Upgrading Solr from 4.2 to 4.3+ on CentOS 6.4

• Bill Hunt

I ran into an issue with a Solr configuration that was working for me locally, but not on our CentOS 6.4 server. I’ve documented below all of the issues I encountered along the way, as the upgrade from Solr 4.2 to 4.3+ is a pretty nasty one, due to major changes in the logging system (LOG4J / SLF4J)

Update: as of January 2015, I have been unable to get Solr 4.10 to run on Tomcat 6, so I’ve defaulted to just using the example Jetty server that’s bundled with it.  It’s less than ideal, but it works.  Here’s good documentation on that process.

Lucene/Solr 4.3+ : The Beginning

The awesome guys at Open Source Connections had created a custom tokenizer for Solr for The State Decoded, which was suddenly throwing this new error:

java.lang.IllegalArgumentException: No enum const class org.apache.lucene.util.Version.LUCENE_43

Which I guessed to mean that they’d specified to use Lucene 4.3 (or in my case, Solr 4.3) in the solr_home/conf/solrconfig.xml file


Since CentOS 6.4 only comes with Solr 4.2 out of the box, I tried changing that to LUCENE_42 but received even more intimidating errors:

org.apache.solr.common.SolrException:org.apache.solr.common.SolrException: Plugin init failure for [schema.xml] fieldType "descendent_facet_hierarchical": Plugin init failure for [schema.xml] analyzer/tokenizer: Error instantiating class: 'com.o19s.RegexPathHierarchyTokenizerFactory'

The full stack dump is here

We guessed that the package needed to be rebuilt from source.


To do that, first I had to install Maven, which was missing from CentOS. Following the instructions here, I went to the Maven site and found the download link for the latest version (in my case, that was 3.1.1). I grabbed that file and stored it in my /usr/local directory (for ease of use), unzipping as usual:

wget http://apache.tradebit.com/pub/maven/maven-3/3.1.1/binaries/apache-maven-3.1.1-bin.tar.gz
tar -xzf ./apache-maven-3.1.1-bin.tar.gz -C /usr/local

Then I created a link to it:

sudo ln -s apache-maven-3.1.1 maven

And added a native profile loader:

sudo vi /etc/profile.d/maven.sh

To add it to the path:

export M2_HOME=/usr/local/maven
export PATH=${M2_HOME}/bin:${PATH}


Now, after all of that, apparently I still did not have the Java Development Kit (aka JDK) installed. You’d think that the package OpenJDK would provide this, by the name, but it turns out that that only contains the Java Virual Machine (JVM). I discovered this as maven complained about a missing file tools.jar

So, I checked yum for the latest version and installed it:

sudo yum list jdk
sudo yum install java-1.6.0-openjdk-devel

And added another profile loader:

sudo vi /etc/profile.d/java.sh

for that path:

export JAVA_HOME=/usr/lib/jvm/java-1.6.0-openjdk-

A quick log out and log in fixed up my paths to use those. All that being done, I tried rebuilding the solr tokenizer, but it still didn’t work. I needed to upgrade Solr first.

Upgrading to Solr4.3+

Now, between Solr 4.2 and Solr 4.3, they removed the native LOG4J support that is by default needed to run Solr. So there are a lot of extra steps here.

Seriously, why they would do this, I have no idea. You install the Solr package, and it just won’t run. And there’s absolutely no documentation on exactly how to fix it. The developers just broke it and left everyone to figure it out on their own. I cannot begin to express my frustration or count the number of hours I lost on this step.

A note on Tomcat logging

As you’re going through and starting and restarting tomcat (sudo service tomcat6 restart),

you’ll probably want to keep an eye on the log file here:

less /var/log/tomcat6/localhost.[DATE].log

Most frustratingly, I found that any errors encountered during the startup of Tomcat were not actually logged until you shut it down. This is generally not how most Apache projects handle logging. (Again, WTF.) So the only way to know if you still had an issue was to restart *twice*.

