Dmitriy, There's a fair number of comments both here and on the doc. Will you have time to respond to these so we can find a path forward?
Cheers, Joshua On Wed, Mar 8, 2017 at 8:44 PM, David McLaughlin <dmclaugh...@apache.org> wrote: > Ticket for replace task primitive already exists: > https://issues.apache.org/jira/browse/MESOS-1280 > > On Wed, Mar 8, 2017 at 6:34 PM, David McLaughlin <dmclaugh...@apache.org> > wrote: > > > Spoke with Zameer offline and he asked me to post additional thoughts > > here. > > > > My motivation for solving this without dynamic reservations is just the > > sheer number of questions I have after reading the RFC and current design > > doc. And most of them are not about the current proposal and goals or the > > MVP but more about how this feature will scale into persistent storage. > > > > I think best-effort dynamic reservations are such a different problem > than > > the reservations that would be needed to support persistent storage. My > > primary concern is around things like quota. For the current proposal and > > the small best-effort feature we're adding, it makes no sense to get into > > the complexities of separate quota for reserved resources vs preferred > > resources, but the reality of exposing such a concept to a large > > organisation where we can't automatically reclaim anything reserved means > > we'd almost definitely want that. The issue with the iterative approach > is > > decisions we take here could have a huge impact on those tasks later, > once > > we expose the reserved tier into the open. That means more upfront design > > and planning, which so far has blocked a super useful feature that I feel > > all of us want. > > > > My gut feeling is we went about this all wrong. We started with dynamic > > reservations and thought about how we could speed up task scheduling with > > them. If we took the current problem brief and started from first > > principals then I think we'd naturally look for something like a > > replaceTask(offerId, taskInfo) type API from Mesos. > > > > I'll bring this up within our team and see if we can put resources on > > adding such an API. Any feedback on this approach in the meantime is > > welcome. > > > > On Wed, Mar 8, 2017 at 5:30 PM, David McLaughlin <dmclaugh...@apache.org > > > > wrote: > > > >> You don't have to store anything with my proposal. Preemption doesn't > >> store anything either. The whole thing is it's just best-effort, and if > the > >> Scheduler restarts the worst that would happen is part of the current > batch > >> would have to go through the current Scheduling loop that users tolerate > >> and deal with today. > >> > >> > >> > >> On Wed, Mar 8, 2017 at 5:08 PM, Zameer Manji <zma...@apache.org> wrote: > >> > >>> David, > >>> > >>> I have two concerns with that idea. First, it would require persisting > >>> the > >>> relationship of <Hostname, Resources> to <Task> for every task. I'm not > >>> sure if adding more storage and storage operations is the ideal way of > >>> solving this problem. Second, in a multi framework environment, a > >>> framework > >>> needs to use dynamic reservations otherwise the resources might be > taken > >>> by > >>> another framework. > >>> > >>> On Wed, Mar 8, 2017 at 5:01 PM, David McLaughlin < > dmclaugh...@apache.org > >>> > > >>> wrote: > >>> > >>> > So I read the docs again and I have one major question - do we even > >>> need > >>> > dynamic reservations for the current proposal? > >>> > > >>> > The current goal of the proposed work is to keep an offer on a host > and > >>> > prevent some other pending task from taking it before the next > >>> scheduling > >>> > round. This exact problem is solved in preemption and we could use a > >>> > similar technique for reserving offers after killing tasks when going > >>> > through the update loop. We wouldn't need to add tiers or > >>> reconciliation or > >>> > solve any of these other concerns. Reusing an offer skips so much of > >>> the > >>> > expensive stuff in the Scheduler that it would be a no-brainer for > the > >>> > operator to turn it on for every single task in the cluster. > >>> > > >>> > > >>> > On Thu, Mar 2, 2017 at 7:52 AM, Steve Niemitz <sniem...