Prevalidate node removal API

POST /_internal/prevalidate_node_removal

This API checks whether attempting to remove the specified node(s) from the cluster is likely to succeed or not. For a cluster with no unassigned shards, removal of any node is considered safe which means the removal of the nodes is likely to succeed. In case the cluster has a red cluster health status, it verifies that the removal of the node(s) would not risk removing the last remaining copy of an unassigned shard.

The response includes the overall safety of the removal of the specified nodes, and a detailed response for each node. The node-specific part of the response also includes more details on why removal of that node might not succeed.

Note that only one of the query parameters (names, ids, or external_ids) must be used to specify the set of nodes.

Note that if the prevalidation result for a set of nodes returns true (i.e. it is likely to succeed), this does not mean that all those nodes could be successfully removed at once, but rather removal of each individual node would potentially be successful. The actual node removal could be handled via the Node lifecycle API.

This example validates whether it is safe to remove the nodes node1 and node2. The response indicates that it is safe to remove node1, but it might not be safe to remove node2. Therefore, the overall prevalidation of the removal of the two nodes returns false.

POST /_internal/prevalidate_node_removal?names=node1,node2

The API returns the following response:

{
  "is_safe": false,
  "message": "cluster health is RED",
  "nodes": [
    {
      "id": "node1-id",
      "name" : "node1",
      "external_id" : "node1-externalId",
      "result" : {
        "is_safe": true,
        "message": ""
      }
    },
    {
      "id": "node2-id",
      "name" : "node2",
      "external_id" : "node2-externalId",
      "result" : {
        "is_safe": false,
        "message": "node may contain a copy of a red index shard"
      }
    }
  ]
}