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Whiskey Disk: embarrassingly fast deployments.
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README.markdown

Whiskey Disk -- embarrassingly fast deployments.

A very opinionated deployment tool, designed to be as fast as technologically possible. (For more background, read the WHY.txt file) Should work with any project which is git hosted, not just Ruby / Ruby on Rails projects. Allows for local deploys as well as remote.

Right-arrow through a short whiskey_disk presentation at http://wd2010.rickbradley.com/ (slide source available here.), covering the 0.2.*-era functionality.

Selling points

  • If you share the same opinions as we do there's almost no code involved, almost no dependencies, and it uses stock *nix tools (ssh, bash, rsync) to get everything done.

  • Written completely spec-first for 100% coverage. We even did that for the rake tasks, the init.rb and the plugin install.rb (if you swing that way).

  • 1 ssh connection per run -- so everything needed to do a full setup is done in one shot. Everything needed to do a full deployment is done in one shot. (Having 8 minute deploys failing because I was on CDMA wireless on a train in india where the connection won't stay up for more than 2-3 minutes is not where I want to be any more.)

  • Deployment configuration is specified as YAML data, not as code. Operations to perform after setup or deployment are specified as rake tasks.

  • You can do local deployments, by this I mean you can use whiskey_disk to deploy fully running instances of your application to the same machine you're developing on. This turns out to be surprisingly handy (well, I was surprised). NOTE: be sure to set your deploy_to to a place other than the current local checkout.

  • You can do multi-project deployments, specifying deployment data in a single deploy.yml config file, or keep an entire directory of project deployment config files.

  • You can separate per-deployment application configuration information (e.g., passwords, database configs, hoptoad/AWS/email config data, etc.) in separate repositories from the application, and whiskey_disk will merge the correct data onto the deployed application at deployment time.

  • You can have per-developer configurations for targets (especially useful for "local" or "development" targets). Use .gitignore, or specify a config_branch and everyone can have their own local setup that just works.

  • There's no before_after_before_after hooks. You've got plenty of flexibility with just a handful of rake hook points to grab onto.

  • You can enable "staleness checks" so that deployments only happen if either the main repo, or the config repo (if you're using one) has changes that are newer than what is currently deployed.

  • Put whiskey_disk in a cron, with staleness checks enabled, and you can do hands-free automated deployments whenever code is pushed to your deployment branch of choice!

Dependencies

rake, ssh, git, rsync on the deployment target server (affectionately referred to as the "g-node" by vinbarnes), bash-ish shell on deployment server.

Assumptions

  • your project is managed via git
  • you are deploying over ssh, or deploying locally and have a bash-compatible shell
  • you are comfortable defining (optional) post-setup and post-deployment actions with rake
  • you have an optional second git repository for per-application/per-target configuration files
  • you have an optional Rakefile in the top directory of your project's checkout

Installation

As a gem:

% gem install whiskey_disk

As a rails plugin:

% script/plugin install git://github.com/flogic/whiskey_disk.git

Configuration

  • look in the examples/ directory for sample configuration files
  • main configuration is in <app_root>/config/deploy.yml
  • config files are YAML, with a section for each target.

Known config file settings (if you're familiar with capistrano and vlad these should seem eerily familiar):

domain:            host on which to deploy (this is an ssh connect string) 
deploy_to:         path to which to deploy main application
repository:        git repo path for main application
branch:            git branch to deploy from main application git repo (default: master)
deploy_config_to:  where to deploy the configuration repository
config_repository: git repository for configuration files
config_branch:     git branch to deploy from configuration git repo (default: master)
project:           project name (used to compute path in configuration checkout)
rake_env:          hash of environment variables to set when running post_setup and post_deploy rake tasks

A simple config/deploy.yml might look like:

qa:
  domain: "ogc@www.ogtastic.com"
  deploy_to: "/var/www/www.ogtastic.com"
  repository: "git@ogtastic.com:www.ogtastic.com.git"
  branch: "stable"
  rake_env:
    RAILS_ENV: 'production'
  • defining a deploy:<target>:post_setup rake task (e.g., in lib/tasks/ or in your project's Rakefile) will cause that task to be run at the end of deploy:setup

  • defining a deploy:<target>:post_deploy rake task (e.g., in lib/tasks/ or in your project's Rakefile) will cause that task to be run at the end of deploy:now

Running via rake

In your Rakefile:

require 'whiskey_disk/rake'

Then, from the command-line:

% rake deploy:setup to=<target>   (e.g., "qa", "staging", "production", etc.)
% rake deploy:now   to=<target>

or, specifying the project name:

% rake deploy:setup to=<project>:<target>   (e.g., "foo:qa", "bar:production", etc.)
% rake deploy:now   to=<project>:<target>

Running from the command-line

% wd setup --to=<target>
% wd setup --to=<project>:<target>
% wd setup --to=foo:qa --path=/etc/whiskey_disk/deploy.yml

% wd deploy --to=<target>
% wd deploy --to=<project>:<target>
% wd deploy --to=foo:qa --path=/etc/whiskey_disk/deploy.yml

Note that the wd command (unlike rake, which requires a Rakefile in the current directory) can be run from anywhere, so you can deploy any project, working from any path, and can even specify where to find the deployment YAML configuration file.

