Mahout in Action Example Code
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Source code for 'Mahout in Action' book

This source code matches to listings from book - they were tested with Mahout 0.5. If you want to experiment with new features from other Mahout versions, then you need to use corresponding mahout-<mahout version> branch in this repository.


To work with source code you need to have Apache Maven installed (if you use Linux, it's better to install it from repository). Use of IDE with Maven support (Eclipse, Netbeans, IntelliJ IDEA) is encouraged.

After you'll get source code of examples, you need to compile it using mvn package command, staying in the MiA directory. This command will fetch all necessary dependencies, compile, and package everything you'll need for work. To correctly compile examples from chapter 16, you need to have Apache Thrift installed. On Linux it will searched in the /usr/local/bin/thrift, while on Mac OS X you can use macports to install it, and it will placed into /opt/local/bin/thrift. If thrift binary is located in another place, then change location in Maven's profile with name profile-buildthrift-linux.

Compiled jars are stored in the target directory. There are several files created:

  • mia-0.1.jar contains only code for examples;
  • mia-0.1-jar-with-dependencies.jar contains examples plus all dependencies;
  • mia-0.1-job.jar contains examples plus all dependencies, excluding Hadoop -- it should be used for Hadoop jobs.

For some examples you will need Apache Mahout distribution. You can grab latest release version from site. Grab both binary and src distributions, and unpack them in some place.

Examples from chapter 16 also require installation of Apache ZooKeeper. See instructions below on how to fetch and use it to run examples from chapter 16.

Work with examples

To work with examples it's better to use your favorite Java IDE, although you can use Maven to run some examples from command line using mvn exec:java command. For example, to run IREvaluatorIntro example from chapter 2, you can use following command:

mvn exec:java -Dexec.mainClass="mia.recommender.ch02.IREvaluatorIntro" -Dexec.args="src/main/java/mia/recommender/ch02/intro.csv"

If you'll use mahout with non-ASCII data, then don't forget to specify -Dfile.encoding=UTF-8 (or other encoding), so Java will use correct encoding for input/output.

Examples for Chapter 5

To deploy recommender as web service you need to do following:

  • copy ratings.dat and gender.dat files from data set into src/main/resources directory;
  • make package with mvn package command;
  • copy target/mia-0.1.jar into taste-web/lib/ directory in Mahout's source code tree;
  • change into taste-web/ directory in Mahout's source code tree;
  • edit file and set property recommender.class to value mia.recommender.ch05.LibimsetiRecommender;
  • run mvn package to create mahout-taste-webapp-0.5.war

Resulting .war file could be deployed to Tomcat or other container, but you can also use built-in Jetty, and run mvn jetty:run-war command to start the web-enabled recommender services on port 8080 on your local machine. Then follow instructions from book to experiment with recommender.

Examples for Chapters 14 & 15

Code for chapters 14 & 15 in this repository is more proof of concept - it was greatly simplified to show main approaches. The real code is in Mahout's distribution, in examples subproject - look onto src/main/java/org/apache/mahout/classifier/sgd/ and other examples from this project.

Examples for Chapter 16

Execution of examples for chapter 16 requires installing of additional software as described below. Actual code is packaged into mia-0.1-jar-with-dependencies.jar that is build as described above.

Install, configure and start Zookeeper

Download and run Apache Zookeeper

tar zxvf zookeeper-3.3.3.tar.gz
cp ./zookeeper-3.3.3/conf/zoo_sample.cfg ./zookeeper-3.3.3/conf/zoo.cfg
# change dataDir parameter in ./zookeeper-3.3.3/conf/zoo.cfg
sudo ./zookeeper-3.3.3/bin/ start

Start the server with no model yet

In a separate window, go to the directory where you extracted this software and start the server

java -cp target/mia-0.1-jar-with-dependencies.jar  mia.classifier.ch16.server.Server


mvn exec:java -Dexec.mainClass="mia.classifier.ch16.server.Server"

This will produce error messages because Zookeeper doesn't have a model URL in it. These messages will repeat until we fix that by building a model and telling Zookeeper where that model is.

