[Xymon] FreeBSD Actual Memory Usage

[Jeremy Laidman]

On 5 December 2013 01:09, <henrik at hswn.dk> wrote:

> The way Xymon reports memory handling is very much due to historical
> events - how it was done in Big Brother. I agree that the
> "one-size-fits-all" approach in the current code is not the best way of
> doing it, unless your OS happens to nicely fit into the real+actual+swap
> metrics mold.
>
I think many OSes do fit that mold these days.  Those that do not can
probably be fudged to do a useful approximation of either real+actual+swap
or actual+swap.  In most cases, the slightly nebulous "actual" number is
all we care about (vs total RAM), as sysadmins who just want to know why
our servers are misbehaving.

So while more data points would be better, perfect is the enemy of good,
and currently there are no useful memory numbers for some OSes.  I don't
believe it would take much to add a few more OSes into the list of those
supported.

But I think there are two goals here.  One is to get "actual" memory
included - that is, raise the usefulness above zero, which would be
infinitely better; the other is to get all available metrics into Xymon to
be available for analysis.  I think the first of these goals needs just a
few minor tweaks, mostly in unix_memory_report().  The second is a much
more daunting task, because of the diversity of OSes, and this is where an
alternative to unix_memory_report() might be warranted.

> You can also send data into an RRD file with a different layout, so you
> can have more data. Getting that rrd-graph to show up on a "memory" status
> is the tricky part, and right now I would recommend that you simply use a
> different name for the memory status.
>
I think the "memory" status should show the simpler set of memory stats
(including "active" if available).  If other memory stats are available,
these should only be shown in trends.

>  So it is not an un-solvable problem, but someone needs to figure out just
> how the memory metrics can be found by the client code, and how it should
> be interpreted over on the Xymon server.
>
Yes.  And for that reason, I think the complex option might never be
completed for most, if not all OSes.  It might be better handled by custom
server-side scripts that people can implement depending on their
requirements.  For this to work, only the Xymon client needs to be
enhanced, to report the numbers.

Let me re-iterate that I'm not complaining about any part of Xymon, and
fully appreciate the difficulties in collecting useful memory data from
heterogeneous systems and presenting them in a uniform and consistent way.
 I think the design of Xymon - even despite being somewhat an "evolved"
beast - is excellent.  So what I'm trying to do is to enhance Xymon in a
way that's consistent with the current architecture and future direction.

Henrik, I'm happy to do much, if not all, of the work to mod client and/or
server code to support these enhancements.  However, I'd like to be
confident that it fits with your future directions for memory monitoring,
and avoid adding yet another data collection method hacked into Xymon, that
gets used by a shrinking minority of installs.  Can you provide guidance on
the best way to implement these features (or not)?  I'm proposing that I/we:

1) Enhance the Xymon client to also send "active" memory usage, for FreeBSD
and any other OSes that can do this.  Also update the Xymon server to
recognise the presence of "active", and make use of it in the same way that
it currently does for Linux.  The client data would be in the form of an
enhanced [meminfo] section of the client message.  (This could use the
already-used-by-Linux [free] section, or the [memory] section used by
bbwin, hpux, osf and solaris; or it could be a completely new section name,
which would not be my preference).

2) Enhance the Xymon client to send the full range of OS-specific memory
metrics available, included in the [meminfo] (or other) section, to apply
to FreeBSD and any other OSes that can do this.  This would allow for
server-side extension scripts to query the [meminfo] client data and create
RRD files as required.  This would provide the _opportunity_ for Xymon to
support parsing and reporting on these metrics, but this could be developed
by champions of each OS who wanted the feature and knew enough to interpret
what the numbers actually mean.

Cheers
Jeremy
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