[sheepdog] [PATCH 1/2] sheep/recovery: get recovering local object right

[Hitoshi Mitake]

On Tue, Mar 3, 2015 at 11:22 AM, Liu Yuan <namei.unix at gmail.com> wrote:
> On Mon, Mar 02, 2015 at 04:02:37PM +0800, Liu Yuan wrote:
>> From: Liu Yuan <liuyuan at cmss.chinamobile.com>
>>
>> One of the acceleration for recovery is we try to recover the object from local
>> node as much as possible. It is straightforward implemented:
>>
>> 1 firstly get the hash of the object to be recoveried from stale directry if any
>> 2 then compare the fingerprint to the remote node
>> 3 if identical, then we can safely recover it from local stale directory.
>>
>> But this logic is never executed in the following case:
>>
>> 0 sheep try to recover object A at from epoch 5, we note it as A.5
>> 1 but sheep find we have a local copy A.2 due to a multiple node events
>> 2 then sheep get the fingerprint of A.2 and then compare to remote node.
>> 3 the figerprints are identical, so this sheep tries to recover it from A.2
>> 4 if, unfortunately, A.5 is as well calcuated onto this node, even though this
>>   sheep dosen't have it, our code will first try to link A.5
>> 5 unfortunately, A.5 is never out there and before we really try to link A.2,
>>   sheep fail out because ->link(A.5) return error.
>>
>> The fix is easy, just try to ->link(A.2) before ->link(A.5).
>
> Hitoshi?...ping...

I cannot allocate time for a while. I'll review it tonight, please
wait for a while.

Thanks,
Hitoshi

> --
> sheepdog mailing list
> sheepdog at lists.wpkg.org
> https://lists.wpkg.org/mailman/listinfo/sheepdog