Downsample

Phases allowed: hot, warm, cold.

Aggregates a time series (TSDS) index and stores pre-computed statistical summaries (min, max, sum, value_count and avg) for each metric field grouped by a configured time interval. For example, a TSDS index that contains metrics sampled every 10 seconds can be downsampled to an hourly index. All documents within an hour interval are summarized and stored as a single document and stored in the downsample index.

This action corresponds to the downsample API.

The name of the resulting downsample index is downsample-<original-index-name>-<random-uuid>. If ILM performs the downsample action on a backing index for a data stream, the downsample index becomes a backing index for the same stream and the source index is deleted.

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

PUT _ilm/policy/datastream_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_docs": 1
          },
          "downsample": {
  	          "fixed_interval": "1h"
  	      }
        }
      }
    }
  }
}