```ruby
require "slimmer/headers"

class ApplicationController < ActionController::Base
  include Slimmer::Headers
  before_filter :set_analytics_headers

  rescue_from GdsApi::TimedOutException, :with => :error_503

protected

  def error_404; error(404); end
  def error_503(e = nil); error(503, e); end

  def error(status_code, exception = nil)
    render :status => status_code, :text => "#{status_code} error"
  end

  def set_analytics_headers
    set_slimmer_headers(format: "smart_answer")
  end

  def set_expiry(duration = 30.minutes)
    # if the artefact returned from the Content API is blank, or if
    # the request to the Content API fails, set a very short cache so
    # we don't cache an incomplete page for a while
    duration = 5.seconds if @presenter.present? and @presenter.artefact.blank?

    unless Rails.env.development?
      expires_in(duration, :public => true)
    end
  end
end
```

Call notify_airbrake from controller error method
user
```ruby
require "slimmer/headers"

class ApplicationController < ActionController::Base
  include Slimmer::Headers
  before_filter :set_analytics_headers

  rescue_from GdsApi::TimedOutException, :with => :error_503

protected

  def error_404; error(404); end
  def error_503(e = nil); error(503, e); end

  def error(status_code, exception = nil)
    if exception and defined? Airbrake
      env["airbrake.error_id"] = notify_airbrake(exception)
    end
    render :status => status_code, :text => "#{status_code} error"
  end

  def set_analytics_headers
    set_slimmer_headers(format: "smart_answer")
  end

  def set_expiry(duration = 30.minutes)
    # if the artefact returned from the Content API is blank, or if
    # the request to the Content API fails, set a very short cache so
    # we don't cache an incomplete page for a while
    duration = 5.seconds if @presenter.present? and @presenter.artefact.blank?

    unless Rails.env.development?
      expires_in(duration, :public => true)
    end
  end
end
```
assistant