virtualenv-tools 1.0

– 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.