku logs --tail
2015-04-07T17:19:30.746857+00:00 heroku[web.1]: source=web.1 dyno=heroku.
23939571.b4d17f84-50f5-4e2f-9fb1-b2124db4addb sample#memory_total=17.86MB
sample#memory_rss=17.85MB sample#memory_cache=0.00MB sample#memory_swap=0.00MB
sample#memory_pgpgin=5311pages sample#memory_pgpgout=740pages
!
2015-04-07T17:19:50.787234+00:00 heroku[web.1]: source=web.1 dyno=heroku.
23939571.b4d17f84-50f5-4e2f-9fb1-b2124db4addb sample#memory_total=17.86MB
sample#memory_rss=17.85MB sample#memory_cache=0.00MB sample#memory_swap=0.00MB
sample#memory_pgpgin=5311pages sample#memory_pgpgout=740pages
log-runtime-metrics

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Dashboard
metrics
organization
add-ons marketplace

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Metrics
devcenter.heroku.com/articles/metrics

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Organizations
devcenter.heroku.com/categories/organization-accounts

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Add-ons Marketplace

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Papertrail

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Rollbar

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New Relic

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And many more …
addons.heroku.com

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Github Integration
devcenter.heroku.com/articles/github-integration

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Automatic Deploys

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Release Diffs

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Heroku Button
1 click to a deployed Heroku app

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app.json

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README.md
[]
(https://heroku.com/deploy?template=https://github.com/
dgouldin/django-playground)

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Try it yourself!
github.com/dgouldin/django-playground

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Bonus: Platform API
devcenter.heroku.com/categories/platform-api

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>>> import json
>>> import requests # python-requests.org
!
>>> heroku = requests.session()
>>> heroku.auth = ('', '{INSERT HEROKU API TOKEN HERE}')
>>> heroku.headers['Accept'] = 'application/vnd.heroku+json; version=3'
>>> heroku.headers['Content-Type'] = 'application/json'
REST API basics

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>>> heroku.get('https://api.heroku.com/apps/happy-pycon-2015').json()
{u'archived_at': None,
...
u'web_url': u'http://dgouldin.herokuapp.com/'}
!
>>> heroku.get('https://api.heroku.com/apps/happy-pycon-2015/config-vars').json()
[35] :
{u'NAME': u'David',
u'REDISCLOUD_URL': u'{REDACTED}'}
!
>>> body = json.dumps({'NAME': 'Robot'})
>>> heroku.patch('https://api.heroku.com/apps/happy-pycon-2015/config-vars', body)
App info; config vars

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>>> heroku.get('https://api.heroku.com/apps/happy-pycon-2015/formation').json()
[{u'command': u'gunicorn hello:app',
u'created_at': u'2015-04-06T16:42:24Z',
u'id': u'928f6618-a0e2-4ded-95ec-e3a23a7795f0',
u'quantity': 2,
u'size': u'1X',
u'type': u'web',
u'updated_at': u'2015-04-06T18:50:02Z'}]
!
>>> body = json.dumps({'quantity': 4})
>>> heroku.patch('https://api.heroku.com/apps/dgouldin/formation/web', body)
Scaling

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Questions and Free Play
dgouldin@heroku.com
@dgouldin