install the pg gem into sensu's ruby installation

pg_gem.rb

# Super hacky way to get the pg gem installed into Sensu's ruby installation.
# Ripped off from https://github.com/hw-cookbooks/postgresql/blob/develop/recipes/ruby.rb
# Credit to chrisroberts for this

gem_installed = system("/opt/sensu/embedded/bin/ruby -e \"require 'pg'\"")
pg_gem_version = '0.18.3'

unless gem_installed
  Chef::Log.warn('pg gem is not installed in the sensu ruby installation. Installing it')

  g = gem_package 'pg' do
    version pg_gem_version
    gem_binary '/opt/sensu/embedded/bin/gem'
    ignore_failure true
  end
  g.run_action(:install)

  if platform_family?('ubuntu', 'debian')
    e = execute 'apt-get update' do
      action :nothing
    end
    e.run_action(:run) unless ::File.exist?('/var/lib/apt/periodic/update-success-stamp')
  end

  node.set['build-essential']['compile_time'] = true
  include_recipe 'build-essential'
  include_recipe 'postgresql::client'

  if node['postgresql']['enable_pgdg_yum']
    repo_rpm_url, repo_rpm_filename, repo_rpm_package = pgdgrepo_rpm_info
    include_recipe 'postgresql::yum_pgdg_postgresql'
    resources("remote_file[#{Chef::Config[:file_cache_path]}/#{repo_rpm_filename}]").run_action(:create)
    resources("package[#{repo_rpm_package}]").run_action(:install)
    ENV['PATH'] = "/usr/pgsql-#{node['postgresql']['version']}/bin:#{ENV['PATH']}"
  end

  if node['postgresql']['enable_pgdg_apt']
    include_recipe 'postgresql::apt_pgdg_postgresql'
    resources('file[remove deprecated Pitti PPA apt repository]').run_action(:delete)
    resources('apt_repository[apt.postgresql.org]').run_action(:add)
  end

  node['postgresql']['client']['packages'].each do |pg_pack|
    resources("package[#{pg_pack}]").run_action(:install)
  end

  # Still here, must be omnibus. Lets make this thing install!
  Chef::Log.warn 'Failed to properly build pg gem. Forcing properly linking and retrying (omnibus fix)'
  gem_dir = File.join('/opt/sensu/embedded/lib/ruby/gems/2.0.0/gems', 'pg-' + pg_gem_version)
  fail unless gem_dir
  gem_name = File.basename(gem_dir)
  ext_dir = File.join(gem_dir, 'ext')
  gem_exec = '/opt/sensu/embedded/bin/gem'
  new_content = <<-EOS
require 'rbconfig'
%w(
configure_args
LIBRUBYARG_SHARED
LIBRUBYARG_STATIC
LIBRUBYARG
LDFLAGS
).each do |key|
  RbConfig::CONFIG[key].gsub!(/-Wl[^ ]+( ?\\/[^ ]+)?/, '')
  RbConfig::MAKEFILE_CONFIG[key].gsub!(/-Wl[^ ]+( ?\\/[^ ]+)?/, '')
end
RbConfig::CONFIG['RPATHFLAG'] = ''
RbConfig::MAKEFILE_CONFIG['RPATHFLAG'] = ''
  EOS

  extconf_path = File.join(ext_dir, 'extconf.rb')
  if File.exist?(extconf_path)
    new_content << File.read(extconf_path)
    File.open(extconf_path, 'w') do |file|
      file.write(new_content)
    end

    lib_builder = execute 'generate pg gem Makefile' do
      # [COOK-3490] pg gem install requires full path on RHEL
      command "PATH=$PATH:/usr/pgsql-#{node['postgresql']['version']}/bin /opt/sensu/embedded/bin/ruby extconf.rb"
      cwd ext_dir
      action :nothing
    end
    lib_builder.run_action(:run)

    lib_maker = execute 'make pg gem lib' do
      command 'make'
      cwd ext_dir
      action :nothing
    end
    lib_maker.run_action(:run)

    lib_installer = execute 'install pg gem lib' do
      command 'make install'
      cwd ext_dir
      action :nothing
    end
    lib_installer.run_action(:run)

    spec_installer = execute 'install pg spec' do
      command "#{gem_exec} spec ./cache/#{gem_name}.gem --ruby > ./specifications/#{gem_name}.gemspec"
      cwd File.join(gem_dir, '..', '..')
      action :nothing
    end
    spec_installer.run_action(:run)

    Chef::Log.warn 'Installation of pg gem successful!'
  end
end