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From Elliott Clark <ecl...@stumbleupon.com>
Subject Re: deprecating (old) metrics in favor of metrics2 framework
Date Tue, 10 Jul 2012 21:01:23 GMT
I think Gary here, and Stack in the other thread have raised enough points
that if I could vote I would vote in favor of holding onto the classes that
might be used externally past 0.96.0.  Right now there's no alternative to
several of our Metrics classes and the deprecations weren't out in 0.94.0.
 With all that said I don't see a large down side with keeping those
classes around while the actual hbase code base starts using something else
(the metrics2 replacements).  I added comment in HBASE-6365 with all of the
classes that I could find that would be deprecated (They all derive from or
use the old metrics code).  There are a lot


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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