Add nodesInfo service dummy/unimpl response for testing.

Signed-off-by: Finn Carroll <carrofin@amazon.com>

server/src/main/java/org/opensearch/grpc/services/nodesInfo/NodesInfoServiceImpl.java

@@ -8,6 +8,7 @@
 
 package org.opensearch.grpc.services.nodesInfo;
 
+import io.grpc.Status;
 import io.grpc.stub.StreamObserver;
 import org.opensearch.action.admin.cluster.node.info.proto.NodesInfoProtoService;
 import org.opensearch.action.admin.cluster.node.info.proto.NodesInfoServiceGrpc;
@@ -16,11 +17,24 @@ public class NodesInfoServiceImpl extends NodesInfoServiceGrpc.NodesInfoServiceI
 
     @Override
     public void getNodesInfo(NodesInfoProtoService.NodesInfoRequest request, StreamObserver<NodesInfoProtoService.NodesInfoResponse> responseObserver) {
-        System.out.println("getNodesInfo");
+        try {
+            System.out.println("getNodesInfo");
+
+            NodesInfoProtoService.NodesInfoResponse response = NodesInfoProtoService.NodesInfoResponse.newBuilder()
+                .setClusterName("test-cluster")
+                .build();
+
+            responseObserver.onNext(response);
+            responseObserver.onCompleted();
+        } catch (Exception e) {
+            responseObserver.onError(e);
+        }
     }
 
     @Override
     public void streamNodesInfo(NodesInfoProtoService.NodesInfoRequest request, StreamObserver<NodesInfoProtoService.NodesInfoResponse> responseObserver) {
-        // Func stub
+        responseObserver.onError(
+            Status.UNIMPLEMENTED.withDescription("Method StreamNodesInfo is not implemented").asRuntimeException()
+        );
     }
 }