107 lines
4.2 KiB
Markdown
107 lines
4.2 KiB
Markdown
---
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layout: default
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title: Auto-follow
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nav_order: 20
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has_children: false
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---
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# Auto-follow for cross-cluster replication
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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.
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You can configure multiple replication rules for a single cluster. The patterns currently only support wildcard matching.
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## Prerequisites
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You need to [set up a cross-cluster connection]({{site.url}}{{site.baseurl}}/replication-plugin/get-started/#set-up-a-cross-cluster-connection) between two clusters before you can enable auto-follow.
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## Permissions
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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]({{site.url}}{{site.baseurl}}/replication-plugin/permissions/).
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## Get started with auto-follow
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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.
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Create a replication rule on the follower cluster:
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```bash
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curl -XPOST -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9200/_plugins/_replication/_autofollow?pretty' -d '
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{
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"leader_alias" : "my-connection-alias",
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"name": "my-replication-rule",
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"pattern": "movies*",
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"use_roles":{
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"leader_cluster_role": "all_access",
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"follower_cluster_role": "all_access"
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}
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}'
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```
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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]({{site.url}}{{site.baseurl}}/replication-plugin/permissions/#map-the-leader-and-follower-cluster-roles).
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{: .tip }
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To test the rule, create a matching index on the leader cluster:
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```bash
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curl -XPUT -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9201/movies-0001?pretty'
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```
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And confirm its replica shows up on the follower cluster:
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```bash
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curl -XGET -u 'admin:admin' -k 'https://localhost:9200/_cat/indices?v'
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```
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It might take several seconds for the index to appear.
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```bash
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health status index uuid pri rep docs.count docs.deleted store.size pri.store.size
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yellow open movies-0001 kHOxYYHxRMeszLjTD9rvSQ 1 1 0 0 208b 208b
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```
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## Retrieve replication rules
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To retrieve a list of existing replication rules configured on a cluster, send the following request:
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```bash
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curl -XGET -u 'admin:admin' -k 'https://localhost:9200/_plugins/_replication/autofollow_stats'
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{
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"num_success_start_replication": 1,
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"num_failed_start_replication": 0,
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"num_failed_leader_calls": 0,
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"failed_indices":[
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],
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"autofollow_stats":[
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{
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"name":"my-replication-rule",
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"pattern":"movies*",
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"num_success_start_replication": 1,
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"num_failed_start_replication": 0,
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"num_failed_leader_calls": 0,
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"failed_indices":[
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]
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}
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]
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}
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```
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## Delete a replication rule
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To delete a replication rule, send the following request:
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```bash
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curl -XDELETE -k -H 'Content-Type: application/json' -u 'admin:admin' 'https://localhost:9200/_plugins/_replication/_autofollow?pretty' -d '
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{
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"leader_alias" : "my-conection-alias",
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"name": "my-replication-rule"
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}'
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```
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OpenSearch stops replicating *new* indices that match the pattern, but existing indices that the rule previously created remain read-only and continue to replicate. If you need to stop existing replication activity and open the indices up for writes, use the [stop replication API operation]({{site.url}}{{site.baseurl}}/replication-plugin/api/#stop-replication).
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