@apache.org> > >>> wrote: > >>> > > >>> > > I read over the docs, it looks like a good start. Personally I > >>> don't see > >>> > > much of a benefit for dynamically reserved cpu/mem, but I'm excited > >>> about > >>> > > the possibility of building off this for dynamically reserved > >>> persistent > >>> > > volumes. > >>> > > > >>> > > I would like to see more detail on how a reservation "times out", > >>> and the > >>> > > configuration options per job around that, as I feel like its the > >>> most > >>> > > complicated part of all of this. Ideally there would also be hooks > >>> into > >>> > > the host maintenance APIs here. > >>> > > > >>> > > I also didn't see any mention of it, but I believe mesos requires > the > >>> > > framework to reserve resources with a role. By default aurora runs > >>> as > >>> > the > >>> > > special "*" role, does this mean aurora will need to have a role > >>> > specified > >>> > > now for this to work? Or does mesos allow reserving resources > >>> without a > >>> > > role? > >>> > > > >>> > > On Thu, Mar 2, 2017 at 8:35 AM, Erb, Stephan < > >>> > stephan....@blue-yonder.com> > >>> > > wrote: > >>> > > > >>> > > > Hi everyone, > >>> > > > > >>> > > > There have been two documents on Dynamic Reservations as a first > >>> step > >>> > > > towards persistent services: > >>> > > > > >>> > > > · RFC: https://docs.google.com/document/d/ > >>> > > > 15n29HSQPXuFrnxZAgfVINTRP1Iv47_jfcstJNuMwr5A/edit#heading=h. > >>> > hcsc8tda08vy > >>> > > > > >>> > > > · Technical Design Doc: https://docs.google.com/docume > >>> nt/d/ > >>> > > > 1L2EKEcKKBPmuxRviSUebyuqiNwaO-2hsITBjt3SgWvE/edit#heading=h. > >>> > klg3urfbnq3v > >>> > > > > >>> > > > Since a couple of days there are also now two patches online for > a > >>> MVP > >>> > by > >>> > > > Dmitriy: > >>> > > > > >>> > > > · https://reviews.apache.org/r/56690/ > >>> > > > > >>> > > > · https://reviews.apache.org/r/56691/ > >>> > > > > >>> > > > From reading the documents, I am under the impression that there > >>> is a > >>> > > > rough consensus on the following points: > >>> > > > > >>> > > > · We want dynamic reservations. Our general goal is to > >>> enable > >>> > the > >>> > > > re-scheduling of tasks on the same host they used in a previous > >>> run. > >>> > > > > >>> > > > · Dynamic reservations are a best-effort feature. If in > >>> doubt, > >>> > a > >>> > > > task will be scheduled somewhere else. > >>> > > > > >>> > > > · Jobs opt into reserved resources using an appropriate > >>> tier > >>> > > > config. > >>> > > > > >>> > > > · The tier config in supposed to be neither preemptible > nor > >>> > > > revocable. Reserving resources therefore requires appropriate > >>> quota. > >>> > > > > >>> > > > · Aurora will tag reserved Mesos resources by adding the > >>> unique > >>> > > > instance key of the reserving task instance as a label. Only this > >>> task > >>> > > > instance will be allowed to use those tagged resources. > >>> > > > > >>> > > > I am unclear on the following general questions as there is > >>> > contradicting > >>> > > > content: > >>> > > > > >>> > > > a) How does the user interact with reservations? There are > >>> > several > >>> > > > proposals in the documents to auto-reserve on `aurora job create` > >>> or > >>> > > > `aurora cron schedule` and to automatically un-reserve on the > >>> > appropriate > >>> > > > reverse actions. But will we also allow a user further control > >>> over the > >>> > > > reservations so that they can manage those independent of the > >>> task/job > >>> > > > lifecycle? For example, how does Borg handle this? > >>> > > > > >>> > > > b) The implementation proposal and patches include an > >>> > > > OfferReconciler, so this implies we don’t want to offer any > >>> control for > >>> > > the > >>> > > > user. The only control mechanism will be the cluster-wide offer > >>> wait > >>> > time > >>> > > > limiting the number of seconds unused reserved resources can > linger > >>> > > before > >>> > > > they are un-reserved. > >>> > > > > >>> > > > c) Will we allow adhoc/cron jobs to reserve resources? Does > >>> it > >>> > even > >>> > > > matter if we don’t give control to users and just rely on the > >>> > > > OfferReconciler? > >>> > > > > >>> > > > > >>> > > > I have a couple of questions on the MVP and some implementation > >>> > details. > >>> > > I > >>> > > > will follow up with those in a separate mail. > >>> > > > > >>> > > > Thanks and best regards, > >>> > > > Stephan > >>> > > > > >>> > > > >>> > > >>> > -- > >>> > Zameer Manji > >>> > > >>> > >> > >> > > >
