This commit updates the cluster allocation explain API documentation to
explain the new request parameters and response formats, and gives
examples of the explain API responses under various scenarios.
Funny node names have been removed in #19456 and replaced by UUID. This commit removes these obsolete node names and replace them by real UUIDs in the documentation.
closes#20065
This adds a new `/_cluster/allocation/explain` API that explains why a
shard can or cannot be allocated to nodes in the cluster. Additionally,
it will show where the master *desires* to put the shard, according to
the `ShardsAllocator`.
It looks like this:
```
GET /_cluster/allocation/explain?pretty
{
"index": "only-foo",
"shard": 0,
"primary": false
}
```
Though, you can optionally send an empty body, which means "explain the
allocation for the first unassigned shard you find".
The output when a shard is unassigned looks like this:
```
{
"shard" : {
"index" : "only-foo",
"index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
"id" : 0,
"primary" : false
},
"assigned" : false,
"unassigned_info" : {
"reason" : "INDEX_CREATED",
"at" : "2016-03-22T20:04:23.620Z"
},
"nodes" : {
"V-Spi0AyRZ6ZvKbaI3691w" : {
"node_name" : "Susan Storm",
"node_attributes" : {
"bar" : "baz"
},
"final_decision" : "NO",
"weight" : 0.06666675,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
},
"Qc6VL8c5RWaw1qXZ0Rg57g" : {
"node_name" : "Slipstream",
"node_attributes" : {
"bar" : "baz",
"foo" : "bar"
},
"final_decision" : "NO",
"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" : "The Symbiote",
"node_attributes" : { },
"final_decision" : "NO",
"weight" : 2.3166666,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
}
}
}
```
And when the shard *is* assigned, the output looks like:
```
{
"shard" : {
"index" : "only-foo",
"index_uuid" : "KnW0-zELRs6PK84l0r38ZA",
"id" : 0,
"primary" : true
},
"assigned" : true,
"assigned_node_id" : "Qc6VL8c5RWaw1qXZ0Rg57g",
"nodes" : {
"V-Spi0AyRZ6ZvKbaI3691w" : {
"node_name" : "Susan Storm",
"node_attributes" : {
"bar" : "baz"
},
"final_decision" : "NO",
"weight" : 1.4499999,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
},
"Qc6VL8c5RWaw1qXZ0Rg57g" : {
"node_name" : "Slipstream",
"node_attributes" : {
"bar" : "baz",
"foo" : "bar"
},
"final_decision" : "CURRENTLY_ASSIGNED",
"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" : "The Symbiote",
"node_attributes" : { },
"final_decision" : "NO",
"weight" : 3.6999998,
"decisions" : [ {
"decider" : "filter",
"decision" : "NO",
"explanation" : "node does not match index include filters [foo:\"bar\"]"
} ]
}
}
}
```
Only "NO" decisions are returned by default, but all decisions can be
shown by specifying the `?include_yes_decisions=true` parameter in the
request.
Resolves#14593
Clinton Gormley
Ali Beyad
Tanguy Leroux
Lee Hinman