[role="xpack"]
[testenv="basic"]
[[set-up-lifecycle-policy]]
== Set up {ilm} policy

In order for an index to use an {ilm} policy to manage its lifecycle we must
first define a lifecycle policy for it to use. The following request creates a
policy called `my_policy` in Elasticsearch which we can later use to manage our
indexes.

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

<1> Rollover the index when it reaches 25GB in size
<2> Delete the index when its 30 days old

{ilm} will manage an index using the policy defined in the
`index.lifecycle.name` index setting. If this setting does not exist in the
settings for a particular index, {ilm} will not manage that index.

To set the policy for an index there are two options:

1. Apply the policy to an index template and bootstrap creating the first index
2. Apply the policy to a new index in a create index request

[[applying-policy-to-template]]
=== Applying a policy to an index template

The `index.lifecycle.name` setting can be set in an index template so that it
is automatically applied to indexes matching the templates index pattern:

[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"
  }
}
-----------------------

<1> This template will be applied to all indexes which have a name starting
with `test-`
<2> The template will set the policy to be used to `my_policy`

Now that a policy exists and is used in an index template we can create an
initial index which will be managed by our policy:

[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.

We can now write data to the `test-alias` alias. Because we have a rollover
action defined in our policy, when the index grows larger than 25GB {ilm} will
create a new index and roll the alias over to use the new index automatically.

=== Apply a policy to a create index request

The `index.lifecycle.name` setting can be set on an individual create index
request so {ilm} immediately starts 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 to use the create index API with a policy that
defines a rollover action. If you do so, the new index as the result of the
rollover will not carry forward the policy. Always use
<<applying-policy-to-template, index templates>> to define policies with rollover
actions.