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Re: [libvirt] qemu: Add timeout for monitor to avoid virsh getting stuck when monitor gets die.



于 2011年04月06日 16:51, Jiri Denemark 写道:
On Wed, Apr 06, 2011 at 12:13:10 +0800, Mark Wu wrote:
Hello Guys,

When the qemu process becomes hung,  virsh will get stuck on the hung
guest and can't move forward.  It can be reproduced by the following steps:

1. setup a virt guest with qemu-kvm, and start it
2. stop qemu process with following:
   kill -STOP  `ps aux | grep qemu | grep -v grep | awk '{print $2}'`
3. run the following command:
virsh list

I think we can add a timeout for qemu monitor to resolve this problem:
using virCondWaitUntil instead of virCondWait in qemuMonitorSend. What's
your opinions?

This is not the right approach. Introducing a timeout into all monitor command
send to qemu is a bad thing. I think the right approach is to have a simple
API which would just return domain's state without talking to its monitor or
doing other complicated stuff. The new API could then be used by virsh list to
list all domains even though they are blocked on qemu monitor. After all,
virsh is not really interested in current memory consumption of domains when
listing them.


IMHO this won't work, if you restart libvirtd after the monitor gets
dead, you even can't get connection to libvirtd anymore, see:

http://www.redhat.com/archives/libvir-list/2011-March/msg01422.html

How to reproduce:
1. setup a virt guest with qemu-kvm, and start it
2. stop qemu process with following:
   # kill -STOP  `ps aux | grep qemu | grep -v grep | awk '{print $2}'`
3. run the following command:
4. # service libvirtd restart
5. # virsh (hangs here)

The new API could also provide a reason which lead to current state so that
one can see the reason even without watching for libvirt events.

Jirka

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