Instrumentation

Since 2.34.0

To enable ActiveSupport notifications, use the instrumentation_enabled option:

# config/application.rb
# Enable ActiveSupport notifications for all ViewComponents
config.view_component.instrumentation_enabled = true
config.view_component.use_deprecated_instrumentation_name = false

Setting use_deprecated_instrumentation_name configures the event name. If false the name is "render.view_component". If true (default) the deprecated "!render.view_component" will be used.

Subscribe to the event:

ActiveSupport::Notifications.subscribe("render.view_component") do |event| # or !render.view_component
  event.name    # => "render.view_component"
  event.payload # => { name: "MyComponent", identifier: "/Users/mona/project/app/components/my_component.rb" }
end

Viewing instrumentation sums in the browser developer tools

When using render.view_component with config.server_timing = true (default in development) in Rails 7, the browser developer tools display the sum total timing information in Network > Timing under the key render.view_component.

Viewing instrumentation breakdowns in rack-mini-profiler

The rack-mini-profiler gem is a popular tool for profiling rack-based Ruby applications.

To profile ViewComponent rendering alongside views and partials:

# config/environments/development.rb
# Profile rendering of ViewComponents
Rack::MiniProfilerRails.subscribe("render.view_component") do |_name, start, finish, _id, payload|
  Rack::MiniProfilerRails.render_notification_handler(
    Rack::MiniProfilerRails.shorten_identifier(payload[:identifier]),
    finish,
    start
  )
end