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From Nick Dimiduk <ndimi...@gmail.com>
Subject Re: [DISCUSS] More Shading
Date Wed, 19 Apr 2017 04:20:47 GMT
On Wed, Apr 12, 2017 at 2:30 PM, Stack <stack@duboce.net> wrote:

> > >> If the above quote is true, then I think what we want is a set of
> > shaded
> > > >> Hadoop client libs that we can depend on so as to not get all the
> > > >> transitive deps. Hadoop doesn't provide it, but we could do so
> > ourselves
> > > >> with (yet another) module in our project. Assuming, that is, the
> > > upstream
> > > >> client interfaces are well defined and don't leak stuff we care
> about.
> >
>
>
> We should do this too (I think you've identified the big 'if' w/ the above
> identified assumption). As you say later, "... it's time we firm up the
> boundaries between us and Hadoop.". There is some precedent with
> hadoop-compat-* modules. Hadoop would be relocated?
>

Ideally we'd relocate any parts of Hadoop that are not part of our public
contract. Not sure if there's an intersection between "ideal" and
"practical" though.

Spitballing, IIUC, I think this would be a big job (once per version and
> the vagaries of hadoop/spark) with no guarantee of success on other end
> because of assumption you call out. Do I have this right?
>

Yeah you have my meaning. My argument is not whether we should shade but
rather how we make it a maintainable deployment tool for our team of
volunteers. Hence interest in compatibility verification tools like we do
with our api compatibility tools.

> Isolating our clients from our deps is best served by our shaded modules.
> > What do you think about turning things on their head: for 2.0 the
> > hbase-client jar is the shaded artifact by default, not the other way
> > around? We have cleanup to get our deps out of our public interfaces in
> > order to make this work.
> >
> >
> We should do this at least going forward. hbase2 is the opportunity.
> Testing and doc is all that is needed? I added it to our hbase2 description
> doc as a deliverable (though not a blocker).
>

I've not tried to consume these efforts. A reasonable test-case to see if
these are ready for prime-time would be to try rebuilding one of the more
complex downstream projects (i.e, Phoenix, Trafodion, Splice) using the
shaded jars and see how bad the diff is.

> This proposal of an external shaded dependencies module sounds like an
> > attempt to solve both concerns at once. It would isolate ourselves from
> > Hadoop's deps, and it would isolate our clients from our deps. However,
> it
> > doesn't isolate our clients from Hadoop's deps, so our users don't really
> > gain anything from it. I also argue that it creates an unreasonable
> release
> > engineering burden on our project. I'm also not clear on the implications
> > to downstreamers who extend us with coprocessors.
> >
>
>
> Other than a missing 'quick-fix' descriptor, you call what is proposed well
> ....except where you think the prebuild will be burdensome. Here I think
> otherwise as I think releases will be rare, there is nought 'new' in a
> release but packaged 3rd-party libs, and verification/vote by PMCers should
> be a simple affair.
>

Maybe it's not such a burden? If the 2.0 and 3.0 RM's are brave and true,
it's worth a go.

Do you agree that the fixing-what-we-leak-of-hadoop-to-downstreamers is
> distinct from the narrower task proposed here where we are trying to
> unhitch ourselves of the netty/guava hadoop uses? (Currently we break
> against hadoop3 because of netty incompat., HADOOP-13866, which we might be
> able to solve w/ exclusions.....but....).
>
> The two tasks can be run in parallel?
>

Indeed, they seem distinct but quite related.

For CPs, they should bring their own bedding and towels and not be trying
> to use ours. On the plus-side, we could upgrade core 3rd-party libs and the
> CP would keep working.
>

All of this sounds like an ideal state.

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