Explain the shard allocations Generally available; Added in 5.0.0

POST /_cluster/allocation/explain
Api key auth Basic auth Bearer auth

All methods and paths for this operation:

GET /_cluster/allocation/explain

POST /_cluster/allocation/explain

Get explanations for shard allocations in the cluster. For unassigned shards, it provides an explanation for why the shard is unassigned. For assigned shards, it provides an explanation for why the shard is remaining on its current node and has not moved or rebalanced to another node. This API can be very useful when attempting to diagnose why a shard is unassigned or why a shard continues to remain on its current node when you might expect otherwise. Refer to the linked documentation for examples of how to troubleshoot allocation issues using this API.

External documentation

Query parameters

  • include_disk_info boolean

    If true, returns information about disk usage and shard sizes.

  • include_yes_decisions boolean

    If true, returns YES decisions in explanation.

  • master_timeout string

    Period to wait for a connection to the master node.

    Values are -1 or 0.

application/json

Body

  • current_node string

    Specifies the node ID or the name of the node to only explain a shard that is currently located on the specified node.

  • index string
  • primary boolean

    If true, returns explanation for the primary shard for the given shard ID.

  • shard number

    Specifies the ID of the shard that you would like an explanation for.

Responses

  • 200 application/json
    Hide response attributes Show response attributes object
    • allocate_explanation string
    • allocation_delay string

      A duration. Units can be nanos, micros, ms (milliseconds), s (seconds), m (minutes), h (hours) and d (days). Also accepts "0" without a unit and "-1" to indicate an unspecified value.

    • allocation_delay_in_millis number

      Time unit for milliseconds

    • can_allocate string

      Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

    • can_move_to_other_node string

      Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

    • can_rebalance_cluster string

      Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

    • can_rebalance_cluster_decisions array[object]
      Hide can_rebalance_cluster_decisions attributes Show can_rebalance_cluster_decisions attributes object
      • decider string Required
      • decision string Required

        Values are NO, YES, THROTTLE, or ALWAYS.

      • explanation string Required
    • can_rebalance_to_other_node string

      Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

    • can_remain_decisions array[object]
      Hide can_remain_decisions attributes Show can_remain_decisions attributes object
      • decider string Required
      • decision string Required

        Values are NO, YES, THROTTLE, or ALWAYS.

      • explanation string Required
    • can_remain_on_current_node string

      Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

    • cluster_info object
      Hide cluster_info attributes Show cluster_info attributes object
      • nodes object Required
        Hide nodes attribute Show nodes attribute object
        • * object Additional properties
          Hide * attributes Show * attributes object
          • node_name string Required
          • least_available object Required
            Hide least_available attributes Show least_available attributes object
            • path string Required
            • total_bytes number Required
            • used_bytes number Required
            • free_bytes number Required
            • free_disk_percent number Required
            • used_disk_percent number Required
          • most_available object Required
            Hide most_available attributes Show most_available attributes object
            • path string Required
            • total_bytes number Required
            • used_bytes number Required
            • free_bytes number Required
            • free_disk_percent number Required
            • used_disk_percent number Required
      • shard_sizes object Required
        Hide shard_sizes attribute Show shard_sizes attribute object
        • * number Additional properties
      • shard_data_set_sizes object
        Hide shard_data_set_sizes attribute Show shard_data_set_sizes attribute object
        • * string Additional properties
      • shard_paths object Required
        Hide shard_paths attribute Show shard_paths attribute object
        • * string Additional properties
      • reserved_sizes array[object] Required
        Hide reserved_sizes attributes Show reserved_sizes attributes object
        • node_id string Required
        • path string Required
        • total number Required
        • shards array[string] Required
    • configured_delay string

      A duration. Units can be nanos, micros, ms (milliseconds), s (seconds), m (minutes), h (hours) and d (days). Also accepts "0" without a unit and "-1" to indicate an unspecified value.

