Preface
Martin Gardner, the mathematics and science writer, once said in an interview:
Beyond calculus, I am lost. That was the secret of my column’s success. It took me so
long to understand what I was writing about that I knew how to write in a way most
readers would understand.
*
In many ways, this is how I feel about Hadoop. Its inner workings are complex, resting
as they do on a mixture of distributed systems theory, practical engineering, and com-
mon sense. And to the uninitiated, Hadoop can appear alien.
But it doesn’t need to be like this. Stripped to its core, the tools that Hadoop provides
for building distributed systems—for data storage, data analysis, and coordination—
are simple. If there’s a common theme, it is about raising the level of abstraction—to
create building blocks for programmers who just happen to have lots of data to store,
or lots of data to analyze, or lots of machines to coordinate, and who don’t have the
time, the skill, or the inclination to become distributed systems experts to build the
infrastructure to handle it.
With such a simple and generally applicable feature set, it seemed obvious to me when
I started using it that Hadoop deserved to be widely used. However, at the time (in
early 2006), setting up, configuring, and writing programs to use Hadoop was an art.
Things have certainly improved since then: there is more documentation, there are
more examples, and there are thriving mailing lists to go to when you have questions.
And yet the biggest hurdle for newcomers is understanding what this technology is
capable of, where it excels, and how to use it. That is why I wrote this book.
The Apache Hadoop community has come a long way. Over the course of three years,
the Hadoop project has blossomed and spun off half a dozen subprojects. In this time,
the software has made great leaps in performance, reliability, scalability, and manage-
ability. To gain even wider adoption, however, I believe we need to make Hadoop even
easier to use. This will involve writing more tools; integrating with more systems; and
* “The science of fun,” Alex Bellos, The Guardian, May 31, 2008, http://www.guardian.co.uk/science/
2008/may/31/maths.science.
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