= SPRINKLE

http://redartisan.com/2008/5/27/sprinkle-intro
http://github.com/crafterm/sprinkle

== DESCRIPTION:

Sprinkle is a software provisioning tool you can use to build remote servers with, after the base operating
system has been installed. For example, to install a Rails or Merb stack on a brand new slice directly after
its been created.

Properties of packages such as their name, type, dependencies, etc, and what packages apply to what machines
is described via a domain specific language that Sprinkle executes (in fact one of the aims of Sprinkle is to
define as concisely as possible a language for installing software).

An example package description follows:

    package :ruby do
      description 'Ruby Virtual Machine'
      version '1.8.6'
      source "ftp://ftp.ruby-lang.org/pub/ruby/1.8/ruby-#{version}-p111.tar.gz"
      requires :ruby_dependencies
      
      verify do
        has_file '/usr/bin/ruby'
      end
    end

This defines a package called 'ruby', that uses the source based installer to build Ruby 1.8.6 from source,
installing the package 'ruby_dependencies' beforehand. Additionally, the package verifies it was installed
correctly by verifying the file '/usr/bin/ruby' exists after installation. If this verification fails, the
sprinkle script will gracefully stop.

Reasonable defaults are set by sprinkle, such as the install prefix, download area, etc, but can be customized
globally or per package (see below for an example).

Since packages come in many forms (eg. gems, pre-compiled debs, compressed source tar.gz, etc), Sprinkle supports
many different installer types, giving you the most amount of flexibility of how you'd like software installed.
New installer types can be added into the system easily.

For example, you could install Rails via gems, nginx via source, and mysql via APT, while retaining the flexibility
of changing installer types as software is updated upstream.

Sprinkle also supports dependencies between packages, allowing you specify pre-requisites that need to be
installed in order.

Packages can be grouped into polices to define several packages that should be installed together.

An example policy:

    policy :rails, :roles => :app do
      requires :rails, :version => '2.1.0'
      requires :appserver
      requires :database
      requires :webserver
    end

This defines a policy called Rails, that applies to machines of role :app. The policy includes the packages
rails (version 2.1.0), appserver, database and webserver.

appserver, database and webserver can be virtual packages, where the user will be prompted for selection if
multiple choices for the virtual package exist.

Sprinkle is architected to be extendable in many ways, one of those areas is in its deployment of commands to
remote hosts. Currently Sprinkle supports the use of Capistrano or Vlad to issue commands on remote hosts via ssh,
but could also be extended to use any other command transport mechanism or be used to simply issue installation
commands on the local system.

An full example Sprinkle deployment script for deploying Rails (via gems), MySQL (via APT), and Apache (via source):

    # Sprinkle Rails deployment script
    #
    # This is an example Sprinkle script, configured to install Rails from gems, Apache and Ruby from source,
    # and mysql from apt on an Ubuntu system. Installation is configured to run via Capistrano (and
    # an accompanying deploy.rb recipe script). Source based packages are downloaded and built into
    # /usr/local on the remote system.
    #
    # A sprinkle script is separated into 3 different sections. Packages, policies and deployment.
    #
    # Packages
    #
    #  Defines the world of packages as we know it. Each package has a name and
    #  set of metadata including its installer type (eg. apt, source, gem, etc). Packages can have
    #  relationships to each other via dependencies
    #
    # Policies
    #
    #  Names a group of packages (optionally with versions) that apply to a particular set of roles.
    #
    # Deployment
    #
    #  Defines script wide settings such as a delivery mechanism for executing commands on the target
    #  system (eg. capistrano), and installer defaults (eg. build locations, etc).

    # Packages

    package :ruby do
      description 'Ruby Virtual Machine'
      version '1.8.6'
      source "ftp://ftp.ruby-lang.org/pub/ruby/1.8/ruby-#{version}-p111.tar.gz"
      requires :ruby_dependencies
    end

    package :ruby_dependencies do
      description 'Ruby Virtual Machine Build Dependencies'
      apt %w( bison zlib1g-dev libssl-dev libreadline5-dev libncurses5-dev file )
    end

    package :mysql, :provides => :database do
      description 'MySQL Database'
      apt %w( mysql-server mysql-client )
    end

    package :apache, :provides => :webserver do
      description 'Apache 2 HTTP Server'
      version '2.2.9'
      source "http://apache.wildit.net.au/httpd/httpd-#{version}.tar.bz2" do
        enable %w( mods-shared=all proxy proxy-balancer proxy-http rewrite cache headers ssl deflate so )
        prefix "/opt/local/apache2-#{version}"
        post :install, 'install -m 755 support/apachectl /etc/init.d/apache2', 'update-rc.d -f apache2 defaults'
      end
      requires :apache_dependencies
    end

    package :apache_dependencies do
      description 'Apache 2 HTTP Server Build Dependencies'
      apt %w( openssl libtool mawk zlib1g-dev libssl-dev )
    end

    package :rubygems do
      description 'Ruby Gems Package Management System'
      version '1.2.0'
      source "http://rubyforge.org/frs/download.php/38646/rubygems-#{version}.tgz" do
        custom_install 'ruby setup.rb'
      end
      requires :ruby
    end

    package :rails do
      description 'Ruby on Rails'
      gem 'rails'
      version '2.1.0'
    end

    package :mongrel do
      description 'Mongrel Application Server'
      gem 'mongrel'
      version '1.1.5'
    end

    package :mongrel_cluster, :provides => :appserver do
      description 'Cluster Management for Mongrel'
      gem 'mongrel_cluster' # :source => 'http://gems.github.com/' for alternate gem server
      version '1.0.5'
      requires :mongrel
    end

    # Policies

    # Associates the rails policy to the application servers. Contains rails, and surrounding
    # packages. Note, appserver, database and webserver are all virtual packages defined above. If
    # there's only one implementation of a virtual package, it's selected automatically, otherwise
    # the user is requested to select which one to use.

    policy :rails, :roles => :app do
      requires :rails, :version => '2.1.0'
      requires :appserver
      requires :database
      requires :webserver
    end

    # Deployment

    # Configures sprinkle to use capistrano for delivery of commands to the remote machines (via
    # the named 'deploy' recipe). Also configures 'source' installer defaults to put package gear
    # in /usr/local

    deployment do

      # mechanism for deployment
      delivery :capistrano do
        recipes 'deploy'
      end

      # source based package installer defaults
      source do
        prefix   '/usr/local'           # where all source packages will be configured to install
        archives '/usr/local/sources'   # where all source packages will be downloaded to
        builds   '/usr/local/build'     # where all source packages will be built
      end

    end

Please see the examples directory for more complete examples of Sprinkle deployment scripts.

Sprinkle is a work in progress and I'm excited to hear if anyone finds it useful - please feel free to
comment, ask any questions, or send in any ideas, patches, bugs. All most welcome.

Marcus Crafter <[email protected]>

== LICENSE:

(The MIT License)

Copyright (c) 2008 Marcus Crafter <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
'Software'), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.