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

Start an upgradeedit

$ 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 optimize.

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.

Check upgrade statusedit

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.

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