Reset desired balance (#94525)

This introduces an endpoint to reset the desired balance.
It could be used if computed balance diverged from the actual one a lot 
to start a new computation from the current state.

Author: idegtiarenko

docs/reference/cluster.asciidoc

@@ -119,3 +119,5 @@ include::cluster/get-desired-nodes.asciidoc[]
 include::cluster/delete-desired-nodes.asciidoc[]
 
 include::cluster/get-desired-balance.asciidoc[]
+
+include::cluster/delete-desired-balance.asciidoc[]

docs/reference/cluster/delete-desired-balance.asciidoc

@@ -0,0 +1,18 @@
+[[delete-desired-balance]]
+=== Delete/reset desired balance API
+++++
+<titleabbrev>Delete/reset desired balance</titleabbrev>
+++++
+
+NOTE: {cloud-only}
+
+Exposes the desired balance and basic metrics.
+
+[[delete-desired-balance-request]]
+==== {api-request-title}
+
+[source,console]
+--------------------------------------------------
+DELETE /_internal/desired_balance
+--------------------------------------------------
+// TEST[skip:Can't reliably test desired balance]

qa/smoke-test-multinode/src/yamlRestTest/resources/rest-api-spec/test/smoke_test_multinode/30_desired_balance.yml

@@ -69,7 +69,7 @@ setup:
 
   - skip:
       version: " - 8.6.99"
-      reason: "Field added in in 8.7.0"
+      reason: "cluster_balance_stats added in in 8.7.0"
 
   - do:
       cluster.state: {}
@@ -117,7 +117,7 @@ setup:
 
   - skip:
       version: " - 8.7.99"
-      reason: "tier preference added in in 8.8.0"
+      reason: "tier_preference added in in 8.8.0"
 
   - do:
       indices.create:
@@ -142,7 +142,7 @@ setup:
 
   - skip:
       version: " - 8.7.99"
-      reason: "Field added in in 8.8.0"
+      reason: "cluster_info added in in 8.8.0"
 
   - do:
       _internal.get_desired_balance: { }

rest-api-spec/src/main/resources/rest-api-spec/api/_internal.delete_desired_balance.json

@@ -0,0 +1,23 @@
+{
+  "_internal.delete_desired_balance":{
+    "documentation":{
+      "url":"https://www.elastic.co/guide/en/elasticsearch/reference/current/delete-desired-balance.html",
+      "description": "This API is a diagnostics API and the output should not be relied upon for building applications."
+    },
+    "stability":"experimental",
+    "visibility":"private",
+    "headers":{
+      "accept": [ "application/json"]
+    },
+    "url":{
+      "paths":[
+        {
+          "path":"/_internal/desired_balance",
+          "methods":[
+            "DELETE"
+          ]
+        }
+      ]
+    }
+  }
+}

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/cluster.desired_balance/10_basic.yml

@@ -5,7 +5,7 @@ setup:
       reason: "API added in in 8.6.0"
 
 ---
-"Test empty desired balance":
+"Test get empty desired balance":
 
   - do:
       _internal.get_desired_balance: { }
@@ -19,12 +19,51 @@ setup:
   - gte: { stats.reconciliation_time_in_millis: 0 }
   - match: { routing_table: {} }
 
