Re: [RFC] Container mini-summit agenda for Sept 3, 2007

[Cedric Le Goater <clg-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org>]

Hello Oren,

Oren Laadan wrote:
> Cedric Le Goater wrote:
>> Hello All,
>>
>> Some of us will meet next week for the first mini-summit on containers.
>> Many thanks to Alasdair Kergon and LCE for the help they provided in 
>> making this mini-summit happen !
>>
>> It will be help on Monday the 3rd of September from 9:00 to 12:45 at LCE
>> in room D. We also might get a phone line for external participants and, 
>> if not, we should be able to set up a skype phone.
>>
>> Here's a first try for the Agenda. 
>>
>> Global items 
>>
>> 	 [ let's try to defer discussion after presentation ]  
>>
>> * Pavel Emelianov status update 
>> * Serge E. Hallyn Container Roadmap including  
>> 	. task containers (Paul Menage)
>> 	. resource management (Srivatsa Vaddagiri) 
>>
>> Special items
>>
>> 	[ brainstorm sessions which we would like to focus on ]
>>
>> * builing the global container object ('a la' openvz or vserver)
>> * container user space tools
>> * container checkpoint/restart  
> 
>         5. checkpoint/restart
>                 memory c/r
>                         (there are a few designs and prototypes)
>                         (though this may be ironed out by then)
>                         per-container swapfile?
>                 overall checkpoint strategy  (one of:)
>                         in-kernel
>                         userspace-driven
>                         hybrid
>                 overall restart strategy
>                 use freezer API
>                 use suspend-to-disk?
> 
>                 sysvipc
>                         "set identifier" syscall
> 		pid namespace
>                         clone_with_pid()
> There are other identifiers - pseudo terminals, message queues (mq)

right, we have plans for developing these if needed (cf 2.)

> (if you insist on supporting these ...). In general, we need a way
> to specify the virtual id of a resource that is created. 

right, pierre peiffer has sent such a pachset for the sysvipc namespace.
I'm looking at a clone_with_pid() for pid namespace.   

> I suggest
> that this should be part of an interface between c/r and containers
> (see below)
> 
> 		live migration
> aka pre-copy (which can be used for live migration but also to reduce
> the downtime due to a checkpoint).

yes that's usually what the buzz term "live migration" is used for. 

> how about adding incremental checkpoint to the list ?

sure. I think it's a bit early to address these topic but we should have 
them in mind as some implementations already exist. And we need to gather 
all the needs.

> I think that it is also important to discuss an interface between c/r and
> containers, each of which stands on it own. For instance, how to request
> a specific virtual id (during restart), define required notifiers (to
> set/unset c/r related data on/off a task), control c/r-related setting of
> container (e.g. frozen, restarting) that may affect behavior, such as
> signal handling, and so forth. 

This is exactly what we want to talk about. 

We need to identify these C/R needs, talk and agree about possible APIS 
and then convince the linux subsystem maintainers that they are useful 
for a large set of C/R solutions based on containers.     

> Also, such an interface can allow existing c/r implementations to work with 
> different virtualization implementations as they become available.

what you call "virtualization" (private identifier namespaces), is I think 
being covered by the namespaces. These namespaces are not complete (like 
we're missing a way to reassign ids) but they are going in the right 
direction, IMO. However, I don't think there will be different 
"virtualization" implementations in mainline.

> Many of these were discussed in a recent Zap paper present in USENIX:
> http://www.ncl.cs.columbia.edu/publications/usenix2007_fordist.pdf
> The paper describes important design choices in Zap (but I'm biased ...).
> I think it may serve as an appetizer for the discussion :P

Thanks, I hope we all have time to read it.

C.