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From Ted Yu <yuzhih...@gmail.com>
Subject Re: deprecating (old) metrics in favor of metrics2 framework
Date Tue, 10 Jul 2012 21:03:59 GMT
Points taken.

Thanks for the education of metrics framework history.

On Tue, Jul 10, 2012 at 1:55 PM, Gary Helmling <ghelmling@gmail.com> wrote:

> I agree that having a new metrics2 implementation in 0.96 would be
> great to see and seems like a natural fit.  I'm 100% for that.  But I
> do think that having metrics2 and (deprecated) metrics v1 in the same
> release would be very helpful to users making the transition.  So to
> me it seems more natural for 0.96 to be that release with both
> implementations, since that's where it seems like the metrics2
> implementation will land.
>
> Otherwise it seems like we risk introducing the same disruptions that
> Hadoop did when metrics2 initially replaced the metrics v1
> implementation, instead of living along side.  This did cause us as a
> project some trouble until metrics v1 was added back in.  So it would
> be unfortunate to repeat the same mistake ourselves.
>
> If there's considerable pain or overhead in having both
> implementations live in parallel, maybe it's worth doing a straight
> switch over in 0.96.  I haven't looked at the differences enough
> myself to know.  But otherwise it seems like an easier migration path
> to deprecate v1 in 0.96 and remove the release after.
>
>
> On Tue, Jul 10, 2012 at 1:35 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> > Gary:
> > Your comment makes sense.
> >
> > Part of this poll originates from the fact that 0.96 is our singularity
> > release. RPC, coprocessor, etc have undergone considerable changes.
> > Users migrating to 0.96 would have to deal with a lot of updates in their
> > codebase.
> >
> > It seems to me that doing all upgrades in one shot is almost the same as
> > upgrading components other than metrics framework.
> >
> > Cheers
> >
> > On Tue, Jul 10, 2012 at 1:29 PM, Gary Helmling <ghelmling@gmail.com>
> wrote:
> >
> >> >
> >> > Whether we support 2 (actually more than 2) metrics frameworks in 0.96
> >> can
> >> > be debated in the next 2 months.
> >> >
> >>
> >> I'm not sure I agree that deprecating without having something in
> >> place for users to move to makes sense.
> >>
> >> > As Todd mentioned in the thread 'HBase 0.94.1', we will try our best
> to
> >> > keep JMX interface the same across 0.94 and 0.96. Does this somehow
> >> reduce
> >> > the concern you raised ?
> >> >
> >>
> >> I think that maintaining consistency with the existing JMX naming
> >> conventions (to the extent possible) is important for operational
> >> concerns, but it's independent of the MetricsContext question and the
> >> question of whether other metrics classes of our own need a proper
> >> deprecation cycle.
> >>
> >> > As for using MetricsContext, I assume the user also uses hadoop in
> his /
> >> > her deployment. Then he / she should be aware of the deprecation of
> >> > metrics.* classes in both hadoop 1.0 and 2.0
> >> > Meaning he / she should be prepared to endorse metrics2 framework.
> >> >
> >>
> >> Hadoop deprecating metrics in favor of metrics2 is independent of us
> >> deprecating HBase metrics classes.  TimeStampingFileContext is one
> >> MetricsContext implementation in HBase that would need to be
> >> deprecated and could be used or possibly extended by current users.
> >>
> >> Ultimately it's up to Lars H as RM for 0.94 to decide what he wants to
> >> include.  It just feels to me like we're rushing to deprecate metrics
> >> in 0.94 so that it can be removed in 0.96, instead of what seems to me
> >> like the more standard path of deprecating metrics in 0.96, while also
> >> including new metrics2 implementations, which would give users a
> >> smoother path to actually switch over.  I'm just not sure I understand
> >> the motivation for deprecating in 0.94 instead of 0.96.
> >>
>

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