+---
+"Test get desired balance for a single shard":
+  - do:
+      indices.create:
+        index: test
+        body:
+          settings:
+            number_of_shards: 1
+            number_of_replicas: 0
+
+  - do:
+      cluster.health:
+        index: test
+        wait_for_status: green
+
+  - do:
+      _internal.get_desired_balance: { }
+
+  - gte: { stats.computation_submitted: 0 }
+  - gte: { stats.computation_executed: 0 }
+  - gte: { stats.computation_converged: 0 }
+  - gte: { stats.computation_iterations: 0 }
+  - gte: { stats.computation_converged_index: 0 }
+  - gte: { stats.computation_time_in_millis: 0 }
+  - gte: { stats.reconciliation_time_in_millis: 0 }
+
+  - match: { routing_table.test.0.current.0.state: 'STARTED' }
+  - match: { routing_table.test.0.current.0.shard_id: 0 }
+  - match: { routing_table.test.0.current.0.index: test }
+  - is_true: 'routing_table.test.0.current.0.node_is_desired'
+  - is_false: 'routing_table.test.0.current.0.relocating_node'
+  - is_false: 'routing_table.test.0.current.0.relocating_node_is_desired'
+  - is_false: 'routing_table.test.0.current.0.forecast_write_load'
+  - is_false: 'routing_table.test.0.current.0.forecast_shard_size_in_bytes'
+  - match: { routing_table.test.0.desired.total: 1 }
+  - gte: { routing_table.test.0.desired.unassigned: 0 }
+  - gte: { routing_table.test.0.desired.ignored: 0 }
+  - is_true: 'routing_table.test.0.desired.node_ids'
+
 ---
 "Test cluster_balance_stats":
 
   - skip:
       version: " - 8.6.99"
-      reason: "Field added in in 8.7.0"
+      reason: "cluster_balance_stats added in in 8.7.0"
 
   - do:
       cluster.state: {}
@@ -72,7 +111,7 @@ setup:
 
   - skip:
       version: " - 8.7.99"
-      reason: "Field added in in 8.8.0"
+      reason: "cluster_info added in in 8.8.0"
 
   - do:
       _internal.get_desired_balance: { }
@@ -84,7 +123,7 @@ setup:
 
   - skip:
       version: " - 8.7.99"
-      reason: "Node ID added in in 8.8.0"
+      reason: "node_id and roles added in in 8.8.0"
 
   - do:
       cluster.state: {}
@@ -98,51 +137,12 @@ setup:
   - is_true: 'cluster_balance_stats.nodes.$node_name.node_id'
   - is_true: 'cluster_balance_stats.nodes.$node_name.roles'
 
----
-"Test get desired balance for single shard":
-  - do:
-      indices.create:
-        index: test
-        body:
-          settings:
-            number_of_shards: 1
-            number_of_replicas: 0
-
-  - do:
-      cluster.health:
-        index: test
-        wait_for_status: green
-
-  - do:
-      _internal.get_desired_balance: { }
-
-  - gte: { stats.computation_submitted: 0 }
-  - gte: { stats.computation_executed: 0 }
-  - gte: { stats.computation_converged: 0 }
-  - gte: { stats.computation_iterations: 0 }
-  - gte: { stats.computation_converged_index: 0 }
-  - gte: { stats.computation_time_in_millis: 0 }
-  - gte: { stats.reconciliation_time_in_millis: 0 }
-
-  - match: { routing_table.test.0.current.0.state: 'STARTED' }
-  - match: { routing_table.test.0.current.0.shard_id: 0 }
-  - match: { routing_table.test.0.current.0.index: test }
-  - is_true: 'routing_table.test.0.current.0.node_is_desired'
-  - is_false: 'routing_table.test.0.current.0.relocating_node'
-  - is_false: 'routing_table.test.0.current.0.relocating_node_is_desired'
-  - is_false: 'routing_table.test.0.current.0.forecast_write_load'
-  - is_false: 'routing_table.test.0.current.0.forecast_shard_size_in_bytes'
-  - match: { routing_table.test.0.desired.total: 1 }
-  - gte: { routing_table.test.0.desired.unassigned: 0 }
-  - gte: { routing_table.test.0.desired.ignored: 0 }
-  - is_true: 'routing_table.test.0.desired.node_ids'
-
 ---
 "Test tier_preference":
 
   - skip:
       version: " - 8.7.99"
-      reason: "tier preference added in in 8.8.0"
+      reason: "tier_preference added in in 8.8.0"
 
