thread_safe_locale_switching

⚙️ Thread-Safe Dynamic Locale Switching

On multi‑threaded servers (Puma/Unicorn), set per‑request locale without leaking it across threads. Use an around_action to wrap requests, falling back to the default locale in ensure.

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  around_action :switch_locale

  private

  def switch_locale(&action)
    locale = params[:locale] || request.headers['Accept-Language']&.scan(/^[a-z]{2}/)&.first
    I18n.with_locale(locale || I18n.default_locale, &action)
  end
end

This approach uses I18n.with_locale, which is thread-safe and guarantees the locale resets after the block, avoiding bleed into other requests.