How to install solr on tomcat7, over Ubuntu 12.04

Tomcat7

Ubuntu 12.04 comes with tomcat easily installable as a package (you need jdk):

apt-get install default-jdk tomcat7 tomcat7-admin tomcat7-user tomcat7-docs

Configure access to the web-admin in /etc/tomcat7/tomcat-users.xml:

<tomcat-users>
  <role rolename="manager-gui"/>
  <user username="manager" password="S3krEt" roles="manager-gui"/>
</tomcat-users>

The tomcat management console is now accessible, through authentication at http://HOST:8080/manager/html

Please, do change username and password in your tomcat-users.xml.

Solr

It can be useful to have different, isolated instances of solr running, corresponding to different solr versions (i.e. 1.2, 1.4, 3.4, …). One of the instances could be a multicore solr instance, able to host multiple indexes under a single app.

This is possible by creating different contexts inside /etc/tomcat7/Catalina/localhost/.

open_parlamento.xml:

<?xml version="1.0" encoding="utf-8"?>
<Context docBase="/home/solr/open_parlamento/apache-solr-1.4.0.war" debug="0" crossContext="true" >
   <Environment name="solr/home" type="java.lang.String" value="/home/solr/open_parlamento" override="true" />
</Context>

open_politici.xml:

<?xml version="1.0" encoding="utf-8"?>
<Context docBase="/home/solr/open_politici/apache-solr-1.2.0.war" debug="0" crossContext="true" >
   <Environment name="solr/home" type="java.lang.String" value="/home/solr/open_politici" override="true" />
</Context>

multicore.xml:

<?xml version="1.0" encoding="utf-8"?>
<Context docBase="/home/solr/multicore/apache-solr-3.4.0.war" debug="0" crossContext="true" >
   <Environment name="solr/home" type="java.lang.String" value="/home/solr/multicore/cores" override="true" />
</Context>

Create this directory tree:

/home/solr
|- open_parlamento
|  |- apache-solr-1.4.0.war
|  |- data
|  |  |- index
|  |  |  |- ...
|  |- conf
|     |- admin-extra.html
|     |- elevate.xml
|     |- italian-stopwords.txt
|     |- mapping-ISOLatin1Accent.txt
|     |- protwords.txt
|     |- schema.xml
|     |- scripts.conf
|     |- solrconfig.xml
|     |- spellings.txt
|     |- stopwords.txt
|     |- synonyms.txt
|- open_polis
|  |- apache-solr-1.2.0.war
|  |- ...
|- multicore
   |- apache-solr.3.4.0.war
   |- cores
   |  |- solr.xml
   |  |- app1
   |  |  |- conf
   |  |- app2
   |  |  |- conf
   |- data
      |- app1
      |  |- index
      |- app2
         |- index

Note:

You need to download the different versions of the solr war from their web site, and you may eventually need to download libraries, as pointed in the solrconfig.xml file to handle advanced tasks, so your mileage may vary.

solr.xml is the configuration file that points to the various cores in the multicore instance:

<?xml version="1.0" encoding="UTF-8" ?>
<solr persistent="false" sharedLib="lib">
  <cores adminPath="/admin/cores" shareSchema="true">
    <core name="app1"  instanceDir="app1"  dataDir="${solr.data.dir:../data}/app1" />
    <core name="app2"  instanceDir="app2"  dataDir="${solr.data.dir:../data}/app2" />
  </cores>
</solr>

The conf directories in cores/appX are standard solr conf directories, with all files needed, according to the solr version.

Permissions

Tomcat is run by the tomcat7 user, so all the data directories need to be writeable to this user:

chgrp -R tomcat7 /home/solr/open_parlamento/data
chmod -R g+w /home/solr/open_parlamento/data

Restart

Is needed whenever a tomcat or solr configuration changes. Under ubuntu:

service tomcat7 restart

The applications are visible under http://HOST:8080/APP_NAME where APP_NAME is the name of the context file (open_parlamento, open_politici) or the name of the core (app1, app2).