Hi Varada, On Tue, 24 Feb 2015, Varada Kari wrote: > Hi Sage, > > We are trying to integrate a new proprietary key value store to CEPH. To > integrate this KV-store, which is a closed source shared library, we propose > a new class to CEPH called PropDBStore which does a dlopen and imports the > required symbols. This framework will help in integrating vendor specific > extensions to CEPH. > > The gist of the implementation is as follows. > > 1. Implement a wrapper around the proprietary KVStore. Let us call it as > KVExtension. This is a shared library which implements all interfaces > required by CEPH KeyValueStore. > 2. A new class is derived from KeyValueDB called PropDBStore, which honors > the semantics of KeyvalueStore and KeyValueDB. This class acts as mediator > between CEPH and KVExtension. This class transforms bufferlist etc... to > const char pointers or strings for the extension to understand. > 3. PropDBStore, loads (dlopen) the KVExtension during OSD initialization. > Path to the KVExtension can be mentioned in ceph.conf. > 4. Interfaces that needs to be implemented in KVExtension, which are imported > by the PropDBStore are added in a new header called PropDBWrapper.h. This > header contains the signatures for the necessary interfaces like init(), > close(), submit_transaction(), get() and get_iterator(). Similarly for > Iterator functionality, PropDBIterator.h, which specifies the signatures of > seek_to_first (), seek_to_last(), lower_bound() and upper_bound() etc... > PropDBStore includes these headers to import the symbols, using dlsym(). > 5. Choosing the proprietary DB as Backend to the OSD is controlled/managed by > config options of the ceph (/etc/ceph/ceph.conf) like rocksdb or leveldb. > 6. Rest of the existing functionality is not disturbed by this change. > Changing the osd backend option will change backend implementation. But this > change is not dynamic. The type of the backend should be chosen at osd > creation time and osd will continue use that backend till that osd is > reformatted again. > 7. The new KVStore we are trying to integrate works on a raw partition, so we > divided the osd drive into two partitions. One partition is given to osd Meta > data (super block, fsid etc...), and the other is given to the new db to > manage it. OSD partition is now not the entire disk, but 2-4GB which needed > for the metadata.
This sounds like a good approach to link to pretty much any external backend (modulo the dlopen part). I need to check with lawyer types before I can promise we'll be able to merge something like this into the main ceph.git, though! Thanks- sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
