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). 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++ This are my 2 cents based on my past experience. On Sun, Sep 7, 2014 at 4:26 AM, Loic Dachary <loic@xxxxxxxxxxx> 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 > -- Milosz Tanski CTO 16 East 34th Street, 15th floor New York, NY 10016 p: 646-253-9055 e: milosz@xxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
