[Backport] Weighted routing 2.x (#5008)

* Weighted round-robin scheduling policy for shard coordination traffic… (#4241)

* Add PUT api to update shard routing weights (#4272)

* Add GET api to get shard routing weights (#4275)

* Fix weighted routing metadata deserialization error during node restart (#4691)

* Delete API for weighted round robin search routing (#4400)

* Mark apis experimental

Signed-off-by: Anshu Agarwal <anshukag@amazon.com>

CHANGELOG.md

@@ -52,6 +52,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Changed
 - Dependency updates (httpcore, mockito, slf4j, httpasyncclient, commons-codec) ([#4308](https://github.com/opensearch-project/OpenSearch/pull/4308))
 - Use RemoteSegmentStoreDirectory instead of RemoteDirectory ([#4240](https://github.com/opensearch-project/OpenSearch/pull/4240))
+- Weighted round-robin scheduling policy for shard coordination traffic ([#4241](https://github.com/opensearch-project/OpenSearch/pull/4241))
 - Add index specific setting for remote repository ([#4253](https://github.com/opensearch-project/OpenSearch/pull/4253))
 - [Segment Replication] Update replicas to commit SegmentInfos instead of relying on SIS files from primary shards. ([#4402](https://github.com/opensearch-project/OpenSearch/pull/4402))
 - Change the version to remove deprecated code of adding node name into log pattern of log4j property file ([#4569](https://github.com/opensearch-project/OpenSearch/pull/4569))
@@ -60,6 +61,10 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Plugin ZIP publication groupId value is configurable ([#4156](https://github.com/opensearch-project/OpenSearch/pull/4156))
 - Further simplification of the ZIP publication implementation ([#4360](https://github.com/opensearch-project/OpenSearch/pull/4360))
 - [Remote Store] Change behaviour in replica recovery for remote translog enabled indices ([#4318](https://github.com/opensearch-project/OpenSearch/pull/4318))
+- PUT api for weighted shard routing ([#4272](https://github.com/opensearch-project/OpenSearch/pull/4272))
+- GET api for weighted shard routing([#4275](https://github.com/opensearch-project/OpenSearch/pull/4275/))
+- Delete api for weighted shard routing([#4400](https://github.com/opensearch-project/OpenSearch/pull/4400/))
+- Fix weighted routing metadata deserialization error on process restart ([#4691](https://github.com/opensearch-project/OpenSearch/pull/4691))
 - Add DecommissionService and helper to execute awareness attribute decommissioning ([#4084](https://github.com/opensearch-project/OpenSearch/pull/4084))
 - Add APIs (GET/PUT) to decommission awareness attribute ([#4261](https://github.com/opensearch-project/OpenSearch/pull/4261))
 - Controlling discovery for decommissioned nodes ([#4590](https://github.com/opensearch-project/OpenSearch/pull/4590))

client/rest-high-level/src/test/java/org/opensearch/client/RestHighLevelClientTests.java

@@ -889,6 +889,9 @@ public void testApiNamingConventions() throws Exception {
             "nodes.reload_secure_settings",
             "search_shards",
             "remote_store.restore",
+            "cluster.put_weighted_routing",
+            "cluster.get_weighted_routing",
+            "cluster.delete_weighted_routing",
             "cluster.put_decommission_awareness",
             "cluster.get_decommission_awareness",
             "cluster.delete_decommission_awareness", };

rest-api-spec/src/main/resources/rest-api-spec/api/cluster.delete_weighted_routing.json

@@ -0,0 +1,19 @@
+{
+  "cluster.delete_weighted_routing": {
+    "documentation": {
+      "url": "https://opensearch.org/docs/latest/opensearch/rest-api/weighted-routing/delete",
+      "description": "Delete weighted shard routing weights"
+    },
+    "stability": "experimental",
+    "url": {
+      "paths": [
+        {
+          "path": "/_cluster/routing/awareness/weights",
+          "methods": [
+            "DELETE"
+          ]
+        }
+      ]
+    }
+  }
+}

rest-api-spec/src/main/resources/rest-api-spec/api/cluster.get_weighted_routing.json

@@ -0,0 +1,25 @@
+{
+  "cluster.get_weighted_routing": {
+    "documentation": {
+      "url": "https://opensearch.org/docs/latest/opensearch/rest-api/weighted-routing/get",
+      "description": "Fetches weighted shard routing weights"
+    },
+    "stability": "experimental",
+    "url": {
+      "paths": [
+        {
+          "path": "/_cluster/routing/awareness/{attribute}/weights",
+          "methods": [
+            "GET"
+          ],
+          "parts": {
+            "attribute": {
+              "type": "string",
+              "description": "Awareness attribute name"
+            }
+          }
+        }
+      ]
+    }
+  }
+}

rest-api-spec/src/main/resources/rest-api-spec/api/cluster.put_weighted_routing.json

@@ -0,0 +1,25 @@
+{
+  "cluster.put_weighted_routing": {
+    "documentation": {
+      "url": "https://opensearch.org/docs/latest/opensearch/rest-api/weighted-routing/put",
+      "description": "Updates weighted shard routing weights"
+    },
+    "stability": "experimental",
+    "url": {
+      "paths": [
+        {
+          "path": "/_cluster/routing/awareness/{attribute}/weights",
+          "methods": [
+            "PUT"
+          ],
+          "parts": {
+            "attribute": {
+              "type": "string",
+              "description": "Awareness attribute name"
+            }
+          }
+        }
+      ]
+    }
+  }
+}