On 12/09/2015 10:39 AM, Prashanth Pai wrote:
However, I’d be even more comfortable with an even simpler approach that
avoids the need to solve what the database folks (who have dealt with
complex transactions for years) would tell us is a really hard problem.
Instead of designing for every case we can imagine, let’s design for the
cases that we know would be useful for improving performance. Open plus
read/write plus close is an obvious one. Raghavendra mentions
create+inodelk as well.
From object interface (Swift/S3) perspective, this is the fop order and flow
for object operations:
GET: open(), fstat(), fgetxattr()s, read()s, close()
Krutika implemented fstat+fgetxattr(http://review.gluster.org/10180). In
posix there is an implementation of GF_CONTENT_KEY which is used to read
a file in lookup by quick-read. This needs to be exposed for fds as well
I think. So you can do all this using fstat on anon-fd.
HEAD: stat(), getxattr()s
Krutika already implemented this for sharding
http://review.gluster.org/10158. You can do this using stat fop.
PUT: creat(), write()s, setxattr(), fsync(), close(), rename()
This I think should be a new compound fop. Nothing similar exists.
DELETE: getxattr(), unlink()
This can also be clubbed in unlink already because xdata exists on the
wire already.
Compounding some of these ops and exposing them as consumable libgfapi APIs
like glfs_get() and glfs_put() similar to librados compound APIs[1] would
greatly improve performance for object based access.
[1]: https://github.com/ceph/ceph/blob/master/src/include/rados/librados.h#L2219
Thanks.
- Prashanth Pai
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