Get started: Automate rollover with ILMedit

This tutorial demonstrates how to use index lifecycle management (ILM) to manage indices that contain time-series data.

When you continuously index timestamped documents into Elasticsearch 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, you:

  1. Create a lifecycle policy with the ILM put policy API.
  2. Create an index template to apply the policy to each new index.
  3. Bootstrap an index as the initial write index.
  4. Verify indices are moving through the lifecycle phases as expected with the ILM explain API.

Create a lifecycle policyedit

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 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.
PUT _ilm/policy/datastream_policy
{
  "policy": {
    "phases": {
      "hot": {                      
        "actions": {
          "rollover": {
            "max_size": "50GB",     
            "max_age": "30d"
          }
        }
      },
      "delete": {
        "min_age": "90d",           
        "actions": {
          "delete": {}              
        }
      }
    }
  }
}

The min_age defaults to 0ms, so new indices enter the hot phase immediately.

Trigger the rollover action when either of the conditions are met.

Move the index into the delete phase 90 days after rollover.

Trigger the delete action when the index enters the delete phase.

See Actions for the complete list of actions available in each phase.

Create an index template to apply the lifecycle policyedit

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 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.
PUT _template/datastream_template
{
  "index_patterns": ["datastream-*"],                 
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "datastream_policy",      
    "index.lifecycle.rollover_alias": "datastream"    
  }
}

Apply the template to a new index if its name starts with datastream-.

The name of the lifecycle policy to apply to each new index.

The name of the alias used to reference these indices. Required for policies that use the rollover action.

Bootstrap the initial time-series indexedit

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.

PUT datastream-000001
{
  "aliases": {
    "datastream": {
      "is_write_index": true
    }
  }
}

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 API.

Checking progressedit

To get status information for managed indices, you use the ILM 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:

GET datastream-*/_ilm/explain

The response below shows that the bootstrap index is waiting in the hot phase’s rollover action. It remains in this state and ILM continues to call attempt-rollover until the rollover conditions are met.

[[36818c6d9f434d387819c30bd9addb14]]

{
  "indices": {
    "datastream-000001": {
      "index": "datastream-000001",
      "managed": true,
      "policy": "datastream_policy",             
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",                              
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "step": "attempt-rollover",                
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "datastream_policy",
        "phase_definition": {                    
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_size": "50gb",
              "max_age": "30d"
            }
          }
        },
        "version": 1,
        "modified_date_in_millis": 1539609701576
      }
    }
  }
}

The policy used to manage the index

The age of the index

The step ILM is performing on the index

The definition of the current phase (the hot phase)

See the ILM APIs for more information.