On Tue, Jan 31, 2012 at 4:33 PM, Sage Weil <sage@xxxxxxxxxxxx> 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). Intent log generation doesn't come free of charge, it adds some load on the system. > > 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. Note that setting expiration on an object is a more lightweight operation than appending the intent log, as it would be done as a sub op in the compound operation that created the object. > > 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. While I think it'd make a nice feature, I also think that the problem space of a garbage collection is a bit different, and given the time constraints it wouldn't make sense implementing this right now anyway. > > 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? If we need to lock the entire pg while removing the objects it wouldn't work. I'm not too familiar with the scrub code, and I don't want to dive here into possible implementation details, but getting the scrub to generate a list of objects for removal may be possible. > > 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? > I don't expect to see many hands going up for "hacking" anything. I would argue that having a garbage collection related job going on inside a maintenance activity is not that far fetched. Not at any cost though. Yehuda -- 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
