@Override
          public TestProtos.EchoResponseProto
            call(TestRpcServiceProtos.TestProtobufRpcProto instance) throws IOException {
            LOG.debug("Default response is " + TestProtos.EchoRequestProto.getDefaultInstance());
            CoprocessorRpcUtils.BlockingRpcCallback<TestProtos.EchoResponseProto> callback =
              new CoprocessorRpcUtils.BlockingRpcCallback<>();
            instance.echo(controller, request, callback);
            TestProtos.EchoResponseProto response = callback.get();
            LOG.debug("Batch.Call returning result " + response);
            return response;
          }
TestEndpoint: test cases to verify coprocessor Endpoint
hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorEndpoint.java