Update and document experimental features (#13348)

* Update and document experimental features
* Updated
* Update experimental-features.md
* Update docs/development/experimental-features.md
Co-authored-by: Abhishek Agarwal <1477457+abhishekagarwal87@users.noreply.github.com>
* Updated after review
* Updated
* Update materialized-view.md
* Update experimental-features.md
Co-authored-by: Abhishek Agarwal <1477457+abhishekagarwal87@users.noreply.github.com>

docs/configuration/index.md

@@ -1375,7 +1375,7 @@ For GCE's properties, please refer to the [gce-extensions](../development/extens
 
 This section contains the configuration options for the processes that reside on Data servers (MiddleManagers/Peons and Historicals) in the suggested [three-server configuration](../design/processes.md#server-types).
 
-Configuration options for the experimental [Indexer process](../design/indexer.md) are also provided here.
+Configuration options for the [Indexer process](../design/indexer.md) are also provided here.
 
 ### MiddleManager and Peons
 
@@ -2188,7 +2188,7 @@ Supported query contexts:
 |Key|Description|Default|
 |---|-----------|-------|
 |`druid.expressions.useStrictBooleans`|Controls the behavior of Druid boolean operators and functions, if set to `true` all boolean values will be either a `1` or `0`. See [expression documentation](../misc/math-expr.md#logical-operator-modes)|false|
-|`druid.expressions.allowNestedArrays`|If enabled, Druid array expressions can create nested arrays. This is experimental and should be used with caution.|false|
+|`druid.expressions.allowNestedArrays`|If enabled, Druid array expressions can create nested arrays.|false|
 ### Router
 
 #### Router Process Configs

docs/development/experimental-features.md

@@ -0,0 +1,68 @@
+---
+id: experimental-features
+title: "Experimental features"
+---
+
+<!--
+  ~ Licensed to the Apache Software Foundation (ASF) under one
+  ~ or more contributor license agreements.  See the NOTICE file
+  ~ distributed with this work for additional information
+  ~ regarding copyright ownership.  The ASF licenses this file
+  ~ to you under the Apache License, Version 2.0 (the
+  ~ "License"); you may not use this file except in compliance
+  ~ with the License.  You may obtain a copy of the License at
+  ~
+  ~   http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing,
+  ~ software distributed under the License is distributed on an
+  ~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  ~ KIND, either express or implied.  See the License for the
+  ~ specific language governing permissions and limitations
+  ~ under the License.
+  -->
+
+The following features are marked [experimental](./experimental.md) in the Druid docs.
+
+This document includes each page that mentions an experimental feature. To graduate a feature, remove all mentions of its experimental status on all relevant pages.
+
+Note that this document does not track the status of contrib extensions, some of which are experimental.
+
+## SQL-based ingestion
+
+- [SQL-based ingestion](../multi-stage-query/index.md)
+- [SQL-based ingestion concepts](../multi-stage-query/concepts.md)
+- [SQL-based ingestion and multi-stage query task API](../multi-stage-query/api.md)
+
+## Nested columns
+
+- [Nested columns](../querying/nested-columns.md)
+
+## Indexer process
+
+- [Indexer process](../design/indexer.md)
+- [Processes and servers](../design/processes.md#indexer-process-optional)
+
+## Kubernetes
+
+- [Kubernetes](../development/extensions-core/kubernetes.md)
+
+## Segment locking
+
+- [Configuration reference](../configuration/index.md#overlord-operations)
+- [Task reference](../ingestion/tasks.md#locking)
+- [Design](../design/architecture.md#availability-and-consistency)
+
+## Moments sketch
+
+- [Aggregations](../querying/aggregations.md#moments-sketch-experimental)
+
+## Front coding
+
+- [Ingestion spec reference](../ingestion/ingestion-spec.md#front-coding)
+
+## Other configuration properties
+
+- [Configuration reference](../configuration/index.md)
+   - `CLOSED_SEGMENTS_SINKS` mode
+   - Expression processing configuration `druid.expressions.allowNestedArrays`

docs/development/extensions-core/druid-lookups.md

@@ -22,9 +22,6 @@ title: "Cached Lookup Module"
   ~ under the License.
   -->
 
-
-> Please note that this is an experimental module and the development/testing still at early stage. Feel free to try it and give us your feedback.
-
 ## Description
 This Apache Druid module provides a per-lookup caching mechanism for JDBC data sources.
 The main goal of this cache is to speed up the access to a high latency lookup sources and to provide a caching isolation for every lookup source.

docs/development/extensions-core/kafka-supervisor-reference.md

@@ -56,8 +56,6 @@ This topic contains configuration reference information for the Apache Kafka sup
 
 ## Task Autoscaler Properties
 
-> Note that Task AutoScaler is currently designated as experimental.
-
 | Property | Description | Required |
 | ------------- | ------------- | ------------- |
 | `enableTaskAutoScaler` | Enable or disable autoscaling. `false` or blank disables the `autoScaler` even when `autoScalerConfig` is not null| no (default == false) |

docs/development/extensions-core/kinesis-ingestion.md

@@ -149,8 +149,6 @@ Where the file `supervisor-spec.json` contains a Kinesis supervisor spec:
 
 #### Task Autoscaler Properties
 
-> Note that Task AutoScaler is currently designated as experimental.
-
 | Property | Description | Required |
 | ------------- | ------------- | ------------- |
 | `enableTaskAutoScaler` | Enable or disable the auto scaler. When false or absent, Druid disables the `autoScaler` even when `autoScalerConfig` is not null.| no (default == false) |

docs/querying/lookups.md

@@ -115,8 +115,8 @@ will not detect this automatically.
 
 Dynamic Configuration
 ---------------------
-> Dynamic lookup configuration is an [experimental](../development/experimental.md) feature. Static
+> Static configuration is no longer supported.
-> configuration is no longer supported.
+
 The following documents the behavior of the cluster-wide config which is accessible through the Coordinator.
 The configuration is propagated through the concept of "tier" of servers.
 A "tier" is defined as a group of services which should receive a set of lookups.