Add WriteLoadConstraintSettings (#130056)

Relates: ES-11989

Author: nicktindall

server/src/main/java/org/elasticsearch/cluster/routing/allocation/WriteLoadConstraintSettings.java

@@ -0,0 +1,101 @@
+/*
+ * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.cluster.routing.allocation;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.cluster.routing.RerouteService;
+import org.elasticsearch.common.Priority;
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.unit.RatioValue;
+import org.elasticsearch.core.TimeValue;
+
+/**
+ * Settings definitions for the write load allocation decider and associated infrastructure
+ */
+public class WriteLoadConstraintSettings {
+
+    private static final String SETTING_PREFIX = "cluster.routing.allocation.write_load_decider.";
+
+    public enum WriteLoadDeciderStatus {
+        /**
+         * The decider is disabled
+         */
+        DISABLED,
+        /**
+         * Only the low-threshold is enabled (write-load will not trigger rebalance)
+         */
+        LOW_ONLY,
+        /**
+         * The decider is enabled
+         */
+        ENABLED
+    }
+
+    public static final Setting<WriteLoadDeciderStatus> WRITE_LOAD_DECIDER_ENABLED_SETTING = Setting.enumSetting(
+        WriteLoadDeciderStatus.class,
+        SETTING_PREFIX + "enabled",
+        WriteLoadDeciderStatus.DISABLED,
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
+    /**
+     * The threshold over which we consider write thread pool utilization "high"
+     */
+    public static final Setting<RatioValue> WRITE_LOAD_DECIDER_HIGH_UTILIZATION_THRESHOLD_SETTING = new Setting<>(
+        SETTING_PREFIX + "high_utilization_threshold",
+        "90%",
+        RatioValue::parseRatioValue,
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
+    /**
+     * The duration for which we need to see "high" utilization before we consider the low threshold exceeded
+     */
+    public static final Setting<TimeValue> WRITE_LOAD_DECIDER_HIGH_UTILIZATION_DURATION_SETTING = Setting.timeSetting(
+        SETTING_PREFIX + "high_utilization_duration",
+        TimeValue.timeValueMinutes(10),
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
+    /**
+     * When the decider is {@link WriteLoadDeciderStatus#ENABLED}, the write-load monitor will call
+     * {@link RerouteService#reroute(String, Priority, ActionListener)} when we see tasks being delayed by this amount of time
+     * (but no more often than {@link #WRITE_LOAD_DECIDER_REROUTE_INTERVAL_SETTING})
+     */
+    public static final Setting<TimeValue> WRITE_LOAD_DECIDER_QUEUE_LATENCY_THRESHOLD_SETTING = Setting.timeSetting(
+        SETTING_PREFIX + "queue_latency_threshold",
+        TimeValue.timeValueSeconds(30),
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
+    /**
+     * How often the data node calculates the write-loads for the individual shards
+     */
+    public static final Setting<TimeValue> WRITE_LOAD_DECIDER_SHARD_WRITE_LOAD_POLLING_INTERVAL_SETTING = Setting.timeSetting(
+        SETTING_PREFIX + "shard_write_load_polling_interval",
+        TimeValue.timeValueSeconds(60),
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
+    /**
+     * The minimum amount of time between successive calls to reroute to address write load hot-spots
+     */
+    public static final Setting<TimeValue> WRITE_LOAD_DECIDER_REROUTE_INTERVAL_SETTING = Setting.timeSetting(
+        SETTING_PREFIX + "reroute_interval",
+        TimeValue.timeValueSeconds(60),
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+}

server/src/main/java/org/elasticsearch/common/settings/ClusterSettings.java

@@ -46,6 +46,7 @@
 import org.elasticsearch.cluster.routing.OperationRouting;
 import org.elasticsearch.cluster.routing.allocation.DataTier;
 import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
+import org.elasticsearch.cluster.routing.allocation.WriteLoadConstraintSettings;
 import org.elasticsearch.cluster.routing.allocation.allocator.AllocationBalancingRoundSummaryService;
 import org.elasticsearch.cluster.routing.allocation.allocator.BalancedShardsAllocator;
 import org.elasticsearch.cluster.routing.allocation.allocator.DesiredBalanceComputer;
@@ -643,6 +644,12 @@ public void apply(Settings value, Settings current, Settings previous) {
         DataStreamFailureStoreSettings.DATA_STREAM_FAILURE_STORED_ENABLED_SETTING,
         IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_SETTING,
         SearchStatsSettings.RECENT_READ_LOAD_HALF_LIFE_SETTING,
-        TransportGetAllocationStatsAction.CACHE_TTL_SETTING
+        TransportGetAllocationStatsAction.CACHE_TTL_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_ENABLED_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_HIGH_UTILIZATION_THRESHOLD_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_HIGH_UTILIZATION_DURATION_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_QUEUE_LATENCY_THRESHOLD_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_SHARD_WRITE_LOAD_POLLING_INTERVAL_SETTING,
+        WriteLoadConstraintSettings.WRITE_LOAD_DECIDER_REROUTE_INTERVAL_SETTING
     );
 }