Re: rbd tool changed format? (breaks compatibility)

[Constantinos Venetsanopoulos <cven@grnet.gr>]

On 11/16/2012 07:14 PM, Josh Durgin wrote:
> On 11/16/2012 06:36 AM, Constantinos Venetsanopoulos wrote:
>> Hello ceph team,
>>
>> As you may already know, our team in GRNET is building a complete open
>> source cloud platform called Synnefo [1], which already powers our
>> production public cloud service ~okeanos [2].
>>
>> Synnefo is using Google Ganeti for the low level VM management part [3].
>> As of Jan 2012, we have merged to upstream Ganeti support for VM disks
>> on RADOS [4].
>>
>> Today we received some feedback, that other people trying to run Ganeti
>> with RADOS get an error because probably the output of the 'rbd
>> showmapped' command has changed.
>>
>> I'd like to ask if indeed the output format of the rbd tool has changed.
>> More specifically:
>>
>> 1. Does the 'rbd showmapped' command still returns just the headers if
>> no device is mapped?
>
> No

Ack.

>
>
>> 2. Has the separator between the 'rbd showmapped' columns changed
>> from \t to ""?
>
> Yes, this is in the release notes for 0.54 
> (http://ceph.com/docs/master/release-notes/#v0-54).
>

Ack.

>> I don't have the latest rbd tool setup (but rather
>> ceph-common=0.48.1argonaut-1~bpo60+1), so I can't test it right now,
>> but I see this commit:
>>
>> https://github.com/ceph/ceph/commit/bed55369a96c2651f513b8c9b1a7bb92fb87550a 
>>
>
> Yeah, that's the commit that changed it.
>
>> How stable can we consider rbd tool's output format?
>> This is something we want to run in production environment. Using the
>> tool rather than the library makes things much simpler.
>
> Generally it won't change much, but I don't think it should be
> considered entirely unchanging. We'll add it to the release notes when
> the output does change. We'll probably switch other commands to use
> TextTable too, with the same results as with showmapped and lock list.
> We could send a message to the mailing list when the output changes as
> well, so you can prepare for a future release.

That would be great, and highly appreciated. Please drop us an email at
the following mailing lists, when the rbd tool's format changes:

synnefo-devel@googlegroups.com
ganeti-devel@googlegroups.com

>
> Perhaps we should add a --format json|plain option so you don't have to
> rely on particular formatting, you just parse the json. This would
> match existing usage by many 'ceph ...' commands, and be easier
> for scripts to use in general.

That would be even better! That would be the best approach for us, since
we use it inside python code. Parsing a json is very simple and we will be
able to maintain compatibility even when the format changes.

Thanks,
Consantinos