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From Gary Helmling <ghelml...@gmail.com>
Subject Re: dynamic RPC and coprocessor changes
Date Wed, 06 Oct 2010 07:12:03 GMT
On Tue, Oct 5, 2010 at 7:41 PM, Andrew Purtell <apurtell@apache.org> wrote:

> With that said, I expect Gary is already working to address this concern
> specifically:
>
> > Looking at some of their names, they are generic sounding
> > and it's not clear to me without digging in that they are
> > part of coprocessors.  Is it possible to move CP stuff into
> > client.cp packages and the like?  Or prefix with CoProc
> > > or some way to keep this stuff separated?
>
>
I'll have a patch with clarified naming and tweaks for other review comments
ready tomorrow morning.

For what it's worth, while I agree that we can't anticipate all client needs
without some real world examples, I think what we have is basic and flexible
enough to be a decent first start.  We could delay release to continue to
experiment with what we have for our own goals, but I don't think that gets
us much closer to anticipating or meeting all end-user needs.  This is about
end-user extensibility and practically I don't think we'll get broad enough
exposure for different enough end-user usage without a release.

The client and RPC functionality is mostly an additional path for the
CoprocessorProtocol invocations, and really should not be disruptive of
existing functionality.  As for what can be invoked, well you're free to
define your own methods, so there's a lot of flexibility there.

For coprocessors, sure there were quite a few changes from the initial
patches to actually using it to implement security, but a lot of that
amounted to paring it down to a core usable scope.  It will doubtless not
address all use cases, but I think that will remain true whether it's
included in 0.90 or 0.92.  Obviously I'm biased but I see those changes more
likely as an extension of the API than a wholesale reworking of it.  Just a
thought, but doesn't Hadoop use annotations to identify level of stability
of interfaces?  Maybe some like experimental is warranted here, not least of
all because you'd be running user code in your regionserver.

--gh

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