[ceph-users] removing cluster name support

Alfredo Deza adeza at redhat.com
Tue Nov 7 04:45:53 PST 2017

On Tue, Nov 7, 2017 at 7:09 AM, kefu chai <tchaikov at gmail.com> wrote:
> On Fri, Jun 9, 2017 at 3:37 AM, Sage Weil <sweil at redhat.com> wrote:
>> At CDM yesterday we talked about removing the ability to name your ceph
>> clusters.  There are a number of hurtles that make it difficult to fully
>> get rid of this functionality, not the least of which is that some
>> (many?) deployed clusters make use of it.  We decided that the most we can
>> do at this point is remove support for it in ceph-deploy and ceph-ansible
>> so that no new clusters or deployed nodes use it.
>> The first PR in this effort:
>>         https://github.com/ceph/ceph-deploy/pull/441
> okay, i am closing https://github.com/ceph/ceph/pull/18638 and
> http://tracker.ceph.com/issues/3253

This brings us to a limbo were we aren't supporting it in some places
but we do in some others.

It was disabled for ceph-deploy, but ceph-ansible wants to support it
still (see:  https://bugzilla.redhat.com/show_bug.cgi?id=1459861 )

Sebastien argues that these reasons are strong enough to keep that support in:

- Ceph cluster on demand with containers
- Distributed compute nodes
- rbd-mirror integration as part of OSPd
- Disaster scenario with OpenStack Cinder in OSPd

The problem is that, as you can see with the ceph-disk PR just closed,
there are still other tools that have to implement the juggling of
custom cluster names
all over the place and they will hit some corner place where the
cluster name was not added and things will fail.

Just recently ceph-volume hit one of these places:

Are we going to support custom cluster names? In what
context/scenarios are we going to allow it?

>> Background:
>> The cluster name concept was added to allow multiple clusters to have
>> daemons coexist on the same host.  At the type it was a hypothetical
>> requirement for a user that never actually made use of it, and the
>> support is kludgey:
>>  - default cluster name is 'ceph'
>>  - default config is /etc/ceph/$cluster.conf, so that the normal
>> 'ceph.conf' still works
>>  - daemon data paths include the cluster name,
>>      /var/lib/ceph/osd/$cluster-$id
>>    which is weird (but mostly people are used to it?)
>>  - any cli command you want to touch a non-ceph cluster name
>> needs -C $name or --cluster $name passed to it.
>> Also, as of jewel,
>>  - systemd only supports a single cluster per host, as defined by $CLUSTER
>> in /etc/{sysconfig,default}/ceph
>> which you'll notice removes support for the original "requirement".
>> Also note that you can get the same effect by specifying the config path
>> explicitly (-c /etc/ceph/foo.conf) along with the various options that
>> substitute $cluster in (e.g., osd_data=/var/lib/ceph/osd/$cluster-$id).
>> Crap preventing us from removing this entirely:
>>  - existing daemon directories for existing clusters
>>  - various scripts parse the cluster name out of paths
>> Converting an existing cluster "foo" back to "ceph":
>>  - rename /etc/ceph/foo.conf -> ceph.conf
>>  - rename /var/lib/ceph/*/foo-* -> /var/lib/ceph/*/ceph-*
>>  - remove the CLUSTER=foo line in /etc/{default,sysconfig}/ceph
>>  - reboot
>> Questions:
>>  - Does anybody on the list use a non-default cluster name?
>>  - If so, do you have a reason not to switch back to 'ceph'?
>> Thanks!
>> sage
>> _______________________________________________
>> ceph-users mailing list
>> ceph-users at lists.ceph.com
>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> --
> Regards
> Kefu Chai
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