Re: [Ganglia-developers] spoofing heartbeats with gmetric broken in 3.1

[Carlo M. A. B. <ca...@sa...>]

On Tue, Oct 28, 2008 at 12:25:18PM -0600, Brad Nicholes wrote:
> >>> On 10/28/2008 at 3:39 AM, in message <20081028093904.GA12156@tapir>, Carlo
> Marcelo Arenas Belon <ca...@sa...> wrote:
> 
> > 2) is spoofing healthchecks really needed?, considering that the last update
> >    from the spoofed host will be updated anyway by the metric report?

the use here of "healthcheck" is incorrect, the issue is for "heartbeats" as
detailed in the subject.

> The health check needs to be there mainly so that the heartbeat metric shows up for the spoofed box in the XML.

every time a spoofed metric is sent, the "REPORTED" value for the host that is
being spoofed will be updated, which is AFAIK the whole point of the
"heartbeat" message anyway.

the "REPORTED" value is tied to the host and not to any specific metric which
is where the term "heartbeat metric" doesn't really fit for a model where the
spoofing is a METRIC attribute instead.

> Once the module spoofing functionality has been accepted for backport, I have an example python module that spoofs the base information such as heartbeat, location, boottime, etc.  By just adding this module, you get all of the spoofed base metrics.

interesting; could that be the reason why while testing gmetric spoofing in
trunk the "GMOND_STARTED" value was apparently getting updated?

haven't yet tracked that bug, as I wanted to focus in the 3.1 code first, but
that is also a regression as it will prevent anyone to identify which hosts
are being spoofed through it (which was one of Yemi's concerns when this was
introduced around 3.0.4)

> > 3) even if using some METADATA with the metric code to indicate the 
> > SPOOF_HOST between gmetric and gmond is that EXTRA_ELEMENT needed in the gmond XML?
> 
> I'm not sure I understand the question.  The EXTRA_ELEMENT XML tag is used because spoofing is an extension to the standard metric data just like TITLE and GROUP.

right; before there was no XML interface because spoofing was being done at
the XDR level, but my concern was directed at why the EXTRA_ELEMENT for
"SPOOF_HOST" was visible from the XML exported from gmond when it has been
already processed and it is indeed redundant.

it is also strange IMHO that the SPOOF_HEARTBEAT doesn't show if the intention
was to keep those EXTRA_ELEMENT in gmond after they were processed.

> The only way to do without the EXTRA_ELEMENT tag would be to rework the standard tags to include some kind of spoofing attribute.

there are already standard XDR tags for spoofing (at least in 3.0) which could
be most likely reused for this if needed, but then I am confused of what the
rationale was behind using instead EXTRA_ELEMENT tag with 3.1 if using XDR was
possible after the XDR refactoring.

Carlo