[sheepdog] [PATCH v2 0/5] garbage collect needless VIDs and inode objects

[Hitoshi Mitake]

At Thu, 12 Mar 2015 14:41:56 +0800,
Liu Yuan wrote:
> 
> On Tue, Jan 13, 2015 at 10:37:40AM +0900, Hitoshi Mitake wrote:
> > Current sheepdog never recycles VIDs. But it will cause problems
> > e.g. VID space exhaustion, too much garbage inode objects.
> > 
> > Keeping deleted inode objects is required because living inodes
> > (snapshots or clones) can point objects of the deleted inodes. So if
> > every member of VDI family is deleted, it is safe to remove deleted
> > inode objects.
> > 
> > v2:
> >  - update test scripts
> 
> All the nodes of our test cluster panic out for the following problem:
> 
> Mar 12 00:05:03  DEBUG [main] zk_handle_notify(1216) NOTIFY
> Mar 12 00:05:03  DEBUG [main] sd_notify_handler(960) op NOTIFY_VDI_ADD, size: 96, from: IPv4 ip:192.168.39.177 port:7000
> Mar 12 00:05:03  DEBUG [main] do_add_vdi_state(362) 7c2b2b, 3, 0, 22, 0
> Mar 12 00:05:03  DEBUG [main] do_add_vdi_state(362) 7c2b2c, 3, 0, 22, 7c2b2b
> Mar 12 00:05:03  EMERG [main] update_vdi_family(127) PANIC: parent VID: 7c2b2b not found
> Mar 12 00:05:03  EMERG [main] crash_handler(286) sheep exits unexpectedly (Aborted), si pid 4786, uid 0, errno 0, code -6
> Mar 12 00:05:03  EMERG [main] sd_backtrace(833) sheep.c:288: crash_handler
> Mar 12 00:05:03  EMERG [main] sd_backtrace(847) /lib64/libpthread.so.0() [0x338200f4ff]
> Mar 12 00:05:03  EMERG [main] sd_backtrace(847) /lib64/libc.so.6(gsignal+0x34) [0x3381c328a4]
> Mar 12 00:05:03  EMERG [main] sd_backtrace(847) /lib64/libc.so.6(abort+0x174) [0x3381c34084]
> Mar 12 00:05:03  EMERG [main] sd_backtrace(833) vdi.c:127: update_vdi_family
> Mar 12 00:05:03  EMERG [main] sd_backtrace(833) vdi.c:398: add_vdi_state
> Mar 12 00:05:03  EMERG [main] sd_backtrace(833) ops.c:711: cluster_notify_vdi_add
> Mar 12 00:05:03  EMERG [main] sd_backtrace(833) group.c:975: sd_notify_handler
> 
> So I tracked back to this patch set. The problem of this patch set tried to
> solve is very clear and come along with sheepdog since its born. This reveals
> actually the defeciency of our vdi allocation algorithm, which we need rethink
> a completely new algorithm to replace it and is not fixable, unfortunately.
> 
> One simple rule, we can't recyle any vid if it is once created because of its
> current hash collision handling. Our current implementation forbigs recycling.
> 
> Instead of fixing the above panic bug, I'd suggest we revert this patch set.
> For the problem this patch set mentioned, I think we need a new algoirthm and
> implementation. But before that, we should stay with old one, it is stable and
> reliable and should work for small size cluster.
> 
> How do you think, Hitoshi and Kazutaka?

How about providing switch turn on/off VID recycling? e.g. dog cluster
format --enable-vid-recycle. The code can easily be pushed into
conditional branches. I can post a patch if this way is good for you.

Thanks,
Hitoshi

> 
> Yuan
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