[PATCH v1 25/25] docs/kbase: introduce migrationinternals.rst

[Michal Privoznik]

On 7/13/20 3:42 PM, Daniel Henrique Barboza wrote:
> 
> 
> 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 at 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 at redhat.com>
> Date:   Mon Jan 24 18:06:16 2011 +0000

Yeah, I was more interested whether we merged recently a patch that 
explicitly forbids same host migration. Speaking of which, to some 
extent we support same host migration (see v6.2.0-rc1~282) if both 
libvirts live in separate containers (and effectively think they run on 
different hosts).

Can you post a diff that I can squash in before merging?

Michal