How do I configure Solr replication with multiple cores

replication, solr

Solution

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>

Problem

Original source