Explain the shard allocations
Generally available; Added in 5.0.0
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.
Query parameters
-
If true, returns information about disk usage and shard sizes.
-
If true, returns YES decisions in explanation.
-
Period to wait for a connection to the master node.
Values are
-1or0.
POST
/_cluster/allocation/explain
Console
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"
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)
Conflicting settings
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]]]"
}
]
}
]
}