Python Playground Part 2: Deploying Flask app on Ubuntu (nginx, uwsgi, supervisor, git)

14 Sep 2012 Tags: python, mvp, devops, git

This is a followup on my previous post on building and getting up and running small online image placeholder generator service - https://noimageyet.com.

This post will list steps to set up a Flask app in Ubuntu Linux server 12.04 using nginx, uWSGI and supervisord. On top of that I will provide installation scripts and deployment scheme using Git SCM.

Credits First

This post (and service deployement in live) would not be possible without these awesome resources:

[1] Conrad Kramer’s “Getting a Flask website up and running in Ubuntu”

[2] Conrad Kramer’s “Deploy a website using git in Ubuntu”

[3] Linode StackScript: shazow’s stack (nginx+uwsgi+postgresql+more)

Installing Python stack

$ sudo apt-get install -y python-software-properties python-dev python-pip
$ sudo pip install virtualenv

NoImageYet also requires Python Imaging Library, which depends on certain native libs. Here it goes:

 
$ sudo apt-get install -y libfreetype6-dev libjpeg62-dev libpng12-dev

 # PIL PIP package fails to install, since it expects libs located in /usr/lib/
 # So, will reset /usr/lib/ *.so references
$ sudo rm -rf /usr/lib/{libfreetype.so,libz.so,libjpeg.so}
$ sudo ln -s /usr/lib/*-linux-gnu/{libfreetype.so,libz.so,libjpeg.so} /usr/lib/

Installing NGINX

$ sudo apt-get install -y nginx
 # Nginx-related: Move the default nginx config name so that it doesn't take
 # priority over our other configurations.
$ sudo mv /etc/nginx/sites-enabled/{default,99_default}

Installing Git, Supervisord and uWSGI

$ sudo apt-get install -y build-essential git-core

$ sudo apt-get install -y supervisor
$ sudo apt-get install -y uwsgi uwsgi-plugin-python python-uwsgidecorators

Creating Deploy / App user

You might want to change password from password to something more applicable ;)

$ sudo adduser --disabled-password --gecos "" deploy

$ sudo passwd deploy <<EOF
password
password
EOF

echo "Adding deploy user to sudoers"
sudo tee -a /etc/sudoers <<EOF
deploy  ALL=(ALL) NOPASSWD:ALL
EOF

Auto-magic deploy script

The script below is derived from [3].

Script summary: scipt creates folder layout, configures NGINX site, updates supervisod config and setups Git repository with post-receive hook to perform re-deploy on push magic.

Script

Script usage / Deploying

Get the script.

$ cd /home/deploy
$ sudo -u deploy wget "https://raw.github.com/gist/3667663/create_project.sh"
$ sudo -u deploy chmod +x create_project.sh

Login as deploy user, e.g. su - deploy
Executing the script. Parameters: app name (theservice) and service domain name (yourdomain.com)

$ ./create_project.sh theservice yourdomain.com
 This script is intended to be run on a remote server, not on a local development environment. It will create a bunch of directories and change a bunch of configurations.
 Are you sure you want to continue? [y/N] y
 ...
  Setup your development clone as follows:
 
     git branch live
     git remote add -t live live ssh://[email protected]/home/deploy/repo/theservice
 
 Now you can deploy:
 
     git checkout live
     git merge master
     git checkout master
     git push live
 
 Or use this handy 'deploy' alias in your ~/.gitconfig file:
 
     deploy = "!merge(){ git checkout $2 && git merge $1 && git push $2 && git checkout ${1#refs/heads/}; }; merge $(git symbolic-ref HEAD) $1"
 
 So you can do (from 'master'):
 
     git deploy live
 
 Happy pushing!

Please follow the script instructions. When pushing please note: the script assumes folder layout is theservice/theservice.py and theservice.py exports Flask application as app. E.g.

# theservice.py file 
#...
app = flask.Flask(__name__)
#...

When application code has been pushed to server (following script recomendations) you should resolce app’s dependecies and do proper app’s configuration (db connections, etc ..)

 # this will install app dependencies
$ source ~/env/noimageyet/local/bin/activate
 # usual way to provide/install dependencies
$ pip install -r deploy/theservice/requirements.txt

 ## restart services
$ sudo service nginx restart
 # supervisor sometimes fails to reload via restart 
$ sudo service supervisor stop
$ sleep 3
$ sudo service supervisor start

Vuala part

We are done. Your service should be available at http://youdomain.com and http://www.youdomain.com.

Deploy part should be as easy as sample below

$ git add noimageyet.py && git commit -m 'the change'
 [master df78831] the change
  1 file changed, 1 insertion(+)
$ git deploy live
 Switched to branch 'live'
 Auto-merging noimageyet.py
 Merge made by the 'recursive' strategy.
  noimageyet.py |    1 +
  1 file changed, 1 insertion(+)
 [email protected]'s password:
 Counting objects: 10, done.
 Delta compression using up to 4 threads.
 Compressing objects: 100% (6/6), done.
 Writing objects: 100% (6/6), 625 bytes, done.
 Total 6 (delta 4), reused 0 (delta 0)
 remote: From /home/deploy/repo/noimageyet
 remote:  * branch            live       -> FETCH_HEAD
 remote: Restarting uwsgi.
 To ssh://[email protected]/home/deploy/repo/noimageyet
    c76aa28..cd59843  live -> live
 Switched to branch 'master'
 Your branch is ahead of 'origin/master' by 1 commit.

Profit

http://knowyourmeme.com/memes/profit

NB. If you've found typos or errors, please suggest a correction or edit on github.

Coding paradigm: line by line all my opinions are belong to me