Re: librados option 'conf' and 'cluster'.

[Josh Durgin <jdurgin@redhat.com>]

On 01/20/2016 06:26 AM, Javen Wu wrote:
> Hi Sage,
>
> I have a quick fixing and will run more testing before post code review.
> The change would be restricted to the config parsing.
>
> With the fixing (hacking) ;)
> 1. When only configuration file is given, cluster name would be the
> prefix of
> the basename of conf file.
> 2. When both configuration file and cluster name are given, both
> arguments are
> respected.
> 3. When only cluster name is given, configuration file would be
> /etc/ceph/$cluster.conf.
>
> With the change,
> 1. openstack cinder-volume rbd driver

1.5 libvirt

> 2. qemu rbd driver
> 3. all consumers of rados_create()
> would be able to support the CEPH clusters not being named 'ceph'
> without change.

I think it's a good idea. It definitely needs to be documented in the
release notes, since it could potentially cause trouble if someone had:

- named their conf file something other than ceph (e.g. 
/etc/ceph/myfriendlyceph.conf)
- named their keyrings with the ceph cluster name, e.g. 
/etc/ceph/ceph.client.images.keyring

We could fall back to using 'ceph' as the cluster name for keyrings if
the 'basename' version isn't found to handle that case, but that
doesn't seem like it's worth the trouble, and might just cause more
confusion.

In the common case I think it would be harmless.

Josh

> Sage Weil wrote:
>> On Mon, 18 Jan 2016, Javen Wu wrote:
>>> Hi buddies,
>>>
>>> Recently, I met a problem about librados option 'conf' and 'cluster'.
>>> I created a CEPH cluster but not name it 'ceph', it triggers a lot of
>>> problems
>>> on my openstack environment.
>>> I found there are consumers of librados or librados python binding only
>>> respect
>>>   'conf' option. However, the option 'cluster' is ignored usually.
>>>
>>> So far, I suffered the problem in:
>>> 1. librados python binding
>>> 2. qemu rbd driver
>>> 3. cinder volume rbd driver
>>>
>>> I saw there is rados_create2() API in librados besides
>>> rados_create(), but
>>> it seems the API is not widedly used by consumers yet.
>>>
>>> I am thinking whether we can do a compromise in librados. If
>>> consumers of
>>> librados does not give an arguments for 'cluster'(cluster name)
>>> explicitly,
>>> Can we use (basename(conffile).split('.conf')[0]) as cluster name by
>>> default in librados?
>>>
>>> So that all consumers of the librados can tolerate the non-'ceph'
>>> cluster name
>>> without any change.
>>>
>>> How do you guys think? If you agree to the change, I can do the quick
>>> fixing.
>> This would be a bit of a hack, but it seems reasonable enough to me--I
>> can't think of anything that would break as a result.
>>
>> Josh, what do you think?  The logic it could even be restricted to the
>> client side only...
>>
>> sage
>>
>
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