ILM Overview

Index lifecycle management (ILM) policies automatically manage indices according to our performance, resiliency, and retention requirements.

• Rollover: Creates a new write index when the current one reaches a certain size, number of docs, or age.
• Shrink: Reduces the number of primary shards in an index.
• Force merge: Triggers a merge to reduce the number of segments in an index's shards.
• Freeze: Freezes an index and makes it read-only.
• Delete: Permanently remove an index, including all of its data and metadata.

With ILM policies we can specify;

• The maximum shard size, number of documents, or age at which you want to roll over to a new index.
• The point at which the index is no longer being updated and the number of primary shards can be reduced.
• When to force a merge to permanently remove documents marked for deletion.
• The point at which the index can be moved to less performant hardware.
• The point at which the availability is not as critical and the number of replicas can be reduced.
• When the index can be safely deleted.