[libvirt] error: server response too large

[Viktor Mihajlovski]

On 10/01/2013 06:19 PM, Daniel P. Berrange wrote:
> 
> What were you doing to get a message greater than 256KB ? This
> patch did not attempt to fix all possible combinations. If a
> API call such as virConnectListAllDomains has so much data that
> it requires > 256KB to encode, this fix won't solve that. There
> is nothing we can do for API calls which have a genuine need to
> exceed the old size limit.
> 
> I was only addressing the case of virStreamPtr data which was
> mistakenly hardcoded in the server to try sending 16 MB of data
> at once. I switched it to only try to send 256 KB of data per
> stream packet.
> 
OK, than it's a misunderstanding from my part (regarding your
intention). The client side error message was the same as in the
"all-at-once" case which would mean that the client somehow
got past receiving the message even then and finally stumbled
trying to decode the message (which is inevitable in such a case).

Our S390 domains happen to be "oversize" due to the large
number of devices (which is harder to reproduce on a PCI based
system because it runs out of bus addresses too quick).
So dumpxml typically raises the condition.

With SCSI it's easier to create large guests, so a script like
the one below can help to reproduce...

#!/bin/bash
cat > scsidom <<EOF
<domain type='kvm'>
  <name>manydevs</name>
  <memory>1048576</memory>
  <os>
    <type>hvm</type>
  </os>
  <devices>
    <controller type='scsi' model='virtio-scsi'/>
EOF
for i in {1..1000}
do
cat >> scsidom <<EOF
    <disk type='file' device='disk'>
      <source file='/var/lib/libvirt/images/vol$i'/>
      <target dev='sda' bus='scsi'/>
      <address type='drive' controller='0' bus='0' target='0' unit='$i'/>
    </disk>
EOF
done
cat >> scsidom <<EOF
  </devices>
</domain>
EOF


-- 

Mit freundlichen Grüßen/Kind Regards
   Viktor Mihajlovski

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