Thanks Michael for the detailed clarification, it is much clear to me
now :-)
And I have a further question regarding persistent volume: I think, similar
with dynamic reservation, persistent volume is also per role now, so that
means a persistent volume created by a framework can be offered to another
framework in the same role, right? I assume the other framework can not
destroy the persistent volume due to ACL.
Regards,
Qian Zhang （张乾）
Developer, IBM Platform Computing
Phone: 86-29-68797144 | Tie-Line: 87144
IBM
E-mail: [email protected]
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From: Michael Park <[email protected]>
To: [email protected]
Date: 08/31/2015 03:58
Subject: Re: Is dynamic reservation per role or per framework
Hello Qian,
Yes, dynamic reservation (at least currently) is per role, rather than the
framework level. The main motivation for such a design was based on the
following thought: "dynamic reservation should simply be a dynamic version
of the existing static reservation."
You're absolutely right that if multiple frameworks are in the same role,
the resources reserved for that role can be offered to any of the
frameworks in that role. The justification for this behavior is that:
that's what happens if we were to statically reserve resources for a role,
and have multiple frameworks in it anyway. If a framework requires sole
ownership of the resources, the operator is required to create a role for
that framework only.
Having said that, I've argued for per-framework reservation. The obvious
benefits are that (1) no need to worry about resources potentially being
shared, (2) no need for operators to set up the ACLs to enforce sole
ownership of resources, etc. An implied benefit is that Mesos can
automatically unreserve the resources reserved by the framework if the
framework leaves and exceeds its reregistration_timeout.
I still believe the per-framework reservation makes more sense, and as long
as there's enough interest for them, we'll get to work on it as follow-up,
post-MVP work.
Thanks,
MPark.
On Sun, Aug 30, 2015 at 9:35 AM Qian AZ Zhang <[email protected]> wrote:
>
>
> Hi,
>
> I took a look at dynamic reservation design doc and the related code in
> Mesos master, it seem dynamic reservation works in role level rather than
> in framework level, that means a framework can only reserve some
resources
> for its role rather than itself. If so, then I am thinking about this
case:
> both Cassandra framework and HDFS framework belongs to role1, and HDFS
> dynamically reserves some resources in a slave for role1, then I think it
> may be possible for allocator to offer those resources to Cassandra since
> it also belongs to role1, but actually HDFS expects to be offered with
> those resources to launch its tasks.
>
> Please anyone correct me if my understanding above was wrong, thanks!
>
>
> Regards,
> Qian Zhang
