[Engine-devel] Managing async tasks

[Adam Litke]

On Mon, Dec 17, 2012 at 12:15:08PM -0500, Saggi Mizrahi wrote:
> 
> 
> ----- Original Message -----
> > From: "Adam Litke" <agl at us.ibm.com> To: vdsm-devel at lists.fedorahosted.org
> > Cc: "Dan Kenigsberg" <danken at redhat.com>, "Ayal Baron" <abaron at redhat.com>,
> > "Saggi Mizrahi" <smizrahi at redhat.com>, "Federico Simoncelli"
> > <fsimonce at redhat.com>, engine-devel at ovirt.org Sent: Monday, December 17,
> > 2012 12:00:49 PM Subject: Managing async tasks
> > 
> > On today's vdsm call we had a lively discussion around how asynchronous
> > operations should be handled in the future.  In an effort to include more
> > people in the discussion and to better capture the resulting conversation I
> > would like to continue that discussion here on the mailing list.
> > 
> > A lot of ideas were thrown around about how 'tasks' should be handled in the
> > future.  There are a lot of ways that it can be done.  To determine how we
> > should implement it, it's probably best if we start with a set of
> > requirements.  If we can first agree on these, it should be easy to find a
> > solution that meets them.  I'll take a stab at identifying a first set of
> > POSSIBLE requirements:
> > 
> > - Standardized method for determining the result of an operation
> > 
> >   This is a big one for me because it directly affects the consumability of
> >   the API.  If each verb has different semantics for discovering whether it
> >   has completed successfully, then the API will be nearly impossible to use
> >   easily.
> Since there is no way to assure if of some tasks completed successfully or
> failed, especially around the murky waters of storage, I say this requirement
> should be removed.  At least not in the context of a task.

I don't agree.  Please feel free to convince me with some exampled.  If we
cannot provide feedback to a user as to whether their request has been satisfied
or not, then we have some bigger problems to solve.

> > 
> > 
> > Sorry.  That's my list :)  Hopefully others will be willing to add other
> > requirements for consideration.
> > 
> > From my understanding, task recovery (stop, abort, rollback, etc) will not
> > be generally supported and should not be a requirement.
> > 

-- 
Adam Litke <agl at us.ibm.com>
IBM Linux Technology Center