Add cache control headers to assets

[code-bunny]

The assets controller as it currently works by streaming the file:

def show
  @asset = Maglev::Asset.find(resource_id)
  send_data @asset.download, filename: @asset.filename, type: @asset.content_type
end

This results in cache-control: max-age=0, private, must-revalidate

The most sensible fix is to respect the config.public_file_server.headers set by in the Rails environment.

I suggest something like below

def show
  @asset = Maglev::Asset.find(resource_id)
  send_data @asset.download, filename: @asset.filename, type: @asset.content_type

  cache_control = Rails.configuration.public_file_server.headers["cache-control"]
  if cache_control && cache_control.match(/max-age=(\d+)/)
    max_age = Regexp.last_match(1).to_i
    expires_in max_age.seconds, public: true
  end
end

[code-bunny]

For now I am using the following in app/overrides/controllers/maglev/assets_controller_override.rb

Maglev::AssetsController.class_eval do
  def show
    @asset = Maglev::Asset.find(resource_id)
    send_data @asset.download, filename: @asset.filename,
                               type: @asset.content_type,
                               disposition: "inline"

    cache_control = Rails.configuration.public_file_server.headers["cache-control"]
    if cache_control && cache_control.match(/max-age=(\d+)/)
      max_age = Regexp.last_match(1).to_i
      expires_in max_age.seconds, public: true
    end
  end
end

[did]

You're absolutely right. I've read (again) https://guides.rubyonrails.org/active_storage_overview.html#putting-a-cdn-in-front-of-active-storage and I believe we should use it instead. It'll save your cache issue.

[code-bunny]

That would indeed be the best solution and would save ballooning costs for people using S3.