Run Nutch In Eclipse on Linux and Windows nutch version 0.9

Run Nutch In Eclipse on Linux and Windows nutch version 0.9

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Tested with

Nutch release 0.9 and 1.0

Eclipse 3.3 - aka Europa

Java 1.6

Ubuntu (should work on most platforms though)

Windows XP

Before you start

Setting
up Nutch to run into Eclipse can be tricky, and most of the time you
are much faster if you edit Nutch in Eclipse but run the scripts from
the command line (my 2 cents). However,
it's very useful to be able to debug Nutch in Eclipse. But again you
might be quicker by looking at the logs (logs/hadoop.log)...

Steps

For Windows Users

If you are running Windows (tested on Windows XP) you must first install cygwin
Download cygwin from http://www.cygwin.com/setup.exe

Install cygwin and set PATH variable for it.
It's in control panel, system, advanced tab, environment variables and edit/add PATH
I have in PATH like:
C:/Sun/SDK/bin;C:/cygwin/bin
If you run "bash" in Start->RUN->cmd.exe it should work.
Then you should install tools from Microsoft website (adding 'whoami' command).
Example for Windows XP and sp2
http://www.microsoft.com/downloads/details.aspx?FamilyId=49AE8576-9BB9-4126-9761-BA8011FABF38&displaylang=en

Then you can follow rest of these steps

Install Nutch

Grab a fresh release of Nutch 0.9 - http://lucene.apache.org/nutch/version_control.html

Do not build Nutch now. Make sure you have no .project and .classpath files in the Nutch directory

Create a new java project in Eclipse

File > New > Project > Java project > click Next

Name the project (Nutch_Trunk for instance)

Select "Create project from existing source" and use the location where you downloaded Nutch

Click on Next, and wait while Eclipse is scanning the folders

Add the folder "conf" to the classpath (third tab and then add class folder)

Go
to "Order and Export" tab, find the entry for added "conf" folder and
move it to the top. It's required to make eclipse take config
(nutch-default.xml, nutch-final.xml, etc.) resources from our "conf"
folder not anywhere else.

Eclipse
should have guessed all the java files that must be added on your
classpath. If it's not the case, add "src/java", "src/test" and all
plugin "src/java" and "src/test" folders to your source folders. Also
add all jars in "lib" and in the plugin lib folders to your libraries

Set output dir to "tmp_build", create it if necessary

DO NOT add "build" to classpath

Configure Nutch

See the Tutorial

Change the property "plugin.folders" to "./src/plugin" on $NUTCH_HOME/conf/nutch-defaul.xml

Make sure Nutch is configured correctly before testing it into Eclipse

Missing org.farng and com.etranslate

Eclipse will complain about some import statements in parse-mp3 and parse-rtf plugins (30 errors in my case). Because
of incompatibility with the Apache license, the .jar files that define
the necessary classes were not included with the source code.
Download them here:
http://nutch.cvs.sourceforge.net/nutch/nutch/src/plugin/parse-mp3/lib/

http://nutch.cvs.sourceforge.net/nutch/nutch/src/plugin/parse-rtf/lib/

Copy the jar files into src/plugin/parse-mp3/lib and src/plugin/parse-rtf/lib/ respectively. Then
add the jar files to the build path (First refresh the workspace by
pressing F5. Then right-click the project folder > Build Path >
Configure Build Path... Then select the Libraries tab, click "Add
Jars..." and then add each .jar file individually).

Build Nutch

If you
setup the project correctly, Eclipse will build Nutch for you into
"tmp_build". See below for problems you could run into.

Create Eclipse launcher

Menu Run > "Run..."

create "New" for "Java Application"

set in Main class

org.apache.nutch.crawl.Crawl

on tab Arguments, Program Arguments

urls -dir crawl -depth 3 -topN 50

in VM arguments

-Dhadoop.log.dir=logs -Dhadoop.log.file=hadoop.log

click on "Run"

if all works, you should see Nutch getting busy at crawling

Java Heap Size problem

If you find in hadoop.log line similar to this:

2009-04-13 13:41:06,105 WARN  mapred.LocalJobRunner - job_local_0001

java.lang.OutOfMemoryError: Java heap space

You should increase amount of RAM for running applications from eclipse.
Just set it in:
Eclipse -> Window -> Preferences -> Java -> Installed JREs -> edit -> Default VM arguments
I've set mine to

-Xms5m -Xmx150m

because I have like 200MB RAM left after runnig all apps
-Xms (minimum ammount of RAM memory for running applications) -Xmx (maximum)

Debug Nutch in Eclipse

Set breakpoints and debug a crawl

It
can be tricky to find out where to set the breakpoint, because of the
Hadoop jobs. Here are a few good places to set breakpoints:

Fetcher [line: 371] - run

Fetcher [line: 438] - fetch

Fetcher$FetcherThread [line: 149] - run()

Generator [line: 281] - generate

Generator$Selector [line: 119] - map

OutlinkExtractor [line: 111] - getOutlinks

If things do not work...

Yes, Nutch and Eclipse can be a difficult companionship sometimes

eclipse: Cannot create project content in workspace

The nutch
source code must be out of the workspace folder. My first attempt was
download the code with eclipse (svn) under my workspace. When I try to
create the project using existing code, eclipse don't let me do it from
source code into the workspace. I use the source code out of my
workspace and it work fine.

plugin dir not found

Make sure
you set your plugin.folders property correct, instead of using a
relative path you can use a absolute one as well in nutch-defaults.xml
or may be better in nutch-site.xml

<property>

<name>plugin.folders</name>

<value>/home/....../nutch-0.9/src/plugin</value>

No plugins loaded during unit tests in Eclipse

During
unit testing, Eclipse ignored conf/nutch-site.xml in favor of
src/test/nutch-site.xml, so you might need to add the plugin directory
configuration to that file as well.

Unit tests work in eclipse but fail when running ant in the command line

Suppose your unit tests work perfectly in eclipse, but each and everyone fail when running ant test
in the command line - including the ones you haven't modified. Check if you defined the plugin.folders
property in hadoop-site.xml. In that case, try removing it from that file and adding it directly to nutch-site.xml
Run ant test
again. That should have solved the problem.
If
that didn't solve the problem, are you testing a plugin? If so, did you
add the plugin to the list of packages in plugin/build.xml, on the test
target?

classNotFound

open the class itself, rightclick

refresh the build dir

debugging hadoop classes

Sometime
it makes sense to also have the hadoop classes available during
debugging. So, you can check out the Hadoop sources on your machine and
add the sources to the hadoop-xxx.jar. Alternatively, you can:

Remove the hadoopXXX.jar from your classpath libraries

Checkout the hadoop brunch that is used within nutch

configure a hadoop project similar to the nutch project within your eclipse

add the hadoop project as a dependent project of nutch project

you can now also set break points within hadoop classes lik inputformat implementations etc.

Original credits: RenaudRichardet