hbase-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From ramkrishna vasudevan <ramkrishna.s.vasude...@gmail.com>
Subject Re: Parallel Scanner
Date Mon, 20 Feb 2017 06:59:05 GMT
Yes. There is way.

Have you seen Endpoints? Endpoints are triggers like points that allows
your client to trigger them parallely in one ore more regions using the
start and end key of the region. This executes parallely and then you may
have to sort out the results as per your need.

But these endpoints have to running on your region servers and it is not a
client only soln.
https://blogs.apache.org/hbase/entry/coprocessor_introduction.

Be careful when you use them. Since these endpoints run on server ensure
that these are not heavy or things that consume more memory which can have
adverse effects on the server.


Regards
Ram

On Mon, Feb 20, 2017 at 12:18 PM, Anil <anilklce@gmail.com> wrote:

> Thanks Ram.
>
> So, you mean that there is no harm in using  HTable#getRegionsInRange in
> the application code.
>
> HTable#getRegionsInRange returned single entry for all my region start key
> and end key. i need to explore more on this.
>
> "If you know the table region's start and end keys you could create
> parallel scans in your application code."  - is there any way to scan a
> region in the application code other than the one i put in the original
> email ?
>
> "One thing to watch out is that if there is a split in the region then
> this start
> and end row may change so in that case it is better you try to get
> the regions every time before you issue a scan"
>  - Agree. i am dynamically determining the region start key and end key
> before initiating scan operations for every initial load.
>
> Thanks.
>
>
>
>
> On 20 February 2017 at 10:59, ramkrishna vasudevan <
> ramkrishna.s.vasudevan@gmail.com> wrote:
>
> > Hi Anil,
> >
> > HBase directly does not provide parallel scans. If you know the table
> > region's start and end keys you could create parallel scans in your
> > application code.
> >
> > In the above code snippet, the intent is right - you get the required
> > regions and can issue parallel scans from your app.
> >
> > One thing to watch out is that if there is a split in the region then
> this
> > start and end row may change so in that case it is better you try to get
> > the regions every time before you issue a scan. Does that make sense to
> > you?
> >
> > Regards
> > Ram
> >
> > On Sat, Feb 18, 2017 at 1:44 PM, Anil <anilklce@gmail.com> wrote:
> >
> > > Hi ,
> > >
> > > I am building an usecase where i have to load the hbase data into
> > In-memory
> > > database (IMDB). I am scanning the each region and loading data into
> > IMDB.
> > >
> > > i am looking at parallel scanner ( https://issues.apache.org/
> > > jira/browse/HBASE-8504, HBASE-1935 ) to reduce the load time and
> HTable#
> > > getRegionsInRange(byte[] startKey, byte[] endKey, boolean reload) is
> > > deprecated, HBASE-1935 is still open.
> > >
> > > I see Connection from ConnectionFactory is HConnectionImplementation by
> > > default and creates HTable instance.
> > >
> > > Do you see any issues in using HTable from Table instance ?
> > >             for each region {
> > >                         int i = 0;
> > >                     List<HRegionLocation> regions =
> > > hTable.getRegionsInRange(scans.getStartRow(), scans.getStopRow(),
> true);
> > >
> > >                     for (HRegionLocation region : regions){
> > >                     startRow = i == 0 ? scans.getStartRow() :
> > > region.getRegionInfo().getStartKey();
> > >                     i++;
> > >                     endRow = i == regions.size()? scans.getStopRow() :
> > > region.getRegionInfo().getEndKey();
> > >                      }
> > >            }
> > >
> > > are there any alternatives to achieve parallel scan? Thanks.
> > >
> > > Thanks
> > >
> >
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message