How to disable logging for ActiveStorage's Disk Service routes

In development, we store files using ActiveStorage's disk service. This means that stored files are served by your Rails application, and every request to a file results in (at least!) one non-trivial log entry which can be annoying. Here is how to disable those log entries.

Example

Here is an example of what loading a single <img> in an example application writes to the Rails log.

Started GET "/rails/active_storage/blobs/redirect/..." for ::1 at ...
Processing by ActiveStorage::Blobs::RedirectController#show as SVG
  Parameters: ...
  ActiveStorage::Blob Load (0.4ms)  SELECT "active_storage_blobs".* FROM "active_storage_blobs" ...
  Disk Storage (0.4ms) Generated URL for file at key: ... (http://localhost:3000/rails/active_storage/disk/...)
Redirected to http://localhost:3000/rails/active_storage/disk/...
Completed 302 Found in 18ms (ActiveRecord: 0.4ms (1 query, 0 cached) | GC: 13.3ms)

Started GET "/rails/active_storage/disk/..." for ::1 at ...
Processing by ActiveStorage::DiskController#show as SVG
  Parameters: ...
Completed 200 OK in 1ms (ActiveRecord: 0.0ms (0 queries, 0 cached) | GC: 0.0ms)

I never care about anything from those requests. It's all happening inside ActiveStorage anyway, and I don't want its noise to distract me from looking at my application's logs.

Especially when rendering a page with many images, this produces an annoying amount of irrelevant rows in my Rails log.

Here are two options to reduce that noise.

Option 1: Silencing logging inside ActiveStorage controller actions

If you want to silence only ActiveStorage::Blob Load or Generated URL for file at key log entries, silence logging in any ActiveStorage controller action like so.

Rails.application.config.to_prepare do
  ActiveStorage::BaseController.around_action do |_controller, block|
    Rails.logger.silence(&block)
  end
end

This will still log all requests from above, but at least avoid ActiveStorage's ActiveRecord loading or URL generation lines.

Option 2: Completely silencing logging for ActiveStorage routes

If you want to silence ActiveStorage requests completely, you need to replace the Rails::Rack::Logger middleware. It's the one that writes the Started GET "/rails/active_storage/disk/..." lines to your log.

This sounds harder than it is. We basically just want a version of it that silences logging for ActiveStorage routes, so we can write it as follows.

class RackLoggerWithSilencedActiveStorageRoutes < Rails::Rack::Logger
  def call(env)
    if env['PATH_INFO']&.start_with?("#{Rails.configuration.active_storage.routes_prefix}/")
      Rails.logger.silence do
        super
      end
    else
      super
    end
  end
end

Rails.configuration.middleware.swap(Rails::Rack::Logger, RackLoggerWithSilencedActiveStorageRoutes)

Put that into an initializer or similar, and wrap with if Rails.env.development?, if necessary.