Continuous Integration and Deployment with Flask & Travis CI

Build environment for Flask development with Grunt for frontend development.
Testing and integration handled by Travis CI. Zero-downtime deployment stack with Nginx and Gunicorn, configured easily with Fabric locally or from Travis CI. Build flow based off of Batista Harahap's configuration

Setup

1. Install the following:
   • git (you probably have this already)
   • Python & pip
   • node.js
2. Run npm install -g bower -g less to install bower & lessc
3. Run bower install to install browser packages from bower.json into /static/bower_components/
4. Install virtualenv using pip install virtualenv (Note: see flask virtualenv install docs for more info)
5. Setup virtualenv:
   1. Run virtualenv env
   2. On Windows: env\scripts\activate; On Linux: . env/bin/activate
6. Install python packages with pip install -r requirements.txt (NOTE: Make sure you have activated the python virtualenv prior.)
7. Copy flask_site/config/config_sample.yml to flask_site/config/config.yml and DO NOT ADD IT TO GIT (do not delete config_sample.yml, it is used for testing)
8. Change secret_key in config.yml

Develop

• New Flask routes are added to routes.yml with associated controllers in the controllers sub-package
• Install JS and CSS plugin resources with bower:
  • Use bower search PACKAGE to find a package.
  • Use bower install PACKAGE --save to install and remember package in bower.json (i.e. bower install animate.css --save)
  • Add resources to bundles in bundles.yml so they are compiled by Flask-Assets
• If you install a new python package with pip, run: pip freeze > requirements.txt
• See Testing Flask Applications for useful info on how to make tests comprehensive.
• If you make any changes to flask_site/config/config.yml, the file must be manually uploaded to /home/$USER/blue-green/config/config.yml

Run

Run python start.py development to start Flask locally at 127.0.0.1:5000.
Run python start.py to test the production configuration.

Test

Run nosetests --with-xunit --with-xcoverage --cover-package=flask_site --cover-erase tests

Deploy

Fabric is used to easily setup and push code to deployment servers. Deployment configuration is based off of the 0-downtime blue-green deployment style.
Tested on Debian wheezy, but with minor alterations to fabfile.py it should work with other distros.

Variables

Several variables are referenced in this section. Following is their descriptions:

• $DEPLOY_HOSTS - the hosts you will deploy to (comma separated - I've only tested with one host)
• $DEPLOY_PASS - the ssh password you will set for your deployment user (default: admin) - NOT THE ROOT PASSWORD
• $LIVE_SERVER_URL - the URL people will use to access your server (i.e. example.com)
• $NEXT_SERVER_URL - the URL you can use to test changes before going live (i.e. dev.example.com)

Setting up

This only has to be done once. If you'd like to use a different user besides admin, change env.user in fabfile.py

From your remote machine as root:

1. apt-get update
2. apt-get install -y sudo (this is only necessary if it's not already installed)
3. adduser admin, and set the password to something feisty.
4. adduser admin sudo

From your local machine:

1. pip install fabric gitric
2. fab -H $DEPLOY_HOSTS -p $DEPLOY_PASS --set LIVE_SERVER_URL=$LIVE_SERVER_URL,NEXT_SERVER_URL=$NEXT_SERVER_URL prod setup_machine

Deploy automatically using Travis CI

See .travis.yml if you're interested in exactly what's going on.
If you'd like to automatically deploy but manually switch from the new version to live, remove cutover from .travis.yml and skip step 1 of the "Deploy Manually" section.

1. Navigate to Travis CI and enable this repository to be built (login with your Github credentials).
2. In settings, add the following environment variables (make sure they are all set to not display in log):
   • DEPLOY_HOSTS
   • DEPLOY_PASS
3. Commit or push some changes to master branch.

Deploy Manually

1. fab -H $DEPLOY_HOSTS -p $DEPLOY_PASS prod deploy, enter $DEPLOY_PASS again when prompted
   • Alternatively, you can:
     • add your local public key to ~/.ssh/authorized_keys on your production servers, or
     • use --set SSH_PUB_KEY_FILE=$YOUR_PUB_KEY_LOCATION to automatically add and remove the key during deployment.
2. (optional) test from $NEXT_SERVER_URL
3. fab -H $DEPLOY_HOSTS -p $DEPLOY_PASS prod cutover

If you don't intend to test the server before going live, you can run the commands at the same time:
fab -H $DEPLOY_HOSTS -p $DEPLOY_PASS prod deploy cutover

Notes

• To skip Travis builds, include [ci skip] in the commit message.
• For a nice git branching model: http://nvie.com/posts/a-successful-git-branching-model/
• Because of Flask-Assets, the first user to visit your newly-deployed site will take a long time to load (while resources compile). Circumvent this by visiting $NEXT_SERVER_URL before running fab cutover