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Deploy Your Environment - using fabric and a whole lot of fairly generic pre-written functions
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README.md

DYE

UNSTABLE SOFTWARE

Please be aware that DYE is not stable yet - it is a rework of our internal deployment scripts to make them easier to reuse, and the rework is a work in progress. Please have a play, test against your dev server and give us feedback. But don't download and immediately run against your production server.

DYE is a bacronym for "Deploy Your Environment" - a set of scripts and functions to deploy your web app along with the required python libraries in a virtualenv, either locally or on a remote server. It is built on fabric. It is most well developed for Django web apps, but we have used it for PHP projects aswell.

You can create a compatible project using cookiecutter - see readme-cookiecutter.rst for details.

Expected Project Structure

A bare bones project structure would be:

/apache                    <- contains config files for apache, for different servers
    staging.conf
    production.conf
/deploy                    <- contains settings and scripts for deployment
    bootstrap.py
    fab.py
    localfab.py            <- optional
    localtasks.py          <- optional
    pip_packages.txt       <- list of python packages to install
    project_settings.py
    tasks.py
    ve_mgr.py
/django
    /website               <- top level for Django project
        manage.py          <- a modified version of manage.py - see examples/
        .ve/               <- contains the virtualenv
        local_settings.py  <- a link to the real local_settings.py.env
        local_settings.py.dev
        local_settings.py.staging
        local_settings.py.production
        manage.py          <- our modified version
        private_settings.py   <- generated by these scripts
        settings.py        <- this will import local_settings.py
        urls.py
/wsgi                      <- holds WSGI handler
    wsgi_handler.py

A certain amount of the directory structure can be overridden in project_settings.py but that is not well tested currently.

Tasks.py

tasks.py is designed to make it easy to get your development environment up and running easily. Once the project is set up, getting going should only require:

cd deploy
./bootstrap.py
./tasks.py deploy:dev
cd ../django/django_project
./manage.py runserver

bootstrap.py will create the virtualenv and install the python packages required

tasks.py deploy:dev will:

  • generate a .private_settings.py. (random database password and Django secret key)
  • link to one of your local_settings files (selects database etc)
  • init and update git submodules (if any)
  • create the database (if using MySQL at least) and run syncdb and migrations

Your Django application will then be good to go.

tasks.py includes a number of other tasks that should make your life easier. It also makes it easy to add your own tasks and integrate them into the deploy task by using:

localtasks.py

This is a file where you can define your own functions to do stuff that you need for your project. You can also override functions from tasklib.py simply by defining a function with the same name as the function in tasklib.py

You can override the main deploy() function, but you might lose out if the deploy function starts to do more. Generally a better strategy is to define a post_deploy() function - when you run ./tasks.py deploy then after the other tasks have completed it will check if there is a function called post_deploy() in localtasks.py and if so it will call it.

manage.py and bootstrap.py

We use a modified version of manage.py that knows about the virtualenv in the .ve/ directory. So when you run manage.py it will automatically relaunch itself inside the virtualenv, so you don't have to worry about activating/deactivating.

It also knows about the list of packages in pip_packages.txt - if that is updated without the virtualenv being updated (or if the virtualenv doesn't exist) then manage.py will complain. You can then create/update the virtualenv with:

../../deploy/bootstrap.py

Note that this will only update the virtualenv if it's required, though you can use --force to do it anyway. Also note that by default it will only update the packages that need updating - use --full-rebuild to force it to delete the virtual env and then rebuild. To see all options use --help.

Fabric and DYE

We have developed a set of fabric functions for our standard project layout. In order to avoid violating the DRY principle, we delegate the work to tasks.py where possible. Our standard fab deploy will:

  • check if you have made any local changes to the server. If it finds any it will alert you to them and give you the choice of whether to continue or not.
  • if using git it will check the branch set in project_settings.py, the branch currently on the server and the branch you are currently on locally. If there is a mismatch it will ask you to confirm what branch you want to use.
  • create a copy of the current deploy in a directory called next/ - or create the directory on the server (if this is the first deploy)
  • checkout or update the project from your repository (git, svn and CVS currently supported). It uses the next/ directory so that your running website is unaffected.
  • remove all *.pyc files. (If x.py is removed by your VCS but x.pyc remains, then as far as python is concerned, x.py is still present).
  • ensure the virtualenv is created and packages installed (as bootstrap.py does)
  • unlink the webserver config and reload the web server (effectively turning off the site)
  • do a database dump in the current directory
  • move the current directory to a subdirectory of previous so that a rollback can occur, and then move next/ to where the current directory is.
  • call tasks.py deploy - which ensures settings are ready and does all the database related stuff.
  • relink the webserver config and reload the web server (effectively turning on the site again)
  • delete excess copies in previous/ (by default 5 copies are retained).

As with tasks.py you can add extra functions and override the default behaviour by putting functions in:

localfab.py

Server Directory Structure

Dye will create /var/django/project_name and in that directory will be:

dev/           <- contains the checked out code
previous/      <- copies for rollback, with directories named by timestamp

During a deploy there will also be:

next/         <- only temporary

You can override the project root with the server_home variable in project_settings.py

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