Re: [PATCH v1 25/25] docs/kbase: introduce migrationinternals.rst
On 7/13/20 10:20 AM, Michal Privoznik wrote:
On 7/13/20 11:49 AM, Daniel Henrique Barboza wrote:
> This document describes briefly how Libvirt migration internals
> works, complementing the info available in migration.html.in.
>
> Signed-off-by: Daniel Henrique Barboza <danielhb413(a)gmail.com>
> ---
> docs/kbase/migrationinternals.rst | 174 ++++++++++++++++++++++++++++++
> 1 file changed, 174 insertions(+)
> create mode 100644 docs/kbase/migrationinternals.rst
>
> diff --git a/docs/kbase/migrationinternals.rst b/docs/kbase/migrationinternals.rst
> new file mode 100644
> index 0000000000..869ee99bd7
> --- /dev/null
> +++ b/docs/kbase/migrationinternals.rst
> @@ -0,0 +1,174 @@
> +===========================
> +Libvirt migration internals
> +===========================
> +
> +.. contents::
> +
> +Migration is a multi-step operation with at least two distinct actors,
> +the source and the destination libvirtd daemons, and a lot of failure
> +points. This document describes the basic migration workflow in the
> +code level, as a way to complement `the base migration docs
<migration.html>`_
> +and help developers to get up to speed quicker with the code.
> +
> +In this document, unless stated otherwise, these conventions are followed:
> +
> +* 'user' refers to any entity that initiates a migration, regardless of
being
> + an human using 'virsh' or a program consuming the Libvirt API;
> +
> +* 'source' refers to the source host of the migration, where the guest
currently
> + exists;
> +
> +* 'destination' refers to the destination host of the migration. As of
> + Libvirt 6.5.0 local migration isn't supported, thus source and destination
> + refers to different hosts;
Is this right? What commit is reponsible for this change?
I guess my wording here is unclear. What I wanted to say is that, at least up to the
current release we're at now (6.5.0), localhost migration (i.e. source and
destination
is the same host) isn't supported. I wanted to mention it this way because
there's always
the chance that Libvirt comes around and implements it.
If you want a commit id, the error message warning about localhost migration appeared
first here:
commit 8654175c5b0c3db9e5f70907f102f0f900355d28
Author: Daniel P. Berrange <berrange(a)redhat.com>
Date: Mon Jan 24 18:06:16 2011 +0000
Introduce migration cookies to QEMU driver
(...)
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -46,0 +196,10 @@
+ qemuReportError(VIR_ERR_INTERNAL_ERROR,
+ "%s", _("missing hostuuid element in migration
data"));
+ goto error;
+ }
+ virUUIDFormat(mig->hostuuid, uuidstr);
+ if (STREQ(tmp, uuidstr)) {
+ qemuReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Attempt to migrate guest to the same host %s"),
+ tmp);
+ goto error;
Michal