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Elastic Docs ›Elasticsearch Guide [7.4] ›REST APIs ›Index APIs

Clone index API

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Clone index API

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Clones an existing index.

POST /twitter/_clone/cloned-twitter-index
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Request

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POST /<index>/_clone/<target-index>

PUT /<index>/_clone/<target-index>

Prerequisites

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To clone an index, the index must be marked as read-only and have a cluster health status of green.

For example, the following request prevents write operations on my_source_index so it can be cloned. Metadata changes like deleting the index are still allowed.

PUT /my_source_index/_settings
{
  "settings": {
    "index.blocks.write": true
  }
}
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Description

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Use the clone index API to clone an existing index into a new index, where each original primary shard is cloned into a new primary shard in the new index.

How cloning works

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Cloning works as follows:

  • First, it creates a new target index with the same definition as the source index.
  • Then it hard-links segments from the source index into the target index. (If the file system doesn’t support hard-linking, then all segments are copied into the new index, which is a much more time consuming process.)
  • Finally, it recovers the target index as though it were a closed index which had just been re-opened.

Clone an index

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

POST /my_source_index/_clone/my_target_index
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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.

Indices can only be cloned if they meet the following requirements:

  • The target index must not exist.
  • The source index must have the same number of primary shards as the target index.
  • The node handling the clone process must have sufficient free disk space to accommodate a second copy of the existing index.

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

POST /my_source_index/_clone/my_target_index
{
  "settings": {
    "index.number_of_shards": 5 
  },
  "aliases": {
    "my_search_indices": {}
  }
}
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The number of shards in the target index. This must be equal to the number of shards in the source index.

Mappings may not be specified in the _clone request. The mappings of the source index will be used for the target index.

Monitor the cloning process

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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.

Wait for active shards

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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.

Path parameters

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<index>
(Required, string) Name of the source index to clone.
<target-index>

(Required, string) Name of the target index to create.

Index names must meet the following criteria:

  • Lowercase only
  • Cannot include \, /, *, ?, ", <, >, |, ` ` (space character), ,, #
  • Indices prior to 7.0 could contain a colon (:), but that’s been deprecated and won’t be supported in 7.0+
  • Cannot start with -, _, +
  • Cannot be . or ..
  • Cannot be longer than 255 bytes (note it is bytes, so multi-byte characters will count towards the 255 limit faster)

Query parameters

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wait_for_active_shards

(Optional, string) The number of shard copies that must be active before proceeding with the operation. Set to all or any positive integer up to the total number of shards in the index (number_of_replicas+1). Default: 1, the primary shard.

See Active shards.

timeout
(Optional, time units) Specifies the period of time to wait for a response. If no response is received before the timeout expires, the request fails and returns an error. Defaults to 30s.
master_timeout
(Optional, time units) Specifies the period of time to wait for a connection to the master node. If no response is received before the timeout expires, the request fails and returns an error. Defaults to 30s.

Request body

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aliases
(Optional, alias object) Index aliases which include the target index. See Update index alias.
settings
(Optional, index setting object) Configuration options for the target index. See Index Settings.
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