Open Stack

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.compute-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.

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.Bell at 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:ceccarel at fnal.gov]
> > Sent: 14 September 2013 20:40
> > To: Tim Bell
> > Cc: openstack at 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:ceccarel at fnal.gov]
> > > > Sent: 14 September 2013 00:11
> > > > To: openstack at 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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> >
>
>
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