Hi Sage, What is the temp collection used for ? Is there a thread / document I could read to learn about it or a piece of code that is mainly about it ? Cheers On 29/08/2013 22:40, Sage Weil wrote: > Here's what I'm thinking: > > Above the ObjectStore, we clear everything from temp on restart anyway. > > We always write bits of a temp object in pieces, and then at the end > copy/move it into the main collection. > > On replay, we should *only* do that final move/rename if the temp object > was replayed in its entirety. > > So: > > - clear out temp collections in the filestore on startup. > > - give temp objects unique names so that they don't collide with non-temp > object fd caching (or whatever else). for the DBObjectMap part there is > probably some futzing though to make this work right. > > - add a new 'move_from_temp' type operation that renames an object a temp > (coll_t::is_temp()) collection to a non-temp one. it will succeed iff the > temp source exists. > > - all operations that write to temp objects fail if the object doesn't > already exist, except an explicit 'create' op > > - all transactions the osds generate that write to temp object start with > that explicit create. > > The combination of these thigns means that we will only have a temp source > for the move_from_temp op if it is complete. Which I think means we can > avoid any of the fsync guard stuff entirely. > > The DBObjectMap I'm very fuzzy on, so I suspect that's where the tricky > part will be. Maybe the temp object name includes the intended hobject_t > in it somewhere, or something, so that the rename can be reflected > in leveldb at the end. > > Thoughts? Maybe we can do a quick hangout this afternoon to make sure > this will work before I start putting it together... > > sage > -- > 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 > -- Loïc Dachary, Artisan Logiciel Libre All that is necessary for the triumph of evil is that good people do nothing.
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