[PATCH RFC 0/3] Add checkpoint/restore support to LXC using CRIU

[Julio Faracco]

Hi Michal and Martin,

Thanks for your reply.
Just an explanation. I'm not interested directly in developing this
specific feature.
If there is a GSoC student addressed to this... Excellent.
I'm interested in developing snapshot and container migration which
unfortunately requires this feature.
Unless you have another opinion.

--
Julio Faracco

Em qui., 1 de abr. de 2021 às 07:33, Michal Privoznik
<mprivozn at redhat.com> escreveu:
>
> On 4/1/21 12:01 AM, Martin Kletzander wrote:
> > On Sat, Feb 27, 2021 at 01:14:29AM -0300, Julio Faracco wrote:
> >> Hi guys,
> >>
> >
> > Hi and sorry for not replying earlier.
> >
>
> Yeah, sorry. I have this marked for review and yet still haven't done so.
>
> >> I marked this series as RFC to discuss some points. I'm interested in
> >> enhancing this specific part of LXC. So, some questions that I would
> >> like to hear as a feedback from community:
> >> 1. I decided to use a tar to compress all CRIU img files into a single
> >> file. Any other suggestions?
> >> 2. If no is the answer to question above, is there a consensus on
> >> preferring to use command line calls or libraries? I would like to use
> >> libtar for instance. I personally think that this approach is ugly.
> >> Not sure if I'm able to do that. The same for CRIU.
> >
> > I remember that for CRIU, back when we were trying to do that, the issue
> > was that the commands were not atomic, did not properly report error
> > messages and maybe something more along the lines.  Either there was no
> > library interface or it was not MT-safe, basically there were couple of
> > issues like that which we were not able to deal with.
> >
> > I do not really remember all the details.  Maybe Michal does as I think
> > he suggested the idea back then.  I Cc'd him.  In the worst scenario we
> > will need to figure this all out again ;)
>
> IIRC the main problem was that we wanted CRIU to be able to send its
> data over a TCP connection. Back then, when a GSoC student was looking
> at this, CRIU was only able to store data into a file (or even multiple
> files in a directory?) and wasn't able to create server/client
> connection. Maybe this has changed since then? If not, then we can use
> tar, sure. And to transfer data we can use so called tunnelled
> migration, where the migration stream is sent over libvirt connection
> rather than directly to the other side (because then we would have to
> have nc or similar involved).
>
> https://libvirt.org/migration.html#transporttunnel
>
> Another issue was that it couldn't handle all namespaces (but I'm not
> certain - it was 5 years ago).
>
> But let me find some time and review patches.
>
> Michal
>