Force merge

Phases allowed: hot, warm.

Force merges the index into the specified maximum number of segments.

This action makes the index read-only.

To use the forcemerge action in the hot phase, the rollover action must be present. If no rollover action is configured, ILM will reject the policy.

Options

max_num_segments
(Required, integer) Number of segments to merge to. To fully merge the index, set to 1.
codec

(Optional, string) Use the best_compression codec. Valid values: best_compression.

Setting "codec": "best_compression" in the ILM forcemerge action causes {ilm-int} to close and then re-open the index prior to the force merge. During this time, the index is unavailable for both read and write operations.

Example

PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "warm": {
        "actions": {
          "forcemerge" : {
            "max_num_segments": 1
          }
        }
      }
    }
  }
}