[sheepdog] [PATCH v2 0/9] sheepdog: reconnect server after connection failure

[Liu Yuan]

On Wed, Jul 24, 2013 at 06:07:21PM +0900, MORITA Kazutaka wrote:
> At Wed, 24 Jul 2013 16:28:30 +0800,
> Liu Yuan wrote:
> > 
> > On Wed, Jul 24, 2013 at 04:56:24PM +0900, MORITA Kazutaka wrote:
> > > Currently, if a sheepdog server exits, all the connecting VMs need to
> > > be restarted.  This series implements a feature to reconnect the
> > > server, and enables us to do online sheepdog upgrade and avoid
> > > restarting VMs when sheepdog servers crash unexpectedly.
> > > 
> > 
> > It doesn't work on my test. I tried start linux-0.2.img stored in sheepdog
> > cluster and then
> > 
> > 1. did some buffered writes
> > 2. restart sheep that this QEMU VM connected to.
> > 3. $ sync
> > 
> > I got following error:
> > 
> > $ ../qemu/x86_64-softmmu/qemu-system-x86_64 --enable-kvm -m 1024 -hda sheepdog:test
> > qemu-system-x86_64: failed to get the header, Resource temporarily unavailable
> > qemu-system-x86_64: Failed to connect to socket: Connection refused
> > qemu-system-x86_64: Failed to connect to socket: Connection refused
> > qemu-system-x86_64: Failed to connect to socket: Connection refused
> > qemu-system-x86_64: Failed to connect to socket: Connection refused
> > qemu-system-x86_64: Failed to connect to socket: Connection refused
> > ...repeat...
> > 
> > QEMU version is master tip
> 
> Your sheep daemon looks like unreachable from qemu.  I tried the same
> procedure, but couldn't reproduce it.
> 
> Is the problem reproducible?  Can you make sure that you can connect
> to the sheep daemon from collie while the error message shows up?
> 

Yesh. Well I try to repeat it with following process:

1. did some buffered write
2. kill the sheep
3. $ sync # at guest, now 'sync' hang for response
4. restart sheep

After 4 'sync' still hangs until timeout with a message
"hda:dma_timer_expiry: dma status == 0x21"

Guest end up freeze.

QEMU output is the same:
qemu-system-x86_64: failed to get the header, Resource temporarily unavailable
qemu-system-x86_64: Failed to connect to socket: Connection refused
qemu-system-x86_64: Failed to connect to socket: Connection refused
qemu-system-x86_64: Failed to connect to socket: Connection refused
qemu-system-x86_64: Failed to connect to socket: Connection refused

But notice, if I did restart sheep with guest doing nothing, your patch set work
like a charm.

Thanks
Yuan