[jira] [Commented] (MESOS-1607) Introduce optimistic offers.

["Itamar Ostricher (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MESOS-1607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14577153#comment-14577153 ] 

Itamar Ostricher commented on MESOS-1607:
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I'd love to see this feature implemented!

I've written a framework that actually takes advantage of such optimistic behavior, by "holding on" to resources, anticipating it will have more work to schedule on them.
As it is now, I need to decline the stored resources after some timeout, to avoid starving other frameworks, and there's a tradeoff between the ability to launch new tasks as they come in, and the starvation due to stored resources.

With optimistic offers, the timeout is not needed anymore, and the tradeoff is resolved optimally! I already have code in place to remove stored resources if they are rescinded :-)

> Introduce optimistic offers.
> ----------------------------
>
>                 Key: MESOS-1607
>                 URL: https://issues.apache.org/jira/browse/MESOS-1607
>             Project: Mesos
>          Issue Type: Epic
>          Components: allocation, framework, master
>            Reporter: Benjamin Hindman
>         Attachments: optimisitic-offers.pdf
>
>
> The current implementation of resource offers only enable a single framework scheduler to make scheduling decisions for some available resources at a time. In some circumstances, this is good, i.e., when we don't want other framework schedulers to have access to some resources. However, in other circumstances, there are advantages to letting multiple framework schedulers attempt to make scheduling decisions for the _same_ allocation of resources in parallel.
> If you think about this from a "concurrency control" perspective, the current implementation of resource offers is _pessimistic_, the resources contained within an offer are _locked_ until the framework scheduler that they were offered to launches tasks with them or declines them. In addition to making pessimistic offers we'd like to give out _optimistic_ offers, where the same resources are offered to multiple framework schedulers at the same time, and framework schedulers "compete" for those resources on a first-come-first-serve basis (i.e., the first to launch a task "wins"). We've always reserved the right to rescind resource offers using the 'rescind' primitive in the API, and a framework scheduler should be prepared to launch a task and have those tasks go lost because another framework already started to use those resources.
> Introducing optimistic offers will enable more sophisticated allocation algorithms. For example, we can optimistically allocate resources that are reserved for a particular framework (role) but are not being used. In conjunction with revocable resources (the concept that using resources not reserved for you means you might get those resources revoked) we can easily create a "spot" market for unused resources, driving up utilization by letting frameworks that are willing to use revocable resources run tasks.
> In the limit, one could imagine always making optimistic resource offers. This bears a striking resemblance with the Google Omega model (an isomorphism even). However, being able to configure what resources should be allocated optimistically and what resources should be allocated pessimistically gives even more control to a datacenter/cluster operator that might want to, for example, never let multiple frameworks (roles) compete for some set of resources.



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