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Accumulo, mail # dev - Re: Hadoop 2 compatibility issues - tangent


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John Vines 2013-05-14, 22:14
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Christopher 2013-05-15, 02:11
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John Vines 2013-05-15, 07:03
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Christopher 2013-05-15, 16:33
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Re: Hadoop 2 compatibility issues - tangent
David Medinets 2013-05-15, 01:40
You can have maven generate a file with the classpath dependencies and also
make a shaded jar. I use the classpath file for normal java processes and
the shaded jar file with 'hadoop jar'.
On Tue, May 14, 2013 at 6:14 PM, John Vines <[EMAIL PROTECTED]> wrote:

> On that note, I was wondering if there were any suggestions for how to deal
> with the laundry list of provided dependencies that Accumulo core has?
> Writing packages against it is a bit ugly if not using the accumulo script
> to start. Are there any maven utilities to automatically dissect provided
> dependencies and make them included.
>
> Sent from my phone, please pardon the typos and brevity.
> On May 14, 2013 6:09 PM, "Keith Turner" <[EMAIL PROTECTED]> wrote:
>
> > One note about option 4.  When using 1.4 users have to include hadoop
> core
> > as a dependency in their pom. This must be done because the 1.4 Accumulo
> > pom marks hadoop-core as provided.  So maybe option 4 is ok if the deps
> in
> > the profile are provided?
> >
> >
> > On Tue, May 14, 2013 at 4:40 PM, Christopher <[EMAIL PROTECTED]>
> wrote:
> >
> > > So, I've run into a problem with ACCUMULO-1402 that requires a larger
> > > discussion about how Accumulo 1.5.0 should support Hadoop2.
> > >
> > > The problem is basically that profiles should not contain
> > > dependencies, because profiles don't get activated transitively. A
> > > slide deck by the Maven developers point this out as a bad practice...
> > > yet it's a practice we rely on for our current implementation of
> > > Hadoop2 support
> > > (http://www.slideshare.net/aheritier/geneva-jug-30th-march-2010-maven
> > > slide 80).
> > >
> > > What this means is that even if we go through the work of publishing
> > > binary artifacts compiled against Hadoop2, neither our Hadoop1
> > > binaries or our Hadoop2 binaries will be able to transitively resolve
> > > any dependencies defined in profiles. This has significant
> > > implications to user code that depends on Accumulo Maven artifacts.
> > > Every user will essentially have to explicitly add Hadoop dependencies
> > > for every Accumulo artifact that has dependencies on Hadoop, either
> > > because we directly or transitively depend on Hadoop (they'll have to
> > > peek into the profiles in our POMs and copy/paste the profile into
> > > their project). This becomes more complicated when we consider how
> > > users will try to use things like Instamo.
> > >
> > > There are workarounds, but none of them are really pleasant.
> > >
> > > 1. The best way to support both major Hadoop APIs is to have separate
> > > modules with separate dependencies directly in the POM. This is a fair
> > > amount of work, and in my opinion, would be too disruptive for 1.5.0.
> > > This solution also gets us separate binaries for separate supported
> > > versions, which is useful.
> > >
> > > 2. A second option, and the preferred one I think for 1.5.0, is to put
> > > a Hadoop2 patch in the branch's contrib directory
> > > (branches/1.5/contrib) that patches the POM files to support building
> > > against Hadoop2. (Acknowledgement to Keith for suggesting this
> > > solution.)
> > >
> > > 3. A third option is to fork Accumulo, and maintain two separate
> > > builds (a more traditional technique). This adds merging nightmare for
> > > features/patches, but gets around some reflection hacks that we may
> > > have been motivated to do in the past. I'm not a fan of this option,
> > > particularly because I don't want to replicate the fork nightmare that
> > > has been the history of early Hadoop itself.
> > >
> > > 4. The last option is to do nothing and to continue to build with the
> > > separate profiles as we are, and make users discover and specify
> > > transitive dependencies entirely on their own. I think this is the
> > > worst option, as it essentially amounts to "ignore the problem".
> > >
> > > At the very least, it does not seem reasonable to complete
> > > ACCUMULO-1402 for 1.5.0, given the complexity of this issue.