[[batch-start-resume-reindex]]
=== Batch start or resume reindex API
++++
<titleabbrev>Batch start or resume reindex</titleabbrev>
++++

experimental["The underlying Upgrade Assistant concepts are stable, but the APIs for managing Upgrade Assistant are experimental."]

Start or resume multiple reindexing tasks in one request. Additionally, reindexing tasks started or resumed
via the batch endpoint will be placed on a queue and executed one-by-one, which ensures that minimal cluster resources
are consumed over time.

[[batch-start-resume-reindex-request]]
==== Request

`POST /api/upgrade_assistant/reindex/batch`

[[batch-start-resume-reindex-request-body]]
==== Request body

`indexNames`::
  (Required, array) The list of index names to be reindexed.

[[batch-start-resume-reindex-codes]]
==== Response code

`200`::
  Indicates a successful call.

[[batch-start-resume-example]]
==== Example

[source,js]
--------------------------------------------------
$ curl -X POST api/upgrade_assistant/reindex/batch
{
  "indexNames": [ <1>
    "index1",
    "index2"
  ]
}
--------------------------------------------------
// KIBANA

<1> The order of the indices determines the order that the reindex tasks are executed.

Similar to the <<start-resume-reindex, start or resume endpoint>>, the API returns the following:

[source,js]
--------------------------------------------------
{
  "enqueued": [ <1>
    {
      "indexName": "index1",
      "newIndexName": "reindexed-v8-index1",
      "status": 3,
      "lastCompletedStep": 0,
      "locked": null,
      "reindexTaskId": null,
      "reindexTaskPercComplete": null,
      "errorMessage": null,
      "runningReindexCount": null,
      "reindexOptions": { <2>
        "queueSettings": {
          "queuedAt": 1583406985489 <3>
        }
      }
    }
  ],
  "errors": [ <4>
    {
      "indexName": "index2",
      "message": "Something went wrong!"
    }
  ]
}
--------------------------------------------------

<1> A list of reindex operations created, the order in the array indicates the order in which tasks will be executed.
<2> Presence of this key indicates that the reindex job will occur in the batch.
<3> A Unix timestamp of when the reindex task was placed in the queue.
<4> A list of errors that may have occurred preventing the reindex task from being created.