[sheepdog] [PATCH v2 1/4] sheep: leave cluster after unpluging all disks

[Liu Yuan]

On Fri, Jun 20, 2014 at 04:21:27PM +0800, Robin Dong wrote:
> From: Robin Dong <sanbai at taobao.com>
> 
> After following steps:
> 
>  1. start 6 sheep cluster, every sheep has 4 data path
>  2. unplug 4 data path for one sheep daemon
> 
> then we will see the sheep daemon which has no data path is also
> in the cluster by using 'dog node list'.But a sheep daemon with
> no data path should be a pure gateway.
> 
> So we should return EIO after unpluging last disk which will cause
> sheep to leave cluster.
> 

sheep will leave cluster by EIO later when it tries to access disks. See
md_handle_eio().

Suppose you unplug all the 4 disks for maintainance and then plug back 4 new
disks. We should allow this use case, so this patch looks wrong to me.

By the way, what is purpose of making a sheep as pure gateway while running?

Thanks
Yuan