[role="xpack"]
[testenv="basic"]
[[ilm-explain-lifecycle]]
=== Explain lifecycle API
++++
<titleabbrev>Explain lifecycle</titleabbrev>
++++

Shows an index's current lifecycle status.

==== Request

`GET <index>/_ilm/explain`

==== Description

Retrieves information about the index's current lifecycle state, such as
the currently executing phase, action, and step. Shows when the index entered
each one, the definition of the running phase, and information
about any failures.

==== Path Parameters

`index` (required)::
  (string) Identifier for the index.

==== Request Parameters

include::{docdir}/rest-api/timeoutparms.asciidoc[]

==== Authorization

You must have the `view_index_metadata` or `manage_ilm` or both privileges on the indices
being managed to use this API.
For more information, see {stack-ov}/security-privileges.html[Security Privileges].

==== Examples

The following example retrieves the lifecycle state of `my_index`:

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

[source,js]
--------------------------------------------------
PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "warm": {
        "min_age": "10d",
        "actions": {
          "forcemerge": {
            "max_num_segments": 1
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

PUT my_index?include_type_name=true
{
  "settings": {
    "index.lifecycle.name": "my_policy",
    "index.number_of_replicas": 0
  }
}

GET /_cluster/health?wait_for_status=green&timeout=10s
--------------------------------------------------
// CONSOLE
// TEST

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

[source,js]
--------------------------------------------------
GET my_index/_ilm/explain
--------------------------------------------------
// CONSOLE
// TEST[continued]

When management of the index is first taken over by ILM, `explain` shows
that the index is managed and in the `new` phase:

[source,js]
--------------------------------------------------
{
  "indices": {
    "my_index": {
      "index": "my_index",
      "managed": true, <1>
      "policy": "my_policy", <2>
      "lifecycle_date_millis": 1538475653281, <3>
      "phase": "new",
      "phase_time_millis": 1538475653317, <4>
      "action": "complete",
      "action_time_millis": 1538475653317, <5>
      "step": "complete",
      "step_time_millis": 1538475653317 <6>
    }
  }
}
--------------------------------------------------
// CONSOLE
// TESTRESPONSE[skip:no way to know if we will get this response immediately]
<1> Shows if the index is being managed by ILM. If the index is not managed by
ILM the other fields will not be shown
<2> The name of the policy which ILM is using for this index
<3> The timestamp used for the `min_age`
<4> When the index entered the current phase
<5> When the index entered the current action
<6> When the index entered the current step

Once the policy is running on the index, the response includes a
`phase_execution` object that shows the definition of the current phase.
Changes to the underlying policy will not affect this index until the current
phase completes.

[source,js]
--------------------------------------------------
{
  "indices": {
    "test-000069": {
      "index": "test-000069",
      "managed": true,
      "policy": "my_lifecycle3",
      "lifecycle_date_millis": 1538475653281,
      "lifecycle_date": "2018-10-15T13:45:21.981Z",
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "phase_time": "2018-10-15T13:45:22.577Z",
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "action_time": "2018-10-15T13:45:22.577Z",
      "step": "attempt-rollover",
      "step_time_millis": 1538475653317,
      "step_time": "2018-10-15T13:45:22.577Z",
      "phase_execution": {
        "policy": "my_lifecycle3",
        "phase_definition": { <1>
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_age": "30s"
            }
          }
        },
        "version": 3, <2>
        "modified_date": "2018-10-15T13:21:41.576Z", <3>
        "modified_date_in_millis": 1539609701576 <4>
      }
    }
  }
}
--------------------------------------------------
// CONSOLE
// TESTRESPONSE[skip:not possible to get the cluster into this state in a docs test]
<1> The JSON phase definition loaded from the specified policy when the index
entered this phase
<2> The version of the policy that was loaded
<3> The date the loaded policy was last modified
<4> The epoch time when the loaded policy was last modified

If {ilm-init} is waiting for a step to complete, the response includes status
information for the step that's being performed on the index.

[source,js]
--------------------------------------------------
{
  "indices": {
    "test-000020": {
      "index": "test-000020",
      "managed": true,
      "policy": "my_lifecycle3",
      "lifecycle_date_millis": 1538475653281,
      "lifecycle_date": "2018-10-15T13:45:21.981Z",
      "phase": "warm",
      "phase_time_millis": 1538475653317,
      "phase_time": "2018-10-15T13:45:22.577Z",
      "action": "allocate",
      "action_time_millis": 1538475653317,
      "action_time": "2018-10-15T13:45:22.577Z",
      "step": "check-allocation",
      "step_time_millis": 1538475653317,
      "step_time": "2018-10-15T13:45:22.577Z",
      "step_info": { <1>
        "message": "Waiting for all shard copies to be active",
        "shards_left_to_allocate": -1,
        "all_shards_active": false,
        "actual_replicas": 2
      },
      "phase_execution": {
        "policy": "my_lifecycle3",
        "phase_definition": {
          "min_age": "0ms",
          "actions": {
            "allocate": {
              "number_of_replicas": 2,
              "include": {
                "box_type": "warm"
              },
              "exclude": {},
              "require": {}
            },
            "forcemerge": {
              "max_num_segments": 1
            }
          }
        },
        "version": 2,
        "modified_date": "2018-10-15T13:20:02.489Z",
        "modified_date_in_millis": 1539609602489
      }
    }
  }
}
--------------------------------------------------
// CONSOLE
// TESTRESPONSE[skip:not possible to get the cluster into this state in a docs test]
<1> Status of the step that's in progress.

If the index is in the ERROR step, something went wrong while executing a
step in the policy and and you will need to take action for the index to proceed
to the next step. To help you diagnose the problem, the explain response shows
the step that failed and the step info provides information about the error.

[source,js]
--------------------------------------------------
{
  "indices": {
    "test-000056": {
      "index": "test-000056",
      "managed": true,
      "policy": "my_lifecycle3",
      "lifecycle_date_millis": 1538475653281,
      "lifecycle_date": "2018-10-15T13:45:21.981Z",
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "phase_time": "2018-10-15T13:45:22.577Z",
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "action_time": "2018-10-15T13:45:22.577Z",
      "step": "ERROR",
      "step_time_millis": 1538475653317,
      "step_time": "2018-10-15T13:45:22.577Z",
      "failed_step": "attempt-rollover", <1>
      "step_info": { <2>
        "type": "resource_already_exists_exception",
        "reason": "index [test-000057/H7lF9n36Rzqa-KfKcnGQMg] already exists",
        "index_uuid": "H7lF9n36Rzqa-KfKcnGQMg",
        "index": "test-000057"
      },
      "phase_execution": {
        "policy": "my_lifecycle3",
        "phase_definition": {
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_age": "30s"
            }
          }
        },
        "version": 3,
        "modified_date": "2018-10-15T13:21:41.576Z",
        "modified_date_in_millis": 1539609701576
      }
    }
  }
}
--------------------------------------------------
// CONSOLE
// TESTRESPONSE[skip:not possible to get the cluster into this state in a docs test]
<1> The step that caused the error
<2> What went wrong
