I see occasional confusion about the explanations emitted by the same-shard
allocation decider, particularly amongst new users setting up a single-node
cluster and trying to determine why their cluster has `yellow` health. For
example:
the shard cannot be allocated to the same node on which a copy of the shard
already exists
This is technically correct but it's quite a complicated sentence. Also, by
starting with "the shard cannot be allocated" it makes it sound like this is
the problem, whereas in fact this message is a good thing and users should
typically focus their attention elsewhere.
This commit simplifies the wording of these messages and makes them sound more
positive, for example:
a copy of this shard is already allocated to this node
Updates several example snippets in the Cluster Allocation Explain API
docs to consistently use the `my_index` index.
Previously, the snippets switches from `my_index` to `idx`, which could
confuse users.
Co-authored-by: Emmanuel DEMEY <demey.emmanuel@gmail.com>
Co-authored-by: Emmanuel DEMEY <demey.emmanuel@gmail.com>
Several files in the REST APIs nav section are included using
:leveloffset: tags. This increments headings (h2 -> h3, h3 -> h4, etc.)
in those files and removes the :leveloffset: tags.
Other supporting changes:
* Alphabetizes top-level REST API nav items.
* Change 'indices APIs' heading to 'index APIs.'
* Changes 'Snapshot lifecycle management' heading to sentence case.
* Console-ify curl statements for allocation explain API docs
Relates to #23001
* Fix tests
* Remove exclusion from build.gradle
* Call out index creation in prose
* Add console back and skip test
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
David Turner
James Rodewig
István Zoltán Szabó
Tanguy Leroux
Florian Hopf
Lee Hinman
Clinton Gormley
Ali Beyad
Lee Hinman