Healthy Elasticsearch cluster turns RED after opening a closed index

Question

I have a managed cluster hosted by elastio.co. Here is the configuration |Platform => Amazon Web Services| |Memory => 4 GB| |Storage => 96 GB| |SSD => Yes| |High availability => Yes 2 data centers|

Each index in this cluster contain log data of exactly one day. Average index size is 15 mb and average doc count is 15000. The cluster is not in any way under any kind of pressure (JVM, Indexing & Searching time, Disk Space all are in very comfort zone)

When I opened a previously closed index the cluster is turned RED. Here are some matrices I found querying the elasticsearch.

GET /_cluster/allocation/explain
{
  "index": "some_index_name",    # 1 Primary shard , 1 replica shard 
  "shard": 0,
  "primary": true
}

Response :

"unassigned_info": {
"reason": "ALLOCATION_FAILED"
"failed_allocation_attempts": 3,
"details": "failed recovery, failure RecoveryFailedException[[some_index_name][0]: Recovery failed on {instance-*****}{Hash}{HASH}{IP}{IP}{logical_availability_zone=zone-1, availability_zone=***, region=***}]; nested: IndexShardRecoveryException[failed to fetch index version after copying it over]; nested: IndexShardRecoveryException[shard allocated for local recovery (post api), should exist, but doesn't, current files: []]; nested: IndexNotFoundException[no segments* file found in store(mmapfs(/app/data/nodes/0/indices/MFIFAQO2R_ywstzqrfbY4w/0/index)): files: []]; ",
"last_allocation_status": "no_valid_shard_copy"
}, 
"can_allocate": "no_valid_shard_copy",
"allocate_explanation": "cannot allocate because all found copies of the shard are either stale or corrupt",
"node_allocation_decisions": [
  {
    "node_name": "instance-***",
    "node_decision": "no",
    "store": {
      "in_sync": false,
      "allocation_id": "RANDOM_HASH",
      "store_exception": {
        "type": "index_not_found_exception",
        "reason": "no segments* file found in SimpleFSDirectory@/app/data/nodes/0/indices/RANDOM_HASH/0/index lockFactory=org.apache.lucene.store.NativeFSLockFactory@346e1b99: files: []"
      }
  }
},
{
  "node_name": "instance-***",
  "node_attributes": {
    "logical_availability_zone": "zone-0",
  },
  "node_decision": "no",
  "store": {
    "found": false
  }
}

I've tried rerouting the shards to a node. Even setting data loss flag to true.

POST _cluster/reroute
{
  "commands" : [
  {"allocate_stale_primary" : {
  "index" : "some_index_name", "shard" : 0,
  "node" : "instance-***",
  "accept_data_loss" : true
    }
  }
  ]
}

Response:

"acknowledged": true,
"state": {
"version": 338190,
"state_uuid": "RANDOM_HASH",
"master_node": "RANDOM_HASH",
"blocks": {
  "indices": {
    "restored_**: {
      "4": {
        "description": "index closed",
        "retryable": false,
        "levels": [
          "read",
          "write"
        ]
      }
    },
    "restored_**": {
      "4": {
        "description": "index closed",
        "retryable": false,
        "levels": [
          "read",
          "write"
        ]
      }
    }
  }
},
"routing_table": {
  "indices": {
    "SOME_INDEX_NAME": {
      "shards": {
        "0": [
          {
            "state": "INITIALIZING",
            "primary": true,
            "relocating_node": null,
            "shard": 0,
            "index": "SOME_INDEX_NAME",
            "recovery_source": {
              "type": "EXISTING_STORE"
            },
            "allocation_id": {
              "id": "HASH"
            },
            "unassigned_info": {
              "reason": "ALLOCATION_FAILED",
              "failed_attempts": 4,
              "delayed": false,
              "details": "same as explanation above ^ ",
              "allocation_status": "no_valid_shard_copy"
            }
          },
          {
            "state": "UNASSIGNED",
            "primary": false,
            "node": null,
            "relocating_node": null,
            "shard": 0,
            "index": "some_index_name",
            "recovery_source": {
              "type": "PEER"
            },
            "unassigned_info": {
              "reason": "INDEX_REOPENED",
              "delayed": false,
              "allocation_status": "no_attempt"
            }
          }
        ]
      }
    },

Any kind of suggestion is welcomed. Thanks and regards.

Answer 1

This occurs when the master-node is brought down abruptly.

Here are the steps I took to resolve the same issue, that I had encountered ,

• Step 1: Check the allocation

  • curl -XGET http://localhost:9200/_cat/allocation?v

• Step 2: Check the shard stores

  • curl -XGET http://localhost:9200/_shard_stores?pretty Look out for "index", "shard" and "node" that has the error that you displayed. The ERROR should be --> "no segments* file found in SimpleFSDirectory@/...."

• Step 3: Now reroute that index as shown below

  • curl -XPOST 'http://localhost:9200/_cluster/reroute?master_timeout=5m' \ -d '{ "commands": [ { "allocate_empty_primary": { "index": "IndexFromStep2", "shard": ShardFromStep2 , "node": "NodeFromStep2", "accept_data_loss" : true } } ] }'

• Step 4: Repeat Step2 and Step3 until you see this output.

  • curl -XGET 'http://localhost:9200/_shard_stores?pretty'

  { "indices" : { } }

Your cluster should go green soon.