[sheepdog] [PATCH v2 3/3] object list cache: reclaim object list cache when receiving a deletion event.

[MORITA Kazutaka]

At Thu, 12 Jul 2012 09:55:27 +0800,
levin li wrote:
> 
> On 2012年07月12日 06:01, MORITA Kazutaka wrote:
> > At Wed, 11 Jul 2012 14:42:47 +0800,
> > levin li wrote:
> >>
> >> From: levin li <xingke.lwp at taobao.com>
> >>
> >> Before reclaiming the cache belonging to the VDI just deleted, we should test
> >> whether the VDI is exist, because after some node delete it and before the
> >> notification is sent to all the node, another node may issus a VDI creation
> >> event and reused the VDI id again, in which case we should reclaim the cached
> >> entry.
> > 
> > Should this be explained in the source code where vdi_exist() is
> > called?

How do you think about this?


> > I'm still a bit confused why we need both objlist_cache_delete and
> > objlist_cache_remove.  If no recovery happens during object deletion,
> > we don't need objlist_cache_delete because objlist_cache_remove
> > removes the entry.  objlist_cache_delete is necessary for the case
> > object deletion and recovery happen at the same time to clean up
> > unhandled entries by objlist_cache_remove.  Is it correct?
> > 
> 
> 
> Well, if no recovery happens before, objlist_cache_remove() can always
> delete the entry in object list cache while VDI deletion, but once recovery
> happens, it's something different.
> 
> For example, obj A and B stay in node n1 at first, but after a recovery,
> A may be migrated from n1 to n2, and B stays in n1, but the objlist entry

Is there any reason we don't remove the objlist entry when we unlink
the object from the farm working directory?

diff --git a/sheep/farm/trunk.c b/sheep/farm/trunk.c
index b45427d..e390a63 100644
--- a/sheep/farm/trunk.c
+++ b/sheep/farm/trunk.c
@@ -297,6 +297,7 @@ int trunk_file_write_recovery(unsigned char *outsha1)
 				goto out;
 			}
 			dprintf("remove file %"PRIx64"\n", entry->raw.oid);
+			objlist_cache_remove(oid);
 			put_entry(entry);
 		}
 	}

Recovery algorithm has been changed from before, so probably I'm
missing something.  Correct me if I'm wrong.

Anyway, the function names (objlist_cache_remove/delete) looks too
confusing.  IIUC, objlist_cache_remove() is used when removing caches
after processing SD_OP_READ_PEER requests, and objlist_cache_delete()
is used to cleanup caches associated with removed objects after vdi
deletion is finished.  Can we use more descriptive names?

Thanks,

Kazutaka