実行されたmiddlewareをロギングしたい

config/initializers 配下に下記のファイルを設置する。

# Trace each middleware module entry/exit. Freely adapted from # https://github.com/DataDog/dd-trace-rb/issues/368 "Trace each middleware in the Rails stack" module MiddlewareTracer def call(env) Rails.logger.debug { "MiddleWare: entry #{self.class.name}" } status, headers, response = super(env) Rails.logger.debug { "MiddleWare: #{self.class.name}, returning with status #{status}" } [status, headers, response] end end # Instrument the middleware stack after initialization so that we # know the stack won't be changed afterwards. Rails.configuration.after_initialize do Rails.application.middleware.each do |middleware| klass = middleware.klass # There are a few odd middlewares that aren't classes. klass.prepend(MiddlewareTracer) if klass.respond_to?(:prepend) end end

出力例

06:54:05 app.1 | MiddleWare: entry Webpacker::DevServerProxy 06:54:05 app.1 | MiddleWare: entry Rack::Cors 06:54:05 app.1 | MiddleWare: entry Raven::Rack 06:54:05 app.1 | MiddleWare: entry ActionDispatch::HostAuthorization 06:54:05 app.1 | MiddleWare: entry Rack::Sendfile 06:54:05 app.1 | MiddleWare: entry ActionDispatch::Static ... 06:54:05 app.1 | MiddleWare: ActionDispatch::Static, returning with status 400 06:54:05 app.1 | MiddleWare: Rack::Sendfile, returning with status 400 06:54:05 app.1 | MiddleWare: ActionDispatch::HostAuthorization, returning with status 400 06:54:05 app.1 | MiddleWare: Raven::Rack, returning with status 400 06:54:05 app.1 | MiddleWare: Rack::Cors, returning with status 400 06:54:05 app.1 | MiddleWare: Webpacker::DevServerProxy, returning with status 400

ruby on rails - Trace Error in Rack Middleware - Stack Overflow