Re: About adding methods to an interface which is part of our public API in minor release

[Josh Elser]

+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<st...@duboce.net>  wrote:

On Wed, Mar 15, 2017 at 10:28 PM, Duo Zhang<zhang...@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.