* (Doc+) Link API to parent Doc part1
---------
Co-authored-by: shainaraskas <shaina.raskas@elastic.co>
Co-authored-by: shainaraskas <58563081+shainaraskas@users.noreply.github.com>
Report node "roles" in the /_cluster/allocation/explain response.
Nodes with limited sets of roles may affect shard distribution in ways
users did not originally consider, so it is helpful to surface this
information along with node allocation decision explanations.
Today the `current_node` parameter is given in several sample requests
illustrating how to explain an unassigned shard using the cluster
allocation explain API. This doesn't make sense, an unassigned shard has
no `current_node`. This commit removes the misleading parameter in these
cases.
The cluster allocation explain API includes a top-level status
indicating to the user whether the shard can be assigned/rebalanced/etc
or not. Today this status is fairly terse and experience shows that
users sometimes struggle to understand how to interpret it and to decide
on follow-up actions.
This commit makes the top-level explanation more detailed and
actionable. For instance, in the cases like `THROTTLED` where the status
is transient we instruct the user to wait; if a shard is lost we say to
restore it from a snapshot; if a shard cannot be assigned we say to
choose a specific node where its assignment is expected and to address
the obstacles.
Co-authored-by: James Rodewig <james.rodewig@elastic.co>
Today we often encounter users that are confused by the behaviour of
calling `GET _cluster/allocation/explain` without a body: it _seems_ to
work, but it explains a random shard, and if this isn't the shard
they're thinking of then it's unclear how to proceed.
With this commit we add a note to the response when a shard was randomly
chosen indicating that it is possible, and possibly useful, to explain a
different shard. We also adjust the exception message in the case when
all shards are assigned to indicate why it's an invalid request and what
to do to make it valid.
Today the only example of calling the cluster allocation explain API above the
fold is the bare `GET /_cluster/allocation/explain` which kind of works but is
not usually what the user wants. This commit changes the docs so that we open
with an example showing how we usually expect it to be called. This will make
it clearer that you should normally specify exactly for which shard you want an
explanation. It also tidies up a few other wrinkles in these docs.
Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>
This commit adds the `index.routing.allocation.prefer._tier` setting to the
`DataTierAllocationDecider`. This special-purpose allocation setting lets a user specify a
preference-based list of tiers for an index to be assigned to. For example, if the setting were set
to:
```
"index.routing.allocation.prefer._tier": "data_hot,data_warm,data_content"
```
If the cluster contains any nodes with the `data_hot` role, the decider will only allow them to be
allocated on the `data_hot` node(s). If there are no `data_hot` nodes, but there are `data_warm` and
`data_content` nodes, then the index will be allowed to be allocated on `data_warm` nodes.
This allows us to specify an index's preference for tier(s) without causing the index to be
unassigned if no nodes of a preferred tier are available.
Subsequent work will change the ILM migration to make additional use of this setting.
Relates to #60848
This commit adds the functionality to allocate newly created indices on nodes in the "hot" tier by
default when they are created.
This does not break existing behavior, as nodes with the `data` role are considered to be part of
the hot tier. Users that separate their deployments by using the `data_hot` (and `data_warm`,
`data_cold`, `data_frozen`) roles will have their data allocated on the hot tier nodes now by
default.
This change is a little more complicated than changing the default value for
`index.routing.allocation.include._tier` from null to "data_hot". Instead, this adds the ability to
have a plugin inject a setting into the builder for a newly created index. This has the benefit of
allowing this setting to be visible as part of the settings when retrieving the index, for example:
```
// Create an index
PUT /eggplant
// Get an index
GET /eggplant?flat_settings
```
Returns the default settings now of:
```json
{
"eggplant" : {
"aliases" : { },
"mappings" : { },
"settings" : {
"index.creation_date" : "1597855465598",
"index.number_of_replicas" : "1",
"index.number_of_shards" : "1",
"index.provided_name" : "eggplant",
"index.routing.allocation.include._tier" : "data_hot",
"index.uuid" : "6ySG78s9RWGystRipoBFCA",
"index.version.created" : "8000099"
}
}
}
```
After the initial setting of this setting, it can be treated like any other index level setting.
This new setting is *not* set on a new index if any of the following is true:
- The index is created with an `index.routing.allocation.include.<anything>` setting
- The index is created with an `index.routing.allocation.exclude.<anything>` setting
- The index is created with an `index.routing.allocation.require.<anything>` setting
- The index is created with a null `index.routing.allocation.include._tier` value
- The index was created from an existing source metadata (shrink, clone, split, etc)
Relates to #60848
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
