[role="xpack"]
[testenv="basic"]

[[getting-started-index-lifecycle-management]]
== Get started: Automate rollover with {ilm-init}

++++
<titleabbrev>Automate rollover</titleabbrev>
++++

This tutorial demonstrates how to use {ilm} ({ilm-init}) 
to manage indices that contain time-series data. 

When you continuously index timestamped documents into {es} using 
Filebeat, Logstash, or some other mechanism, 
you typically use an index alias so you can periodically roll over to a new index.
This enables you to implement a hot-warm-cold architecture to meet your performance
requirements for your newest data, control costs over time, enforce retention policies,
and still get the most out of your data.

To automate rollover and management of time-series indices with {ilm-init}, you:

. <<ilm-gs-create-policy, Create a lifecycle policy>> with the {ilm-init} put policy API.  
. <<ilm-gs-apply-policy, Create an index template>> to apply the policy to each new index.
. <<ilm-gs-bootstrap, Bootstrap an index>> as the initial write index.
. <<ilm-gs-check-progress, Verify indices are moving through the lifecycle phases>> 
as expected with the {ilm-init} explain API. 

[float]
[[ilm-gs-create-policy]]
=== Create a lifecycle policy

A lifecycle policy specifies the phases in the index lifecycle
and the actions to perform in each phase. A lifecycle can have up to four phases:
`hot`, `warm`, `cold`, and `delete`. Policies are defined in JSON 
and added through the {ilm-init} put policy API. 

For example, the following request creates a `datastream_policy` with two phases:
 
* The `hot` phase defines a `rollover` action to specify that an index rolls over when it 
reaches either a `max_size` of 50 gigabytes or a `max_age` of 30 days.
* The `delete` phase uses `min_age` to remove the index 90 days after rollover.
Note that this value is relative to the rollover time, not the index creation time. 

[source,console]
------------------------
PUT _ilm/policy/datastream_policy 
{
  "policy": {                       
    "phases": {
      "hot": {                      <1>
        "actions": {
          "rollover": {             
            "max_size": "50GB",     <2>
            "max_age": "30d"
          }
        }
      },
      "delete": {
        "min_age": "90d",           <3>
        "actions": {
          "delete": {}              <4>
        }
      }
    }
  }
}
------------------------
<1> The `min_age` defaults to `0ms`, so new indices enter the `hot` phase immediately. 
<2> Trigger the `rollover` action when either of the conditions are met.
<3> Move the index into the `delete` phase 90 days after rollover.
<4> Trigger the `delete` action when the index enters the delete phase.

See <<_actions>> for the complete list of actions available in each phase.

[float]
[[ilm-gs-apply-policy]]
=== Create an index template to apply the lifecycle policy

To automaticaly apply a lifecycle policy to the new write index on rollover, 
specify the policy in the index template used to create new indices.

For example, the following request creates a `datastream_template` that is applied to new indices
whose names match the `datastream-*` index pattern. 
The template configures two {ilm-init} settings:

* `index.lifecycle.name` specifies the name of the lifecycle policy to apply to all new indices that match 
the index pattern.  
* `index.lifecycle.rollover_alias` specifies the index alias to be rolled over 
when the rollover action is triggered for an index.

[source,console]
-----------------------
PUT _template/datastream_template
{
  "index_patterns": ["datastream-*"],                 <1>
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "datastream_policy",      <2>
    "index.lifecycle.rollover_alias": "datastream"    <3>
  }
}
-----------------------
// TEST[continued]

<1> Apply the template to a new index if its name starts with `datastream-`. 
<2> The name of the lifecycle policy to apply to each new index.
<3> The name of the alias used to reference these indices. 
Required for policies that use the rollover action.

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

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

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

[float]
[[ilm-gs-bootstrap]]
=== Bootstrap the initial time-series index

To get things started, you need to bootstrap an initial index and 
designate it as the write index for the rollover alias specified in your index template. 
The name of this index must match the template's index pattern and end with a number. 
On rollover, this value is incremented to generate a name for the new index. 

For example, the following request creates an index called `datastream-000001` 
and makes it the write index for the `datastream` alias.

[source,console]
-----------------------
PUT datastream-000001
{
  "aliases": {
    "datastream": {
      "is_write_index": true
    }
  }
}
-----------------------
// TEST[continued]

When the rollover conditions are met, the `rollover` action:

* Creates a new index called `datastream-000002`. 
This matches the `datastream-*` pattern, so the settings from `datastream_template` are applied to the new index.
* Designates the new index as the write index and makes the bootstrap index read-only.

This process repeats each time rollover conditions are met. 
You can search across all of the indices managed by the `datastream_policy` with the `datastream` alias. 
Write operations are routed to the current write index. 

For more information about write indices and rollover, see the <<rollover-index-api-desc, rollover API>>.

[float]
[[ilm-gs-check-progress]]
=== Checking progress

To get status information for managed indices, you use the {ilm-init} explain API. 
This lets you find out things like:

* What phase an index is in and when it entered that phase.
* The current action and what step is being performed.
* If any errors have occurred or progress is blocked.

For example, the following request gets information about the `datastream` indices: 

[source,console]
--------------------------------------------------
GET datastream-*/_ilm/explain
--------------------------------------------------
// TEST[continued]

The response below shows that the bootstrap index is waiting in the `hot` phase's `rollover` action.
It remains in this state and {ilm-init} continues to call `attempt-rollover` 
until the rollover conditions are met. 

[[36818c6d9f434d387819c30bd9addb14]]
[source,console-result]
--------------------------------------------------
{
  "indices": {
    "datastream-000001": {
      "index": "datastream-000001",
      "managed": true,                           
      "policy": "datastream_policy",             <1>
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",                              <2>
      "phase": "hot",                            
      "phase_time_millis": 1538475653317,
      "action": "rollover",                      
      "action_time_millis": 1538475653317,
      "step": "attempt-rollover",                <3>
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "datastream_policy",
        "phase_definition": {                    <4>
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_size": "50gb",
              "max_age": "30d"
            }
          }
        },
        "version": 1,                            
        "modified_date_in_millis": 1539609701576
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[skip:no way to know if we will get this response immediately]

<1> The policy used to manage the index 
<2> The age of the index
<3> The step {ilm-init} is performing on the index
<4> The definition of the current phase (the `hot` phase)

See the <<index-lifecycle-management-api,ILM APIs>> for more information.