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Message-ID: <20100115131522.GK28498@discord.disaster>
Date: Sat, 16 Jan 2010 00:15:22 +1100
From: Dave Chinner <david@...morbit.com>
To: Mike Mestnik <cheako911@...il.com>
Cc: Andreas Dilger <adilger@....com>,
Al Viro <viro@...iv.linux.org.uk>,
Toshiyuki Okajima <toshi.okajima@...fujitsu.com>,
Theodore Ts'o <tytso@....edu>, linux-fsdevel@...r.kernel.org,
linux-ext4@...r.kernel.org,
"James C. Browne" <browne@...utexas.edu>
Subject: Re: [REPOST][PATCH][RFC] vfs: add message print mechanism for the
mount/umount into the VFS layer
On Fri, Jan 15, 2010 at 05:44:01AM -0600, Mike Mestnik wrote:
> On Fri, Jan 15, 2010 at 5:02 AM, Dave Chinner <david@...morbit.com> wrote:
> > On Thu, Jan 14, 2010 at 11:36:25PM -0500, Andreas Dilger wrote:
> >> On 2010-01-14, at 20:24, Dave Chinner wrote:
> >>> On Thu, Jan 14, 2010 at 10:33:42AM -0500, Andreas Dilger wrote:
> >>>> Sure, it is _possible_ to do this, but you miss the fact that there
> >>>> are
> >>>> many system monitoring tools that already scrape /var/log/messages
> >>>> and
> >>>> integrate with event managers. What you are suggesting is that every
> >>>> such tool implement an extra, completely ad-hoc mechanism just for
> >>>> monitoring the mount/unmount of filesystems on Linux. That doesn't
> >>>> make
> >>>> sense.
> >>>
> >>> We already report various events through a netlink interface, but not
> >>> to the log files (e.g. quota warnings), so those system monitoring
> >>> tools are already going to be missing interesting information.
> >>>
> >>> Using log files for system event notification used to be the only
> >>> way to communicate such events. Now we have much more advanced and
> >>> efficient mechanisms for notifications so I think we should use
> >>> them.
> > ....
> >> However, there are many reasons why it still makes sense to do this:
> >> - it is in plain text format. I can't recall the number of times
> >> people were proposing crazy schemes to have a text interface to the
> >> kernel (via /sys/blah, or /debugfs/blah) for things that are much
> >> better suited to an ioctl, since they are largely handled by binaries
> >> (applications), yet in the case where we have an existing plain-text
> >> interface (dmesg and /var/log/messages) that are meant (at least
> >> partly) for human consumption we are proposing a binary interface
> >> - every system monitoring tool in existence has a /var/log/messages
> >> scraping interface, because this is the lowest common denominator,
> >> but I'd suspect that few/none have a netlink interface, or if they
> >> do it probably can't be easily added to by a user
> >
> > A daemon that captures the events from netlink and writes them to
> > syslog is all that is needed to support log file scraping
> > monitoring tools. The message they scrape does not have to come from
> > the kernel...
> >
> klogd. Do we need another wheel?
That's just another syslog implementation for directing printk
messages to files. It's not an event notification framework.
Cheers,
Dave.
--
Dave Chinner
david@...morbit.com
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