308 lines
11 KiB
Plaintext
308 lines
11 KiB
Plaintext
[[cluster-allocation-explain]]
|
|
== Cluster Allocation Explain API
|
|
|
|
The 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 moved 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.
|
|
|
|
[float]
|
|
=== Explain API Request
|
|
|
|
To explain the allocation of a shard, first an index should exist:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
PUT /myindex
|
|
--------------------------------------------------
|
|
// TESTSETUP
|
|
|
|
And then the allocation for shards of that index can be explained:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
GET /_cluster/allocation/explain
|
|
{
|
|
"index": "myindex",
|
|
"shard": 0,
|
|
"primary": true
|
|
}
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
|
|
Specify the `index` and `shard` id of the shard you would like an explanation
|
|
for, as well as the `primary` flag to indicate whether to explain the primary
|
|
shard for the given shard id or one of its replica shards. These three request
|
|
parameters are required.
|
|
|
|
You may also specify an optional `current_node` request parameter to only explain
|
|
a shard that is currently located on `current_node`. The `current_node` can be
|
|
specified as either the node id or node name.
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
GET /_cluster/allocation/explain
|
|
{
|
|
"index": "myindex",
|
|
"shard": 0,
|
|
"primary": false,
|
|
"current_node": "nodeA" <1>
|
|
}
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
// TEST[skip:no way of knowing the current_node]
|
|
<1> The node where shard 0 currently has a replica on
|
|
|
|
You can also have Elasticsearch explain the allocation of the first unassigned
|
|
shard that it finds by sending an empty body for the request:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
GET /_cluster/allocation/explain
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
|
|
[float]
|
|
=== Explain API Response
|
|
|
|
This section includes examples of the cluster allocation explain API response output
|
|
under various scenarios.
|
|
|
|
The API response for an unassigned shard:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"index" : "idx",
|
|
"shard" : 0,
|
|
"primary" : true,
|
|
"current_state" : "unassigned", <1>
|
|
"unassigned_info" : {
|
|
"reason" : "INDEX_CREATED", <2>
|
|
"at" : "2017-01-04T18:08:16.600Z",
|
|
"last_allocation_status" : "no"
|
|
},
|
|
"can_allocate" : "no", <3>
|
|
"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_t1",
|
|
"transport_address" : "127.0.0.1:9401",
|
|
"node_decision" : "no", <4>
|
|
"weight_ranking" : 1,
|
|
"deciders" : [
|
|
{
|
|
"decider" : "filter", <5>
|
|
"decision" : "NO",
|
|
"explanation" : "node does not match index setting [index.routing.allocation.include] filters [_name:\"non_existent_node\"]" <6>
|
|
}
|
|
]
|
|
},
|
|
{
|
|
"node_id" : "7Wr-QxLXRLKDxhzNm50pFA",
|
|
"node_name" : "node_t0",
|
|
"transport_address" : "127.0.0.1:9400",
|
|
"node_decision" : "no",
|
|
"weight_ranking" : 2,
|
|
"deciders" : [
|
|
{
|
|
"decider" : "filter",
|
|
"decision" : "NO",
|
|
"explanation" : "node does not match index setting [index.routing.allocation.include] filters [_name:\"non_existent_node\"]"
|
|
}
|
|
]
|
|
}
|
|
]
|
|
}
|
|
--------------------------------------------------
|
|
<1> The current state of the shard
|
|
<2> The reason for the shard originally becoming unassigned
|
|
<3> Whether to allocate the shard
|
|
<4> Whether to allocate the shard to the particular node
|
|
<5> The decider which led to the `no` decision for the node
|
|
<6> An explanation as to why the decider returned a `no` decision, with a helpful hint pointing to the setting that led to the decision
|
|
|
|
You can return information gathered by the cluster info service about disk usage
|
|
and shard sizes by setting the `include_disk_info` parameter to `true`:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
GET /_cluster/allocation/explain?include_disk_info=true
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
|
|
Additionally, if you would like to include all decisions that were factored into the final
|
|
decision, the `include_yes_decisions` parameter will return all decisions for each node:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
GET /_cluster/allocation/explain?include_yes_decisions=true
|
|
--------------------------------------------------
|
|
// CONSOLE
|
|
|
|
The default value for `include_yes_decisions` is `false`, which will only
|
|
include the `no` decisions in the response. This is generally what you would
|
|
want, as the `no` decisions indicate why a shard is unassigned or cannot be moved,
|
|
and including all decisions include the `yes` ones adds a lot of verbosity to the
|
|
API's response output.
|
|
|
|
The API response output for an unassigned primary shard that had previously been
|
|
allocated to a node in the cluster:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"index" : "idx",
|
|
"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"
|
|
}
|
|
--------------------------------------------------
|
|
|
|
The API response output for a replica that is unassigned due to delayed allocation:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"index" : "idx",
|
|
"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", <1>
|
|
"configured_delay_in_millis" : 60000,
|
|
"remaining_delay" : "59.8s", <2>
|
|
"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" : { <3>
|
|
"matching_size" : "4.2kb",
|
|
"matching_size_in_bytes" : 4325
|
|
},
|
|
"deciders" : [
|
|
{
|
|
"decider" : "same_shard",
|
|
"decision" : "NO",
|
|
"explanation" : "the shard cannot be allocated to the same node on which a copy of the shard already exists [[idx][0], node[3sULLVJrRneSg0EfBB-2Ew], [P], s[STARTED], a[id=eV9P8BN1QPqRc3B4PLx6cg]]"
|
|
}
|
|
]
|
|
}
|
|
]
|
|
}
|
|
--------------------------------------------------
|
|
<1> The configured delay before allocating a replica shard that does not exist due to the node holding it leaving the cluster
|
|
<2> The remaining delay before allocating the replica shard
|
|
<3> Information about the shard data found on a node
|
|
|
|
The API response output for an assigned shard that is not allowed to
|
|
remain on its current node and is required to move:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"index" : "idx",
|
|
"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", <1>
|
|
"can_remain_decisions" : [ <2>
|
|
{
|
|
"decider" : "filter",
|
|
"decision" : "NO",
|
|
"explanation" : "node does not match index setting [index.routing.allocation.include] filters [_name:\"non_existent_node\"]"
|
|
}
|
|
],
|
|
"can_move_to_other_node" : "no", <3>
|
|
"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:\"non_existent_node\"]"
|
|
}
|
|
]
|
|
}
|
|
]
|
|
}
|
|
--------------------------------------------------
|
|
<1> Whether the shard is allowed to remain on its current node
|
|
<2> The deciders that factored into the decision of why the shard is not allowed to remain on its current node
|
|
<3> Whether the shard is allowed to be allocated to another node
|
|
|
|
The API response output for an assigned shard that remains on its current node
|
|
because moving the shard to another node does not form a better cluster balance:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"index" : "idx",
|
|
"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", <1>
|
|
"can_rebalance_to_other_node" : "no", <2>
|
|
"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", <3>
|
|
"weight_ranking" : 1
|
|
}
|
|
]
|
|
}
|
|
--------------------------------------------------
|
|
<1> Whether rebalancing is allowed on the cluster
|
|
<2> Whether the shard can be rebalanced to another node
|
|
<3> The reason the shard cannot be rebalanced to the node, in this case indicating that it offers no better balance than the current node
|