The `GET /_cluster/state` API returns an internal representation of the cluster
state that does change from version to version. It's useful for debugging, but
it is not intended for regular use by clients.
This change adjusts the documentation of `GET /_cluster/state` to clarify that
this API yields an internal representation that should not be expected to
remain stable between versions.
Relates #40061, #40016
Currently, the only way to get the REST response for the `/_cluster/state`
call to return the `cluster_uuid` is to request the `metadata` metrics,
which is one of the most expensive response structures. However, external
monitoring agents will likely want the `cluster_uuid` to correlate the
response with other API responses whether or not they want cluster
metadata.
This commit adds the size of the cluster state to the response for the
get cluster state API call (GET /_cluster/state). The size that is
returned is the size of the full cluster state in bytes when compressed.
This is the same size of the full cluster state when serialized to
transmit over the network. Specifying the ?human flag displays the
compressed size in a more human friendly manner. Note that even if the
cluster state request filters items from the cluster state (so a subset
of the cluster state is returned), the size that is returned is the
compressed size of the entire cluster state.
Closes#3415
The possibility of filtering for index templates in the cluster state API
had been introduced before there was a dedicated index templates API. This
commit removes this support from the cluster state API, as it was not really
clean, requiring you to specify the metadata and the index templates.
Closes#4954
Instead of specifying what kind of data should be filtered, this commit
streamlines the API to actually specify, what kind of data should be displayed.
This makes its behaviour similar to the other requests, like NodeIndicesStats.
A small feature has been added as well: If you specify an index to select on, not
only the metadata, but also the routing tables are filtered by index in order
to prevent too big cluster states to be returned.
Also the CAT apis have been changed to only return the wanted data in order to keep
network traffic as small as needed.
Tests for the cluster state API filtering have been added as well.
Note: This change breaks backwards compatibility with 0.90!
Closes#4065
David Turner
Chris Earle
Tanguy Leroux
Ali Beyad
Alexander Reelsen
Shay Banon
Clinton Gormley