[libvirt] [PATCH] migration: support all toURI and proto combos

[Nikolay Shirokovskiy]

On 08.09.2015 15:14, Jiri Denemark wrote:
> On Tue, Sep 08, 2015 at 13:43:09 +0300, Nikolay Shirokovskiy wrote:
>> Current implementation of 'toURI' migration interfaces does not support all
>> combinations of interface versions and protocol versions. For example 'toURI2'
>> with p2p flag will not migrate if driver supports only v3params proto.
> 
> In general, this patch is pretty large and hard to review, I suggest
> splitting it into a series of several shorter patches. They all need to
> compile and work, but it shouldn't be too hard in this case.
> 
>> This is not convinient as drivers that starts to support migration have to
>> manually support older versions of protocol. I guess this should be done in
>> one place, namely here.
> 
> Well, the thing is all the code you're changing runs on a *client* and
> then the appropriate API calls are sent as RPC to a daemon. So just
> checking what APIs are implemented by the *client's* remote driver to
> choose what API will be called on the daemon is wrong. The client can be
> new enough to support all migration APIs while the daemon may be pretty
> old supporting only a few of them. Thus, for backward compatibility, the
> client has to either check what API is supported by the daemon (via
> VIR_DRV_SUPPORTS_FEATURE(..., VIR_DRV_FEATURE_MIGRATION_...)) or it has
> to be conservative and call the oldest API which supports the parameters
> passed by the application/user.
This approach(namely checking driver capabilities beforehand) is already
present in code and i dont change it.

> 
> Overall, if you see a way to refactor and improve the code so that it's
> more readable and maintainable, just go ahead, but be careful about this
> kind of changes in behavior.
> 
Ok. I'll split into a more managable patches.
> Jirka
>