Error tracking tools and "let it crash" philosophy

Assuming correct configuration, sentry or app signal wont see those errors, as they have been handled by other means.

Those error trackers/aggregators are to give you insight into errors that haven’t been handled, or that have been sent to the tracker explicitely.

Sentry (and I’m assuming most error tracking services) allow you to filter errors before they’re sent to the 3rd party service.

You can set up your own custom filter with Sentry, as documented here.

But even without any special configuration on your part, Sentry will by default use essentially the following filter (seen here). You can see that it ignores exceptions of type Phoenix.Router.NoRouteError as well as a few others.

defmodule Sentry.DefaultEventFilter do
  @behaviour Sentry.EventFilter

  @ignored_exceptions [Phoenix.Router.NoRouteError] # …others included here, too

  def exclude_exception?(%x{}, :plug) when x in @ignored_exceptions do
    true
  end

  # …etc.
end

This should all happen in memory and be quite efficient, so I don’t imagine it being a big concern from a DDoS standpoint.