    • configured_delay_in_millis number

      Time unit for milliseconds

    • current_node object
      Hide current_node attributes Show current_node attributes object
      • id string Required
      • name string Required
      • roles array[string] Required

        Values are master, data, data_cold, data_content, data_frozen, data_hot, data_warm, client, ingest, ml, voting_only, transform, remote_cluster_client, or coordinating_only.

      • attributes object Required
        Hide attributes attribute Show attributes attribute object
        • * string Additional properties
      • transport_address string Required
      • weight_ranking number Required
    • current_state string Required
    • index string Required
    • move_explanation string
    • node_allocation_decisions array[object]
      Hide node_allocation_decisions attributes Show node_allocation_decisions attributes object
      • deciders array[object] Required
        Hide deciders attributes Show deciders attributes object
        • decider string Required
        • decision string Required

          Values are NO, YES, THROTTLE, or ALWAYS.

        • explanation string Required
      • node_attributes object Required
        Hide node_attributes attribute Show node_attributes attribute object
        • * string Additional properties
      • node_decision string Required

        Values are yes, no, worse_balance, throttled, awaiting_info, allocation_delayed, no_valid_shard_copy, or no_attempt.

      • node_id string Required
      • node_name string Required
      • roles array[string] Required

        Values are master, data, data_cold, data_content, data_frozen, data_hot, data_warm, client, ingest, ml, voting_only, transform, remote_cluster_client, or coordinating_only.

      • store object
        Hide store attributes Show store attributes object
        • allocation_id string Required
        • found boolean Required
        • in_sync boolean Required
        • matching_size_in_bytes number Required
        • matching_sync_id boolean Required
        • store_exception string Required
      • transport_address string Required
      • weight_ranking number Required
    • primary boolean Required
    • rebalance_explanation string
    • remaining_delay string

      A duration. Units can be nanos, micros, ms (milliseconds), s (seconds), m (minutes), h (hours) and d (days). Also accepts "0" without a unit and "-1" to indicate an unspecified value.

    • remaining_delay_in_millis number

      Time unit for milliseconds

    • shard number Required
    • unassigned_info object
      Hide unassigned_info attributes Show unassigned_info attributes object

      • at string | number Required

        A date and time, either as a string whose format can depend on the context (defaulting to ISO 8601), or a number of milliseconds since the Epoch. Elasticsearch accepts both as input, but will generally output a string representation.

        One of:
        string-1 string UnitMillis number

        Time unit for milliseconds

      • last_allocation_status string
      • reason string Required

        Values are INDEX_CREATED, CLUSTER_RECOVERED, INDEX_REOPENED, DANGLING_INDEX_IMPORTED, NEW_INDEX_RESTORED, EXISTING_INDEX_RESTORED, REPLICA_ADDED, ALLOCATION_FAILED, NODE_LEFT, REROUTE_CANCELLED, REINITIALIZED, REALLOCATED_REPLICA, PRIMARY_FAILED, FORCED_EMPTY_PRIMARY, or MANUAL_ALLOCATION.

