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From Dmitriy Lyubimov <>
Subject Re: The perennial "Error: java.lang.ClassNotFoundException: org.apache.mahout.math.Vector" problem
Date Mon, 09 May 2011 04:55:56 GMT
I never actually ran in this error. I guess my backend code never
called anything ouside the jar.

But i do, or, rather, did have similar problems with my project. I
think i alreday voiced my opinion on this last time.

One solution is to use shade plugin or similar technique to create one
job jar with all dependencies in it. Which i deem as a bad bractice,
because it unjars existing dependencies jar, and it breaks things on
occasion (e.g. if one of dependencies is a signed jar, such as
BouncyCastle). Projects get into using shade plugin only to require
major retrofit when they hit dependency like this.

A better and hadoop-like technique is to rework standard driver class
so that it tosses everything assembly placed into lib into backend
classpath explicitly using DistributedCache. Warning: this
functionality is kind of broken in standard 0.20.2 somewhat, requires
a hack to work.


On Sun, May 8, 2011 at 5:09 PM, Jake Mannix <> wrote:
> I haven't run a post 0.4 mahout build on a production hadoop cluster before
> this, and I'm baffled that we have a job jar which simply -does not work-.
> Is this really not me, and our stock examples jobs are broken on hadoop?
>  -jake
> On May 8, 2011 4:14 PM, "Sean Owen" <> wrote:
> (The build error indicates you have some old class files somewhere --
> "clean" first)
> Here, the lib/ directory definitely has the right dependencies and it
> still doesn't work. Benson investigated and found out it's just how
> Hadoop works in this case.
> On Mon, May 9, 2011 at 12:06 AM, Ken Krugler <>
> wrote: > I haven't been ...

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