Rados multi-object transaction use cases

Rados multi-object transaction use cases

[Samuel Just]

In the Infernalis CDS, we had a session on RADOS multi-object transactions.  I'd like to continue the discussion at the upcoming Jewel CDS.  I thought I'd prime the discussion by asking: if librados supported multi-object read and write transactions, what would you use them for?  Some idea of use cases would be valuable when considering things like deadlock coping strategies.
-Sam

Re: Rados multi-object transaction use cases

[Yehuda Sadeh-Weinraub]

----- Original Message -----
> From: "Samuel Just" <sjust@redhat.com>
> To: "ceph-devel" <ceph-devel@vger.kernel.org>
> Sent: Friday, June 12, 2015 3:15:02 PM
> Subject: Rados multi-object transaction use cases
> 
> In the Infernalis CDS, we had a session on RADOS multi-object transactions.
> I'd like to continue the discussion at the upcoming Jewel CDS.  I thought
> I'd prime the discussion by asking: if librados supported multi-object read
> and write transactions, what would you use them for?  Some idea of use cases
> would be valuable when considering things like deadlock coping strategies.

Here are a few for rgw:
 - update bucket index when creating / modifying / deleting an object
 - store multiple metadata objects atomically: e.g., user info + user access keys + user email (currently not atomic)
 - store bucket entry point + bucket instance info atomically
 - creating a bucket and adding it to the user's list of buckets

Yehuda

RE: Rados multi-object transaction use cases

[Somnath Roy]

Also, wouldn't this help in case of some kind of write coalescing for librbd/librados and sending one transaction down in case of multiple ?

Thanks & Regards
Somnath


-----Original Message-----
From: ceph-devel-owner@vger.kernel.org [mailto:ceph-devel-owner@vger.kernel.org] On Behalf Of Yehuda Sadeh-Weinraub
Sent: Friday, June 12, 2015 3:21 PM
To: Samuel Just
Cc: ceph-devel
Subject: Re: Rados multi-object transaction use cases



----- Original Message -----
> From: "Samuel Just" <sjust@redhat.com>
> To: "ceph-devel" <ceph-devel@vger.kernel.org>
> Sent: Friday, June 12, 2015 3:15:02 PM
> Subject: Rados multi-object transaction use cases
>
> In the Infernalis CDS, we had a session on RADOS multi-object transactions.
> I'd like to continue the discussion at the upcoming Jewel CDS.  I
> thought I'd prime the discussion by asking: if librados supported
> multi-object read and write transactions, what would you use them for?
> Some idea of use cases would be valuable when considering things like deadlock coping strategies.

Here are a few for rgw:
 - update bucket index when creating / modifying / deleting an object
 - store multiple metadata objects atomically: e.g., user info + user access keys + user email (currently not atomic)
 - store bucket entry point + bucket instance info atomically
 - creating a bucket and adding it to the user's list of buckets

Yehuda
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Re: Rados multi-object transaction use cases

[Li Wang]

Hi Samuel,
   We have made significant progress towards this implementation,
we submitted a BP at 
http://tracker.ceph.com/projects/ceph/wiki/Rados_-_multi-object_transaction_support 
several days ago, so far it is just a
place holder, I will post our detailed progress soon, and great to hear 
your comments.

Cheers,
Li Wang

On 2015/6/13 10:06, Samuel Just wrote:
> In the Infernalis CDS, we had a session on RADOS multi-object transactions.  I'd like to continue the discussion at the upcoming Jewel CDS.  I thought I'd prime the discussion by asking: if librados supported multi-object read and write transactions, what would you use them for?  Some idea of use cases would be valuable when considering things like deadlock coping strategies.
> -Sam
> --
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