How to Set up a Repeater for Solr Replication

A master may be able to serve only so many slaves without affecting performance. Some organizations have deployed slave servers across multiple data centers. If each slave downloads the index from a remote data center, the resulting download may consume too much network bandwidth. To avoid performance degradation in cases like this, you can configure one or more slaves as repeaters. A repeater is simply a node that acts as both a master and a slave.

To configure a server as a repeater, both the master and slave configuration lists need to be present inside the ReplicationHandler requestHandler in the solrconfig.xml file.
Be sure to have replicateAfter ‘commit’ setup on repeater even if replicateAfter is set to optimize on the main master. This is because on a repeater (or any slave), only a commit is called after index is downloaded. Optimize is never called on slaves.
Optionally, one can configure the repeater to fetch compressed files from the master through the ‘compression’ parameter (see ‘slave’ section for details) to reduce the index download time.

Example configuration of a repeater:

<requestHandler name="/replication">
    <lst name="master">
      <str name="replicateAfter">commit</str>
      <str name="confFiles">schema.xml,stopwords.txt,synonyms.txt</str>
    </lst>
    <lst name="slave">
      <str name="masterUrl">http://master.solr.company.com:8080/solr/replication</str>
      <str name="pollInterval">00:00:60</str>
    </lst>
  </requestHandler>

Also See How to set up Solr Replication