Java Rest API does not allow ForceMergeAction for hot phase in LifeCyclePolicy

[ismarslomic]

While Elasticsearch REST API allows defining forcemerge action for hot phase, Java Rest API (v7.10.2) does not.

This is allowed:

PUT _ilm/policy/custom-ilm-policy
{
  "policy": {
    "phases": {
      "hot": {
        "min_age": "0ms",
        "actions": {
          "rollover": {
            "max_age": "1d"
          },
          "forcemerge": {
            "max_num_segments": 1
          },
          "set_priority": {
            "priority": 200
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {
            "delete_searchable_snapshot": true
          }
        }
      }
    }
  }
}

This is not allowed:

Map<String, LifecycleAction> hotActions = new HashMap<>();

// Rollover action
hotActions.put(RolloverAction.NAME, new RolloverAction(
        new ByteSizeValue(50, ByteSizeUnit.GB), null, null));

// Forcemerge action
hotActions.put(ForceMergeAction.NAME, new ForceMergeAction(1));

phases.put("hot", new Phase("hot", TimeValue.ZERO, hotActions)); 

IllegalArgumentException is thrown with error invalid action [forcemerge] defined in phase [hot]. See LifeCyclePolicy