Add cluster setting for searchable snapshot local cache block size

Author: finnegancarroll

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

@@ -697,6 +697,7 @@ public void apply(Settings value, Settings current, Settings previous) {
 
                 // Settings related to Searchable Snapshots
                 Node.NODE_SEARCH_CACHE_SIZE_SETTING,
+                Node.NODE_SEARCH_CACHE_BLOCK_SHIFT_SETTING,
                 FileCacheSettings.DATA_TO_FILE_CACHE_SIZE_RATIO_SETTING,
 
                 // Settings related to Remote Refresh Segment Pressure

server/src/main/java/org/opensearch/node/Node.java

@@ -383,6 +383,13 @@ public class Node implements Closeable {
         Property.NodeScope
     );
 
+    public static final Setting<String> NODE_SEARCH_CACHE_BLOCK_SHIFT_SETTING = new Setting<>(
+        "node.search.cache.block_size",
+        s -> (DiscoveryNode.isDedicatedSearchNode(s)) ? "23" : ZERO,
+        Node::validateFileCacheBlockSizeShift,
+        Property.NodeScope
+    );
+
     private static final String CLIENT_TYPE = "node";
 
     /**
@@ -2061,6 +2068,21 @@ private static String validateFileCacheSize(String capacityRaw) {
         return capacityRaw;
     }
 
+    private static String validateFileCacheBlockSizeShift(String blockSizeShiftRaw) {
+        int shift = Integer.parseInt(blockSizeShiftRaw);
+        if (shift >= 31 || shift <= 10) {
+            throw new SettingsException(
+                "Unable to initialize the "
+                    + DiscoveryNodeRole.SEARCH_ROLE.roleName()
+                    + " node: "
+                    + NODE_SEARCH_CACHE_BLOCK_SHIFT_SETTING.getKey()
+                    + " must be between 10 and 30"
+            );
+        }
+
+        return blockSizeShiftRaw;
+    }
+
     /**
      * Returns the {@link FileCache} instance for remote search node
      * Note: Visible for testing