[libvirt] [PATCH 2/2] Reload snapshots on SIGHUP

Philipp Hahn hahn at univention.de
Sat Sep 3 05:18:52 UTC 2011

Hello Eric,

Am Dienstag 30 August 2011 19:02:50 schrieb Eric Blake:
> On 08/30/2011 08:59 AM, Philipp Hahn wrote:
> > On receiving SIGHUP, libvirtd currently only reloads all persistent
> > configs for qemu domains, but fails to reload the associated snapshot
> > data.
> Are you sure this is still relevant?  In my testing, after this was
> applied, I got lots of errors:
> 10:58:09.987: 15794: error : virDomainSnapshotAssignDef:11113 : internal
> error unexpected domain snapshot 1308171632 already exists
> and without the patch, it looked to me like the snapshots were still all
> present in memory across SIGHUP without reloading them from disk.  I
> have to wonder if commit 6766ff10d made the difference in how things are
> behaving?  Perhaps your patch is still needed, but if so, can you give
> me the test scenario you used that shows the difference in behavior pre-
> and post-patch?

I posted that patch more for consistency, since sending a SIGHUP to libvirtd 
re-scans for changes in the domain XMl files under /etc/libvirt/qemu/, but 
would miss new or updates snapshots under /var/lib/libvirt/qemu/snapshot/.

> Were you hand-modifying the contents of
> /var/lib/libvirt/qemu/snapshot/dom/*.xml behind libvirt's back and
> expecting the SIGHUP to have libvirt incorporate the new xml contents
> from the disk?

Yes, see my other post on snapshots-on-a-shared-storage: I had to get that 
working with 0.8.7 and just forward-ported my patch to HEAD.

> Are you missing a step that nukes all existing snapshot 
> data in memory before re-reading snapshot data from the disk?

Might be, will re-check.

Philipp Hahn           Open Source Software Engineer      hahn at univention.de
Univention GmbH        Linux for Your Business        fon: +49 421 22 232- 0
Mary-Somerville-Str.1  D-28359 Bremen                 fax: +49 421 22 232-99
Treffen Sie Univention auf der IT&Business vom 20. bis 22. September 2011
auf dem Gemeinschaftsstand der Open Source Business Alliance in Stuttgart in
Halle 3 Stand 3D27-7.
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