Upgrade

The upgrade API allows to upgrade one or more indices to the latest Lucene format through an API. The upgrade process converts any segments written with older formats.

Start an upgrade

$ curl -XPOST 'http://localhost:9200/twitter/_upgrade'

Upgrading is an I/O intensive operation, and is limited to processing a single shard per node at a time. It also is not allowed to run at the same time as an optimize/force-merge.

This call will block until the upgrade is complete. If the http connection is lost, the request will continue in the background, and any new requests will block until the previous upgrade is complete.

Request Parameters

The upgrade API accepts the following request parameters:

only_ancient_segments

If true, only very old segments (from a previous Lucene major release) will be upgraded. While this will do the minimal work to ensure the next major release of Elasticsearch can read the segments, it’s dangerous because it can leave other very old segments in sub-optimal formats. Defaults to false.

Check upgrade status

Use a GET request to monitor how much of an index is upgraded. This can also be used prior to starting an upgrade to identify which indices you want to upgrade at the same time.

The ancient byte values that are returned indicate total bytes of segments whose version is extremely old (Lucene major version is different from the current version), showing how much upgrading is necessary when you run with only_ancient_segments=true.

curl 'http://localhost:9200/twitter/_upgrade?pretty&human'
{
  "size": "21gb",
  "size_in_bytes": "21000000000",
  "size_to_upgrade": "10gb",
  "size_to_upgrade_in_bytes": "10000000000"
  "size_to_upgrade_ancient": "1gb",
  "size_to_upgrade_ancient_in_bytes": "1000000000"
  "indices": {
    "twitter": {
      "size": "21gb",
      "size_in_bytes": "21000000000",
      "size_to_upgrade": "10gb",
      "size_to_upgrade_in_bytes": "10000000000"
      "size_to_upgrade_ancient": "1gb",
      "size_to_upgrade_ancient_in_bytes": "1000000000"
    }
  }
}

The level of details in the upgrade status command can be controlled by setting level parameter to cluster, index (default) or shard levels. For example, you can run the upgrade status command with level=shard to get detailed upgrade information of each individual shard.