Unfortunately, every time that Tomcat encountered a configuration error, it would delete my web app configuration file entirely. (Aside: Seriously why would anyone think this is a good idea?) So I had to create it multiple times. That file lives under the Catalina configuration directory here:


And looks like this:

<Context docBase="/opt/solr/solr.war" debug="0" crossContext="false" >
   <Environment name="solr/home" type="java.lang.String" value="/opt/solr" override="true"/>

Now back to the good part

Now, I was finally ready to install the latest version of Solr. I headed over to the Solr downloads page and found that 4.5.1 was the latest. I grabbed the download from that page (after several redirects in between), and extracted it to my home directory:

wget http://mirrors.gigenet.com/apache/lucene/solr/4.5.1/solr-4.5.1.tgz
tar -xzf ./solr-4.5.1.tgz

Now, solr does not actually need to be built, just copied over. The previous installation of solr on the system was under /opt/solr, and just in case I broke everything, I wanted to keep a copy of that. If you’re not upgrading from a previous version, you don’t need to do this to move that out of the way:

sudo mv /opt/solr /opt/solr-4.2.1

Then I copied the new version of solr’s example to the opt directory, and symlinked it into place.

sudo cp -R ~/solr-4.5.1/example/solr /opt/solr-4.5.1
cd /opt
sudo ln -s solr-4.5.1 solr

I needed the solr.war file as well, and also symlinked that.

cd /opt/solr
sudo cp ~/solr-4.5.1/dist/solr-4.5.1.war ./
sudo ln -s solr-4.5.1.war solr.war

Next, I received nasty errors in the localhost.log about missing SLF4J:

SEVERE: Exception starting filter SolrRequestFilter
org.apache.solr.common.SolrException: <strong>Could not find necessary SLF4j logging jars.</strong> If using Jetty, the SLF4j logging jars need to go in the jetty lib/ext directory. For other containers, the corresponding directory should be used. For more information, see: http://wiki.apache.org/solr/SolrLogging

I assumed you needed to provide the extra libraries to tomcat in the obvious way:

sudo cp ~/solr-4.5.1/example/lib/ext/* /var/lib/tomcat6/lib/
sudo cp ~/solr-4.5.1/dist/solrj-lib/* /var/lib/tomcat6/lib/

And others to solr:

sudo cp -R ~/solr-4.5.1/dist/* /opt/solr/lib/

But apparently the libraries needed to be somewhere else also, which I found absolutely no documentation on anywhere. This post finally got me to the right answer.

sudo cp ~/solr-4.5.1/dist/solrj-lib/* /var/lib/tomcat6/webapps/solr/WEB-INF/lib/

Last, I needed to tweak the default solr file for the multicore support that we needed, allowing us to run multiple Solr indexes on one box.

sudo vi /opt/solr/solr.xml

and a added new line for the second core:

<cores adminPath="/admin/cores" defaultCoreName="collection1" host="${host:}" hostPort="${jetty.port:}" hostConte    xt="${hostContext:}" zkClientTimeout="${zkClientTimeout:15000}">
    <core name="collection1" instanceDir="collection1" />
    <core name="baltimorecode_dev_www" instanceDir="baltimorecode/www/staging/statedecoded" />

Finally Rebuilding the custom Solr tokenizer

From there, I just needed to rebuild the custom tokenizer that we had.

cd /opt/solr/baltimorecode/www/staging/statedecoded/src/

sudo mvn package

cp target/regex-path-tokenizer-0.0.1-SNAPSHOT.jar ../lib/regex-path-tokenizer-0.0.1-SNAPSHOT.jar

A final restart of tomcat:

sudo service tomcat6 restart

And I could hit the localhost version of solr for that core!

lynx http://localhost:8080/solr/baltimorecode_dev_www/admin/ping

I created an SSH Tunnel to verify that this was indeed working as expected:

ssh -L 8009:localhost:8080 user@removtehost.org -N

And then fired up a browser to point at http://localhost:8009/solr/ and solr was running perfectly.

Finishing Up

The last little thing that caught me up in my sleep-deprived state was that the PHP Solarium package requires allow_url_fopen to be set to On. This seems rather obvious, but is not the default value on CentOS.

That was a long day.

Here are a few of the articles that I used to get this far:

  1. Patrick Reilly: How to install maven on CentOS
  2. Solr: MultiCore
  3. Apache Tomcat configuration: HTTP Connectors
  4. Andrew Jaimes: Installing Lucene/Solr on CentOS with Tomcat
  5. Hipsnip Cookbooks issues: Solr Fails to start missing SLF4j
  6. StackOverflow: Solr 4.3 Tomcat6 Ubuntu installation exception (More confusing than helpful.)
  • Xrigher: Install Lucene Solar with Tomcat on Windows (This was the one that got me to the right answer!)