Cluster Allocation Explain APIedit
The cluster allocation explanation API is designed to assist in answering the question "why is this shard unassigned?". To explain the allocation (on unassigned state) of a shard, issue a request like:
The cluster allocation explain API is new and should still be considered experimental. The API may change in ways that are not backwards compatible.
$ curl -XGET 'http://localhost:9200/_cluster/allocation/explain' -d'{
"index": "myindex",
"shard": 0,
"primary": false
}'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 a primary or
replica shard.
The response looks like:
{
"shard" : {
"index" : "myindex",
"index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
"id" : 0,
"primary" : false
},
"assigned" : false, 
"shard_state_fetch_pending": false, 
"unassigned_info" : {
"reason" : "INDEX_CREATED", 
"at" : "2016-03-22T20:04:23.620Z"
},
"allocation_delay_ms" : 0, 
"remaining_delay_ms" : 0, 
"nodes" : {
"V-Spi0AyRZ6ZvKbaI3691w" : {
"node_name" : "H5dfFeA",
"node_attributes" : { 
"bar" : "baz"
},
"store" : {
"shard_copy" : "NONE" 
},
"final_decision" : "NO", 
"final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
"weight" : 0.06666675, 
"decisions" : [ { 
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
},
"Qc6VL8c5RWaw1qXZ0Rg57g" : {
"node_name" : "bGG90GE",
"node_attributes" : {
"bar" : "baz",
"foo" : "bar"
},
"store" : {
"shard_copy" : "AVAILABLE"
},
"final_decision" : "NO",
"final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
"weight" : -1.3833332,
"decisions" : [ {
"decider" : "same_shard",
"decision" : "NO",
"explanation" : "the shard cannot be allocated on the same node id [Qc6VL8c5RWaw1qXZ0Rg57g] on which it already exists"
} ]
},
"PzdyMZGXQdGhqTJHF_hGgA" : {
"node_name" : "DKDM97B",
"node_attributes" : { },
"store" : {
"shard_copy" : "NONE"
},
"final_decision" : "NO",
"final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
"weight" : 2.3166666,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
}
}
}
| Whether the shard is assigned or unassigned |
| Whether information about the shard is still being fetched |
| Reason for the shard originally becoming unassigned |
| Configured delay before the shard can be allocated |
| Remaining delay before the shard can be allocated |
| User-added attributes the node has |
| The shard copy information for this node and error (if applicable) |
| Final decision and explanation of whether the shard can be allocated to this node |
| Weight for how much the allocator would like to allocate the shard to this node |
| List of node decisions factoring into final decision about the shard |
For a shard that is already assigned, the output looks similar to:
{
"shard" : {
"index" : "only-foo",
"index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
"id" : 0,
"primary" : true
},
"assigned" : true,
"assigned_node_id" : "Qc6VL8c5RWaw1qXZ0Rg57g",
"shard_state_fetch_pending": false,
"allocation_delay_ms" : 0,
"remaining_delay_ms" : 0,
"nodes" : {
"V-Spi0AyRZ6ZvKbaI3691w" : {
"node_name" : "bGG90GE",
"node_attributes" : {
"bar" : "baz"
},
"store" : {
"shard_copy" : "NONE"
},
"final_decision" : "NO",
"final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
"weight" : 1.4499999,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
},
"Qc6VL8c5RWaw1qXZ0Rg57g" : {
"node_name" : "I8hydUG",
"node_attributes" : {
"bar" : "baz",
"foo" : "bar"
},
"store" : {
"shard_copy" : "AVAILABLE"
},
"final_decision" : "ALREADY_ASSIGNED",
"final_explanation" : "the shard is already assigned to this node",
"weight" : 0.0,
"decisions" : [ {
"decider" : "same_shard",
"decision" : "NO",
"explanation" : "the shard cannot be allocated on the same node id [Qc6VL8c5RWaw1qXZ0Rg57g] on which it already exists"
} ]
},
"PzdyMZGXQdGhqTJHF_hGgA" : {
"node_name" : "H5dfFeA",
"node_attributes" : { },
"store" : {
"shard_copy" : "NONE"
},
"final_decision" : "NO",
"final_explanation" : "the shard cannot be assigned because one or more allocation decider returns a 'NO' decision",
"weight" : 3.6999998,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
}
}
}
| Node the shard is currently assigned to |
| The decision is "ALREADY_ASSIGNED" because the shard is currently assigned to this node |
You can also have Elasticsearch explain the allocation of the first unassigned shard it finds by sending an empty body, such as:
$ curl -XGET 'http://localhost:9200/_cluster/allocation/explain'
If you would like to include all decisions that were factored into the final
decision, the include_yes_decisions parameter will return all decisions:
$ curl -XGET 'http://localhost:9200/_cluster/allocation/explain?include_yes_decisions=true'
Additionally, 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:
$ curl -XGET 'http://localhost:9200/_cluster/allocation/explain?include_disk_info=true'