Re: Storing cls and erasure code plugins in a pool

[Loic Dachary <loic@dachary.org>]

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On 07/09/2014 15:38, Milosz Tanski wrote:
> If you're planning on having plugins that are not shipped with the
> host software you have to worry about both API and ABI stability.
> Traditionally (and in my personal experience) keeping a C++ ABI
> compatible is hard. For those reasons, I would strongly campaign for
> having the plugins interface be in C (or et least their interface
> would be C linkage).

Hi Milosz,

That's a good point indeed.

> Otherwise here's some things you can read read about C++ ABI stability
> (from the KDE people):
> https://techbase.kde.org/Policies/Binary_Compatibility_Issues_With_C++

Thanks, I did not even think C++ ABI compatibility was possible at all ;-) The web site is down at the moment but I'll take a look.

Cheers

> 
> This are my 2 cents based on my past experience.
> 
> On Sun, Sep 7, 2014 at 4:26 AM, Loic Dachary <loic@dachary.org> wrote:
>> Hi Ceph,
>>
>> There is a need for a cluster to share code such as cls https://github.com/ceph/ceph/tree/master/src/cls or erasure code plugins https://github.com/ceph/ceph/tree/master/src/erasure-code/.
>>
>> These plugins could have a life cycle independent of Ceph, as long as they comply to the supported API ( https://github.com/ceph/ceph/blob/master/src/erasure-code/ErasureCodeInterface.h ). For erasure code plugins it currently works this way (or it will as soon as https://github.com/ceph/ceph/pull/2397 is merged):
>>
>> a) upgrade from Hammer to I* half the OSD nodes. The new I* have new erasure code plugins
>> b) the MON will refuse to create an erasure coded pool using the new I* plugins, otherwise the Hammer nodes will find themselves unable to participate in the pool
>>
>> Instead it could work this way:
>>
>> a) upgrade from Hammer to I* half the OSD nodes. The new I* have new erasure code plugins
>> b) the new erasure code plugins are uploaded to a "plugins" pool
>> c) an erasure coded pool is created using a new plugin from I*
>> d) the Hammer OSD downloads the plugin from the pool and can participate in the pool
>>
>> It is easier said than done and there are a lot of details to consider. However it not different from maintaining an Operating System that includes shared libraries and the path to do so properly is well known.
>>
>> Thoughts ?
>>
>> Cheers
>>
>> --
>> Loïc Dachary, Artisan Logiciel Libre
>>
> 
> 
> 

-- 
Loïc Dachary, Artisan Logiciel Libre


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