   - do:
       indices.create:
@@ -173,3 +173,13 @@ setup:
       _internal.get_desired_balance: { }
 
   - gte: { stats.computed_shard_movements: 0 }
+
+---
+"Test reset desired balance":
+
+  - skip:
+      version: " - 8.7.99"
+      reason: "reset API added in in 8.8.0"
+
+  - do:
+      _internal.delete_desired_balance: { }

server/src/main/java/org/elasticsearch/action/ActionModule.java

@@ -11,8 +11,10 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.admin.cluster.allocation.ClusterAllocationExplainAction;
+import org.elasticsearch.action.admin.cluster.allocation.DeleteDesiredBalanceAction;
 import org.elasticsearch.action.admin.cluster.allocation.GetDesiredBalanceAction;
 import org.elasticsearch.action.admin.cluster.allocation.TransportClusterAllocationExplainAction;
+import org.elasticsearch.action.admin.cluster.allocation.TransportDeleteDesiredBalanceAction;
 import org.elasticsearch.action.admin.cluster.allocation.TransportGetDesiredBalanceAction;
 import org.elasticsearch.action.admin.cluster.configuration.AddVotingConfigExclusionsAction;
 import org.elasticsearch.action.admin.cluster.configuration.ClearVotingConfigExclusionsAction;
@@ -310,6 +312,7 @@
 import org.elasticsearch.rest.action.admin.cluster.RestClusterStatsAction;
 import org.elasticsearch.rest.action.admin.cluster.RestClusterUpdateSettingsAction;
 import org.elasticsearch.rest.action.admin.cluster.RestCreateSnapshotAction;
+import org.elasticsearch.rest.action.admin.cluster.RestDeleteDesiredBalanceAction;
 import org.elasticsearch.rest.action.admin.cluster.RestDeleteDesiredNodesAction;
 import org.elasticsearch.rest.action.admin.cluster.RestDeleteRepositoryAction;
 import org.elasticsearch.rest.action.admin.cluster.RestDeleteSnapshotAction;
@@ -621,6 +624,7 @@ public <Request extends ActionRequest, Response extends ActionResponse> void reg
         actions.register(ClearVotingConfigExclusionsAction.INSTANCE, TransportClearVotingConfigExclusionsAction.class);
         actions.register(ClusterAllocationExplainAction.INSTANCE, TransportClusterAllocationExplainAction.class);
         actions.register(GetDesiredBalanceAction.INSTANCE, TransportGetDesiredBalanceAction.class);
+        actions.register(DeleteDesiredBalanceAction.INSTANCE, TransportDeleteDesiredBalanceAction.class);
         actions.register(ClusterStatsAction.INSTANCE, TransportClusterStatsAction.class);
         actions.register(ClusterStateAction.INSTANCE, TransportClusterStateAction.class);
         actions.register(ClusterHealthAction.INSTANCE, TransportClusterHealthAction.class);
@@ -799,6 +803,7 @@ public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {
         registerHandler.accept(new RestNodesHotThreadsAction());
         registerHandler.accept(new RestClusterAllocationExplainAction());
         registerHandler.accept(new RestGetDesiredBalanceAction());
+        registerHandler.accept(new RestDeleteDesiredBalanceAction());
         registerHandler.accept(new RestClusterStatsAction());
         registerHandler.accept(new RestClusterStateAction(settingsFilter, threadPool));
         registerHandler.accept(new RestClusterHealthAction());

server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/DeleteDesiredBalanceAction.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.cluster.allocation;
+
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.action.ActionType;
+
+public class DeleteDesiredBalanceAction extends ActionType<ActionResponse.Empty> {
+
+    public static final DeleteDesiredBalanceAction INSTANCE = new DeleteDesiredBalanceAction();
+    public static final String NAME = "cluster:admin/desired_balance/reset";
+
+    DeleteDesiredBalanceAction() {
+        super(NAME, in -> ActionResponse.Empty.INSTANCE);
+    }
+}