[[indices-clone-index]]
=== Clone index API
++++
<titleabbrev>Clone index</titleabbrev>
++++

Clones an existing index.

[source,console]
--------------------------------------------------
POST /twitter/_clone/cloned-twitter-index
--------------------------------------------------
// TEST[s/^/PUT twitter\n{"settings":{"index.number_of_shards" : 5,"blocks.write":true}}\n/]


[[clone-index-api-request]]
==== {api-request-title}

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

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


[[clone-index-api-prereqs]]
==== {api-prereq-title}

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

[source,console]
--------------------------------------------------
PUT /my_source_index/_settings
{
  "settings": {
    "index.blocks.write": true
  }
}
--------------------------------------------------
// TEST[s/^/PUT my_source_index\n/]


[[clone-index-api-desc]]
==== {api-description-title}

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.

[[cloning-works]]
===== How cloning works

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-index]]
===== Clone an index

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

[source,console]
--------------------------------------------------
POST /my_source_index/_clone/my_target_index
--------------------------------------------------
// TEST[continued]

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.

[IMPORTANT]
=====================================

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 <<indices-create-index, `create index` API>>
and accepts `settings` and `aliases` parameters for the target index:

[source,console]
--------------------------------------------------
POST /my_source_index/_clone/my_target_index
{
  "settings": {
    "index.number_of_shards": 5 <1>
  },
  "aliases": {
    "my_search_indices": {}
  }
}
--------------------------------------------------
// TEST[s/^/PUT my_source_index\n{"settings": {"index.blocks.write": true, "index.number_of_shards": "5"}}\n/]

<1> The number of shards in the target index. This must be equal to the
    number of shards in the source index.


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

[[monitor-cloning]]
===== Monitor the cloning process

The cloning process can be monitored with the <<cat-recovery,`_cat recovery`
API>>, or the <<cluster-health, `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, {es} will try to allocate any
replicas and may decide to relocate the primary shard to another node.

[[clone-wait-active-shards]]
===== Wait for active shards

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


[[clone-index-api-path-params]]
==== {api-path-parms-title}

`<index>`::
(Required, string)
Name of the source index to clone.

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=target-index]


[[clone-index-api-query-params]]
==== {api-query-parms-title}

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=wait_for_active_shards]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=timeoutparms]


[[clone-index-api-request-body]]
==== {api-request-body-title}

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=target-index-aliases]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=target-index-settings]
