how to see if directory is sent

[Arichy]

hi, i am running a server with 30kb rate and burst and both orport and
dirport open. from time to time there is the message 

"directory_handle_command_get(): Client asked for the mirrored
directory, but we've been writing too many bytes lately. Sending 503
Dir busy."

in server info log. 

I would like to see how many times the directory is successfully sent.
What is the message for that that in the info log or how otherwise i
can see that ? 

because if most of the time there is no bandwidth left for
directory-traffic, i could(should?) turn dirport off.