Shard unassigned NODE_LEFT

[kpiyush (Piyush Kumar)]

Hi,

I have restarted the Elsaticsearch worker nodes. After restarting, one of the indexes is stuck on INITIALIZING mode and it is been quite a long time.
I ran:

curl -k -XGET 'https://eu1.elasticsearch.svc.cluster.local:31000/_cluster/allocation/explain?pretty' -H 'Content-Type: application/json' -d'{"index": "index-1","shard":2,"primary": true}'
{
  "index" : "index-1",
  "shard" : 2,
  "primary" : true,
  "current_state" : "initializing",
  "unassigned_info" : {
    "reason" : "NODE_LEFT",
    "at" : "2020-11-10T16:16:37.317Z",
    "details" : "node_left [ktIXm-hVRliZA7FbWElCAw]",
    "last_allocation_status" : "throttled"
  },
  "current_node" : {
    "id" : "PrPXcMPpTuGvVxBkwXNt1w",
    "name" : "elasticsearch-es-default-1",
    "transport_address" : "10.1.218.232:9300",
    "attributes" : {
      "ml.machine_memory" : "12884901888",
      "ml.max_open_jobs" : "20",
      "xpack.installed" : "true"
    }
  },
  "explanation": "the shard is in the process of initializing on node [elasticsearch-es-default-1], wait until initialization has completed"
}

The reason stated NODE_LEFT, I am not able to understand that because out of all shards only one shard is stuck and all the other shards on that elasticsearch-es-default-1 node are assigned.

index-1     2 p INITIALIZING    10.1.218.232 elasticsearch-es-default-1
index-1     2 r UNASSIGNED

What can be done to fix this?