Made PSBA child class of PSA

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

@@ -34,6 +34,7 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.opensearch.cluster.node.DiscoveryNode;
 import org.opensearch.cluster.routing.RecoverySource;
 import org.opensearch.cluster.routing.RoutingNode;
 import org.opensearch.cluster.routing.RoutingNodes;
@@ -47,6 +48,7 @@
 
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
@@ -192,4 +194,17 @@ protected static List<NodeAllocationResult> buildDecisionsForAllNodes(ShardRouti
         }
         return results;
     }
+
+
+    protected interface INodeShardState {
+        BaseNodeGatewayStartedShards getShardState();
+        DiscoveryNode getNode();
+    }
+    protected interface INodeShardStates<T, V> {
+        void add(V value);
+        void add(T key, V value);
+        V get(T key);
+        int size();
+        Iterator<? extends INodeShardState> iterator();
+    }
 }

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

@@ -0,0 +1,19 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.gateway;
+
+import org.opensearch.indices.replication.checkpoint.ReplicationCheckpoint;
+
+public interface BaseNodeGatewayStartedShards {
+
+    String allocationId();
+    boolean primary();
+    ReplicationCheckpoint replicationCheckpoint();
+    Exception storeException();
+}