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

[Martin Kletzander]

On Thu, Apr 01, 2021 at 10:16:36AM -0300, Julio Faracco wrote:
>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.
>

That student was working on it, but that was 5 years ago as Michal said.
I'm afraid that it's either you or nobody who does that =)

>--
>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
>>
>
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