Re: efficient removal of old objects

[Josh Durgin <josh.durgin@dreamhost.com>]

On 01/31/2012 04:33 PM, Sage Weil wrote:
> Currently rgw logs objects it wants to delete after some period of time,
> and an radosgw-admin command comes back later to process the log.  It
> works, but is currently slow (one sync op at a time).
>
> A better approach would be to mark objects for later removal, and have the
> OSD do it in some more efficient way.  wip-objs-expire has a client side
> (librados) interface for this.
>
> I think there are a couple questions:
>
> Should this be generalized to saying "do these osd ops at time X" instead
> of "delete at time X".  Then it could setxattr, remove, call into a class,
> whatever.
>
> How would the OSD implement this?  A kludgey way would be to do it during
> scrub.  The current scrub implementation may make that problematic because
> it does a whole PG at time, and we probably don't want to issue a whole
> PG's worth of deletes at a time.  Is there a way to make that less
> painful?
>
> Not using scrub means we need some sort of index to keep track of objects
> with delayed events.  Using a collection for this might work, but loading
> all this state into memory would be slow if there were too many events
> registered.
>
> Given all that, and that we need a solution to the expiration soon
> (weeks), do we
>   - do a complete solution now,
>   - parallelize radosgw-admin log processing,
>   - or hack it into scrub?
>
> sage