Hi,
we are using cloud-init to do the VM host contextualization (ie: set the
right hostname). For this to work we need proper OpenStack metadata, for
instance we'd like the public-hostname to default to the DNS resolved
public-ipv4 (or ipv6, if present).
Right now the default behaviour is that public-hostname is the same as
the hostname and the local-hostname, which is the user-defined instance
name. I'm not sure if current behaviour is a bug or a feature, but I'd
expect public-hostname to be related to public-ipv4.
Maybe we're missing something obvious or doing something wrong, are we?
If not, is there any way we can setup OpenStack (NOVA?) to setup the
public-hostname metadata to the resolved public-ipv4 name automatically
for each VM?
Thanks,
Gerard Bernabeu
FermiCloud and FermiGrid Services at Fermilab
Phone (+1) 630-840-6509
On 09/15/2013 07:54 PM, laclasse wrote:
Agreed, unique FQDNs on every instances is still a big issue for
common workloads, hopefully solved by DNS services coming to OpenStack
soon... I fully agree that the instance name and the FQDN of the
instances should be 2 separate things, and even better, I think
instances by default should try a reverse lookup first when they get
on the network, and if available, collect a hostname, set it locally
and display it in an additional column in the DB/tables/webUI, and
allows OpenStack services clients to use either instance ID, name or
hostname.
What the OP is trying to do is also feasible by installing a bind
service somewhere on the same subnet (bind9 minimum) and using the
$GENERATE directive in your zone file, see here on how to write your
zone file using that directive:
http://www.oit.uci.edu/dcslib/bind/bind-9.2.1/Bv9ARM.ch06.html#AEN4097
FWIW, AWS EC2 has a simple iterator that composes a unique hostname to
any instance by parsing the public IP address, replacing '.' (dots)
with '-' (to make it viable in a long hostname) and adding
prefix/suffix to compose the hostname (compute zones and domain) with
added dots for example: "ec2-54-211-89-105.co
<http://ec2-54-211-89-105.co>mpute-1.amazonaws.com
<http://mpute-1.amazonaws.com>" is an instance with IP 54.211.89.105
... it a simple and useful solution. You can check it yourself:
$ host 54.211.89.105
105.89.211.54.in-addr.arpa domain name pointer
ec2-54-211-89-105.compute-1.amazonaws.com
<http://ec2-54-211-89-105.compute-1.amazonaws.com>.
Not having a unique FQDN on cloud instances can break many apps, and
DNS services in IaaS should not be taken for granted (failure may
happen), so IMHO, the best approach should be:
- boot instance, get on the network, do a reverse look up on IP to see
if a DNS server answers with a FQDN , collect it and set it
- if the look up fails, then resort to the iterator running and still
end up with an unique hostname per instance.
It seems a lot of public services hide this issue by allowing to
launch only one instance at the time, but AFAIK, if you launch several
instances at once using the nova CLI, you will end up with ALL
instances having the same hostname (which is the instance name you
have given to nova CLI) ... which breaks so many things it is not
funny ... and is generally not a good idea or best practices either.
If this functionality lands (very soon we hope), it will obviously
also allows users to deal with hostnames directly rather than IP
address, which in 2013, could give an archaic and
old fashioned unfinished impression to users.
Cheers, sorry for the mini-rant but I would think this is one of the
most urgent issues to address to see real automation and large scale apps.
On Sun, Sep 15, 2013 at 12:39 PM, Tim Bell <tim.b...@cern.ch
<mailto:tim.b...@cern.ch>> wrote:
I don’t think there is a formal exit inside OpenStack to do this.
You may have to make a small patch to Nova.
It would be an interesting feature to define a plug-in
architecture for this which would have several other uses.
Tim
> -----Original Message-----
> From: Francesco Ceccarelli [mailto:cecca...@fnal.gov
<mailto:cecca...@fnal.gov>]
> Sent: 14 September 2013 20:40
> To: Tim Bell
> Cc: openstack@lists.openstack.org
<mailto:openstack@lists.openstack.org>
> Subject: Re: [Openstack] openstack meta-data
>
> Hello,
> thanks for the help! I hadn't seen the command in the
documentation, this can be helpful.
> BTW my problem is to update metadata every time a machine is
launched.
> For example let's talk about the hostname. Every time I launch a
machine, I would like to have well-configured metadata, with the
> parameter public-hostname already set to a customized value. I
don't want the instance name as public-hostname.
>
> I hope I was clear and thanks again for the help, Francesco
>
>
>
> On Sat, 2013-09-14 at 07:18 +0000, Tim Bell wrote:
> > You can update the metadata associated with an instance using
the 'nova meta' command. However, this only updates the metadata
> (i.e.
> > key value pairs) rather than the other attributes.
> >
> > Changing the server name would not alter the hostname of the
VM, it would only alter the description in Nova.
> >
> > Can you explain a little more what you would like to be doing ?
> >
> > Tim
> >
> > > -----Original Message-----
> > > From: Francesco Ceccarelli [mailto:cecca...@fnal.gov
<mailto:cecca...@fnal.gov>]
> > > Sent: 14 September 2013 00:11
> > > To: openstack@lists.openstack.org
<mailto:openstack@lists.openstack.org>
> > > Subject: [Openstack] openstack meta-data
> > >
> > > Is it possible to update instance meta-data, for example to
set the public hostname?
> > >
> > > Thanks in advance,
> > > Francesco
> > >
> > >
> > > _______________________________________________
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