Mastermind

We need more than "ssh-in-a-for-loop". Our infrastructure get more complex every day and we need a tool that can choreograph an intricate dance of services, servers and commands in a manageable way.

Mastermind is an infrastructure orchestration engine. Its purpose is to provide the ability to compose and automate complex tasks with predefined and reproducible outcomes.

Mastermind uses a special domain-specific language for its process definitions, but if you're familiar with Ruby, it should feel right at home.

Using Mastermind

Here's an example of a basic sysadmin workflow, as implemented by Mastermind. Here, we create and destroy an EC2 instance, while notifying a Campfire room of each action performed.

definition = Definition.new({
  name: "create_and_destroy_ec2_server",
    content: %q{
    create_ec2_server image_id: '${image_id}',
      flavor_id: '${flavor_id}',
      key_name: '${key_name}',
      region: '${region}',
      availability_zone: '${availability_zone}',
      groups: '$f:groups', 
      tags: '$f:tags'

    # ${instance_id} is a field added by the `create_ec2_server` action
    notify_campfire message: "${instance_id} created!"

    destroy_ec2_server instance_id: '${instance_id}', region: '${region}'

    notify_campfire message: "${instance_id} destroyed!"
  }
})

job = Job.new({
  name: "new ec2 instance workflow",
  definition: "create_and_destroy_ec2_server",
  fields: {
    flavor_id: "t1.micro",
    image_id: "ami-fe5bd4ce",
    region: "us-west-2",
    availability_zone: "us-west-2a",
    key_name: "storm",
    groups: [ "default" ],
    tags: { 'Name' => "foo.example.com" }
  }
})

job.launch

Mastermind has four basic pieces: a job; a definition; a participant; and a target.

Job

A job is a template, tied to a definition. Jobs launch workflows.

Attributes

• name (String) - The name of the job.
• definition (String) - The name of the definition that this job will launch.
• fields (Hash) - The initial attributes used by the definition, and ultimately each participant.

Example job

job = Job.new({
  name: "do the needful",
  definition: "execute remote ssh",
  fields: {
    host: "db-master.example.com",
    user: "root",
    key_data: "-----BEGIN RSA PRIVATE KEY-----\n-----END RSA PRIVATE KEY-----"
    command: "rm -rf /"
  }
})

Definition

A definition is the workflow itself. It's the document that describes exactly what tasks will be performed, and in what order.

Attributes

• name (String) - The name of the definition.
• content (Array) - The process definition.

Dollar notation ${...}

Mastermind scans strings in process definition for ${...} placeholders and substitutes them for fields provided by the job or fields added by participants during the execution of the process. Any field interpolated by ${...} will be the string representation of the value. If the literal value of the field is needed (for instance, if a field holds an array of values), use the $f: notation instead.

Given the job fields:

{
  :name => "Dan Ryan",
  :titles => [ "Future Mayor of Lansing, MI", "Thoulght Leader" ]
}

The following definition...:

person :name => "${name}", :titles => "$f:titles"

...gets compiled to:

person :name => "Dan Ryan", :titles => [ "Future Mayor of Lansing, MI", "Thoulght Leader" ]

Example definition

Definition.new(
  :name => "standard syntax",
  :content => %q{
    run_ssh host:     '${host}',
            user:     '${user}',
            key_data: '${key_data}',
            command:  '${command}'
  }
).to_pdef

# => compiled definition
#
# ["define",
#  {"name"=>"watee"},
#  [["run_ssh",
#    {"host"=>"${host}",
#     "user"=>"${user}",
#     "key_data"=>"${key_data}",
#     "command"=>"${command}"},
#    []]]]

The previous example uses Ruby 1.9-style hash syntax. If you prefer the look of the "hash rocket", you are more than welcome to use it instead!

Definition.new(
  :name => "hash rockets",
  :content => %q{
    run_ssh :host     => '${host}', 
            :user     => '${user}', 
            :key_data => '${key_data}', 
            :command  => '${command}'
  }
).to_pdef

# => compiled definition
#
# ["define",
#  {"name"=>"watee"},
#  [["run_ssh",
#    {"host"=>"${host}",
#     "user"=>"${user}",
#     "key_data"=>"${key_data}",
#     "command"=>"${command}"},
#    []]]]

You can even mix in plain old Ruby if you're feeling adventurous!

hosts = %w( host1.example.com host2.example.com host3.example.com )

Definition.new(
  :name => "plain ol' ruby!",
  :content => %q{
    hosts = %w( host1.example.com host2.example.com host3.example.com )
    hosts.each do |host|
      run_ssh :host     => host, 
              :user     => '${user}', 
              :key_data => '${key_data}', 
              :command  => '${command}'
    end
  }
).to_pdef

# => compiled definition
#
# ["define",
#  {"name"=>"watee"},
#  [["run_ssh",
#    {"host"=>"host1.example.com",
#     "user"=>"${user}",
#     "key_data"=>"${key_data}",
#     "command"=>"${command}"},
#    []],
#   ["run_ssh",
#    {"host"=>"host2.example.com",
#     "user"=>"${user}",
#     "key_data"=>"${key_data}",
#     "command"=>"${command}"},
#    []],
#   ["run_ssh",
#    {"host"=>"host3.example.com",
#     "user"=>"${user}",
#     "key_data"=>"${key_data}",
#     "command"=>"${command}"},
#    []]]]

Participant

A participant is responsible for performing tasks as specified by the definition. There are many types of participants. A participant can provision a server, send notifications, or even execute remote commands.

Attributes

Participant attributes vary depending on their purpose.

Example participant

require 'net/ssh'

module Participant::Remote
  class SSH < Participant
    register :ssh
    
    action :run do
      requires :host, :user, :key_data, :command
      
      target.output = run_ssh(target.command)
      return {}
    end

    def run_ssh(command)
      session = Net::SSH.start(target.host, target.user, { key_data: target.key_data })
      output = nil

      session.open_channel do |ch|
        ch.request_pty
        ch.exec command do |ch, success|
          raise ArgumentError, "Cannot execute #{target.command}" unless success
          ch.on_data do |ichannel, data|
            output = data
          end
        end
      end

      session.loop
      session.close
      return output if output
    end
  end
end

Target

A target is the resource that the participant modifies. The target can have a variety of attributes, depending on the participant's needs. The target performs the majority of validations to ensure the participant has the right fields to execute its actions.

Attributes

Target attributes vary depending on their purpose.

Example target

# Modules are used as namespaces.
module Target::Remote

  # All targets inherit from Target
  class SSH < Target
  
    # We'll refer to this target elsewhere by the name we use to register it.
    register :ssh

    # Various attributes of the target. The :type option typecasts the attribute.
    attribute :command, type: String
    attribute :host, type: String
    attribute :user, type: String
    attribute :key_data, type: String  
    attribute :output, type: String
    
    # Validate the target to ensure we have the right details.
    validates! :command, :host, :user, :key_data,
      presence: true
  end
end

Dependencies

• Ruby >= 1.9.2
• Ruote
• PostgreSQL
• Redis

Mastermind uses PostgreSQL to store jobs and process definitions, Redis as a queue for workflow processes, and Ruote as the underlying "operating system" for workflow execution.

API

raise NotImplementedError, "Documentation coming soon!"

Custom participants/targets

raise NotImplementedError, "Documentation coming soon!"