Why is replica shard in UNASSIGNED state if it exists on disk?

Elastic Stack Elasticsearch
1

I would like to ask question regarding the shard allocation for rolling restart,.

I am trying to figure out why shard allocation happens after following steps for rolling restart. I have done below test.

Environment

  1. 1 cluster with 2 master eligible nodes.
  2. elasticsearch v6.1.1

Steps

1.Create index

PUT test-indices
{
     "settings" : {
      "number_of_shards": 2,
      "number_of_replicas": 1
   }
}

2.Check which node each shard is located. Primary shard are spread on each node.

GET _cat/shards/test-indices?v
index        shard prirep state   docs store ip           node
test-indices 1     r      STARTED    0  233b 172.31.27.43 node2
test-indices 1     p      STARTED    0  233b 172.31.27.43 node1
test-indices 0     p      STARTED    0  233b 172.31.27.43 node2
test-indices 0     r      STARTED    0  233b 172.31.27.43 node1

3.Disable shard reallocation and do sync flush.

PUT _cluster/settings
{
   "persistent" : {
      "cluster.routing.allocation.enable" : "none"
   }
}
 
POST _flush/synced

4.Shutdown node2
5.Start node2

6.Check shards before re-enabling shard allocation. All replicas are UNASSIGNED . Even the replica for shard 0 .

GET _cat/shards/test-indices?v
index        shard prirep state      docs store ip           node
test-indices 1     p      STARTED       0  264b 172.31.27.43 node1
test-indices 1     r      UNASSIGNED                         
test-indices 0     p      STARTED       0  264b 172.31.27.43 node1
test-indices 0     r      UNASSIGNED

7 Also check the cluster state API and replica for shard 0 is UNASSIGNED

GET _cluster/state/routing_table/test-indices

{
  "cluster_name": "mycluster",
  "compressed_size_in_bytes": 15865,
  "routing_table": {
    "indices": {
      "test-indices": {
        "shards": {
          "0": [
            {
              "state": "STARTED",
              "primary": true,
              "node": "g-_vH5rwT-inWJuhHyjHcA",
              "relocating_node": null,
              "shard": 0,
              "index": "test-indices",
              "allocation_id": {
                "id": "QR-dWeL6ToGYShiHIROEDg"
              }
            },
            {
              "state": "UNASSIGNED",
              "primary": false,
              "node": null,
              "relocating_node": null,
              "shard": 0,
              "index": "test-indices",
              "recovery_source": {
                "type": "PEER"
              },
              "unassigned_info": {
                "reason": "NODE_LEFT",
                "at": "2018-02-01T10:40:13.350Z",
                "delayed": false,
                "details": "node_left[nB9E_CoCQmuC-Gjx4gvucA]",
                "allocation_status": "no_attempt"
              }
            }
          ],
          "1": [
            {
              "state": "STARTED",
              "primary": true,
              "node": "g-_vH5rwT-inWJuhHyjHcA",
              "relocating_node": null,
              "shard": 1,
              "index": "test-indices",
              "allocation_id": {
                "id": "5ZWVGFTgS0Gsg1R2Sf8iQQ"
              }
            },
            {
              "state": "UNASSIGNED",
              "primary": false,
              "node": null,
              "relocating_node": null,
              "shard": 1,
              "index": "test-indices",
              "recovery_source": {
                "type": "PEER"
              },
              "unassigned_info": {
                "reason": "NODE_LEFT",
                "at": "2018-02-01T10:40:13.350Z",
                "delayed": false,
                "details": "node_left[nB9E_CoCQmuC-Gjx4gvucA]",
                "allocation_status": "no_attempt"
              }
            }
          ]
        }
      }
    }
  }
}

It makes sense for replica shard on shard 1to be UNASSIGNED because it was promoted to primary shard, however, why is the replica shard for shard 0 UNASSIGNED if it exists on the disk ?

2

That's bad, see Important Configuration Changes | Elasticsearch: The Definitive Guide [2.x] | Elastic

How did you enable allocation after the restart?

3

@warkolm

Thank you for the reply.

That's bad, see Important Configuration Changes | Elasticsearch: The Definitive Guide [2.x] | Elastic

Yes. Thanks for mentioning.

How did you enable allocation after the restart?

No . I have not enabled the allocation. cluster.routing.allocation.enable is set as none .

4

If allocation is still disabled, what you are seeing is expected.

5

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