Solr Replication Repeater - Leader Repeater and Followers

A repeater is an index that follows a leader and is, at the same time, the leader of its own followers. One leader feeds the repeater, and the repeater feeds the rest, so the leader serves one copy instead of many.

The leader serves one copy, the repeater serves the followers.

01 · When it helps

Many followers would otherwise all poll the same leader.

The followers are in another region: one copy crosses the distance, the rest stay local.

A large index where every extra copy from the leader costs time and bandwidth.

02 · The repeater's solrconfig.xml

One replication handler with both blocks: it follows the leader and offers what it receives.

<requestHandler name="/replication" class="solr.ReplicationHandler">
  <lst name="follower">
    <str name="leaderUrl">https://LEADER_HOST/solr/LEADER_INDEX</str>
    <str name="pollInterval">00:00:30</str>
    <str name="httpBasicAuthUser">LEADER_USERNAME</str>
    <str name="httpBasicAuthPassword">LEADER_PASSWORD</str>
  </lst>
  <lst name="leader">
    <str name="replicateAfter">commit</str>
    <str name="confFiles">schema.xml,stopwords.txt,elevate.xml</str>
  </lst>
</requestHandler>

03 · The followers

Each follower points leaderUrl at the repeater instead of the leader, with the repeater's username and password. The follower block itself is the one from manual index replication.

04 · Rules that keep the chain healthy

The same schema.xml on the leader, the repeater and every follower.

IP rules at every link: the leader allows the repeater on /replication, the repeater allows its followers (IP Restriction).

A slightly longer pollInterval on the repeater than on its followers.

Every extra hop adds delay before a change reaches the last follower. Keep the chain short.

Solr 9 and newer use leader / follower / leaderUrl; older versions use master / slave / masterUrl.

05 · Example

Role	Index	Pulls from
Leader	`catalog`	nobody: you write here
Repeater	`catalog_eu`	`catalog`
Follower	`catalog_uk`	`catalog_eu`
Follower	`catalog_de`	`catalog_eu`

Replication

Manual index replication: leader and follower

Replication repeater: leader, repeater and followers (this page)