Re: Stateful Vs Stateless Instances Findings

[David Lutterkort <lu...@redhat.com>]

To revive this discussion, and put a firm proposal to resolve this
forward, here's what I think the best plan of action is:

Deltacloud
----------

Need to add the following capabilities to the API:

      * Indicate for each image whether it can be used for launching a
        stateful or stateless instance [1]
      * Make it possible to copy/clone an existing image to a new image

Aeolus
------

Since Aeolus wants to pretend that all clouds only support stateless
images, Condor will start all instances in a two-step process:

     1. Ensure a stateless image for the instance exists: if the image
        is stateful clone it, otherwise just use the original image
     2. Launch the instance of the image from step (1)
     3. Delete the cloned image, if necessary, when the instance is
        terminated

David

[1] just to keep things clean, we should also indicate whether there is
a restriction on how many instances can be launched off an image
simultaneously (to guard against a freakish cloud that can only launch a
single instance of a stateless image)

Re: Stateful Vs Stateless Instances Findings

[David Lutterkort <lu...@redhat.com>]

On Thu, 2011-03-03 at 08:18 -0500, John R. Dunning wrote:
> From: David Lutterkort <lu...@redhat.com>
>     Date: Wed, 02 Mar 2011 16:21:29 -0800
>     
> High level question:
> 
> Are we trying to resolve
> 
> 1.  Does aeoulous/cloud-engine require that its backends support
> stateless images?
> 
> 2.  Is the deltacloud api, itself, stateless?
> 
> 3.  Both 1 and 2.
> 
> 4.  Something else.
> 
> 
> My understanding is that the answer to 1 has always been "Yes", and
> that it continues to be.  I'm agnostic about 2.

The answer to (1) is 'No' - with my proposal, Aeolus would simulate
stateless instances on top of stateful images by cloning images itself.

Aeolus would still present only stateless instances to the user, and the
stateful/stateless gyrations would be contained within Condor.

The big reason to do this in Aeolus rather than Deltacloud is that this
simulation requires a lot of state, and cleanup if things go wrong. If
we put this into Deltacloud, we'd have to have a task queue and similar
functionality in no time (at that point we'd just as well pull Condor
into Deltacloud)

> 
>     To revive this discussion, and put a firm proposal to resolve this
>     forward, here's what I think the best plan of action is:
>     
>     Deltacloud
>     ----------
>     
>     Need to add the following capabilities to the API:
>     
>           * Indicate for each image whether it can be used for launching a
>             stateful or stateless instance [1]
>           * Make it possible to copy/clone an existing image to a new image
>     
> 
> Are these futures?  Hugh, is there now discussion of adding stateful
> image support to CE for rev1?
> 
> If CE doesn't need it, I wouldn't take it as a requirement for DC,
> unless there's some unrelated-to-CE reason to think the api needs it. 

Doing it this way is the cleanest way to expose that functionality
without blowing the complexity of DC up by an order of magnitude.

David

Re: Stateful Vs Stateless Instances Findings

["John R. Dunning" <jr...@redhat.com>]

    From: David Lutterkort <lu...@redhat.com>
    Date: Wed, 02 Mar 2011 16:21:29 -0800
    
High level question:

Are we trying to resolve

1.  Does aeoulous/cloud-engine require that its backends support
stateless images?

2.  Is the deltacloud api, itself, stateless?

3.  Both 1 and 2.

4.  Something else.


My understanding is that the answer to 1 has always been "Yes", and
that it continues to be.  I'm agnostic about 2.


    To revive this discussion, and put a firm proposal to resolve this
    forward, here's what I think the best plan of action is:
    
    Deltacloud
    ----------
    
    Need to add the following capabilities to the API:
    
          * Indicate for each image whether it can be used for launching a
            stateful or stateless instance [1]
          * Make it possible to copy/clone an existing image to a new image
    

Are these futures?  Hugh, is there now discussion of adding stateful
image support to CE for rev1?

If CE doesn't need it, I wouldn't take it as a requirement for DC,
unless there's some unrelated-to-CE reason to think the api needs it. 

    Aeolus
    ------
    
    Since Aeolus wants to pretend that all clouds only support stateless
    images, Condor will start all instances in a two-step process:
    
         1. Ensure a stateless image for the instance exists: if the image
            is stateful clone it, otherwise just use the original image
         2. Launch the instance of the image from step (1)
         3. Delete the cloned image, if necessary, when the instance is
            terminated
    
    David
    
    [1] just to keep things clean, we should also indicate whether there is
    a restriction on how many instances can be launched off an image
    simultaneously (to guard against a freakish cloud that can only launch a
    single instance of a stateless image)