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From Josh Elser <els...@apache.org>
Subject Re: About adding methods to an interface which is part of our public API in minor release
Date Thu, 16 Mar 2017 18:02:34 GMT
+1 to the JDK8 default implementation approach. I'd say this would be 
good to push forward for the future.

For 1.x, I see no reason why we couldn't provide concrete 
implementations as a stop-gap. Identifying and creating those classes is 
probably the biggest barrier :). I don't think anything really stops us 
from doing this now...

James Taylor wrote:
> How about the idea of HBase having base implementations for common
> interfaces? That would often help applications built on top of HBase to
> maintain backward compatibility from release to release.
> On Wed, Mar 15, 2017 at 10:38 PM Stack<stack@duboce.net>  wrote:
>> On Wed, Mar 15, 2017 at 10:28 PM, Duo Zhang<zhangduo@apache.org>  wrote:
>>> There are some comments in https://issues.apache.org/
>>> jira/browse/HBASE-17584
>>> .
>>> In HBASE-17584, we want to remove Scan.getScanMetrics and move the method
>>> to ResultScanner  which is an interface and part of our public API.
>>> In our refguide, it is clear that we can do this for a major release.
>>> And for patch release, it is also clear that we are not allowed to do
>> this.
>>> New APIs introduced in a patch version will only be added in a source
>>> compatible way [1<http://hbase.apache.org/book.html#_footnote_1>]: i.e.
>>> code that implements public APIs will continue to compile.
>>> But for minor release, it is a liitle inexplicit.
>>> A minor upgrade requires no application/client code modification. Ideally
>>> it would be a drop-in replacement but client code, coprocessors, filters,
>>> etc might have to be recompiled if new jars are used.
>>> If no client code modification is required, then we are not allowed to
>> add
>>> methods to interface as it will cause compliation error if user extends
>> the
>>> interface as on branch-1, we still need to support JDK7 which does not
>>> support default method. But I think this will make minor release almost
>> the
>>> same with patch release? And another point is that, for most users, they
>>> only use the interface and do not implement it, so adding methods will
>> not
>>> break their code.
>>> So here we want to see what the community think of whether we should
>> allow
>>> adding methods to interface in minor release. Any comments are welcomed.
>> I'd suggest we add to the refguide a clarification that allows addition of
>> new methods to Interfaces in minor releases. Here is a suggested addition:
>> "For a minor release, IF YOU HAVE IMPLEMENTED AN INTERFACE, you may have to
>> recompile. We reserve the right to add new methods to existing Interfaces
>> on minor updates (this will be less of an issue in hbase-2.0.0 which
>> requires JDK8; JDK8 allows specification of 'default' implementations of
>> Interface methods)"
>> I could add a further qualifier only applies to hbase-1.4.0 and beyond?
>> St.Ack
>>> Thanks.

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