Using Chef for Continuous Deployment with Django.

1. Snakes on a Treadmill
Noah Kantrowitz
2011-07-06

2. Chef
• Configuration management
• Deployment logic?
• Best practices! (mostly
• Not all Ruby code, I promise

3. Deploy Resource
• Pull from source
• Atomic updates via symlinks
• Fast rollback
• We all do this already, right?

4. Deploy Resource
deploy_revision '/srv/myapp' do
repo 'git@github.com/coderanger/myapp'
branch 'release'
user 'www-data'
end

5. Folder Layout
• /srv/myapp
• /srv/myapp/shared
• /srv/myapp/shared/releases
• /srv/myapp/shared/releases/4faedb2ee...
• /srv/myapp/shared/releases/9457be295...
• ...
• /srv/myapp/current

6. Folder Layout
• /srv/myapp
• /srv/myapp/shared
• /srv/myapp/shared/releases
• /srv/myapp/shared/releases/4faedb2ee...
• /srv/myapp/shared/releases/9457be295...
• ...
• /srv/myapp/current

7. Resets
purge_before_symlink []
• Rails-specific defaults create_dirs_before_symlink []
• :-( symlinks({})
symlink_before_migrate({})

8. Symlinks
template '/srv/myapp/shared/settings_local.py' do
source 'settings_local.py.erb'
vars ...
end
• Put config files in shared
• ‘path/in/shared’ => ‘path/in/app’ deploy_revision '/srv/myapp' do
...
• symlink vs. before_migrate
symlink_before_migrate(
'settings_local.py'=>'conf/settings_local.py'
)
end

9. Migrations
deploy_revision '/srv/myapp' do
...
migrate true
• Run migrations automatically migration_command '/srv/myapp/shared/env/bin/python '
• Only on “master” machine? end
'/srv/myapp/current/manage.py syncdb --migrate'
migrate node[:roles].include? 'migrator'

10. Packages
• before_migrate
deploy_revision '/srv/myapp' do
• before_symlink ...
before_migrate '/srv/myapp/shared/env/bin/pip install -r '
• before_restart
end
'/srv/myapp/current/requirements.txt'
• after_restart

11. NIH
{
"id": "myapp",
"server_roles": [
"myapp"
],
"type": {
"myapp": [
"django"
]
},
• application::django "repository": "git@github.com:coderanger/myapp.git",
"revision": {
• http://ckbk.it/application
},
"production": "release"
• Data-driven deployment "databases": {
"production": {
• PyChef! "username": "db_user",
"adapter": "postgres",
"database": "production"
}
},
"owner": "www-data",
"group": "www-data",
"packages": {
"curl": "7.19.5-1ubuntu2"
},

12. Other Cookbooks
• python
• pip packages
• python_virtualenv
• application::gunicorn
• postgres
• nginx

13. Want More?
• http://wiki.opscode.com/
• http://community.opscode.com/cookbooks/
• http://help.opscode.com/kb/otherhelp/build-a-django-stack
• https://github.com/ericholscher/chef-django-example
• My DjangoCon talk (hopefully!)

14. PyChef
• pip install pychef import chef
• Reads knife.rb or client.rb
api = chef.autoconfigure()
• chef.Object(‘id’)
bag = chef.DataBag('applications')
• chef.Object.list()
item = bag['myapp']
• obj.save() item['revision']['production'] = 'v1.1'
• obj.delete() item.save()

15. Search
• Search(‘index’, ‘query’)
• row.object
import chef
api = chef.autoconfigure()
for row in chef.Search('node', 'role:myapp'):
print row.object['fqdn']

16. T-Shirts and stickers!

17. Noah Kantrowitz
noah@opscode.com
@kantrn