The --path argument can take either a file or a directory. When given a file it will use that file as the configuration file. When given a directory it will look in that directory for deploy/<project>/<target>.yml, then deploy/<project>.yml, then deploy/<target>.yml, then <target>.yml, and finally, deploy.yml.

All this means you can manage a large number of project deployments (local or remote) and have a single scripted deployment manager that keeps them up to date. Configurations can live in a centralized location, and developers don't have to be actively involved in ensuring code gets shipped up to a server. Win.

A note about post__{setup,deploy} Rake tasks

If you want actions to run on the deployment target after you do a whiskey_disk setup or whiskey_disk deploy, you will need to make sure that whiskey_disk is available on the target system (either by gem installation, as a rails plugin in the Rails application to be deployed, or as a vendored library in the application to be deployed). Whiskey_disk provides the basic deploy:post_setup and deploy:post_deploy hooks which get called. You can also define these tasks yourself if you want to eliminate the dependency on whiskey_disk on the deployment target system.

Staleness checks

Enabling staleness checking will cause whiskey_disk to check whether the deployed checkout of the repository is out of date ("stale") with respect to the upstream version in git. If there is a configuration repository in use, whiskey_disk will check the deployed checkout of the configuration repository for staleness as well. If the checkouts are already up-to-date the deployment process will print an up-to-date message and stop rather than proceeding with any of the deployment actions. This makes it easy to simply run whiskey_disk out of cron so that it will automatically perform a deployment whenever changes are pushed to the upstream git repositories.

To turn on staleness checking, simply set the 'check' environment variable:

check='yes' wd deploy --to=foobar:production

Configuration Repository

What's all this about a second repository for configuration stuff?

This is completely optional, but we really are digging this, so maybe you should try it. Basically it goes like this...

We have a number of web applications that we manage. Usually there's a customer, there might be third-party developers, or the customer might have access to the git repo, or their designer might, etc. We also tend to run a few instances of any given app, for any given customer. So, we'll run a "production" site, which is the public- facing, world-accessible main site. We'll usually also run a "staging" site, which is roughly the same code, maybe the same data, running on a different URL, which the customer can look at to see if the functionality there is suitable for deploying out to production. We sometimes run a "development" site which is even less likely to be the same code as production, etc., but gives visibility into what might end up in production one day soon.

So we'll store the code for all of these versions of a site in the same git repo, typically using a different remote branch for each target ("qa", "production", "staging", "development").

One thing that comes up pretty quickly is that there are various files associated with the application which have more to do with configuration of a running instance than they have to do with the application in general. In the rails world these files are probably in config, or config/initializers/. Think database connection information, search engine settings, exception notification plugin data, email configuration, Amazon S3 credentials, e-commerce back-end configuration, etc.

We don't want the production site using the same database as the development site. We don't want staging using (and re-indexing, re-starting, etc.) production's search engine server. We don't want any site other than production to send account reset emails, or to push orders out to fulfillment, etc.

For some reason, the answer to this with cap and/or vlad has been to have recipes which reference various files up in a shared area on the server, do copying or symlinking, etc. Where did those files come from? How did they get there? How are they managed over time? If they got there via a configuration tool, why (a) are they not in the right place, or (b) do we have to do work to get them into the right place?

So, we decided that we'd change how we deal with the issue. Instead of moving files around or symlinking every time we deploy, we will manage the configuration data just like we manage other files required by our projects -- with git.

So, each project we deploy is associated with a config repo in our git repository. Usually many projects are in the same repo, because we're the only people to see the data and there's no confidentiality issue. But, if a customer has access to their git information then we'll make a separate config repo for all that customers' projects. (This is easier to manage than it sounds if you're using gitosis, btw.)

Anyway, a config repo is just a git repo. In it are directories for every project whose configuration information is managed in that repo. For example, there's a "larry" directory in our main config repo, because we're deploying the larry project to manage our high-level configuration data.

Note, if you set the 'project' setting in deploy.yml, that determines the name of the top-level project directory whiskey_disk will hunt for in your config repo. If you don't it uses the 'repository' setting (i.e., the git URL) to try to guess what the project name might be. So if the URL ends in foo/bar.git, or foo:bar.git, or /bar, or :bar, whiskey_disk is going to guess "bar". If it's all bitched up, just set 'project' manually in deploy.yml.

Inside the project directory is a directory named for each target we might deploy to. Frankly, we've been using "production", "staging", "development", and "local" on just about everything.

Inside the target directory is a tree of files. So, e.g., there's config/, which has initializers/ and database.yml in it.

Long story short, load up whatever configuration files you're using into the repo as described, and come deployment time exactly those files will be overlaid on top of the most recent checkout of the project. Snap.

project-config/
  |
  +---larry/
        |
        +---production/
        |     |
        |     +---config/
        |           |
        |           +---initializers/
        |           |
        |           +---database.yml
        |
        +---staging/
        |     |
        |     |
        |     +---config/
        |           |
        |           ....
        |
        +---development/
        |     |
        |     +---config/
        |           |
        |           ....
        |
        +---local/
              |
              +---config/
                    |
                    ....

More Examples:

Future Directions

Check out the TODO.txt file to see what we have in mind for the near future.

Resources

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