Log "tear-off" mechanism

[Carter Bullard]

Hey Peter,
   Thanks, I forgot to mention that we closed the
datafile, before creating the new one, which is of
course very important.

Carter



> -----Original Message-----
> From: owner-argus-info at lists.andrew.cmu.edu 
> [mailto:owner-argus-info at lists.andrew.cmu.edu] On Behalf Of 
> Peter Van Epp
> Sent: Tuesday, June 17, 2003 11:01 AM
> To: argus-info at lists.andrew.cmu.edu
> Subject: Re: Log "tear-off" mechanism
> 
> 
> 	While reading the source or waiting for Carter to 
> comment would be 
> best, as I recall argus stats the output file and when the 
> stat changes (as
> when the file gets renamed) closes and reopens the logfile 
> (using the file name
> it was given on invocation to open the new logfile) while 
> puffing its cheeks up 
> in memory with the current data until the new logfile is open 
> and writable to.
> 	For your watchdog what you want to do is have the 
> argusarchive script
> write the current time when it renames the log file in to a 
> file. When your
> watchdog wakes up and finds the output file missing it looks 
> for the file
> from argusarchive, reads the time that the change was made 
> and uses the 
> elapsed time to see if there is a problem or not (if 
> insufficient time has 
> elapsed to be sure there is a problem, sleep for a while and 
> check again to
> see if a new logfile has been created). Once a new logfile is 
> running the 
> watchdog deletes the file created by argusarchive ready for 
> the next log roll.
> 
> Peter Van Epp / Operations and Technical Support 
> Simon Fraser University, Burnaby, B.C. Canada
> 
> 
> On Tue, Jun 17, 2003 at 08:40:21AM -0400, John Hermes wrote:
> > Howdy,
> > 
> > I am hoping someone might be able to help me understand how
> > Argus deals with having the open logfile pulled out from under
> > the daemon (using the argusarchive script for example). If you
> > could decribe it in terms of file descriptors and pointers,
> > that would be most helpful. For instance, does Argus get
> > an I/O error and create a new file in response? Why does the
> > OS (Linux, FreeBSD, etc.) allow me to move an open file? Why
> > can't I remember this stuff from college? :-)
> > 
> > I have a watchdog daemon that I configured to stat the
> > logfile on a continuous basis, and now I need to write a
> > compatible monitor that won't mind that the file is missing
> > for the few seconds before Argus creates a new logfile. Any
> > info related to moving open files would be a great help!
> > 
> > Thanks!
> > 
> > -- 
> > John Hermes
> > Systems Engineer
> > Infoglobe, Inc
> > 937-225-9999 x317
> > 937-226-1623 Fax
> > jhermes at infoglobe.com
>