EM-Swirl

Swirl is an evented EC2 version agnostic client for EC2 written in Ruby. It gets out of your way.

The secret is it's simple input extraction and output compacting. Your input parameters and expanded and EC2's (terrible) xml output is compacted.

Some simple examples:

# Input
{ "InstanceId" => ["i-123k2h1", "i-0234d3"] }

is expanded to:

{ "InstanceId.0" => "i-123k2h1", "InstanceId.1" => "i-0234d3" }

in the case that .n isn't at the end of the key:

{ "Foo.#.Bar" => ["a", "b"] }

is expanded to:

{ "Foo.0.Bar" => "a", "Foo.1.Bar" => "b" }

and

# Output
{
  "reservationSet" => {
    "item" => {
      "instancesSet" => { "item" => [ ... ] }
    }
  }
}

and it's variations are now compacted to:

{ "reservationSet" => { "instancesSet" => [ { ... }, { ... } ] } }

Some things worth noting is that compact ignores Symbols. This allows you to pass the params into call and use them later without affecting the API call (i.e. chain of responsibility); a nifty trick we use in (Rack)[http://github.com/rack/rack]

Use

$ gem install em-swirl
$ vim something.rb


require 'em-swirl'

EM.run do
  ec2 = Swirl::EC2.new

  # Describe all instances
  ec2.call "DescribeInstances" do |reservation_set|
    p reservation_set
  end

  # Describe specific instances
  r = ec2.call "DescribeInstances", "InstanceId" => ["i-38hdk2f", "i-93nndch"] do |reservation_set|
    p reservation_set 
  end

  # Catch an error if the request gets one
  # NOTE:  If you don't catch errors, they will be swollowed
  r.error do |e|
    p e
  end

end

em-swirl

Runtime

EM-Swirl

Use