Edit, June 17, 2011

• Wrote a new post revisiting installing Solr on Ubuntu -- it is both simpler and lighter-weight than the approach described in this post.

Original post

Apache Solr is a fast, open-source search solution. People are doing some very cool things with Solr. I personally have only begun to scratch the surface of what is possible with Solr, but have seen amazing returns with a relatively small investment (thanks entirely to Daniel Lindsley's excellent search framework, django-haystack). There are instructions for getting up and running with Solr + Jetty -- the purpose of this blog entry is to walk through setting up multi-core Solr with Apache Tomcat.

Let's go

First step, install the server:

sudo apt-get install tomcat6

Next you'll want to get Solr and extract it to a temporary directory

mkdir -p ~/tmp/solr/
cd ~/tmp/solr/
wget http://apache.multihomed.net/lucene/solr/1.4.0/apache-solr-1.4.0.tgz
tar xzf apache-solr-1.4.0.tgz

All the solr cores and indexes will go in /var/solr:

sudo mkdir -p /var/solr

Copy the Solr webapp and the example multicore configuration files:

sudo cp apache-solr-1.4.0/dist/apache-solr-1.4.0.war /var/solr/solr.war
sudo cp -R apache-solr-1.4.0/example/multicore/* /var/solr/
sudo chown -R tomcat6 /var/solr/

OK, now just need to point Catalina at Solr:

echo -e '<Context docBase="/var/solr/solr.war" debug="0" privileged="true" allowLinking="true" '\
'crossContext="true">\n<Environment name="solr/home" type="java.lang.String" value="/var/solr" '\
'override="true" />\n</Context>' | sudo tee -a /etc/tomcat6/Catalina/localhost/solr.xml
echo 'TOMCAT6_SECURITY=no' | sudo tee -a /etc/default/tomcat6

I edited the init script (/etc/init.d/tomcat6) to set solr.home, pointing it at /var/solr. I made this change near the top of the file other environment vars are set up:

JAVA_OPTS="$JAVA_OPTS -Dsolr.home=/var/solr"

Restart Tomcat6 and luxuriate in your newfound power:

sudo /etc/init.d/tomcat6 restart

Navigate to http://localhost:8080/solr/ - you should get something like this:

Where to now?

The solrconfig.xml files provided for each core are pretty barebones, so you'll want to replace those with something more like the solrconfig.xml at

~/tmp/solr/apache-solr-1.4.0/example/solr/conf/solrconfig.xml

I personally copy all the stuff from the example conf directory into any new cores I create and use that as a starting place.

The Django Connection

Are you using Django? If so, get yourself a checkout of haystack and configure your project.