Notifier when FTP Polling starts to read a file

Hi! I'm trying to audit a route which starts with *from("ftp:*)*. The
objetive is to log (in another class) when the FTP Consumer detect a file
and the consumer start to process the FIle (move or delete, or anything).

My first approach is to create a Notifier and process the exchanges, but i
don't know if intercepting the ExchangeSendingEvent is the correct way. When
I intercept that exchange is when the consumer is sending the exchange when
it finish to process the file.

Is there another event to make this possible? Or should I use an
interceptor?