logrotate(8) and copytruncate as default

[P J P]

   Hello Jan,

----- Original Message -----
> From: Jan Kaluža <jkaluza at redhat.com>
> Subject: Re: logrotate(8) and copytruncate as default
> 
> I'm not sure right now if the benefits of the "copytruncate" usage are 
> strong enough in comparison with the possibility to lost the messages 
> during rotation.

   I did a small experiment to test how much data loss would incur in copy-truncate.
First command constantly writes to a file. While the second one uses an
exclusive lock to temporarily halt the write operation, do a copy, truncate and
release the exclusive lock so that the write continues where it was stopped.


===
$ cd /tmp/exp/

# Following command continuously writes to a file.
#

$ (count=0; while(true); do count=`expr $count + 1`;  \
    echo `date "+%d %a %Y %T"` $count; done >> test.log &)

# Following command uses exclusive lock to halt the write

# operation, perform copy-truncate, and release the lock.
#

$ flock -x test.log -c 'cp test.log test.log.1; > test.log'

$

$ 

$ tail -n -4 test.log.1
27 Thu 2013 21:14:14 7317
27 Thu 2013 21:14:14 7318
27 Thu 2013 21:14:14 7319
27 Thu 2013 21:14:14 7320
$ head -n 4 test.log
27 Thu 2013 21:14:14 7321
27 Thu 2013 21:14:14 7322
27 Thu 2013 21:14:14 7323
27 Thu 2013 21:14:14 7324

===


As can be seen above, there does not seem to be any data loss at all.


Thank you.

---
Regards
   -Prasad
http://feedmug.com