Backport of the recently introduced snapshot pagination and scalability improvements listed below.
Merged as a single backport because the `7.x` and master snapshot status API logic had massively diverged between master and 7.x. With the work in the below PRs, the logic in master and 7.x once again has been aligned very closely again.
#72842#73172#73199#73570#73952#74236#74451 (this one is only partly applicable as it was mainly a change to master to align `master` and `7.x` branches)
Both of these APIs don't parse request bodies, the parameters are all taken
from the query string. Also, included the master timeout param include
as it was missing here also.
This commit adds some per-index statistics to the `SnapshotInfo` blob:
- number of shards
- total size in bytes
- maximum number of segments per shard
It also exposes these statistics in the get snapshot API.
Backport of #71754 to 7.x
This PR expands the meaning of `include_global_state` for snapshots to include system indices. If `include_global_state` is `true` on creation, system indices will be included in the snapshot regardless of the contents of the `indices` field. If `include_global_state` is `true` on restoration, system indices will be restored (if included in the snapshot), regardless of the contents of the `indices` field. Index renaming is not applied to system indices, as system indices rely on their names matching certain patterns. If restored system indices are already present, they are automatically deleted prior to restoration from the snapshot to avoid conflicts.
This behavior can be overridden to an extent by including a new field in the snapshot creation or restoration call, `feature_states`, which contains an array of strings indicating the "feature" for which system indices should be snapshotted or restored. For example, this call will only restore the `watcher` and `security` system indices (in addition to `index_1`):
```
POST /_snapshot/my_repository/snapshot_2/_restore
{
"indices": "index_1",
"include_global_state": true,
"feature_states": ["watcher", "security"]
}
```
If `feature_states` is present, the system indices associated with those features will be snapshotted or restored regardless of the value of `include_global_state`. All system indices can be omitted by providing a special value of `none` (`"feature_states": ["none"]`), or included by omitting the field or explicitly providing an empty array (`"feature_states": []`), similar to the `indices` field.
The list of currently available features can be retrieved via a new "Get Snapshottable Features" API:
```
GET /_snapshottable_features
```
which returns a response of the form:
```
{
"features": [
{
"name": "tasks",
"description": "Manages task results"
},
{
"name": "kibana",
"description": "Manages Kibana configuration and reports"
}
]
}
```
Features currently map one-to-one with `SystemIndexPlugin`s, but this should be considered an implementation detail. The Get Snapshottable Features API and snapshot creation rely upon all relevant plugins being installed on the master node.
Further, the list of feature states included in a given snapshot is exposed by the Get Snapshot API, which now includes a new field, `feature_states`, which contains a list of the feature states and their associated system indices which are included in the snapshot. All system indices in feature states are also included in the `indices` array for backwards compatibility, although explicitly requesting system indices included in a feature state is deprecated. For example, an excerpt from the Get Snapshot API showing `feature_states`:
```
"feature_states": [
{
"feature_name": "tasks",
"indices": [
".tasks"
]
}
],
"indices": [
".tasks",
"test1",
"test2"
]
```
Co-authored-by: William Brafford <william.brafford@elastic.co>
* [DOCS] Adding get snapshot API docs (#59098)
* Adding page for get snapshot API.
* Adding values for state and cleaning up some other formatting.
* Adding missing forward slash to GET request.
* Updating values for start_time and end_time in TESTRESPONSE.
* Swap "return" for "retrieve"
* Swap "return" for "retrieve" 2
* Change .snapshot to .response
* Adding response parameters and incorporating edits from review.
* Update response example to include repository info
* Change dash to underscore
* Add data type for snapshot in response
* Incorporating review comments and adding missing response definitions.
* Minor rewording in description.
* Removing multi-snapshot support for 7.x.
* Changing end_time value from build error.
* Removing .response from snippet testing.
