Subject: RE: append writes (con't)

From: "Noveck, Dave" <[email-masked]>
Date: Fri, 16 Mar 2001 14:16:23 -0800

Spencer Shepler wrote: 
> On Fri, Noveck, Dave wrote:
> >  
> > > On Fri, Noveck, Dave wrote:
> > 
> > > > The question is whether multiple processes appending to a log file
> > > > belongs in that class.  I don't think it does.  That is why people
> > > > keep trying to solve it.  The problem isn't that it is an
> > > 
> > > "people" refers to customers or system vendors?
> > 
> > In this case, "people" refers to engineers, who work for system
> > vendors.  System vendors are usually corporations and not people, 
> > although I'm sure there are exceptions.
>
> So there must be a customer somewhere that wants this if engineers are
> spending their time on this difficult problem.  It would be nice to
> know about the customers and what they are attempting to accomplish.

People write log files for many reasons.  All OS's that I know of
have an append mode for this very purpose.  It would be very inconvenient
for each process to have it's own log due to the volume of files and
the fact that you would have to post-process to get any coherent
view.  This is why OS's typically allow multiple processes to write,
in append mode, to the same file with a coherent result, on local
file systems.  What are the customers that use this feature trying to
accomplish?  Just get their work done without wasting time doing 
something complex.  They prefer to have a facility that makes their
life simple.

In a networked environment the same hold true.  To have to log 
application data based on the machine on which the process executed
is undesirable.  You can program around this and some people have
but it is clearly not desirable and anybody who has to kludge
around this would certainly choose to spend his time otherwise.

---

From: Spencer Shepler <[email-masked]>
Date: Fri, 16 Mar 2001 16:31:34 -0600

> People write log files for many reasons.  All OS's that I know of

So you don't have specific instances of customers that have lamented
about the lack of append mode writes on a distributed filesystem?

> something complex.  They prefer to have a facility that makes their

So let's talk about the client APIs for a moment.  For this to work,
the NFS client agent will need to force each write() to the server for
the append.  That is different than current behavior and it may be
considered too much of a performance burden for applications that are
not writing to a log that is shared amongst various systems.  So how
does the application indicate its true desire about O_APPEND.

> around this would certainly choose to spend his time otherwise.

It seems much easier to write an open-source library that provides a
distributed logging mechanism and corresponding aggregation
methodology.  Maybe something like the syslog service.

-- 

- Spencer -