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From Jean-Marc Spaggiari <jean-m...@spaggiari.org>
Subject Re: splits and merge
Date Wed, 15 Jul 2015 14:54:32 GMT
Hi Ivan,


For #1, let's consider regions A, B, C and D all in server S.

If you merge A and B togher and C and D togher, still in S, you will have
A' and C' regions only on S.

Now, if you try to merge again A' and C' into a new bigger region, this
will fail silently until A' and C' are major compacted.

Indeed, before major compaction, A' and C' will both still contain
references to A+B and C+D files/regions. So to be able to merge A' and C'
you need this to be cleaned and so you need to major compact them.

HTH,

JM

2015-07-15 10:43 GMT-04:00 Ted Yu <yuzhihong@gmail.com>:

> bq. that some times merge just does not work.
>
> Can you identify under what scenario the merge doesn't work (through closer
> inspection of the region server log - assuming you have DEBUG logging
> turned on) ?
>
> bq. Are there minimum requirements for two regions to be merged?
>
> If the two adjacent regions to be merged are on different servers, HBase
> would move one of them to the other region's server.
>
> bq. If those requirements are not met, does the merge process exit
> silently?
>
> Nothing I am aware of.
>
> Cheers
>
> On Wed, Jul 15, 2015 at 3:08 AM, Ivan Brondino <ibrondino@fi.upm.es>
> wrote:
>
> > Hi,
> >
> > We are using Hbase 0.98.6 and Hadoop 2.5.0 - cdh 5.3.5.
> >
> > We have a couple of questions regarding splits and merge:
> >
> > 1) Since both split and merge are async invocations on the client side,
> we
> > have a naîve
> > workaround to make it synchronous that is to look at the RS Info Server
> via
> > an HttpClient checking
> > for pending tasks to be finished. Once all tasks are finished in all RS
> we
> > issue the next split/merge for the same table. Is there a better way to
> do
> > it?
> >
> > 2) Regarding merges, we've noticed that some times merge just does not
> > work. We see on the master log that merge request is issued and it
> forwards
> > it to the corresponding RS but then on the RS nothing happens. We always
> > merge two regions on the same region server.
> > Are there minimum requirements for two regions to be merged? If those
> > requirements are not met, does the merge process exit silently?
> >
> > Thanks in advance,
> >
> > Iván
> >
>

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