[syslog-ng] Simple Doubt

Tom Le dottom at gmail.com
Wed Jun 6 18:18:02 CEST 2007

> > On 6/5/07, Alexander Clouter <ac56 at soas.ac.uk> wrote:
> > >
> > >If you are logging to a file and having Perl munch on a log file you
> can
> > >remove the perl script and pipe from the whole works.  syslog-ng can be
> > >configured to read in directly a log file; it effectively does a 'tail
> -f'
> > >on the file.
> >
> > Except for cases where you need the Perl script to post-process the log
> file
> > to produce a normalized or custom syslog message format.
> >
> Agreed, however a better design would be:
> <Log> ---> <Perl> ---> <Log2>
> <Log2> --[using 'tail' function]--> syslog-ng -> syslog-ng
> These would be disconnected and you would not run into any nasty problems.
> Another advantage being that if the perl code soaks up the CPU cycles and
> the
> logging is not urgent (needed at the final destination ASAP) you could
> nice
> down the priority of the process to prevent it stomping in on syslog-ng's
> performance.

But that scenario only supports logs that are "syslog friendly".  If you
have to do any kind of normalization or post-processing or dealing with
multi-line records in a log file, you have to use a post-processing process
such as Perl.  Not all logs have human-friendly readable text and the
post-processing Perl script can translate the log record into something more

The CPU cycles required by Perl parsing is minimal and is a common myth that
Perl is a CPU hog.  I have Perl scripts processing billions of log events
per week.
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