Cluster allocation explain API
editCluster allocation explain API
editProvides an explanation for a shard’s current allocation.
GET _cluster/allocation/explain { "index": "my-index-000001", "shard": 0, "primary": false, "current_node": "my-node" }
Prerequisites
edit-
If the Elasticsearch security features are enabled, you must have the
monitor
ormanage
cluster privilege to use this API.
Description
editThe purpose of the cluster allocation explain API is to provide explanations for shard allocations in the cluster. For unassigned shards, the explain API provides an explanation for why the shard is unassigned. For assigned shards, the explain API 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.
Query parameters
edit-
include_disk_info
-
(Optional, Boolean) If
true
, returns information about disk usage and shard sizes. Defaults tofalse
. -
include_yes_decisions
-
(Optional, Boolean) If
true
, returns YES decisions in explanation. Defaults tofalse
.
Request body
edit-
current_node
- (Optional, 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
- (Optional, string) Specifies the name of the index that you would like an explanation for.
-
primary
-
(Optional, Boolean) If
true
, returns explanation for the primary shard for the given shard ID. -
shard
- (Optional, integer) Specifies the ID of the shard that you would like an explanation for.
Examples
editUnassigned primary shard
editThe following request gets an allocation explanation for an unassigned primary shard.
GET _cluster/allocation/explain { "index": "my-index-000001", "shard": 0, "primary": true }
The API response indicates the shard is allocated to a nonexistent node.
{ "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" : "cannot allocate because allocation is not permitted to any of the nodes", "node_allocation_decisions" : [ { "node_id" : "8qt2rY-pT6KNZB3-hGfLnw", "node_name" : "node-0", "transport_address" : "127.0.0.1:9401", "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\"]" } ] } ] }
The current state of the shard. |
|
The reason for the shard originally becoming unassigned. |
|
Whether to allocate the shard. |
|
Whether to allocate the shard to the particular node. |
|
The decider which led to the |
|
An explanation as to why the decider returned a |
The following response contains an allocation explanation for an unassigned primary shard that was previously allocated.
{ "index" : "my-index-000001", "shard" : 0, "primary" : true, "current_state" : "unassigned", "unassigned_info" : { "reason" : "NODE_LEFT", "at" : "2017-01-04T18:03:28.464Z", "details" : "node_left[OIWe8UhhThCK0V5XfmdrmQ]", "last_allocation_status" : "no_valid_shard_copy" }, "can_allocate" : "no_valid_shard_copy", "allocate_explanation" : "cannot allocate because a previous copy of the primary shard existed but can no longer be found on the nodes in the cluster" }
Unassigned replica shard
editThe following response contains an allocation explanation for a replica that’s unassigned due to delayed allocation.
{ "index" : "my-index-000001", "shard" : 0, "primary" : false, "current_state" : "unassigned", "unassigned_info" : { "reason" : "NODE_LEFT", "at" : "2017-01-04T18:53:59.498Z", "details" : "node_left[G92ZwuuaRY-9n8_tc-IzEg]", "last_allocation_status" : "no_attempt" }, "can_allocate" : "allocation_delayed", "allocate_explanation" : "cannot allocate because the cluster is still waiting 59.8s for the departed node holding a replica to rejoin, despite being allowed to allocate the shard to at least one other node", "configured_delay" : "1m", "configured_delay_in_millis" : 60000, "remaining_delay" : "59.8s", "remaining_delay_in_millis" : 59824, "node_allocation_decisions" : [ { "node_id" : "pmnHu_ooQWCPEFobZGbpWw", "node_name" : "node_t2", "transport_address" : "127.0.0.1:9402", "node_decision" : "yes" }, { "node_id" : "3sULLVJrRneSg0EfBB-2Ew", "node_name" : "node_t0", "transport_address" : "127.0.0.1:9400", "node_decision" : "no", "store" : { "matching_size" : "4.2kb", "matching_size_in_bytes" : 4325 }, "deciders" : [ { "decider" : "same_shard", "decision" : "NO", "explanation" : "a copy of this shard is already allocated to this node [[my-index-000001][0], node[3sULLVJrRneSg0EfBB-2Ew], [P], s[STARTED], a[id=eV9P8BN1QPqRc3B4PLx6cg]]" } ] } ] }
Assigned shard
editThe following response contains an allocation explanation for an assigned shard. The response indicates the shard is not allowed to remain on its current node and must be reallocated.
{ "index" : "my-index-000001", "shard" : 0, "primary" : true, "current_state" : "started", "current_node" : { "id" : "8lWJeJ7tSoui0bxrwuNhTA", "name" : "node_t1", "transport_address" : "127.0.0.1:9401" }, "can_remain_on_current_node" : "no", "can_remain_decisions" : [ { "decider" : "filter", "decision" : "NO", "explanation" : "node does not match index setting [index.routing.allocation.include] filters [_name:\"nonexistent_node\"]" } ], "can_move_to_other_node" : "no", "move_explanation" : "cannot move shard to another node, even though it is not allowed to remain on its current node", "node_allocation_decisions" : [ { "node_id" : "_P8olZS8Twax9u6ioN-GGA", "node_name" : "node_t0", "transport_address" : "127.0.0.1:9400", "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\"]" } ] } ] }
Whether the shard is allowed to remain on its current node. |
|
The deciders that factored into the decision of why the shard is not allowed to remain on its current node. |
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Whether the shard is allowed to be allocated to another node. |
The following response contains an allocation explanation for a shard that must remain on its current node. Moving the shard to another node would not improve cluster balance.
{ "index" : "my-index-000001", "shard" : 0, "primary" : true, "current_state" : "started", "current_node" : { "id" : "wLzJm4N4RymDkBYxwWoJsg", "name" : "node_t0", "transport_address" : "127.0.0.1:9400", "weight_ranking" : 1 }, "can_remain_on_current_node" : "yes", "can_rebalance_cluster" : "yes", "can_rebalance_to_other_node" : "no", "rebalance_explanation" : "cannot rebalance as no target node exists that can both allocate this shard and improve the cluster balance", "node_allocation_decisions" : [ { "node_id" : "oE3EGFc8QN-Tdi5FFEprIA", "node_name" : "node_t1", "transport_address" : "127.0.0.1:9401", "node_decision" : "worse_balance", "weight_ranking" : 1 } ] }
No arguments
editIf you call the API with no arguments, Elasticsearch retrieves an allocation explanation for an arbitrary unassigned primary or replica shard.
GET _cluster/allocation/explain
If the cluster contains no unassigned shards, the API returns a 400
error.