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From Ted Yu <yuzhih...@gmail.com>
Subject Re: How to replace MetaUtils.ScannerListener?
Date Fri, 22 Mar 2013 16:31:24 GMT
Point taken.

But I don't think previous discussion was about removing offline merge.

On Fri, Mar 22, 2013 at 8:19 AM, Jonathan Hsieh <jon@cloudera.com> wrote:

> Let me offer a counter argument.  The offline splitting code is still
> present even though online splitting isn't the problem it used to be. We
> actually added an extenal wal replayer even though we have wal replay in
> our normal recovery path.  Copy table still exists even though snapshots
> and snapshot export exists.  Would we consider removing these?
>
> IMO, until online merge has been proven and hardened (gone through few
> releases and folk using) I don't feel comfortable removing it.
>
> Jon.
>
> On Thu, Mar 21, 2013 at 7:07 PM, Jean-Marc Spaggiari <
> jean-marc@spaggiari.org> wrote:
>
> > Hi Enis,
> >
> > I totaly agree. But even if online merge are available, maybe offline
> > merges can still usefull in case the cluster is down for maintenance,
> > or because there is any issue to start it, or anything else? We have
> > it, so we should maybe try to keep it?
> >
> > JM
> >
> > 2013/3/21 Enis Söztutar <enis.soz@gmail.com>:
> > > Thanks J-M.
> > >
> > > What I am trying to understand is that whether we should cut the cord
> for
> > > offline merge once online is working. If you think about it, there
> should
> > > not be a need to merge offline tables.
> > >
> > > Enis
> > >
> > >
> > > On Thu, Mar 21, 2013 at 3:16 PM, Jean-Marc Spaggiari <
> > > jean-marc@spaggiari.org> wrote:
> > >
> > >> Offline merge is already there and working fine.
> > >>
> > >> The usecase here was to retreive all the regions for a given table to
> > >> merge them 2 by 2, offline.
> > >>
> > >> It's working fine, but since the Meta rework it's not working anymore
> > >> and I'm trying to rebase the patch.
> > >>
> > >> Like J-D is saying, yes, it's used only in the offline merge... And
> > >> since the online merge is coming, I think it's cleaner to keep the
> > >> code in the offline merge since it will disapear soon, but in the
> > >> meantime, at least, we will have the offline one.
> > >>
> > >> JM
> > >>
> > >> 2013/3/21 Enis Söztutar <enis.soz@gmail.com>:
> > >> > What is the use case behind offline merge? Is it because we cannot
> do
> > >> > online merge yet? If we can get HBASE-7403 in, is there still need
> to
> > >> > support offline merge?
> > >> >
> > >> > Enis
> > >> >
> > >> >
> > >> > On Thu, Mar 21, 2013 at 2:56 PM, Jean-Daniel Cryans <
> > jdcryans@apache.org
> > >> >wrote:
> > >> >
> > >> >> As far as I can tell, only the merge code uses MetaUtils to do
> > offline
> > >> >> work. If this is the code you are in then pull it back into
> MetaUtils
> > >> >> I think.
> > >> >>
> > >> >> J-D
> > >> >>
> > >> >> On Thu, Mar 21, 2013 at 2:44 PM, Jean-Marc Spaggiari
> > >> >> <jean-marc@spaggiari.org> wrote:
> > >> >> > Vector is because of a very old bad habit ;) I will change
that
> to
> > >> >> ArrayList.
> > >> >> >
> > >> >> > So far I have inlined the scanMetaRegion feature into the
Merge,
> > but
> > >> >> > maybe it should be cleaner to put it back in?
> > >> >> >
> > >> >> > Anyway, I will keep the inlined one until everything is cleaned.
> > >> >> >
> > >> >> > 2013/3/21 Enis Söztutar <enis.soz@gmail.com>:
> > >> >> >> The problem around current META scanning is that there
is more
> > than
> > >> one
> > >> >> way
> > >> >> >> to do these, and the META layout is exposed. We should
refrain
> > from
> > >> >> >> exposing the META details.
> > >> >> >> AFAIK, these do the same thing:
> > >> >> >>  MetaReader.Visitor
> > >> >> >>  MetaScanner.MetaScannerVisitor, and
> > >> >> >>  MetaUtils.ScannerListener
> > >> >> >>
> > >> >> >> More concerning is that the code for managing META is
spread
> over
> > >> >> >> MetaEditor, MetaReader, MetaScanner, MetaUtils, HRegionInfo
(and
> > >> maybe
> > >> >> >> more). There are a couple of issues to rework these interfaces,
> > but I
> > >> >> did
> > >> >> >> not get the chance to work on those.
> > >> >> >>
> > >> >> >>
> > >> >> >> Enis
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >>
> > >> >> >> On Thu, Mar 21, 2013 at 2:18 PM, Jean-Daniel Cryans <
> > >> >> jdcryans@apache.org>wrote:
> > >> >> >>
> > >> >> >>> Mmmm I may have been trigger happy. You could pull
back the
> > >> >> >>> ScannerListener and scanMetaRegion.
> > >> >> >>>
> > >> >> >>> BTW, why are you using a Vector instead of ArrayList?
> > >> >> >>>
> > >> >> >>> J-D
> > >> >> >>>
> > >> >> >>> On Thu, Mar 21, 2013 at 2:05 PM, Jean-Marc Spaggiari
> > >> >> >>> <jean-marc@spaggiari.org> wrote:
> > >> >> >>> > Hi,
> > >> >> >>> >
> > >> >> >>> > In trunk, since HBASE-3171 (Drop ROOT and instead
store META
> > >> >> >>> > location(s) directly in ZooKeeper ) there is
no more
> > >> >> >>> > MetaUtils.ScannerListener.
> > >> >> >>> >
> > >> >> >>> > In the merge, I used it to retreive all the
regions belonging
> > to a
> > >> >> >>> > specific table, from the META. kind of scan.
> > >> >> >>> >
> > >> >> >>> >           // Retrieve the list of regions for
this table.
> > >> >> >>> >           final List<HRegionInfo> regions
= new
> > >> >> Vector<HRegionInfo>();
> > >> >> >>> >
> > utils.scanMetaRegion(HRegionInfo.FIRST_META_REGIONINFO,
> > >> new
> > >> >> >>> > MetaUtils.ScannerListener() {
> > >> >> >>> >             public boolean processRow(HRegionInfo
info) {
> > >> >> >>> >               if ((info != null) &&
> > >> >> >>> > (Bytes.compareTo(info.getTableName(), tableName)
== 0)) {
> > >> >> >>> >                 regions.add(info);
> > >> >> >>> >               }
> > >> >> >>> >               return true;
> > >> >> >>> >             }
> > >> >> >>> >           });
> > >> >> >>> >
> > >> >> >>> >
> > >> >> >>> > Is there a recommanded way to replace that?
The Merge is
> > running
> > >> >> >>> > offline, so I can't do a scan.
> > >> >> >>> >
> > >> >> >>> > Thanks,
> > >> >> >>> >
> > >> >> >>> > JM
> > >> >> >>>
> > >> >>
> > >>
> >
>
>
>
> --
> // Jonathan Hsieh (shay)
> // Software Engineer, Cloudera
> // jon@cloudera.com
>

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