[Bug 985489] Re: nova-compute stops processing compute.$HOSTNAME occasionally on libvirt

[You, Ji]

Description of this problem

I have met this problem before. This bug is mainly caused by libvirt &
openstack-compute driver for libvirt.

When you meet this problem. You may type command.

$ virsh list --all

If this command get stucked, you may face this problem. Another
interesting appearance is that, if you type

$ ps aux | grep libvirtd

You may find two libvirtd service is running.  Such as,

......     /usr/sbin/libvirtd -d
......    /usr/sbin/libvirtd -d

You kill one process, then libvirt will be ok. But sometimes later, the
bug will come out again.


Reasons of this problem

Why this bug comes out?
1 This bug mainly caused by libvirt. The older verion of libvirt has multi-process/multi-threads lock bugs. Sometimes, when multi-processes access libvirt/libvirtd services by libvirt-api, this error will happen. Especially, if you access libvirt from differe process or threads,  then this bug will come out. All accesses of libvirt will get stucked.

2 The driver of libvirt in OpenStack, access libvirt/libvirtd service
too frequently. Especially, when you have a lot of vms running on
libvirt.

Solutions for this bug:

1 You have to update you libvirt/libvirtd services. My advice is your libvirt version should > 0.9.13. 
2 We may have some methods to get  lower frequent of these accesses.

I think I can fix this Bug. ^_^. I have fix it in my env of openstack.

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https://bugs.launchpad.net/bugs/985489

Title:
  nova-compute stops processing compute.$HOSTNAME occasionally on
  libvirt

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