fireteam / Virtualenv Tools

-- virtualenv-tools

 This repository contains scripts we're using at Fireteam for our
 deployment of Python code.  We're using them in combination with
 salt to build code on one server on a self contained virtualenv
 and then move that over to the destination servers to run.

 Why not virtualenv --relocatable?

   For starters: because it does not work.  relocatable is very
   limited in what it does and it works at runtime instead of
   making the whole thing actually move to the new location.  We
   ran into a ton of issues with it and it is currently in the
   process of being phased out.

 Why would I want to use it?

   The main reason you want to use this is for build caching.  You
   have one folder where one virtualenv exists, you install the
   latest version of your codebase and all extensions in there, then
   you can make the virtualenv relocate to a target location, put it
   into a tarball, distribute it to all servers and done!

 Example flow:

   First time: create the build cache

     $ mkdir /tmp/build-cache
     $ virtualenv --distribute /tmp/build-cache

   Now every time you build:

     $ . /tmp/build-cache/bin/activate
     $ pip install YourApplication

   Build done, package up and copy to whatever location you want to have
   it.

   Once unpacked on the target server, use the virtualenv tools to
   update the paths and make the virtualenv magically work in the new
   location.  For instance we deploy things to a path with the
   hash of the commit in:

     $ virtualenv-tools --update-path /srv/your-application/<hash>

   To also update the Python executable in the virtualenv to the
   system one you can reinitialize it in one go:

     $ virtualenv-tools --reinitialize /srv/your-application/<hash>


 Compile once, deploy whereever.  Virtualenvs are completely self
 contained.  In order to switch the current version all you need to
 do is to relink the builds.