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Segment replication configuration

Segment replication is an experimental feature. Therefore, we do not recommend the use of segment replication in a production environment. For updates on the progress of segment replication or if you want to leave feedback that could help improve the feature, see the Segment replication issue.

To enable the segment replication type, reference the steps below.

Enabling the feature flag

There are several methods for enabling segment replication, depending on the install type. You will also need to set the replication strategy to SEGMENT when creating the index.

Enable on a node using a tarball install

The flag is toggled using a new jvm parameter that is set either in OPENSEARCH_JAVA_OPTS or in config/jvm.options.

1. Option 1: Update config/jvm.options by adding the following line:

    -Dopensearch.experimental.feature.replication_type.enabled=true
   

2. Option 2: Use the OPENSEARCH_JAVA_OPTS environment variable:

    export OPENSEARCH_JAVA_OPTS="-Dopensearch.experimental.feature.replication_type.enabled=true"
   

3. Option 3: For developers using Gradle, update run.gradle by adding the following lines:

    testClusters {
      runTask {
        testDistribution = 'archive'
        if (numZones > 1) numberOfZones = numZones
        if (numNodes > 1) numberOfNodes = numNodes
        systemProperty 'opensearch.experimental.feature.replication_type.enabled', 'true'
      }
    }
   

Enable with Docker containers

If you’re running Docker, add the following line to docker-compose.yml underneath the opensearch-node and environment section:

OPENSEARCH_JAVA_OPTS="-Dopensearch.experimental.feature.replication_type.enabled=true" # Enables segment replication

Setting the replication strategy on the index

To set the replication strategy to segment replication, create an index with replication.type set to SEGMENT:

PUT /my-index1
{
  "settings": {
    "index": {
      "replication.type": "SEGMENT" 
    }
  }
}

Known limitations

1. Enabling segment replication for an existing index requires reindexing.
2. Rolling upgrades are currently not supported. Full cluster restarts are required when upgrading indexes using segment replication. Issue 3881.
3. Cross-cluster replication does not currently use segment replication to copy between clusters.
4. Increased network congestion on primary shards. Issue - Optimize network bandwidth on primary shards.
5. Shard allocation algorithms have not been updated to evenly spread primary shards across nodes.
6. Integration with remote-backed storage as the source of replication is currently unsupported.

Further resources regarding segment replication

1. Known issues.
2. Steps for testing (link coming soon).
3. Segment replication blog post (link coming soon).