[role="xpack"]
[testenv="basic"]
[[set-up-lifecycle-policy]]
== Configure lifecycle policy [[ilm-policy-definition]]

For {ilm-init} to manage an index, a valid policy 
must be specified in the `index.lifecycle.name` index setting. 

To configure a lifecycle policy for rolling indices, 
you create the policy and add it to the index template.

To use a policy to manage an index that doesn't roll over,
you can specify the policy directly when you create it.

[discrete]
[[ilm-create-policy]]
=== Create lifecycle policy

You use the <<ilm-put-lifecycle,create policy API>> to define a new lifecycle policy. 
For example, the following request creates `my_policy`, a
policy that defines a hot and and delete phase.
When the index reaches 25GB, it rolls over directly to the delete phase.
The index is deleted 30 days after rollover.

[source,console]
------------------------
PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_size": "25GB" <1>
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {} <2>
        }
      }
    }
  }
}
------------------------

<1> Roll over the index when it reaches 25GB in size
<2> Delete the index 30 days after rollover

NOTE: {ilm-init} policies are stored in the global cluster state and can be included in snapshots by  
setting `include_global_state` to `true` when you <<snapshots-take-snapshot, take the snapshot>>. 
Restoring {ilm-init} policies from a snapshot is all-or-nothing. 
The entire global state, including all policies, is overwritten when you restore the snapshot.

[discrete]
[[apply-policy-template]]
=== Apply lifecycle policy with an index template

To use a policy that triggers the rollover action, 
you need to configure the policy in the index template used to create each new index.
 
In addition to specifying the name of the policy in the `index.lifecycle.name` setting, 
you specify a `index.lifecycle.rollover_alias` for referencing
the indices managed by this policy. 

[source,console]
-----------------------
PUT _template/my_template
{
  "index_patterns": ["test-*"], <1>
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "my_policy", <2>
    "index.lifecycle.rollover_alias": "test-alias" <3>
  }
}
-----------------------

<1> Use this template for all new indices whose names begin with `test-`
<2> Apply `my_policy` to new indices created with this template
<3> Define an index alias for referencing indices managed by `my_policy`

//////////////////////////

[source,console]
--------------------------------------------------
DELETE /_template/my_template
--------------------------------------------------
// TEST[continued]

//////////////////////////

[discrete]
[[create-initial-index]]
==== Create an initial managed index

You need to manually create the first index managed by a policy that uses the rollover action
and designate it as the write index.
The name of the index must match the pattern defined in the index template and end with a number.
This number is incremented to generate the name of indices created by the rollover action.

For example, the following request creates the `test-00001` index. 
Because it matches the index pattern specified in `my_template`, 
{es} automatically applies the settings from that template.

[source,console]
-----------------------
PUT test-000001
{
  "aliases": {
    "test-alias":{
      "is_write_index": true <1>
    }
  }
}
-----------------------

<1> Set this initial index to be the write index for this alias.

Now you can start indexing data to the rollover alias specified in the lifecycle policy. 
With the sample `my_policy` policy, the rollover action is triggered once the initial
index exceeds 25GB. 
{ilm-init} then creates a new index that becomes the write index for the `test-alias`.

[discrete]
[[apply-policy-manually]]
=== Apply lifecycle policy manually

When you create an index directly, you can apply a lifecycle policy 
by specifying the `index.lifecycle.name` setting.
This causes {ilm-init} to immediately start managing the index.

[source,console]
-----------------------
PUT test-index
{
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "my_policy"
  }
}
-----------------------

IMPORTANT: Do not manually apply a policy that uses the rollover action.
Policies that use rollover must be applied by the <<apply-policy-template, index template>>. 
Otherwise, the policy is not carried forward when the rollover action creates a new index.