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Auto-follow for cross-cluster replication

Auto-follow lets you automatically replicate indices created on the leader cluster based on matching patterns. When you create an index on the leader cluster with a name that matches a specified pattern (for example, index-01*), a corresponding follower index is automatically created on the follower cluster.

You can configure multiple replication rules for a single cluster. The patterns currently only support wildcard matching.

Prerequisites

You need to set up a cross-cluster connection between two clusters before you can enable auto-follow.

Permissions

If the security plugin is enabled, non-admin users need to be mapped to the appropriate permissions in order to perform replication actions. For index and cluster-level permissions requirements, see Cross-cluster replication permissions.

Get started with auto-follow

Replication rules are a collection of patterns that you create against a single remote cluster. When you create a replication rule, it automatically starts replicating any new indices that match the pattern, but does not replicate matching indices that were previously created.

Create a replication rule on the follower cluster:

curl -XPOST -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9200/_plugins/_replication/_autofollow?pretty' -d '
{
   "leader_alias" : "my-connection-alias",
   "name": "my-replication-rule",
   "pattern": "movies*",
   "use_roles":{
      "leader_cluster_role": "all_access",
      "follower_cluster_role": "all_access"
   }
}'

If the security plugin is disabled, you can leave out the use_roles parameter. If it’s enabled, however, you need to specify the leader and follower cluster roles that OpenSearch uses to authenticate requests. This example uses all_access for simplicity, but we recommend creating a replication user on each cluster and mapping it accordingly.

To test the rule, create a matching index on the leader cluster:

curl -XPUT -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9201/movies-0001?pretty'

And confirm its replica shows up on the follower cluster:

curl -XGET -u 'admin:admin' -k 'https://localhost:9200/_cat/indices?v'

It might take several seconds for the index to appear.

health status index        uuid                     pri rep docs.count docs.deleted store.size pri.store.size
yellow open   movies-0001  kHOxYYHxRMeszLjTD9rvSQ     1   1          0            0       208b           208b

Retrieve replication rules

To retrieve a list of existing replication rules configured on a cluster, send the following request:

curl -XGET -u 'admin:admin' -k 'https://localhost:9200/_plugins/_replication/autofollow_stats'

{
   "num_success_start_replication": 1,
   "num_failed_start_replication": 0,
   "num_failed_leader_calls": 0,
   "failed_indices":[
      
   ],
   "autofollow_stats":[
      {
         "name":"my-replication-rule",
         "pattern":"movies*",
         "num_success_start_replication": 1,
         "num_failed_start_replication": 0,
         "num_failed_leader_calls": 0,
         "failed_indices":[
            
         ]
      }
   ]
}

Delete a replication rule

When you delete a replication rule, OpenSearch stops replicating new indices that match the pattern, but existing indices that the rule previously created continue to replicate. If you need to stop existing replication activity, use the stop replication API operation.

curl -XDELETE -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9200/_plugins/_replication/_autofollow?pretty' -d '
{
   "leader_alias" : "my-conection-alias",
   "name": "my-replication-rule"
}'