If I understand what you are asking, you could run the risk of downloading and parsing the same log twice. To avoid it I suggest this:

• Each time you download a log, calculate its MD5 checksum and save it.
• when you download a new log after a minute, calculate its checksum and compare with the last one: if they are the same wait some seconds and then repeat
• when you find them different, discard the old checksum and save the new one, then parse the log

To calculate the checksum you could use the md5sum command that you may have on your system (if you are running a Unix), or directly use Digest::MD5

I hope this helps

Update: matija is right, go his way if you have a chance!