Train a model

To build a model for the 20 news groups data, download the data:

tar zxvf 20news-bydate.tar.gz

Then run the training program:

java -mx1000m -cp target/mia-0.1-jar-with-dependencies.jar mia.classifier.ch16.train.TrainNewsGroups 20news-bydate-train/


 MAVEN_OPTS="-Xmx1024m" mvn exec:java -Dexec.mainClass="mia.classifier.ch16.train.TrainNewsGroups" -Dexec.args="20news-bydate-train/"

This will produce lots of output. It will take a few minutes to finish completely but will produce interim model results along the way. Once you see a file called /tmp/news-group-3000.model you will be ready to tell the server to load that model. The final result should give you the most accuracy. It is stored in /tmp/news-group.model

  1. Tell the server about the new model via Zookeeper

Run the Zookeeper command line interface:

    ... log output lines ...
[zk: localhost:2181(CONNECTED) 0] create /model-service/model-to-serve file:/tmp/news-group-3000.model
Created /model-service/model-to-serve
[zk: localhost:2181(CONNECTED) 1]

Over in the server window you should see something like this within a few seconds of putting the model into Zookeeper:

11/05/27 20:48:27 WARN server.Server: Loading model from file:/tmp/news-group-3000.model
11/05/27 20:48:27 INFO server.Server: done loading version 0

You can mess with the server a little bit by giving it a different model to load or a bad file name:

[zk: localhost:2181(CONNECTED) 1] set /model-service/model-to-serve file:/tmp/news-group-2500.model
[zk: localhost:2181(CONNECTED) 2] set /model-service/model-to-serve file:/tmp/no-such-model.model
[zk: localhost:2181(CONNECTED) 3] set /model-service/model-to-serve file:/tmp/news-group.model

Each time you change this file on Zookeeper, the server should respond. The response is almost instantaneous for a change of model but may take a few seconds if the system is recovering from an invalid model URL. The server output should look something like this:

11/05/27 20:50:31 WARN server.Server: Loading model from file:/tmp/news-group-2500.model
11/05/27 20:50:31 INFO server.Server: done loading version 1
11/05/27 20:50:51 WARN server.Server: Loading model from file:/tmp/no-such-model.model
11/05/27 20:50:51 ERROR server.Server: Failed to load model from file:/tmp/no-such-model.model /tmp/no-such-model.model (No such file or directory)
    at Method)
    at mia.classifier.ch16.server.Server$1.process(
    at org.apache.zookeeper.ClientCnxn$
11/05/27 20:51:06 WARN server.Server: Loading model from file:/tmp/news-group-3000.model
11/05/27 20:51:06 INFO server.Server: done loading version 3

Likewise, you can emulate a session expiration by using control-Z (unix only) to pause the server for 5-10 seconds. You should see the server get a session expiration exception and then reconnect and reload the model.

  1. Classify some data

You can send a few classification requests to the server by running the sample client program.

java -cp target/mia-0.1-jar-with-dependencies.jar mia.classifier.ch16.client.Client


mvn exec:java -Dexec.mainClass="mia.classifier.ch16.client.Client"

This should produce something a lot like the following output:

[0.05483312524126582, 0.053387027084160675, 0.05795630872834058, 0.04814920647604757, 0.04887495120450682, 0.05698449034115856, 0.052402388767486686, 0.03649784548083628, 0.04226219872179097, 0.049113831862600925, 0.038592728765213045, 0.06002963714513155, 0.049295643929958714, 0.06970468082142053, 0.04716914240563989, 0.07185404022050569, 0.0380260644141448, 0.046699086048427596, 0.035600312091787614, 0.04256729024957558]
[0.06330439515922226, 0.056560054064692764, 0.02343542325381652, 0.05177427523603212, 0.036665787679528015, 0.05178567849176077, 0.02683583498898842, 0.08456194834549986, 0.026447663784874308, 0.04003566819867149, 0.032012526444505175, 0.16526835135003673, 0.0507057974805552, 0.04553203091882379, 0.0669502827598342, 0.041071210037759195, 0.04465434770121597, 0.026757171129609885, 0.03789223925903782, 0.027749313715535663]

Highest score at index 11 which corresponds to sci.crypt

The last line there is the important one. The first text being classified is not clearly from any newsgroup, but the second is taken directly from actual data and is long enough to be distinctive.

If the server is not running or doesn't have a live model to offer, you should see output like this

  Exception in thread "main" java.lang.IllegalStateException: No servers to query
    at mia.classifier.ch16.client.Client.main(

Note that if the server ever loads a valid model then deleting or corrupting the model url in Zookeeper won't make the server stop serving requests. Instead, the server will keep the last valid model it saw.