eca9d21e6c
Post-copy migration has been broken on the source since commit
v3.8.0-245-g32c29f10db which implemented support for
pause-before-switchover QEMU migration capability.
Even though the migration itself went well, the source did not really
know when it switched to the post-copy mode despite the messages logged
by MIGRATION event handler. As a result of this, the events emitted by
source libvirtd were not accurate and statistics of the completed
migration would cover only the pre-copy part of migration. Moreover, if
migration failed during the post-copy phase for some reason, the source
libvirtd would just happily resume the domain, which could lead to disk
corruption.
With the pause-before-switchover capability enabled, the order of events
emitted by QEMU changed:
pause-before-switchover
disabled enabled
MIGRATION, postcopy-active STOP
STOP MIGRATION, pre-switchover
MIGRATION, postcopy-active
The STOP even handler checks the migration status (postcopy-active) and
sets the domain state accordingly. Which is sufficient when
pause-before-switchover is disabled, but once we enable it, the
migration status is still active when we get STOP from QEMU. Thus the
domain state set in the STOP handler has to be corrected once we are
notified that migration changed to postcopy-active.
This results in two SUSPENDED events to be emitted by the source
libvirtd during post-copy migration. The first one with
VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED detail, while the second one reports
the corrected VIR_DOMAIN_EVENT_SUSPENDED_POSTCOPY detail. This is
inevitable because we don't know whether migration will eventually
switch to post-copy at the time we emit the first event.
https://bugzilla.redhat.com/show_bug.cgi?id=1647365
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.1 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: