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

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

Start a new reindex or resume a paused reindex. Following steps are performed during 
a reindex task:

. Setting the index to read-only
. Creating a new index
. {ref}/docs-reindex.html[Reindexing] documents into the new index
. Creating an index alias for the new index
. Deleting the old index



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

`POST <kibana host>:<port>/api/upgrade_assistant/reindex/myIndex`

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

`200`::
  Indicates a successful call.

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

The API returns the following:

[source,sh]
--------------------------------------------------
{
  "indexName": ".ml-state",
  "newIndexName": ".reindexed-v7-ml-state", <1>
  "status": 0, <2>
  "lastCompletedStep": 0, <3>
  "reindexTaskId": null, <4>
  "reindexTaskPercComplete": null, <5>
  "errorMessage": null <6>
}
--------------------------------------------------

<1> The name of the new index.
<2> The reindex status. For more information, refer to <<status-code,Status codes>>.
<3> The last successfully completed step of the reindex. For more information, refer to <<step-code,Step codes>>.
<4> The task ID of the {ref}/docs-reindex.html[reindex] task in {es}. Appears when the reindexing starts.
<5> The progress of the {ref}/docs-reindex.html[reindexing] task in {es}. Appears in decimal form, from 0 to 1.
<6> The error that caused the reindex to fail, if it failed.