Forwardプラグインで投げるときにホスト名を追加する

out_forward_with_hostname.rb

#
# Forward with hostname
#
# harukasan <harukasan@pixiv.com>
#
# == configure
#   key (optional):: キー名(default: host)
#

class ForwardWithHostnameOutput < Fluent::ForwardOutput
  Fluent::Plugin.register_output('forward_with_hostname', self)

  config_param :host_key, :string, :default => 'host'

  def start
    @hostname = `hostname`.strip

    super
  end

  def emit(tag, es, chain)
    es.each do |time, record|
      record[@host_key] = @hostname
    end
    super(tag, es, chain)
  end
end