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From Karthik Kambatla <ka...@cloudera.com>
Subject Re: "Reservation" ambiguity
Date Wed, 05 Aug 2015 15:20:13 GMT
Inline.

On Tue, Aug 4, 2015 at 6:48 PM, Chris Douglas <cdouglas@apache.org> wrote:

> How visible are (1) reservations? They're an internal, implementation
> detail exposed in metrics only to explain the edge cases they create.
> Are users typically aware of them?
>

This is internal, and I don't think users are aware of the mechanics.
However, they do see metrics for "reserved" resources.


>
> SLA reservations (2) are user-visible, and express the contract with
> users/operators symmetrically. While (1) is a concept, renaming (2)
> would require user-breaking code changes.
>

Yes, I don't think we should rename (2).


>
> Unless you're discussing the intersection- the effect of reservations
> (1) on a reservation (2)- it's usually clear from context... I'd
> rather avoid breaking anyone listening to the metrics in Hadoop-3.
>

I propose to add new metrics holdMB, holdCores for reservedMB,
reseveredCores. Could we deprecate the older metrics in Hadoop-2 and
Hadoop-3, and remove them in Hadoop-4?


>
> Maybe reservations (2) could have been named "sessions", but that
> collided with applications that already used it for a similar concept.
> -C
>
> On Wed, Jul 29, 2015 at 10:37 AM, Karthik Kambatla <kasha@cloudera.com>
> wrote:
> > Hi folks
> >
> > We use the word "reservation" to mean both (1) reservations on nodes to
> > avoid starvation of big container asks, and (2) the recent SLA work. This
> > is confusing both to developers and end-users.
> >
> > I was wondering if people are open to calling the first one a "hold" and
> > the second one a "reservation". We can change the terminology in the code
> > and add new metrics for hold in branch-2 and remove the metrics for
> > reserved* in Hadoop-3?
> >
> > Thoughts?
>

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