I have opened a branch for 0.20 (currently 0.20.3 RC2) updated to run on Hadoop 0.21
(currently 0.21-dev) It's passing all unit tests now.

  http://svn.apache.org/repos/asf/hadoop/hbase/branches/0.20_on_hadoop-0.21

The aim is for client API compatibility. This is an intermediate step for upgrading
to 0.21 so HDFS improvements, e.g. hflush and we hope also HDFS-630, can be
incorporated immediately through an upgrade of the deployment but without requiring
any change to users of the HBase client API or the Thrift or Stargate connectors.

Unlike the 0.20 on Hadoop 0.18.3 branch, the 0.20 on 0.21 branch has a more
aggressive strategy for back end changes -- things that touch HDFS and/or a major
performance win may go in, evaluated on a case by case basis, as long as they do
not change client side API or semantics. For example, the HLog and related THBase
improvements from HBase trunk have been backported.

I do not expect to maintain this branch beyond some transition period, maybe until
0.21.1.

   - Andy

If it is just API compat, why not re-add the 0.19 API to 0.21.  It
hasn't even been a year since the new 0.20 API was released...
Maintaining the old API costs nothing in terms of core code (ie: its
not preventing us from doing features).

-ryan

On Mon, Jan 25, 2010 at 6:40 PM, Andrew Purtell <apurtell@apache.org> wrote:
> I have opened a branch for 0.20 (currently 0.20.3 RC2) updated to run on Hadoop 0.21
> (currently 0.21-dev) It's passing all unit tests now.
>
>  http://svn.apache.org/repos/asf/hadoop/hbase/branches/0.20_on_hadoop-0.21
>
> The aim is for client API compatibility. This is an intermediate step for upgrading
> to 0.21 so HDFS improvements, e.g. hflush and we hope also HDFS-630, can be
> incorporated immediately through an upgrade of the deployment but without requiring
> any change to users of the HBase client API or the Thrift or Stargate connectors.
>
> Unlike the 0.20 on Hadoop 0.18.3 branch, the 0.20 on 0.21 branch has a more
> aggressive strategy for back end changes -- things that touch HDFS and/or a major
> performance win may go in, evaluated on a case by case basis, as long as they do
> not change client side API or semantics. For example, the HLog and related THBase
> improvements from HBase trunk have been backported.
>
> I do not expect to maintain this branch beyond some transition period, maybe until
> 0.21.1.
>
>   - Andy
>
>
>
>
>

Not 0.19, 0.20.

RPC compatibility is the key. Let 0.20.3 or 0.20.2 clients operate against
HBase running on HDFS 0.21 (with durable WAL etc.) without any change to
the client side.

   - Andy

----- Original Message ----
> From: Ryan Rawson <ryanobjc@gmail.com>
> To: hbase-user@hadoop.apache.org
> Cc: hbase-dev@hadoop.apache.org
> Sent: Tue, January 26, 2010 11:34:26 AM
> Subject: Re: new HBase 0.20 on Hadoop 0.21 branch
>
> If it is just API compat, why not re-add the 0.19 API to 0.21.  It
> hasn't even been a year since the new 0.20 API was released...
> Maintaining the old API costs nothing in terms of core code (ie: its
> not preventing us from doing features).
>
> -ryan
>
> On Mon, Jan 25, 2010 at 6:40 PM, Andrew Purtell wrote:
> > I have opened a branch for 0.20 (currently 0.20.3 RC2) updated to run on
> Hadoop 0.21
> > (currently 0.21-dev) It's passing all unit tests now.
> >
> >  http://svn.apache.org/repos/asf/hadoop/hbase/branches/0.20_on_hadoop-0.21
> >
> > The aim is for client API compatibility. This is an intermediate step for
> upgrading
> > to 0.21 so HDFS improvements, e.g. hflush and we hope also HDFS-630, can be
> > incorporated immediately through an upgrade of the deployment but without
> requiring
> > any change to users of the HBase client API or the Thrift or Stargate
> connectors.
> >
> > Unlike the 0.20 on Hadoop 0.18.3 branch, the 0.20 on 0.21 branch has a more
> > aggressive strategy for back end changes -- things that touch HDFS and/or a
> major
> > performance win may go in, evaluated on a case by case basis, as long as they
> do
> > not change client side API or semantics. For example, the HLog and related
> THBase
> > improvements from HBase trunk have been backported.
> >
> > I do not expect to maintain this branch beyond some transition period, maybe
> until
> > 0.21.1.
> >
> >   - Andy
> >
> >
> >
> >
> >