diff options
Diffstat (limited to 'actionview/lib/action_view/renderer/streaming_template_renderer.rb')
-rw-r--r-- | actionview/lib/action_view/renderer/streaming_template_renderer.rb | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/actionview/lib/action_view/renderer/streaming_template_renderer.rb b/actionview/lib/action_view/renderer/streaming_template_renderer.rb new file mode 100644 index 0000000000..3ab2cd36fc --- /dev/null +++ b/actionview/lib/action_view/renderer/streaming_template_renderer.rb @@ -0,0 +1,103 @@ +require 'fiber' + +module ActionView + # == TODO + # + # * Support streaming from child templates, partials and so on. + # * Integrate exceptions with exceptron + # * Rack::Cache needs to support streaming bodies + class StreamingTemplateRenderer < TemplateRenderer #:nodoc: + # A valid Rack::Body (i.e. it responds to each). + # It is initialized with a block that, when called, starts + # rendering the template. + class Body #:nodoc: + def initialize(&start) + @start = start + end + + def each(&block) + begin + @start.call(block) + rescue Exception => exception + log_error(exception) + block.call ActionView::Base.streaming_completion_on_exception + end + self + end + + private + + # This is the same logging logic as in ShowExceptions middleware. + # TODO Once "exceptron" is in, refactor this piece to simply re-use exceptron. + def log_error(exception) #:nodoc: + logger = ActionView::Base.logger + return unless logger + + message = "\n#{exception.class} (#{exception.message}):\n" + message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code) + message << " " << exception.backtrace.join("\n ") + logger.fatal("#{message}\n\n") + end + end + + # For streaming, instead of rendering a given a template, we return a Body + # object that responds to each. This object is initialized with a block + # that knows how to render the template. + def render_template(template, layout_name = nil, locals = {}) #:nodoc: + return [super] unless layout_name && template.supports_streaming? + + locals ||= {} + layout = layout_name && find_layout(layout_name, locals.keys) + + Body.new do |buffer| + delayed_render(buffer, template, layout, @view, locals) + end + end + + private + + def delayed_render(buffer, template, layout, view, locals) + # Wrap the given buffer in the StreamingBuffer and pass it to the + # underlying template handler. Now, every time something is concatenated + # to the buffer, it is not appended to an array, but streamed straight + # to the client. + output = ActionView::StreamingBuffer.new(buffer) + yielder = lambda { |*name| view._layout_for(*name) } + + instrument(:template, :identifier => template.identifier, :layout => layout.try(:virtual_path)) do + fiber = Fiber.new do + if layout + layout.render(view, locals, output, &yielder) + else + # If you don't have a layout, just render the thing + # and concatenate the final result. This is the same + # as a layout with just <%= yield %> + output.safe_concat view._layout_for + end + end + + # Set the view flow to support streaming. It will be aware + # when to stop rendering the layout because it needs to search + # something in the template and vice-versa. + view.view_flow = StreamingFlow.new(view, fiber) + + # Yo! Start the fiber! + fiber.resume + + # If the fiber is still alive, it means we need something + # from the template, so start rendering it. If not, it means + # the layout exited without requiring anything from the template. + if fiber.alive? + content = template.render(view, locals, &yielder) + + # Once rendering the template is done, sets its content in the :layout key. + view.view_flow.set(:layout, content) + + # In case the layout continues yielding, we need to resume + # the fiber until all yields are handled. + fiber.resume while fiber.alive? + end + end + end + end +end |