How do I configure Solr replication with multiple cores

Question

I have Solr running with multiple cores. Because of the heavy load, I want to set up a slave containing the exact same indexes.

The documentation http://wiki.apache.org/solr/SolrReplication states "Add the replication request handler to solrconfig.xml for each core", but I only have one solrconfig.xml.

My configuration:
Config: /data/solr/web/solr/conf/config files
Data: /data/solr/data/solr/core data dirs

Is it really necessary to copy the solrconfig.xml for each core?
And where should I put these multiple solrconfig files?

solr.xml

<?xml version="1.0" encoding="UTF-8" ?>
  <solr persistent="true">
  <property name="dih.username" value="user"/>
  <property name="dih.password" value="passwd"/>
  <property name="jdbclib" value="/usr/progress/dlc102b/java"/>
  <property name="dih.dburl" value="jdbc:datadirect:openedge://172.20.7.218:31380;databaseName=easource"/> <cores adminPath="/admin/cores">
    <core instanceDir="/data/solr/web/trunk/" name="product" dataDir="/data/solr/data/trunk/product-swap">
      <property name="dih-config" value="dih-config-product.xml"/>
    </core>
    <core instanceDir="/data/solr/web/trunk/" name="product-swap" dataDir="/data/solr/data/trunk/product">
      <property name="dih-config" value="dih-config-product.xml"/>
    </core>
    <core instanceDir="/data/solr/web/trunk/" name="periodp" dataDir="/data/solr/data/trunk/periodp">
      <property name="dih.config" value="dih-config-periodp.xml"/>
    </core>
    <core instanceDir="/data/solr/web/trunk/" name="periodp-swap" dataDir="/data/solr/data/trunk/periodp-swap">
      <property name="dih.config" value="dih-config-periodp.xml"/>
    </core>
  </cores>
</solr>

Answer 1

What you need to do is copy the solr instance that you have on the slave server and configure the replication handler on the solrconfig.xml. It's best practice to have a different instanceDir directory for each core since usually every core has its own schema.xml and solrconfig.xml. Anyway you can use the same conf just configuring your solr.xml to point to the same instanceDir but a different dataDir, which you configure as dataDir in your solrconfig.xml as well:

<solr persistent="true" sharedLib="lib">
    <cores adminPath="/admin/cores">
        <core name="core0" instanceDir="core">
            <property name="dataDir" value="/data/core0" />
        </core>
        <core name="core1" instanceDir="core">
            <property name="dataDir" value="/data/core1" />
        </core>
    </cores>
</solr>

This should be your situation if you currently have multiple cores but a single solrconfig.xml.

The solrconfig.xml replication section on the slaves need to contain the url of the master, including the core name, which of course is different for each core. But you can use the placeholder ${solr.core.name} like this:

<requestHandler name="/replication" class="solr.ReplicationHandler" >
    <lst name="slave">
        <str name="masterUrl">http://master_host:port/solr/${solr.core.name}/replication</str>
        <str name="pollInterval">00:00:20</str>
    </lst>
</requestHandler>

In fact, some properties like solr.core.name are automatically added to the core scope and you can refer to them in your configuration. As a result, the replication section can be the same for every core if you don't have any core specific settings.

Furthermore, you could use the same config for master and slave with the following configuration and just change the value (true or false) that you assign to the environment variables enable.master and enable.slave based on what you want to do. I mean that you can use the same file, but of course it's going to be on different machines since it wouldn't make a lot of sense to have master and slaves on the same machine.

<requestHandler name="/replication" class="solr.ReplicationHandler" >
    <lst name="master">
        <str name="enable">${enable.master:false}</str>
        <str name="replicateAfter">commit</str>
    </lst>
    <lst name="slave">
        <str name="enable">${enable.slave:false}</str>
        <str name="masterUrl">http://master_host:8983/solr/${solr.core.name}/replication</str>
        <str name="pollInterval">00:00:60</str>
    </lst>
</requestHandler>