class ParallelInstaller

def self.call(*args) 

def self.call(*args)
  new(*args).call
end

def self.max_threads

Returns max number of threads machine can handle with a min of 1 
def self.max_threads
  [Bundler.settings[:jobs].to_i - 1, 1].max
end

def call 

def call
  enqueue_specs
  process_specs until @specs.all?(&:installed?)
ensure
  worker_pool && worker_pool.stop
end

def collect_post_install_message(spec) 

def collect_post_install_message(spec)
  Bundler::Installer.post_install_messages[spec.name] = spec.post_install_message
end

def enqueue_specs

are installed.
previously installed specifications. We continue until all specs
Later we call this lambda again to install specs that depended on
We enqueue all gem specs that do not have any dependencies.
Keys in the remains hash represent uninstalled gems specs. 
def enqueue_specs
  @specs.select(&:ready_to_enqueue?).each do |spec|
    if spec.dependencies_installed? @specs
      worker_pool.enq spec
      spec.state = :enqueued
    end
  end
end

def initialize(installer, all_specs, size, standalone, force) 

def initialize(installer, all_specs, size, standalone, force)
  @installer = installer
  @size = size
  @standalone = standalone
  @force = force
  @specs = all_specs.map {|s| SpecInstallation.new(s) }
end

def process_specs

dequeue.
processed so the call to `enqueue_specs` is important after every
Some specs might've had to wait til this spec was installed to be
remaining specs.
Dequeue a spec and save its post-install message and then enqueue the 
def process_specs
  spec = worker_pool.deq
  spec.state = :installed
  collect_post_install_message spec if spec.has_post_install_message?
  enqueue_specs
end

def worker_pool 

def worker_pool
  @worker_pool ||= Bundler::Worker.new @size, "Parallel Installer", lambda { |spec_install, worker_num|
    message = Bundler::GemInstaller.new(
      spec_install.spec, @installer, @standalone, worker_num, @force
    ).install_from_spec
    spec_install.post_install_message = message unless message.nil?
    spec_install
  }
end