Hi,
while looking at taking advantage of host spoofing a few things came
up that I'd like to discuss. Assuming that host spoofing can be used
for:
a) overriding host names because using PTRs can be a PITA depending on
the infrastructure (for example if you have tun/ethX prefixes)
b) streamlining appliances into ganglia
I see a problem of how to manage this "spoofed hosts collection" and
would love to see some kind of standard emerging.
/etc/ganglia/conf.d/spoofing.cfg could be added containing definitions
like:
spoofed_host {
hostname = spf1.example.org
ip = 10.0.0.0
metrics = disk_spoof, cpu_spoof
}
At this point metrics should read that file and figure out if they
should be doing any spoofing and if so for which hosts. Not sure about
C, but with the current python setup each module should include some
kind of lib to do that lookup, or maybe the approach should be changed
entirely.
One problem I see is with a) is treating every host as a spoofed host,
which might end up being confusing. Furthermore it's arguable that the
concept of spoofing isn't itself misleading, take this example:
- an host named myhost with a public and private interface
- the public one resolves to task.domain.tld while the internal to
int.task.domain.tld
- monitoring traffic is kept on the internal network
- as a result data is recorded and shows up as int.host.domain.tld
What I'm arguing here is that "int." could be considered spoofed since
the one the user is going to be thinking of is "task" and not int.task
or even that both are spoofed since the real host name is myhost. You
could blame it on poor naming and DNS practices, but I believe there
are legit examples where simply using the PTR to save data doesn't cut
it or whose result can be confusing. Imho much better would be to
allow the user to specify an arbitrary name, just use what hostname
unix command returns, and/or fallback on PTR.
So I guess what I'm asking here is: should this be accomplished with
host spoofing, maybe allowing a hostname = something in gmond.conf and
hiding it from the user or do people feel that PTR is The Way and if
you want otherwise you deal with it yourself using spoofing.cfg or
something like that?
On a related note, initially I believed the spoofing functionality to
be tied to the python modules, but then I noticed this in the STATUS
file:
* Allow both a C and python module to create a metric that will spoof a
specific host. This provides the same spoofing functionality as gmetric
but through a metric module. It is done by adding SPOOF_HOST and
SPOOF_NAME as extra metadata to the metric description
Based on that it should be possible to allow spoofing from the
standard C modules distributed with ganglia, correct? How would that
be done? I've looked at some of the existing metrics and noticed calls
to MMETRIC_ADD_METADATA, would that be it?
thanks
--
"Behind every great man there's a great backpack" - B.
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