Enabled Async Shard Batch Fetch by default

Signed-off-by: Manik Garg <[email protected]>

Author: gargmanik13

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased 3.x]
 ### Added
+- Enabled Async Shard Batch Fetch by default ([#17987](https://github.com/opensearch-project/OpenSearch/pull/17987))
 
 ### Changed
 

server/src/main/java/org/opensearch/cluster/routing/allocation/ExistingShardsAllocator.java

@@ -64,21 +64,19 @@ public interface ExistingShardsAllocator {
 
     /**
      * Boolean setting to enable/disable batch allocation of unassigned shards already existing on disk.
-     * This will allow sending all Unassigned Shards to the ExistingShard Allocator to  make decision to allocate
+     * This will allow sending all Unassigned Shards to the ExistingShard Allocator to make decision to allocate
      * in one or more go.
-     *
-     * Enable this setting if your ExistingShardAllocator is implementing the
+     * <p>
+     * This setting is enabled by default. In your ExistingShardAllocator implement the
      * {@link ExistingShardsAllocator#allocateAllUnassignedShards(RoutingAllocation, boolean)} method.
      * The default implementation of this method is not optimized and assigns shards one by one.
-     *
-     * If no plugin overrides {@link ExistingShardsAllocator} then default implementation will be use for it , i.e,
+     * <p>
+     * If no plugin overrides {@link ExistingShardsAllocator} then default implementation will be used for it , i.e,
      * {@link ShardsBatchGatewayAllocator}.
-     *
-     * This setting is experimental at this point.
      */
     Setting<Boolean> EXISTING_SHARDS_ALLOCATOR_BATCH_MODE = Setting.boolSetting(
         "cluster.allocator.existing_shards_allocator.batch_enabled",
-        false,
+        true,
         Setting.Property.NodeScope
     );
 

server/src/main/java/org/opensearch/gateway/ShardsBatchGatewayAllocator.java

@@ -85,6 +85,7 @@ public class ShardsBatchGatewayAllocator implements ExistingShardsAllocator {
     private TimeValue replicaShardsBatchGatewayAllocatorTimeout;
     private volatile Priority followUpRerouteTaskPriority;
     public static final TimeValue MIN_ALLOCATOR_TIMEOUT = TimeValue.timeValueSeconds(20);
+    public static final TimeValue DEFAULT_ALLOCATOR_TIMEOUT = TimeValue.timeValueSeconds(20);
     private final ClusterManagerMetrics clusterManagerMetrics;
 
     /**
@@ -105,7 +106,7 @@ public class ShardsBatchGatewayAllocator implements ExistingShardsAllocator {
      */
     public static final Setting<TimeValue> PRIMARY_BATCH_ALLOCATOR_TIMEOUT_SETTING = Setting.timeSetting(
         PRIMARY_BATCH_ALLOCATOR_TIMEOUT_SETTING_KEY,
-        TimeValue.MINUS_ONE,
+        DEFAULT_ALLOCATOR_TIMEOUT,
         TimeValue.MINUS_ONE,
         new Setting.Validator<>() {
             @Override
@@ -129,7 +130,7 @@ public void validate(TimeValue timeValue) {
      */
     public static final Setting<TimeValue> REPLICA_BATCH_ALLOCATOR_TIMEOUT_SETTING = Setting.timeSetting(
         REPLICA_BATCH_ALLOCATOR_TIMEOUT_SETTING_KEY,
-        TimeValue.MINUS_ONE,
+        DEFAULT_ALLOCATOR_TIMEOUT,
         TimeValue.MINUS_ONE,
         new Setting.Validator<>() {
             @Override