      • details string
      • failed_allocation_attempts number
      • delayed boolean
      • allocation_status string
    • note string Generally available; Added in 7.14.0
POST /_cluster/allocation/explain 
GET _cluster/allocation/explain
{
  "index": "my-index-000001",
  "shard": 0,
  "primary": false,
  "current_node": "my-node"
}
resp = client.cluster.allocation_explain(
    index="my-index-000001",
    shard=0,
    primary=False,
    current_node="my-node",
)
const response = await client.cluster.allocationExplain({
  index: "my-index-000001",
  shard: 0,
  primary: false,
  current_node: "my-node",
});
response = client.cluster.allocation_explain(
  body: {
    "index": "my-index-000001",
    "shard": 0,
    "primary": false,
    "current_node": "my-node"
  }
)
$resp = $client->cluster()->allocationExplain([
    "body" => [
        "index" => "my-index-000001",
        "shard" => 0,
        "primary" => false,
        "current_node" => "my-node",
    ],
]);
curl -X GET -H "Authorization: ApiKey $ELASTIC_API_KEY" -H "Content-Type: application/json" -d '{"index":"my-index-000001","shard":0,"primary":false,"current_node":"my-node"}' "$ELASTICSEARCH_URL/_cluster/allocation/explain"
client.cluster().allocationExplain(a -> a
    .currentNode("my-node")
    .index("my-index-000001")
    .primary(false)
    .shard(0)
);
Request example
Run `GET _cluster/allocation/explain` to get an explanation for a shard's current allocation. 
{
  "index": "my-index-000001",
  "shard": 0,
  "primary": false,
  "current_node": "my-node"
}
Response examples (200)
An example of an allocation explanation for an unassigned primary shard. In this example, a newly created index has an index setting that requires that it only be allocated to a node named `nonexistent_node`, which does not exist, so the index is unable to allocate. 
{
  "index" : "my-index-000001",
  "shard" : 0,
  "primary" : true,
  "current_state" : "unassigned",
  "unassigned_info" : {
    "reason" : "INDEX_CREATED",
    "at" : "2017-01-04T18:08:16.600Z",
    "last_allocation_status" : "no"
  },
  "can_allocate" : "no",
  "allocate_explanation" : "Elasticsearch isn't allowed to allocate this shard to any of the nodes in the cluster. Choose a node to which you expect this shard to be allocated, find this node in the node-by-node explanation, and address the reasons which prevent Elasticsearch from allocating this shard there.",
  "node_allocation_decisions" : [
    {
      "node_id" : "8qt2rY-pT6KNZB3-hGfLnw",
      "node_name" : "node-0",
      "transport_address" : "127.0.0.1:9401",
      "roles" : ["data", "data_cold", "data_content", "data_frozen", "data_hot", "data_warm", "ingest", "master", "ml", "remote_cluster_client", "transform"],
      "node_attributes" : {},
      "node_decision" : "no",
      "weight_ranking" : 1,
      "deciders" : [
        {
          "decider" : "filter",
          "decision" : "NO",
          "explanation" : "node does not match index setting [index.routing.allocation.include] filters [_name:\"nonexistent_node\"]"
        }
      ]
    }
  ]
}
An example of an allocation explanation for an unassigned primary shard that has reached the maximum number of allocation retry attempts. After the maximum number of retries is reached, Elasticsearch stops attempting to allocate the shard in order to prevent infinite retries which may impact cluster performance. 
{
  "index" : "my-index-000001",
  "shard" : 0,
  "primary" : true,
  "current_state" : "unassigned",
  "unassigned_info" : {
    "at" : "2017-01-04T18:03:28.464Z",
    "failed shard on node [mEKjwwzLT1yJVb8UxT6anw]: failed recovery, failure RecoveryFailedException",
    "reason": "ALLOCATION_FAILED",
    "failed_allocation_attempts": 5,
    "last_allocation_status": "no",
  },
  "can_allocate": "no",
  "allocate_explanation": "cannot allocate because allocation is not permitted to any of the nodes",
  "node_allocation_decisions" : [
    {
      "node_id" : "3sULLVJrRneSg0EfBB-2Ew",
      "node_name" : "node_t0",
      "transport_address" : "127.0.0.1:9400",
      "roles" : ["data_content", "data_hot"],
      "node_decision" : "no",
      "store" : {
        "matching_size" : "4.2kb",
        "matching_size_in_bytes" : 4325
      },
      "deciders" : [
        {
          "decider": "max_retry",
          "decision" : "NO",
          "explanation": "shard has exceeded the maximum number of retries [5] on failed allocation attempts - manually call [POST /_cluster/reroute?retry_failed] to retry, [unassigned_info[[reason=ALLOCATION_FAILED], at[2024-07-30T21:04:12.166Z], failed_attempts[5], failed_nodes[[mEKjwwzLT1yJVb8UxT6anw]], delayed=false, details[failed shard on node [mEKjwwzLT1yJVb8UxT6anw]: failed recovery, failure RecoveryFailedException], allocation_status[deciders_no]]]"
        }
      ]
    }
  ]
}