Clone index API

Cloning works as follows:

To clone my_source_index into a new index called my_target_index, issue the following request:

response = client.indices.clone(
  index: 'my_source_index',
  target: 'my_target_index'
)
puts response

POST /my_source_index/_clone/my_target_index

The above request returns immediately once the target index has been added to the cluster state — it doesn’t wait for the clone operation to start.

The _clone API is similar to the create index API and accepts settings and aliases parameters for the target index:

response = client.indices.clone(
  index: 'my_source_index',
  target: 'my_target_index',
  body: {
    settings: {
      'index.number_of_shards' => 5
    },
    aliases: {
      my_search_indices: {}
    }
  }
)
puts response

POST /my_source_index/_clone/my_target_index
{
  "settings": {
    "index.number_of_shards": 5 
  },
  "aliases": {
    "my_search_indices": {}
  }
}

The cloning process can be monitored with the _cat recovery API, or the cluster health API can be used to wait until all primary shards have been allocated by setting the wait_for_status parameter to yellow.

The _clone API returns as soon as the target index has been added to the cluster state, before any shards have been allocated. At this point, all shards are in the state unassigned. If, for any reason, the target index can’t be allocated, its primary shard will remain unassigned until it can be allocated on that node.

Once the primary shard is allocated, it moves to state initializing, and the clone process begins. When the clone operation completes, the shard will become active. At that point, Elasticsearch will try to allocate any replicas and may decide to relocate the primary shard to another node.

Because the clone operation creates a new index to clone the shards to, the wait for active shards setting on index creation applies to the clone index action as well.